Hydrocarbon Formation and the Charge Field

Reduction of Carbon Dioxide by Magnetite:  Implications for the Primordial Synthesis of Organic Molecules

Q. W. ChenDetlef W. Bahnemann
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Cite this: J. Am. Chem. Soc. 2000, 122, 5, 970-971
Publication Date:January 20, 2000

https://doi.org/10.1021/ja991278y

Copyright 2000 American Chemical Society

https://pubs.acs.org/
...

A closer look at supercritical water

Giulia Galli and Ding Pan

Additional article information

Water, the fluid of life at ambient pressure (P) and temperature (T), is mostly present under supercritical conditions in the Earth’s crust and mantle (1): that is, above the vapor-liquid critical point (647 K and 221 MPa). As a free fluid or dissolved in silicate minerals, supercritical water greatly influences the structure and dynamics of our planet. From a technological standpoint, there are several, new emerging applications for supercritical water as a green solvent (2), including the catalytic conversion of biomass into fuels and the oxidation of hazardous materials.

In PNAS, the article by Sahle et al. (3) points at two intertwined issues: the yet unsolved structural properties of supercritical water: in particular, whether the system is homogeneous and hydrogen bonds (HBs) are still present, and the need to combine simulations and experiments to understand the complex changes the fluid undergoes under supercritical conditions. The spectroscopic measurements presented in the report provide benchmarks for atomic and electronic structural models and represent a step forward in gathering the data required to unravel the complexity of supercritical water.

As pointed out in numerous studies (3–5), water’s properties exhibit dramatic changes under supercritical conditions: the fraction of HB molecules greatly decreases with respect to ambient P and T, and there appears to be a consensus on the persistence of some HBs up to at least 600 °C and 134 MPa (3). The HB network, where present, is substantially distorted. Whether supercritical water is homogeneous [or composed of patches of clearly defined HB regions and non-HB ones (5)], and over which length-scale possible density heterogeneities might appear, are still matters of debate. The presence of inhomogeneous patterns in the density has long been a contentious topic for the liquid at ambient conditions as well (6–10). Again, a tenuous consensus is forming in the scientific community around the idea that possible heterogeneities represent transient rather than equilibrium states of the liquid or supercritical fluid (8–10).

Changes in structure and bonding as a function of T and P are accompanied by variations of the dielectric constant (11), and hence the reactivity of water, which can then itself work as an acid or base catalyst. The variation detected in the dielectric constant ε, from ε ∼78 at ambient conditions to ∼6 at the vapor-liquid critical point, affects the solubility of minerals in the Earth (1) with important implications [e.g., for the transport of oxidized carbon (11)]. In general, the solubility and nucleation rates of various inorganic and organic compounds are modified (2), making it possible to use water in hydrothermal processes to produce a variety of functional materials without the use of polluting organic solvents. For example, supercritical water is used in the chemical recycling of waste polymers, including resins widely present in electronic devices, and in oxide material recovery (2).

Measurements in supercritical conditions are challenging, and experiments are difficult to interpret without the help of detailed microscopic models that account for the changes in chemical bonding as a function of T and P. The need for such models calls for quantum mechanical, first principles descriptions of water, as provided for example, by ab initio molecular dynamics (MD) (12), where interatomic forces are evaluated using density functional theory. This is the methodology of choice in the report of Sahle et al. (3). Numerous ab initio MD simulations of water have been carried out in the last 20 y and have contributed significantly to understanding basic structural and electronic properties of aqueous solutions and hydrated surfaces.

However, the description of liquid water from first principles is an ongoing challenge and intense research is underway in many groups to establish the accuracy of different density functional descriptions, with focus on the performance of hybrid (13) and van der Waals functionals (14), and on the role of proton quantum effects (ref. 15 and references therein). In addition, special care must be exercised in obtaining robust numerical convergence of ab initio MD (16). Hybrid and some van der Waals functionals overcome (13, 14) some of the deficiencies of semilocal ones, such as slow diffusion of the liquid at ambient conditions and the overestimate of tetrahedral order and underestimate of entropy. Under supercritical conditions, where the proportion of HBs is greatly decreased, simple semilocal functionals seem to perform better than at ambient T and P: for example, for the equation of state of the fluid (11), the melting line (17), and the dielectric properties (11, 17). However, the larger error bars of high-pressure measurements may conceal some of the inaccuracies of the theory in the supercritical regime.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3631657/

GEOLOGY WIKI


Serpentinite

Serpentinite is a rock composed of one or more serpentine group minerals. Minerals in this group are formed by serpentinization, a hydration and metamorphic transformation of ultramafic rock from the Earth's mantle. The alteration is particularly important at the sea floor at tectonic plate boundaries.

Formation and petrology

Serpentinization is a geological low-temperature metamorphic process involving heat and water in which low-silica mafic and ultramafic rocks are oxidized (anaerobic oxidation of Fe2+ by the protons of water leading to the formation of H2) and hydrolyzed with water into serpentinite. Peridotite, including dunite, at and near the seafloor and in mountain belts is converted to serpentine, brucite, magnetite, and other minerals — some rare, such as awaruite (Ni3Fe), and even native iron. In the process large amounts of water are absorbed into the rock increasing the volume and destroying the structure.[1]

The density changes from 3.3 to 2.7 g/cm3 with a concurrent volume increase on the order of 30-40%. The reaction is highly exothermic and rock temperatures can be raised by about
Convert,[1] providing an energy source for formation of non-volcanic hydrothermal vents. The magnetite-forming chemical reactions produce hydrogen gas under anaerobic conditions prevailing deep in the mantle, far from the Earth's atmosphere. Carbonates and sulfates are subsequently reduced by hydrogen and form methane and hydrogen sulfide. The hydrogen, methane, and hydrogen sulfide provide energy sources for deep sea chemotroph microorganisms.[1]

Serpentinite reactions

Serpentinite is formed from olivine via several reactions, some of which are complementary. Olivine is a solid solution between the magnesium-endmember forsterite and the iron-endmember fayalite. Serpentinite reactions 1a and 1b, below, exchange silica between forsterite and fayalite to form serpentine group minerals and magnetite. These are highly exothermic reactions.

Reaction 1a:
Fayalite + water → magnetite + aqueous silica + hydrogen

3Fe2SiO4 + 2H2O → 2Fe3O4 + 3SiO2 + 2H2

Reaction 1b:
Forsterite + aqueous silica → serpentine

3Mg2SiO4 + SiO2 + 4H2O → 2Mg3Si2O5(OH)4

Reaction 1c:
Forsterite + water → serpentine + brucite

2Mg2SiO4 + 3H2O → Mg3Si2O5(OH)4 + Mg(OH)2
Reaction 1c describes the hydration of olivine with water only to yield serpentine and Mg(OH)2 (brucite). Serpentine is stable at high pH in the presence of brucite like calcium silicate hydrate, (C-S-H) phases formed along with portlandite (Ca(OH)2) in hardened Portland cement paste after the hydration of belite (Ca2SiO4), the artificial calcium equivalent of forsterite.

https://geology.fandom.com/wiki/Serpentinite

Impact of Organics and Carbonates on the Oxidation and Precipitation of Iron during Hydraulic Fracturing of Shale

Adam D. Jew*†‡
OrcidMegan K. Dustin‡
Anna L. Harrison†‡
Claresta M. Joe-Wong‡
OrcidDana L. Thomas‡
Katharine Maher‡
Gordon E. Brown, Jr.†‡
John R. Bargar†
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Cite this: Energy Fuels 2017, 31, 4, 3643-3658
Publication Date:March 6, 2017

https://doi.org/10.1021/acs.energyfuels.6b03220

Abstract
Hydraulic fracturing of unconventional hydrocarbon reservoirs is critical to the United States energy portfolio; however, hydrocarbon production from newly fractured wells generally declines rapidly over the initial months of production. One possible reason for this decrease, especially over time scales of several months, is the mineralization and clogging of microfracture networks and pores proximal to propped fractures. One important but relatively unexplored class of reactions that could contribute to these problems is oxidation of Fe(II) derived from Fe(II)-bearing phases (primarily pyrite, siderite, and Fe(II) bound directly to organic matter) by the oxic fracture fluid and subsequent precipitation of Fe(III)-(oxy)hydroxides. The extent to which such reactions occur and their rates, mineral products, and physical locations within shale pore spaces are unknown. To develop a foundational understanding of potential impacts of shale iron chemistry on hydraulic stimulation, we reacted sand-sized (150–250 μm) and whole rock chips (cm-scale) of shales from four different formations (Marcellus Fm., New York; Barnett Fm., Central Texas; Eagle Ford Fm., Southern Texas; and Green River Fm., Colorado) at 80 °C with synthetic fracture fluid, with and without HCl. These four shales contain variable abundances of clays, carbonates, and total organic carbon (TOC). We monitored Fe concentration in solution and evaluated changes in Fe speciation in the solid phase using synchrotron-based techniques. Solution pH was the most important factor affecting the release of Fe into solution. For reactors with an initial solution pH of 2.0 and low carbonate content in the initial shale, the sand-sized shale showed an initial release of Fe into solution during the first 96 h of reaction, followed by a plateau or significant drop in solution Fe concentration, indicating that mineral precipitation occurred. In contrast, in reactors with high pH buffering capacity, little to no Fe was detected in solution throughout the course of the experiments. In reactors that contained no added acid (initial pH 7.1), there was no detectable Fe release into solution. The carbonate-poor whole rock samples showed a steady increase, then a plateau in Fe concentration during 3 weeks of reaction, indicating slower Fe release and subsequently slower Fe precipitation. Synchrotron-based X-ray fluorescence mapping coupled with X-ray absorption spectroscopy (both bulk and micro) showed that when solution pH was above 3.25, Fe(III)-bearing phases precipitated in the shale matrix. Initially, ferrihydrite precipitated on and in the shale, but as experimental time increased, the ferrihydrite transformed to either goethite (at pH 2.0) or hematite (pH > 6.5). Additionally, not all of the released Fe(II) was oxidized to Fe(III), resulting in the precipitation of mixed-valence phases such as magnetite. Idealized systems containing synthetic fracture fluid and dissolved ferrous chloride but no shale showed that in reactors open to the atmosphere at low pH (<3.0), Fe(II) oxidation is inhibited. Surprisingly, the addition of bitumen, which is often extracted by organic compounds in the fracture fluid, can override this inhibition of Fe(II) oxidation caused by low pH. Nonetheless, O2 in the system is still the most important factor controlling Fe(II) oxidation. These results indicate that Fe redox cycling is an important and complex part of hydraulic fracturing and provide evidence that Fe(III)-bearing precipitates derived from oxidation of Fe(II)-bearing phases could negatively impact hydrocarbon production by inhibiting transport.

Formation of abiotic hydrocarbon from reduction of carbonate in subduction zones: Constraints from petrological observation and experimental simulation

https://www.sciencedirect.com/science/article/pii/S0016703718304368

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Renbiao
TaoaYingwei
Feiae
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https://doi.org/10.1016/j.gca.2018.08.008
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Under a Creative Commons licenseopen access

Abstract

Subduction is a key process for linking the carbon cycle between the Earth’s surface and its interior. Knowing the carbonation and decarbonation processes in the subduction zone is essential for understanding the global deep carbon cycle. In particular, the potential role of hydrocarbon fluids in subduction zones is not well understood and has long been debated. Here we report graphite and light hydrocarbon-bearing inclusions in the carbonated eclogite from the Southwest (S.W.) Tianshan subduction zone, which is estimated to have originated at a depth of at least 80 kilometers. The formation of graphite and light hydrocarbon likely results from the reduction of carbonate under low oxygen fugacity (∼FMQ - 2.5 log units). To better understand the origin of light hydrocarbons, we also investigated the reaction between iron-bearing carbonate and water under conditions relevant to subduction zone environments using large-volume high-pressure apparatus. Our high-pressure experiments provide additional constraints on the formation of abiotic hydrocarbons and graphite/diamond from carbonate-water reduction. In the experimental products, the speciation and concentration of the light hydrocarbons including methane (CH4), ethane (C2H6), and propane (C3H8) were unambiguously determined using gas chromatograph techniques. The formation of these hydrocarbons is accompanied by the formation of graphite and oxidized iron in the form of magnetite (Fe3O4). We observed the identical mineral assemblage (iron-bearing dolomite, magnetite, and graphite) associated with the formation of the hydrocarbons in both naturally carbonated eclogite and the experimental run products, pointing toward the same formation mechanism. The reduction of the carbonates under low oxygen fugacity is, thus, an important mechanism in forming abiotic hydrocarbons and graphite/diamond in the subduction zone settings.

Resolution of a Big Argument About Tiny Magnetic Minerals in Martian Meteorite
--- Magnetic minerals in Martian meteorite ALH 84001 formed as a result of impact heating and decomposition of carbonate; they were never used as compasses by Martian microorganisms.
Written by Edward R. D. Scott (Hawai'i Institute of Geophysics and Planetology) and David J. Barber (University of Greenwich, University of Essex, UK)

Tiny grains of magnetite, an iron oxide mineral, from a Martian meteorite are markedly similar in size, shape, and composition to the little oxide magnets used by bacteria on Earth and different from other naturally formed magnetites. Is this good evidence for life on Mars? Or did the Martian magnetite grains form by another process? Our studies reveal that the planes of atoms in the Martian magnetites are aligned with atomic planes in the carbonate in which the magnetites are embedded. This shows that the magnetites formed in the rock and not inside microorganisms.

References:

Barber, D. J. and Scott, E. R. D. (2002) Origin of supposedly biogenic magnetite in the Martian meteorite Allan Hills 84001. Proceedings of the National Academy of Sciences 99, 6556-6561.
Thomas-Keprta, K. L., Clement, S. J., Bazylinski, D. A., Kirschvink, J. L., McKay, D. S., Wentworth, S. J., Vali, H., Gibson, E. K., Jr., McKay, M. F., and Romanek, C. S. (2001). Truncated hexa-octahedral magnetite crystals in ALH 84001: presumptive biosignatures. Proceedings of the National Academy of Sciences 98, 2164-2169.

Magnetite crystals in ALH 84001

Since the startling report in 1996 of possible evidence for life in the Martian meteorite ALH 84001, Data link from Meteoritical Database [See PSRD article: Life on Mars?] attention has increasingly focused on the origin of the meteoritic magnetite, as this mineral appears to provide the most compelling evidence for biogenic activity. The magnetite grains reside in tiny grains of iron-magnesium-calcium carbonates, which are typically 50-200 micrometers across and are dispersed throughout the ALH 84001 meteorite as disk-shaped or spheroidal grains, or, in the case of carbonates that enclose silicate fragments, as irregularly shaped grains.

crossed polarized image of carbonate disk
Mosaic of transmitted light images of a thin section of ALH 84001 between crossed polarizing filters. The pyroxene crystals are transformed into a kaleidoscopic display of colors that help us to decipher the history of the rock. The gray criss-crossing bands are shattered pyroxene crystals that formed when an impact on Mars squeezed the rock, momentarily twisting and tearing the crystals. Black chromite crystals were also wrenched apart by the impact. The white arrow near the bottom of the mosaic marks a carbonate disk (shown below) that formed in a fracture. Maximum width shown of this mosaic is 8.5 millimeters.

The magnetites are too small to be seen using optical microscopes as they are 4-100 nanometers in size. (The smallest magnetites are about as wide as 15 oxygen atoms.)

focusing on carbonate disk
This simple movie of a truncated carbonate disk with a pale orange core was made from thirteen separate micrographs of a thin section of ALH 84001. The carbonate is about 130 x 4 micrometers in size and is embedded inside a greyish-white pyroxene crystal. The movie shows how a change in focus of the microscope reveals that the carbonate disk formed in an inclined fracture in the pyroxene crystal. The magnetite crystals are concentrated in the two concentric black lines near the rim of the carbonate disk. (Image credit: Ed Scott.)

Kathie Thomas-Keprta (Lockheed Martin) and her colleagues at the NASA Johnson Space Center have used electron microscopes to analyze the composition and morphology of the magnetite crystals in considerable detail. Studies of thin slices of the rock show that the magnetites are found at the rims of carbonate grains in optically opaque regions and throughout the interior of the carbonate grains. By dissolving 600 magnetite crystals out of the carbonate, they found that about 25% were faceted crystals with width/length ratios of >0.4 (called elongated prisms), ~65% were irregularly shaped and 7% were more elongate with width/length ratios of <0.4. Thomas-Keprta and her colleagues showed that the elongated prisms were remarkably similar in size, shape, and composition to the magnetites made by one strain of bacteria that uses chains of single-domain crystals of magnetite as a compass to aid in navigation. Since the bacterial compasses are made with great precision and efficiency and appear to differ from abiogenic magnetites in shape and composition (but not size), they interpreted the elongated prism magnetites as Martian fossils.

Although all workers agree that the magnetites in ALH 84001 were formed on Mars and may contain an important record of an ancient Martian magnetic field, many have argued against a biological origin for the magnetites. Peter Buseck (Arizona State University) and coworkers have questioned whether the putative Martian biogenic magnetites and the bacterial magnetites are identical in shape. John Bradley (Georgia Institute of Technology) and colleagues concluded that magnetites with width/length ratios of ~0.1 to 0.2 grew on the surface of the carbonate because their crystal lattices are aligned where they make contact. They inferred that these so-called whisker-shaped magnetites could not have been made by bacteria but had condensed from a vapor above 120oC. Thomas-Keprta and colleagues did not dispute that these magnetites were probably abiogenic. However, they argued that whisker-shaped magnetites formed at lower temperatures in the interior of the carbonate grains whereas the elongated prisms were concentrated in the opaque rims by a different process.

http://www.psrd.hawaii.edu/May02/ALH84001magnetite.html

Relationship between magnetic anomalies and hydrocarbon microseepage above the Jingbian gas field, Ordos basin, China

Abstract

In this study, soil magnetic measurements (susceptibility and hysteretic parameters) and soil hydrocarbon analyses were conducted on samples from three profiles (profiles I and II run across, and profile III runs parallel to the trend of the Jingbian gas field in the Ordos basin, central China) to determine the relationship between the magnetic anomalies (e.g., volume-specific magnetic susceptibility k) and the hydrocarbon seepage environments. The results document a strong correlation between magnetic susceptibility and soil-gas hydrocarbon concentration. Furthermore, the spatial distribution of k and hydrocarbon anomalies correlate with those of the gas field. In addition, magnetic minerals in the soils with higher susceptibility are predominantly magnetite, with little or no substitution of titanium compared to that of samples with lower susceptibility (<7 × 10-5 SI [International Unit of susceptibility]). These results provide strong evidences for the formation of highly magnetic minerals in close association with hydrocarbon seepage. Recognition of such seepage-induced magnetic anomalies can be used to facilitate the exploration for oil and gas in China and elsewhere. 2004. The American Association of Petroleum Geologists. All rights reserved.

https://www.researchgate.net/publication/240743938_Relationship_between_magnetic_anomalies_and_hydrocarbon_microseepage_above_the_Jingbian_gas_field_Ordos_basin_China

Generation of methane in the Earth's mantle: In situ high pressure–temperature measurements of carbonate reduction

Henry P. Scott, Russell J. Hemley, Ho-kwang Mao, Dudley R. Herschbach, Laurence E. Fried, W. Michael Howard, and Sorin Bastea

PNAS September 28, 2004 101 (39) 14023-14026; https://doi.org/10.1073/pnas.0405930101

Abstract

We present in situ observations of hydrocarbon formation via carbonate reduction at upper mantle pressures and temperatures. Methane was formed from FeO, CaCO3-calcite, and water at pressures between 5 and 11 GPa and temperatures ranging from 500°C to 1,500°C. The results are shown to be consistent with multiphase thermodynamic calculations based on the statistical mechanics of soft particle mixtures. The study demonstrates the existence of abiogenic pathways for the formation of hydrocarbons in the Earth's interior and suggests that the hydrocarbon budget of the bulk Earth may be larger than conventionally assumed.

Understanding the speciation of carbon at the high pressures and temperatures that prevail within the Earth has a long and controversial history. It is well known that terrestrial carbon exists in several forms: native, oxidized, and reduced in a wide variety of hydrocarbons. This complexity is demonstrated by many examples: diamonds in kimberlite formations; graphite in metamorphic rocks; CO2 emission from volcanoes; ubiquitous carbonate minerals in the crust; methane hydrates on and beneath the ocean floor; and petroleum reservoirs in sedimentary basins. Of particular interest are the stability and formation of reduced species such as methane and heavier hydrocarbons. The stability, formation, and occurrence of methane under low-pressure conditions of the Earth's crust are well established. Recently, methane and C2-C4 alkanes have been documented to occur in many locations for which isotopic evidence points to an abiogenic origin (1, 2). Furthermore, it has been shown that nickel-iron alloys can catalyze the formation of CH4 from bicarbonate (3), and that a variety of transition metal-bearing minerals can catalyze Fischer–Tropsch-type formation of hydrocarbons at conditions relevant to the upper crust (4, 5). Yet the evidence is considered to rule out a globally significant abiogenic source of hydrocarbons (2), and hydrothermal experiments suggest that with the exception of methane a vapor phase is required for the formation of heavier hydrocarbons (5). In contrast, theoretical calculations and experimental data have been presented in support of a persistent assertion that petroleum originates chiefly through abiogenic processes at the high pressures and temperatures found <100 km (6). The experiments, extending to 5 GPa and 1,500°C, involved mass spectroscopic analysis of quenched samples and found methane and smaller amounts of C2-C6 hydrocarbons. We report here in situ high pressure and temperature experiments to show that methane readily forms by reduction of carbonate under conditions typical for the Earth's upper mantle. The results may have significant implications for the hydrocarbon budget at depth in the planet.

Many factors are known to control the stability of carbon-bearing phases in the C-O-H system, including pressure, temperature, C/H ratio, and oxidation state, and it has long been appreciated that the relevant species in this system are C, O2,H2, CO, CO2,CH4, and H2O (7). At low pressures this system is well understood, and available thermodynamic databases can accurately predict phase stability. For example, studies of the C-O-H system in relation to crustal fluids and fluid inclusions have been carried out by using well established techniques (7, . Notably, theoretical modeling is both thermodynamically and observationally consistent at pressures <≈1 GPa (e.g., ref. 9) and can satisfactorily treat organic species (10). Previous experimental and theoretical work has shown that methane may be an important fluid phase at pressures of up to 1 GPa and low oxygen fugacities, and that methane may be the dominant C-bearing fluid phase at substantially reducing conditions (e.g., ref. . Furthermore, it has been shown that meteorite hydrocarbons can be formed by the thermal decomposition of FeCO3-siderite at low pressure (11). Thermodynamic calculations can be performed at higher pressures (12), but the system is poorly constrained by experimental work under the high-pressure conditions of the upper mantle (13). The importance of pressure is straightforward as it increases by ≈1 GPa (10 kbar) for every 30 km of depth in the Earth. Kimberlite eruptions, for example, typically come from depths near 150 km (5 GPa). Higher-pressure work has been completed on the effects of various species in the C-O-H system on the melt characteristics of mantle minerals (14, 15), but these results do not directly assess the stability of carbon-bearing phases.

Methods
We have conducted in situ high-pressure and temperature experiments specifically designed to detect methane formation under geologically relevant conditions for the Earth's upper mantle. Starting materials were natural CaCO3-calcite, FeO-wüstite, and distilled H2O. Experiments were conducted by using diamond anvil cell (DAC) techniques: simultaneous high-pressure and high-temperature conditions were produced by both resistive (16) (T < 600°C) and laser heating (T > 1,000°C) methods. We used three different laser heating systems, including both single- and double-sided and both CO2 and Nd-YLF lasers (17, 18). DACs with anvil culets ranging between 350 and 700 μm in diameter were used. Sample chambers were constructed by drilling a hole ≈70% of the culet diameter into an initially 260-μm-thick spring steel foil, which was used as a gasket material; the gaskets were preindented before drilling to a thickness of ≈60 μm. Pressure was measured by use of the ruby fluorescence technique (19). CO2 and double-sided Nd-YLF laser heating experiments and Raman scattering and optical microscopy analyses were performed at the Geophysical Laboratory (17, 18). Pyrometry was used to determine sample temperature in selected runs. The x-ray measurements and double-sided Nd-YLF laser heating were performed at the High Pressure Collaborative Access Team facilities of the Advanced Photon Source, Argonne National Laboratory, Argonne, CA.

https://www.pnas.org/content/101/39/14023

An overview of full-waveform inversion in exploration geophysics

J. Virieux1 and S. Operto

ABSTRACT

Full-waveform inversion FWI is a challenging data-fitting procedure based on full-wavefield modeling to extract quantita-tive information from seismograms. High-resolution imaging at half the propagated wavelength is expected.

https://jean-virieux.obs.ujf-grenoble.fr/IMG/pdf/GPY_2009_VIRIEUX.pdf

Rust under pressure could explain deep Earth anomalies
June 9, 2016

Read more : https://www.geologypage.com/2016/06/rust-under-pressure-could-explain-deep-earth-anomalies.html#ixzz6K02uTcOt

An artwork depicting the decomposition of FeOOH in lower mantle conditions. The cycle starts from α-FeOOH (blue dot on the top) to its high-pressure form (brown dot), to FeO2 (center crystal) and hydrogen (cyan bubbles), and finally produce other minerals (bubbles on the left side). Credit: Ms. Xiaoya.

Using laboratory techniques to mimic the conditions found deep inside the Earth, a team of Carnegie scientists led by Ho-Kwang “Dave” Mao has identified a form of iron oxide that they believe could explain seismic and geothermal signatures in the deep mantle. Their work is published in Nature.

Iron and oxygen are two of the most geochemically important elements on Earth. The core is rich in iron and the atmosphere is rich in oxygen, and between them is the entire range of pressures and temperatures on the planet.

“Interactions between oxygen and iron dictate Earth’s formation, differentiation—or the separation of the core and mantle—and the evolution of our atmosphere, so naturally we were curious to probe how such reactions would change under the high-pressure conditions of the deep Earth,” said Mao.

The research team—Qingyang Hu, Duck Young Kim, Wenge Yang, Liuxiang Yang, Yue Meng, Li Zhang, & Ho-Kwang Mao—put ordinary rust, or FeOOH, under about 900,000 times normal atmospheric pressure and at about 3200 degrees Fahrenheit and were able to synthesize a form of iron oxide, FeO2, that structurally resembles pyrite, also known as fool’s gold. The reaction gave off hydrogen in the form of H2.

FeOOH is found in iron ore deposits that exist in bogs, so it could easily move into the deep Earth at plate tectonic boundaries, as could samples of ferric oxide, Fe2O3, which along with water will also form the pyrite-like iron oxide under deep lower mantle conditions.

Why does this interest the researchers? For one thing, this type of reaction could have started in Earth’s infancy, and understanding it could inform theories of our own planet’s evolution, as well as its current geochemistry.
Recommended For You Most Earth-like worlds have yet to be born

Furthermore, the H2 released in this reaction would work its way upward, possibly reacting with other materials on its way. Meanwhile, the iron oxide would settle planet’s depths and form reservoirs of oxygen there, particularly if one of these patches of iron oxide moved upward along the pressure gradient to the middle part of the mantle and separated into iron and O2.

“Pools of free oxygen under these conditions could create many reactions and chemical phases, which might be responsible for seismic and geochemical signatures of the deep Earth,” Mao explained.

“Our experiments mimicking mantle conditions demonstrate that more research is needed on this pyrite-like phase of iron oxide.” Hu added.

The research team believes their findings could even offer an alternate explanation for the Great Oxygenation Event that changed Earth’s atmosphere between 2 and 2.5 billion years ago. The rise of bacteria performing photosynthesis, which releases oxygen as a byproduct, is often considered the source of the rapid increase in atmospheric oxygen, which had previously been scarce. But releases of oxygen from upwelling of deep mantle FeO2 patches could provide an abiotic explanation for the phenomenon, they say.

Reference:
FeO2 and FeOOH under deep lower-mantle conditions and Earth’s oxygen–hydrogen cycles, Nature, DOI:10.1038/nature18018

Note: The above post is reprinted from materials provided by Carnegie Institution for Science.

Read more : https://www.geologypage.com/2016/06/rust-under-pressure-could-explain-deep-earth-anomalies.html#ixzz6K03JGiEp

Characterization of the deposition and transport of magnetite particles in supercritical water

Author links open overlay panelKeigoKarakamaa
Steven N.RogakaAkramAlfantazib
https://doi.org/10.1016/j.supflu.2012.06.015
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Abstract

Several online and offline techniques for characterizing the deposition and transport of magnetite particles in supercritical water were investigated using a once-through flow apparatus. Ferrous chloride and ferrous sulfate precursor solutions were injected into a 1.8m heated test section at temperatures ranging from 200 °C to 400 °C. Silver membrane filters of 0.2 μm pore size were used to collect particles under supercritical conditions. Thermal resistance monitoring on the test section showed asymptotic, linear fouling and deposition-removal cycles. A novel method for qualitatively determining the strength of the oxide to the tube surface using a combination of ultrasonic and acid wash procedures demonstrated that at supercritical conditions, a stronger bond is formed which is speculated to be caused by the precipitation of dissolved ferrous species. A comparison between different conditions of pH, heat flux, and precursor were examined using the experimental techniques which are presented in this study. It was found that multiple techniques are needed to characterize the fouling process if the underlying rate-limiting steps are not known a priori.

Highlights

► Magnetite particles of 200–2000 nm were formed in sub- and supercritical water. ► Particles were in turbulent flows with different values of pH and temperature. ► Microscopy and tube cleaning techniques were used to analyze deposits. ► Deposits formed at supercritical temperature were strong. ► Deposits formed at subcritical temperature were relatively weak.

https://www.sciencedirect.com/science/article/pii/S0896844612002185

Interesting paper showing how Magenitite in Steam Boilers can affect Porosity and Permeability of boiler liners:

https://www.milhous.com/revised%20may%202017%20Electromagnetic%20Filtering%20of%20Magnetite%20from%20Steam%20Boiler%20Condensate;%20ver%201,%2019%20Sept%202013.pdf

Also link on GeoChemistry of Magenetite: https://pubs.usgs.gov/pp/0440kk/report.pdf
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Electromagnetic Filtering of Magnetite from Steam Boiler Condensate

by Joel Meissner

Magnetiteformation within a steam boiler system is costly to plant managers as a result of increased maintenance and lost production time. Does your steam plant have problems with Magnetite? Talking with pulp and papermill managers has yielded surprising responses to that question. While some understand the complexities of water chemistry and the resulting formation of Magnetite along with the difficulties these particles present, others have stated “We don’t have a problem with Magnetite; in fact it helps our system.”


So is Magnetitea problem or not? It is true that a thin film of Magnetitealong the water side of a steam boiler tube is beneficial as it passivates the tube surface and aids in the prevention of corrosion. Chemical additives are often added to the makeup water upon commissioning a new boiler to accelerate the formation of this protective layer. An additional benefit comes from the fact that the film acts to improve thermal transfer efficiency.Magnetite FormationTo fully understand the benefit of Magnetitelet’s first look at how Magnetiteis formed within a steam boiler system. Magnetite is a product of the iron oxide called Hematite. It is formedon the steam side of the boiler tubes under pressure and high temperature in the presence of water and can be expressed by the following equation.

Fe + 4 Fe2O3 →3 Fe3O4

So if a Magnetitefilm protects the boiler tubes from corrosion and increases thermal transfer efficiency, why is Magnetite formation a problem? The Magnetite film is actually comprised of two layers. The inner layer, directly in contact with the boiler tubes, is dense, compactand continuous, providing excellent corrosion protection. The outer layer is less dense, porous, and loosely bound to the inner layer. Each of these layers will continue to increase in thickness due to water diffusion in the outer porous layer, and latticed diffusion in the inner layer. Quite simply, over time the water system will enter into these microscopic pores and begin to corrode the steel tubing.(2)Magnetite Scale Problems

Within the boiler itself, the biggest problems caused by scale is overheating leading to the rupture of boiler tubes. While the thin dense film of Magnetite is thermally conductive, thicker porous layers create a more ceramic-like insulating layer which limits the thermal transfer. It is estimated that a scale thickness of 1/16” will increase fuel consumption by as much as 12.5%. This phenomenon leads to premature failure through softening, bulging and eventual rupturing of the boiler tubes. Even before a catastrophic rupture occurs, loss of heat transfer efficiency, reduced flow, and complete plugging of the tubes will lead to reduced performance and increased cost to maintain temperatures and flow. In summary, Magnetite scale can cause thermal damage increased cost to maintain performanceincreased cost to clean and repair tubes unscheduled downtime reduced working life of a boiler. While excessive Magnetite scale not only damages heat transfer surfaces within the boiler, the shedding of this scale creates numerous downstream problems in the form of fouling. Fouling is the restriction of flow in piping and equipment. Process equipment, filters, sand beds, screens,needle valves, and steam traps are susceptible to reduced performance and in some cases complete blockage from Magnetite particles. This fouling directly affects both the equipment availability and cost of operations.Corrosion products and impuritiescan accumulate in the secondary side of steam generators, causing accelerated corrosion, steam flow disruption and heat transfer loss. Components are cleaned either mechanically, such as by scrubbing and grinding, or chemically through acid etching

OXYGEN AND CARBON ISOTOPE OF SERPENTINES, MAGNETITES, AND CALCITES

Serpentine and Magnetite



Oxygen isotope results for serpentine are reported in Table 6. The oxygen isotope compositions for all the lizardite samples are strongly enriched in 18O (between 8.8‰ and 12.2‰), in comparison to the normal mantle 18O values for fresh peridotite olivine and pyroxene minerals (5‰ to 6‰; Taylor, 1968; Javoy, 1970) except for chrysotile from Sample 149-897D-16R-2, 35-42 cm, which is depleted in 18O. As oxygen is the principal constituent of silicate minerals in peridotites, such a large modification of the initial 18O requires interaction with large quantities of hydrothermal fluids during the serpentinization. High water-rock ratio conditions have been shown to be generally met in continental serpentinizing systems (Barnes and O'Neil, 1971) and oceanic serpentinized peridotites (Kimball and Gerlach, 1986; Snow and Dick, in press).

For two samples (149-897C-72R-1, 40-47 cm, and 149-897D-23R-1, 62-68 cm) the coexisting magnetite and lizardite have been measured for their 18O values. In both cases oxygen isotope fractionation, 18Oserpentine–magnetite, is very large (11.0‰ and 12.5‰, respectively) and is similar to the previously published values for oceanic serpentinized peridotites (Wenner and Taylor, 1973). Although the 18O fractionation between serpentine and magnetite has not yet been calibrated vs. temperature by laboratory experiments, some natural observations and regularities have led Wenner and Taylor (1971) to propose the following "tentative" geothermometer:

1000 ln[18Oserpentine–magnetite] = 1.69 (106/T2) + 1.68.

This calibration has been recently supported by the theoretical calculations of Zheng and Simon (1991) and Zheng (1993). Accordingly, the measured 18Oserpentine–magnetite values for Sample 149-897C-72R-1, 40-47 cm, and for Sample 149-897D-23R-1, 62-68 cm, correspond to temperatures of 150°C and 120°C (±50°C), respectively. These temperatures are in the range of those determined for the lizardites (and the chrysotiles also) of the oceanic serpentinized peridotites (70° to 250°C; Wenner and Taylor, 1971; Sheppard, 1980; Bonatti et al., 1984; Hébert et al., 1990). As the associated uncertainties in these calibrations are probably considerable, these estimated temperatures mean that the serpentinization has occurred at low temperature, namely less than 200°C.

The other high 18O values of nonmagnetite paired samples are similar to the previous samples and are therefore compatible with low-temperature serpentinization processes (below 150°C) in seawater-dominated conditions. In this respect, these serpentines are similar to the serpentines from Hole 637A to the north (Agrinier et al., 1988; Evans and Girardeau, 1988). No significant difference among the various serpentine types analyzed are observed: white serpentine from veins or from the background mesh, colorless, and pale-green fibrous serpentine from vein margins, all have 18O values around 10‰. As the 18O composition of serpentine is highly sensitive to temperature change, especially at low temperature (Wenner and Taylor, 1971, 1973), this narrow range of 18O values suggests that serpentinization mostly affected these peridotites during a single (low-temperature) stage. Less equivocal than the low-temperature serpentinization conditions that can be found down to 5 km below seafloor (see estimates of the temperature gradient made from heat flux measurements; Louden and Mareschal; this volume), the high 18O values of serpentines (around 10‰) necessarily imply that serpentinization occurred under very high seawater-rock ratios (Taylor, 1977). Such seawater-rock ratio conditions are unlikely to be met deep in the crust or in the mantle. This low-temperature serpentinization very likely started when they were brought to near seafloor position.

The contrasting vein chrysotile sample (149-897D-16R-2, 35-42 cm) with a low 18O value of +3.8‰ is lower than any observed in Hole 637A and in Holes 897C, 897D, and 899B. If it results from the serpentinization of the fresh peridotite, we infer that it formed in the presence of significant amounts of fluid (high water-rock ratio) because the 18O value of this chrysotile is also strongly shifted relative to its precursors (fresh olivine and orthopyroxene have 18O around 5.5‰). Since the serpentine-water oxygen isotope fractionation decreases with temperature, its low 18O value suggests that it formed at a significantly higher temperature (possibly 300°C). This chrysotile could be a remnant of the high-temperature serpentinization episode exemplified by the chlorites and the amphiboles. No other chrysotile vein sample has been recorded in Leg 149 serpentinites. The textural relationships of this sample suggest that chrysotile formed first in a vein and then was mantled by lizardite during the low-temperature serpentinization episode.
Calcite

The carbon isotope values of calcites range from -0.7‰ to 2.4‰. They are similar to those commonly reported for seawater marine carbonates and vein carbonates from the upper oceanic crust (Javoy and Fouillac, 1979; Bonatti et al., 1980; Stakes and O'Neil, 1982). In contrast to the calcites from Hole 637A peridotites (Agrinier et al., 1988), there is no evidence for low 13C values, which would reveal some contribution from mantle carbon (Javoy and Fouillac, 1979). Calcites from veins, cracks, or from the serpentine mesh have similar 13C and 18O values. The oxygen isotope values of these calcites range from 29.6‰ to 31.1‰. This narrow range corresponds to that of low-seawater-temperature marine carbonates. Assuming the calcites formed from seawater (18O = 0‰), calcite isotopic temperatures between 19° and 13°C can be derived (O'Neil et al., 1969). These inferred temperatures would not significantly change (less than 10°C) if these calcites formed from low-temperature 18O-depleted pore waters (18O between 0‰ and –3‰, Lawrence et al., 1975).

DISCUSSION AND CONCLUSION

In Leg 149 ultramafic rocks, metasomatic hydrous fluids have left mineralogical imprints that imply a polyphase hydrothermal history:

Apart from the kaersutite of Sample 149-897D-14R-4, 95-100 cm, whose growth is related to an interaction high temperature (>800°C) with a magma (see Cornen et al., this volume, chapter 21), all the amphiboles from serpentinites plot in the tremolite field, along the typical line connecting tremolite and pargasite end members. These amphiboles are different from those of the flaser gabbros and the amphibolites, which are either in pargasitic field or defined a steeper trend between the hornblende and the tremolite fields. As in Hole 637A peridotites, some of these tremolite formed by the hydration of clinopyroxene (Fig. 3), but they differ by their chemical composition (low AlIV content systematically, (Fig. 2) which suggests they formed under greenschist facies conditions (<500°C, Evans, 1982; Jenkins, 1983). In contrast to Hole 637A peridotites, there is no evidence of amphiboles formed at higher temperatures by interactions with hydrothermal fluids.

Although several deformation episodes affected these peridotites (Beslier et al., this volume), only tremolites in ribbons are clearly associated with a deformation event. These tremolites were formed by the penetration of hydrous fluids within high permeability zones. The other tremolites, which occur in pockets as pseudomorphs of clinopyroxene, have identical compositions and are contemporaries. The crystallization of the tremolites also predates the extensive cold complex fracturing that occurred during the serpentinization. We interpret these tremolitic amphiboles to result from the penetration of hydrothermal fluids during the uplift of the peridotites. The question of whether the hydrothermal fluid was seawater or seawater-derived fluids or neither remains equivocal.

Chlorites formed in two different situations: (1) those that syncrystallized with amphiboles as pseudomorphs of clinopyroxene and orthopyroxene (which we concluded were formed contemporaneously with amphiboles at temperatures below 500°C); and (2) those that grew after spinel. Their relative high degree of Tschermak substitution indicates conditions of metamorphism corresponding at least to greenschist facies and temperatures close to 500°C.

During this high-temperature hydrous episode, there is potential for the serpentinization of olivine since olivine is not stable below 620°C in the presence of water. Meanwhile, the case of Zabargad Island, where peridotites are completely devoid of serpentine but do contain greenschist hornblendes and actinolites (Agrinier et al., 1993), demonstrates that hydrous episodes do not necessarily imply serpentinization. However, in the case of serpentinization, according to the serpentine phase diagram (Evans et al., 1976; Caruso and Chernovsky, 1979; Chernovsky et al., 1988), antigorite should form from olivine and talc from orthopyroxene in these conditions, while formation of chrysotile and lizardite is only possible at extremely low pressures (<2 kbar) and temperatures (<250°C).

The serpentines are predominantly lizardite, and, as shown by their 18O/16O compositions and the oxygen isotope fractionation between lizardite and magnetite, they were formed by low-temperature hydration. This hydration stage was accompanied by a complex cold fractionation associated with the emplacement of peridotites on the seafloor (Beslier et al., this volume). Apart from a single occurrence of chrysotile in a vein, which probably reflects higher temperatures of serpentinization (possibly around 300°C), we have no evidence for high-temperature (300°-400°C) serpentinization, since neither talc nor antigorite have been detected in Site 897 and 899 peridotites. Coexisting hydroxides, iowaite, and brucite confirm that the seawater-serpentinized peridotite interaction has occurred at very low temperatures and is probably still occurring. These serpentinizing conditions of the peridotites are similar to those described for the Hole 637A peridotites.

The calcites, which precipitated locally in veins and impregnate the upper parts of the serpentinized peridotites, formed at low temperature and result from circulating cold seawater within open cracks of the serpentinized peridotites. The same aspect is observed in Hole 637A peridotites.

The lack of high-temperature serpentine minerals that would form by the hydration of the Leg 149 peridotites at 5 km depth below the top of the sediment-free basement is puzzling, considering that the extent of high-temperature serpentinization of the peridotites at depth must be large—around 25% according to Christensen (1972)—to produce the decrease in Vp from 8.1 to 7 km/s.

Tremolites and chlorites are too few (less than 5%) to produce such a large decrease in Vp. Nor can this Vp decrease be due to formation of lizardite from olivine because lizardite is not stable at pressure higher than 2 kbar, according to the serpentine phase diagram (Evans et al., 1976). In the present state of the rift this lithostatic pressure is reached at 6 km below sea level. This constraint is not compatible with the serpentinization by deep penetration of cold seawater to the deep low-velocity zone (now at a depth of 10 km below sea level; Boillot et al., 1980; Whitmarsh et al, 1993) where lithostatic pressure 2.4 kbar) tops the upper stability limit of chrysotile and lizardite.

As mentioned above, Al-rich lizardite is stable to pressure and temperature conditions (greenschist facies) that are expected at 10 km depth. Accordingly, we may suggest that the S horizon is made of Al-rich lizardites formed by bastitization of orthopyroxene. Although the abundance of (bastitized) orthopyroxene is large enough, up to 20% in the Leg 149 peridotites, to account for the Vp decrease, this possibility does not explain the absence of antigorite, which should form correlatively according to the serpentine phase diagram.

Finally, we think that three explanations can be made for this absence in the Leg 149 peridotites:

1. The high-temperature phases (talc, antigorite) formed at 10 km depth but were retrogressed to low-temperature phases (lizardite) when the peridotites reached their present seafloor position. If so, since these phases are not observed, this back-reaction process must have recrystallized the original high-temperature phases totally and readjusted the oxygen isotope compositions. This complete recrystallization is not supported by two facts. First, the Hole 899B peridotites, in which the low-temperature serpentinization overprinted the peridotites much less intensively, do not show either these of high-temperature phases. One would expect the Hole 899B peridotites to preserve at least some evidence of this presumed high-temperature serpentinization. Second, unless complete dissolution-precipitation processes affect the entire high-temperature serpentines during the back reaction, it is very difficult at low temperatures (<200°C) to reset the 18O of the serpentines from the low values compatible with the high-temperature serpentinization (like that of singular vein chrysotile) to the high values compatible with the low-temperature serpentinization. Experimental studies (O'Neil and Kharaka, 1976) and geological evidence (Yeh and Savin, 1976) show that the rate of oxygen exchange between clay minerals and water is extremely slow at low temperatures (<200°C) and that the antigorite to lizardite phase transformation alone is unlikely to readjust significantly the 18O of the serpentines.

2. The Leg 149 peridotites did not record a high-temperature serpentinization episode because the high-temperature phases (talc, antigorite) did not form. Most likely, the serpentinization conditions were not met at that time but were later reached when the peridotites were set near seafloor position. As said above, the Zabargad Island peridotites exemplify such a possibility. And as far as the Leg 149 peridotites are concerned in determining the nature of the deep low-velocity zone, this possibility suggests that it would not be made of serpentines.

http://www-odp.tamu.edu/publications/149_SR/chap_32/c32_8.htm

Supercritical Fluid Synthesis of Magnetic Hexagonal Nanoplatelets of Magnetite

   Zhonglai Li†‡Jeffrey F. Godsell§Justin P. O’Byrne†‡Nikolay Petkov∥Michael A. Morris†‡Saibal Roy§Justin D. Holmes*†‡

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Cite this: J. Am. Chem. Soc. 2010, 132, 36, 12540-12541
Publication Date:August 18, 2010
https://doi.org/10.1021/ja105079y

https://pubs.acs.org/doi/suppl/10.1021/ja105079y/suppl_file/ja105079y_si_001.pdf

Copyright 2010 American Chemical Society

A supercritical fluid technique was used to prepare hexagonal nanoplatelets of magnetite. Ferrocene was used as the Fe source, and sc-CO2 acted as both a solvent and oxygen source in the process. Powder X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and magnetic measurements were used to characterize the products. It was found that the morphology and structure of the product strongly depended on the reaction conditions.
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Structural purity of magnetite nanoparticles in magnetotactic bacteria

Anna Fischer, Manuel Schmitz, Barbara Aichmayer, Peter Fratzl, and Damien Faivre*
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Abstract

Magnetosome biomineralization and chain formation in magnetotactic bacteria are two processes that are highly controlled at the cellular level in order to form cellular magnetic dipoles. However, even if the magnetosome chains are well characterized, controversial results about the microstructure of magnetosomes were obtained and its possible influence in the formation of the magnetic dipole is to be specified. For the first time, the microstructure of intracellular magnetosomes was investigated using high-resolution synchrotron X-ray diffraction. Significant differences in the lattice parameter were found between intracellular magnetosomes from cultured magnetotactic bacteria and isolated ones. Through comparison with abiotic control materials of similar size, we show that this difference can be associated with different oxidation states and that the biogenic nanomagnetite is stoichiometric, i.e. structurally pure whereas isolated magnetosomes are slightly oxidized. The hierarchical structuring of the magnetosome chain thus starts with the formation of structurally pure magnetite nanoparticles that in turn might influence the magnetic property of the magnetosome chains.

Keywords: biomineralization, magnetite, magnetotactic bacteria, synchrotron X-ray diffraction, lattice parameter, hierarchical structuring

1. Introduction

Biomineralized nanoparticles are as diverse as the functions they fulfil in the multiple organisms in which they are formed [1]. The organisms control the synthesis and organization of hybrid materials to achieve higher functional properties [2]. In magnetotactic bacteria, one of the simplest biomineralizing organisms, the genetic blueprint information is translated into complex inorganic and cellular structures, i.e. the magnetosomes [3,4]. Prokaryotes have developed a genetic apparatus enabling them to synthesize monodisperse crystals of magnetite (Fe3O4) for effective magnetic orientation [5,6]. Control of crystal size via physico-chemical [7] or genetic [8] means, the associated magnetic properties [9,10] together with the tuning of the magnetic properties, thanks to the addition of given metallic ions [11,12], have attracted a multi-disciplinary interest to the magnetosomes, specifically using them for bio- and nanotechnological applications [13,14].

The magnetosomes are assembled into a linear chain, representing a first level of structural hierarchy at the sub-micrometer scale [15,16]. Moreover, the biomineralization of the intracellular magnetite is controlled to dimensions within the stable single-magnetic-domain size range, representing the second level of hierarchical structuring at the nanometre-scale. In such a configuration, the total magnetic dipole moment is the sum of the moments of individual particles, thereby generating an optimized configuration for function and applications [5,13,17,18]. However, long-standing debates concerning the structural perfection of magnetosomes at the ångström level and the possible presence of maghemite (α-Fe2O3) still remain [19–22]. Specifically, the limited precision of electron diffraction with respect to lattice parameter determination prevented detailed quantitative comparison between different biogenic magnetites and abiotic magnetites. However, as shown for biogenic aragonite [23] and calcite [24,25]—when compared with analogous abiotic crystals—anisotropic lattice distortions could be revealed by high-resolution X-ray diffraction (XRD), justifying the need for precise characterization of the microstructure of biogenic magnetite. High-resolution powder XRD was thus used to measure lattice parameters of nano-sized biogenic magnetite at the BESSY II synchrotron [26]. Whole cells of Magnetospirillum gryphiswaldense (strain MSR-1), Magnetospirillum magneticum (strain AMB-1) and ΔmamGFDC, a deletion mutant of M. gryphiswaldense with altered crystallite size [8], as well as isolated and detergent-treated MSR-1 magnetosomes [27] were measured. Abiotic reference magnetite and maghemite were used for comparison.

M. gryphiswaldense (MSR-1) [28] and M. magneticum (AMB-1) [29] cells were used throughout the experiments. AMB-1 and MSR-1 strains were chosen because they are the most widely used model organisms of magnetotactic bacteria, partly because they have been sequenced and their genetic systems have been established [4]. ΔmamGFDC was provided by D. Schüler (LMU Munich, Microbiology department) and was used to determine if size effects on lattice parameter are present. All strains were cultured in the rubber cap-sealed culture tubes under microaerobic conditions in MSR-1 standard media [27]. Bacterial growth was determined by measuring the optical density (OD) at 565 nm (Shimadzu UV-1201V spectrophotometer). The magnetic orientation of cells was determined by optical measurements (Cmag) [30]. The tubes were inoculated with 1 ml of a respective pre-culture (OD ≈ 0.4; Cmag ≈ 0. and incubated at 28°C and 100 r.p.m. for 24 h.

Magnetosome isolation and treatment were realized as described in literature [27]. Isolated magnetosomes with membrane are denoted as MAG + MM and without membrane, after sodium dodecyl sulphate (SDS) treatment, as MAG−MM. The synthetic magnetite (MGT) and maghemite (MGH) samples were provided by the German Federal Institute for Materials Research and Testing (BAM)

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3104334/

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Modulated Self-Reversed Magnetic Hysteresis Produced in Iron Oxides

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Liam Critchley, M.Sc.By Liam Critchley, M.Sc.Mar 3 2017

Image Credit: shutterstock.com/sakkmesterke

https://www.azom.com/article.aspx?ArticleID=13653

https://www.azom.com/article.aspx?ArticleID=13653#

Self-reversed magnetic hysteresis (SRMH) is a unique hysteresis phenomenon containing an antiparallel magnetisation to an applied magnetic field. This leads to an inverted hysteresis loop with a ‘negative’ net area. A couple of Chinese researchers have developed a scalable and versatile method to produce iron oxide particles that can absorb metal cations by utilising the ‘negative’ area, leading to unique SRMH properties being discovered for iron oxide particles.

Iron-based materials with a SRMH loop typically possess diamagnetic features, but they shape like ferromagnetic loops. In ferromagnetism, the saturation of the loop is located within the first and third quadrants, but SRMH saturation is positioned within the second and fourth quadrants. It is often thought that the negative area violates the thermo-mechanical second law and has been proposed that SRMH arises from inappropriate or asymmetric sample positioning, or misinterpretation of data. As such, it is a phenomenon that is often ignored.

Despite these non-existent assumptions, SRMH can be found in ferrous-containing rocks, but as two magnetic phases- a stable phase and a metastable “x” phase. The “x” phase becomes weakly magnetised in the presence of an applied field, during a cooling process. The “x” phase becomes negatively coupled and strongly magnetised with the stable phase at low temperatures. This is found to be the basic mechanism as to why SRMH occurs.


SRMH is an important phenomenon in both academia and industry as it possesses interdisciplinary features. SRMH has been found in naturally occurring rocks and is used to reinforce the theory of reverse magnetisation at the north and south poles throughout Earth’s history. However, whilst observable in nature, there has been great problems to produce simple and effective methods to synthetically produce materials with tuneable SRMH features. Previously, this has been due to lack of the understanding towards the internal mechanism of SRMH.

In a new and major development in SMRH research, this research team has managed to produce a facile, repeatable and versatile method to produce SRMH iron oxides. The researchers studied the logical results in-depth to provide an effective and tailored approach to tune the desired SMRH characteristics of the materials.

To produce such tuneable and potentially large scale materials, the researchers tested various iron oxide-based nanoparticles that have naturally-occurring negative zeta potentials. Magnetite, maghemite and haematite, of different dimensions, were soaked in FeCl3 and the Fe3+ ions were electrostatically adsorbed onto surface of the iron-oxide materials, due to a negative surface zeta potential. Such particles investigated, ranged from 0D magnetite/maghemite nanoparticles to 2D pine-like and 3D flower-like Fe2O3 nanoparticles.

The cation absorption produces an iron core-shell nanoparticle. Such nanoparticles were shown to exhibit well defined SRMH features, displaying both ferromagnetic and diamagnetic characteristics. The SRMH phenomenon arises in the core-shell nanoparticles through negatively magnetic exchange coupling of the pre-magnetised Fe3+ particles in the paramagnetic shell and the post-magnetised iron oxide in the superparamagentic core. Under no field, the orientation of the magnetic moment in the Fe3+ shell is random, but becomes aligned towards the direction of the field, yielding a weak paramagnetism. The magnetic couplings are highly frustrated which degrades the ferromagnetism in the ions, producing essentially ‘dead’ nanoparticles. It is these nanoparticles that negatively couple and bind with the core.

The utilisation of multiple architectures alongside controlling the amount of Fe3+ ions in the solution can be used to change the core size of the nanoparticle and thus, easily and controllably tune its properties.

The development of synthetically-made, SRMH tuneable materials is a big step forward from previous research and it is anticipated that these materials will be used to facilitate the improvement of spintronics, magnetic recording and other magnetically-related fields.

Source:

Ma J., Chen K., Modulated self-reversed magnetic hysteresis in iron oxides, Scientific Reports, 7, 42312

Liam Critchley

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Modulated self-reversed magnetic hysteresis in iron oxides

Ma, Ji; Chen, Kezheng

Abstract

The steadfast rule of a ferromagnetic hysteresis loop claims its saturation positioned within the first and third quadrants, whereas its saturation positioned in the second and fourth quadrants (named as self-reversed magnetic hysteresis) is usually taken as an experimental artifact and is always intentionally ignored. In this report, a new insight in this unique hysteresis phenomenon and its modulation were discussed in depth. Different iron oxides (magnetite, maghemite and hematite) with varying dimensions were soaked in FeCl3 aqueous solution and absorbed Fe3+ cations due to their negative enough surface zeta potentials. These iron oxides@Fe3+ core-shell products exhibit well pronounced self-reversed magnetic hysteresis which concurrently have typical diamagnetic characteristics and essential ferromagnetic features. The presence of pre-magnetized Fe3+ shell and its negatively magnetic exchange coupling with post-magnetized iron-oxide core is the root cause for the observed phenomena. More strikingly, this self-reversed magnetic hysteresis can be readily modulated by changing the core size or by simply controlling Fe3+ concentration in aqueous solution. It is anticipated that this work will shed new light on the development of spintronics, magnetic recording and other magnetically-relevant fields.


Publication:
Scientific Reports, Volume 7, id. 42312 (2017).
Pub Date:
February 2017
DOI:
10.1038/srep42312

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Magnetic and mineralogical characteristics of hydrocarbon microseepage above oil/gas reservoirs of Tuoku region, northern Tarim Basin, China

Qingsheng Liu, Shugen Liu, Zan Qu, Zhongxiang Xu & Weiguo Hou

Science in China Series D: Earth Sciences volume 41, pages121–129(1998)Cite this article

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Abstract

The Tuoku region in northern Tarim Basin of China is a key area for studying oil/gas reservoir rocks. The magnetic and mineralogical parameters of well cuttings from two wells, well S7, situated on oil/gas field, and well S6, at an oil/water interface, were measured. The two wells are located in the same structure with similar strata and types of lithology, but well S6 is a showing well of oil and gas 5 km northwest of well S7. The purpose of this paper is to evaluate the possibility and distribution of secondary magnetic alteration that may have occurred due to hydrocarbon migration above an oil/gas accumulation. It is concluded that the magnetism of well cuttings from major strata in well S7, including source rocks, oil reservoir rocks and cap rocks, and in Quaternary (Q) soil is higher than that from well S6. The Cambrian oil-bearing strata and cap rocks have even higher magnetism in well S7. The shape and parameters of magnetic hysteresis loops indicate that soft (H c<20 mT,H s<0.3 T) ferrimagnetic components dominate the magnetic carriers within the strongly magnetic strata of well S7, whereas a mixed paramagnetic and ferrimagnetic distribution occurs in well S6 (for example, low coecivityH c and nonsaturating magnetized character). Analysis of heavy minerals shows that the contents of iron oxide (magnetite, maghemite and hematite) in well S7 are often higher than those in well S6. The magnetite content in samples of cuttings from Cambrian rocks can reach 9.7% in oil-bearing strata in well S7, and in strata Ekm and N1j are 1.215% and1.498%, respectively. Typical spherical magnetite grains are found within the main source rocks and the soils in well S7. By analysis of surface microtexture and of trace element contents, we infer that the spherical magnetite is composed of aggregates of ultrafine particles that are probably authigenic magnetite formed in a hydrocarbon halo background.

https://link.springer.com/article/10.1007/BF02932430
www.geophy.cn/EN/abstract/abstract4111.shtml
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Professor of Chemical & Biomolecular Engineering

email: jrlong@berkeley.edu (link sends e-mail)
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Recent Publications(link is external)

Research Expertise and Interest

Inorganic and materials chemistry; synthesis of inorganic molecules and higher dimensional solids; precise tailoring of chemical and physical properties; gas storage, molecular separations, and catalysis in porous materials; magnetic and conductive materials.
Description

Research in the Long group focuses on the design and controlled synthesis of novel inorganic materials and molecules toward the fundamental understanding of new physical phenomena, with applications in gas storage, molecular separations, conductivity, catalysis, and magnetism. We employ a range of physical methods to analyze and characterize our materials comprehensively, including by gas adsorption analysis, X-ray and neutron diffraction, various spectroscopic techniques, and SQUID magnetometry. For more information about the Long group and a full list of publications, please visit the group website(link is external).

Metal–Organic Frameworks

A major focus of research in the Long group is the design and study of metal–organic frameworks—porous, inorganic solids built of metal nodes connected by organic linkers—that are of interest for applications ranging from gas storage and molecular separations to catalysis and battery applications.

Industrial separations account for a staggering 10-15% of the total global energy consumption, and developing more efficient separations processes is a therefore key strategy toward reducing worldwide energy consumption. Additionally, now more than ever global warming is necessitating a dramatic reduction in our global greenhouse emissions. One of the most promising short-term emissions mitigation strategies—and therefore a crucial separations need—is the removal of CO2 directly from the flue gas streams of coal- and natural gas-fired power plants. Toward this end, we are studying a new class of diamine-appended frameworks developed in our group that exhibit high CO2 separation capacities in the presence of water, with minimal energy requirements arising from an unprecedented cooperative adsorption mechanism. Beyond terrestrial separations technologies, we are seeking to optimize this cooperative mechanism for applications as far reaching as air purification in submarines and spacecraft, and are applying fundamental insights from this work to the design of novel materials and mechanisms for the cooperative adsorption of other key, industrially-relevant gas molecules.

We are also targeting metal–organic frameworks featuring polarizing open metal sites and shape-discriminating pore structures for the enhanced binding of H2 and CH4 near ambient temperatures and the separation of hydrocarbon isomers, respectively. The high-capacity storage of hydrogen and natural gas is especially relevant for automotive transportation, as these gases represent promising cleaner alternatives to liquid hydrocarbon fuels, and yet major advances in adsorbent technologies are necessary to overcome the costly limitations currently imposed by low-temperature and high-pressure on-board storage requirements. Seeking to capitalize on the separation capabilities of our best performing framework materials and the robust nature of polymer membranes, we are also designing metal–organic framework/polymer composites toward the development of novel membranes that exhibit high selectivities and permeabilities for applications ranging from the purification of natural gas to olefin/paraffin separations.

Catalysis and Conductivity

In addition to their function as molecular sieves, metal–organic frameworks are promising as robust, efficient catalysts with isolated and well-defined active sites. We are seeking to use coordinatively-unsaturated framework metal centers as catalytic sites and also installing these metal centers post-synthetically via chelating groups built into the framework ligands. In a separate endeavor, we are using this post-synthetic modification strategy to reduce or oxidize insulating frameworks and target conductive materials with high charge densities for applications ranging from battery components to chemical sensors. Along with their unique electronic properties, we are discovering unprecedented magnetic phenomena in some of these materials, and thus these efforts represent new directions in fundamental materials science.

Molecular Magnetism

Research in the Long group is also heavily focused on the design of molecules exhibiting a strong directional dependence to their magnetization (known as magnetic anisotropy) and magnetic phenomena such as magnetic hysteresis, a property previously thought to be relegated to bulk magnetic materials. These compounds—collectively known as single-molecule magnets—were discovered in the early 20th century and are of interest for applications in information storage, spin-based electronics, and quantum computing. Nearly thirty years after their discovery, however, the highest performing single-molecule magnets still only exhibit operating temperatures as high as ~60 K, with the vast majority only functioning at temperatures of a few K—as cold as deep space. At higher temperatures, thermal energy causes random fluctuations of the molecular magnetization that precludes the controlled manipulation of spin that is necessary for practical applications.

The Long group is employing new design motifs and architectures precisely chosen to enhance operating temperatures, focusing primarily on the synthesis of multinuclear, radical-bridged molecules incorporating the late trivalent lanthanides and low-coordinate, mononuclear complexes of the transition metals. In particular, the trivalent lanthanides possess large magnetic moments and unquenched orbital angular momentum that can give rise to large magnetic anisotropy when paired with the appropriate ligand environment, and the group is a foremost leader in the design of high-performing, radical-bridged lanthanide single-molecule magnets.

While the lanthanide ions are unsurpassed in their physical properties and the fundamental advantages they bring to the design of single-molecule magnets, the increasing costs associated with lanthanide extraction are also spurring interest in the development of molecules incorporating the less costly and abundant transition metals as magnetic centers. Transition metals led the charge with the development of single-molecule magnets, as magnetic centers in large, multinuclear clusters, and the group is now targeting mononuclear transition metal complexes of iron and cobalt that exhibit “lanthanide-like” electronic structure imparted by the appropriate weak, low-coordinate ligand field. The group is also pursuing new avenues in the design of multinuclear transition metal compounds with large spin and magnetic anisotropy, as well as mononuclear and multinuclear complexes of the 5f-elements.
Biography

Born 1969
B.A. Cornell University (1991)
Ph.D. Harvard University (1995)
Office of Naval Research Predoctoral Fellow (1991-1994)
National Science Foundation Postdoctoral Fellow, University of California, Berkeley (1996-1997)
Research Corporation Research Innovation Award (1998)
Hellman Family Faculty Award (1999)
Camille Dreyfus Teacher-Scholar Award (2000)
Alfred P. Sloan Research Fellow (2001-2003)
Wilson Prize (Harvard University, 2002)
TR100 Award (2002)
National Science Foundation Special Creativity Award (2003-2005 and 2009-2011)
National Fresenius Award (2004)
Miller Research Professor (2011)
Honorary Professor, Jilin University (2013)
Director, Center for Gas Separations (2014-present)
Inorganic Chemistry Lectureship (2014)
UC Berkeley Graduate Assembly Faculty Mentor Award (2014)
France-Berkeley Fund Early-Career Research Award (2014)
Bakar Fellow (2016-2020)
Department of Energy Hydrogen and Fuel Cells Program R&D Award (2016)

Power Point Paper on Lithologies, Traps, Carbonates, Karst and Reservoir formation:
----------------

Natural Fracture Systems in Carbonate Reservoirs

Jo Garland & Andy Horbury
with contributions from Pete Gutteridge, Julie Dewit and Sarah Thompson
Cambridge Carbonates Ltd

Introduction

• 
  •Carbonate fields: typically >50% fractured, considerably more than in clastics
  •Why the difference?–Not simply tectonic fracture mechanism
  •Exploration –The presence of fractures or karst can influence the economics of a prospect
  •Reservoir development–Well planning and location–Do you avoid or intersect fractures?–Methods of secondary recovery
  •AIMS of presentation–Demonstrate the different fracture mechanisms in carbonates–Implications for reservoir geometries and reservoir quality
  

https://38559b81a8bdc9f7a43e-61cdd80dc1a7a416127c70ccd69fa98c.ssl.cf1.rackcdn.com/FP%2023.01.18%20Jo%20Garland_Cambridge%20Carbonates%20Ltd.pdf

-----

Carbonate formations:

Depositional setting and geometry of carbonate facies


Summary

The varied depositional settings in which carbonate accumulate have become better known largely through the exploration for more hydrocarbon reserves and their exploitation in the last 35 years. Though reefs and grainstone shoals have been cited as common hydrocarbon exploration targets and so have been more intensively examined, other carbonate facies from both basin and/or platform interior settings have also been recognized to be important and have been studied too.

http://www.sepmstrata.org/page.aspx?&pageid=90&4

Bouguer anomaly

https://en.m.wikipedia.org/wiki/Free-air_gravity_anomaly


In geodesy and geophysics, the Bouguer anomaly (named after Pierre Bouguer) is a gravity anomaly, corrected for the height at which it is measured and the attraction of terrain.[1] The height correction alone gives a free-air gravity anomaly.


Bouguer anomaly map of the state of New Jersey (USGS)
Anomaly Edit
The Bouguer anomaly is related to the observed gravity {\displaystyle g_{obs}}g_{{obs}} as follows:

{\displaystyle g_{B}=g_{obs}-g_{\lambda }+\delta g_{F}-\delta g_{B}+\delta g_{T}}{\displaystyle g_{B}=g_{obs}-g_{\lambda }+\delta g_{F}-\delta g_{B}+\delta g_{T}}
{\displaystyle g_{B}=g_{F}-\delta g_{B}}g_{B}=g_{{F}}-\delta g_{B}
Here,

{\displaystyle g_{B}}g_{B} is the Bouguer anomaly;
{\displaystyle g_{obs}}g_{{obs}} is the observed gravity;
{\displaystyle g_{\lambda }}g_{\lambda } is the correction for latitude (because the Earth is not a perfect sphere);
{\displaystyle \delta g_{F}}\delta g_{F} is the free-air correction;
{\displaystyle \delta g_{B}}\delta g_{B} is the Bouguer correction which allows for the gravitational attraction of rocks between the measurement point and sea level;
{\displaystyle g_{F}}g_F is the free-air gravity anomaly.
{\displaystyle \delta g_{T}}{\displaystyle \delta g_{T}} is a terrain correction which allows for deviations of the surface from an infinite horizontal plane
A Bouguer reduction is called simple or incomplete if the terrain is approximated by an infinite flat plate called the Bouguer plate. A refined or complete Bouguer reduction removes the effects of terrain precisely. The difference between the two, the differential gravitational effect of the unevenness of the terrain, is called the terrain effect. It is always negative.[2]

The gravitational acceleration {\displaystyle g}g outside a Bouguer plate is perpendicular to the plate and towards it, with magnitude 2πG times the mass per unit area, where {\displaystyle G}G is the gravitational constant. It is independent of the distance to the plate (as can be proven most simply with Gauss's law for gravity, but can also be proven directly with Newton's law of gravity). The value of {\displaystyle G}G is 6.67 × 10−11 N m2 kg−2, so {\displaystyle g}g is 4.191 × 10−10 N m2 kg−2 times the mass per unit area. Using 1 Gal = 0.01 m s−2 (1 cm s−2) we get 4.191 × 10−5 mGal m2 kg−1 times the mass per unit area. For mean rock density (2.67 g cm−3) this gives 0.1119 mGal m−1.

The Bouguer reduction for a Bouguer plate of thickness {\displaystyle \scriptstyle H}\scriptstyle H is

{\displaystyle \delta g_{B}=2\pi \rho GH} \delta g_B = 2\pi\rho G H
where {\displaystyle \rho }\rho is the density of the material and {\displaystyle G}G is the constant of gravitation.[2] On Earth the effect on gravity of elevation is 0.3086 mGal m−1 decrease when going up, minus the gravity of the Bouguer plate, giving the Bouguer gradient of 0.1967 mGal m−1.

More generally, for a mass distribution with the density depending on one Cartesian coordinate z only, gravity for any z is 2πG times the difference in mass per unit area on either side of this z value. A combination of two equal parallel infinite plates does not produce any gravity inside.

Better syntax at link:

https://en.m.wikipedia.org/wiki/Bouguer_anomaly

Naturally occurring bacteria converts CO2 into calcium carbonate

By Darren Quick
February 23, 2009

Calcium carbonate in powder form
VIEW 1 IMAGES

Expensive carbon capture and storage (CCS) projects are gaining momentum around the world as a way to combat greenhouse gas emissions (or is that sweep them under the carpet?), India’s Economic Times has reported that a team of Indian scientists have discovered a naturally occurring bacteria that could help fight global warming by converting CO2 into calcium carbonate (CaCO3) - a common compound found as rock all the world over.

The scientists found that when the bacteria, which has been extracted from a number of places including brick kilns in the Indian city of Satna, is used as an enzyme it converts CO2 into CaCO3. Dr Anjana Sharma says the resulting CaCO3 can fetch minerals of economic value, as CaCO3 has a variety of uses from being used in the purification of iron from iron ore, neutralizing acidic effects in soil and water, and even as a dietary calcium supplement or antacid.

Project coordinator, Dr Sadhana Rayalu, says, "The enzyme can be put to work in any situation, like in a chamber fitted inside a factory chimney through which CO2 would pass before being emitted into the atmosphere, and it would convert the greenhouse gas into calcium carbonate.

More at link: https://newatlas.com/bacteria-convert-co2-calcium-carbonate/11069/

...


Formations of calcium carbonate minerals by bacteria and its multiple applications

Periasamy Anbu, Chang-Ho Kang, [...], and Jae-Seong So

Additional article information

Abstract

Biomineralization is a naturally occurring process in living organisms. In this review, we discuss microbially induced calcium carbonate precipitation (MICP) in detail. In the MICP process, urease plays a major role in urea hydrolysis by a wide variety of microorganisms capable of producing high levels of urease. We also elaborate on the different polymorphs and the role of calcium in the formation of calcite crystal structures using various calcium sources. Additionally, the environmental factors affecting the production of urease and carbonate precipitation are discussed. This MICP is a promising, eco-friendly alternative approach to conventional and current remediation technologies to solve environmental problems in multidisciplinary fields. Multiple applications of MICP such as removal of heavy metals and radionuclides, improve the quality of construction materials and sequestration of atmospheric CO2 are discussed. In addition, we discuss other applications such as removal of calcium ions, PCBs and use of filler in rubber and plastics and fluorescent particles in stationary ink and stationary markers. MICP technology has become an efficient aspect of multidisciplinary fields. This report not only highlights the major strengths of MICP, but also discusses the limitations to application of this technology on a commercial scale.

Keywords: Biomineralization, Calcite, CO2 sequestration, MICP, Urease, Urea hydrolysis

Background

Biomineralization is the chemical alteration of an environment by microbial activity that results in the precipitation of minerals (Stocks-Fischer et al. 1999; Barkay and Schaefer 2001; Phillips et al. 2013). In nature, biomineralization is a widespread phenomenon leading to the formation of more than 60 different biological minerals (Sarikaya 1999) that exists as extracellularly inorganic crystals (Dhami et al. 2013a) or intracellularly (Konishi et al. 2006; Yoshida et al. 2010). Extracellular mineralization syntheses (for e.g., carbonate precipitation) from all groups of living organisms are widespread and well known phenomena (Lowenstam 1981). Most crystals formed through biomineralization consist of inorganic minerals, but they may also contain trace elements of organic compounds, which can regulate the biomineralization process (Yoshida et al. 2010). There are three different mechanisms involved in the production of biominerals: (1) Biologically controlled mineralization consists of cellular activities that specifically direct the formation of minerals (Lowenstam and Weiner 1989; Benzerara et al. 2011; Phillips et al. 2013). In this process, organisms control nucleation and growth of minerals. The minerals are directly synthesized at a specific location within or on the cell, but only under certain conditions. (2) Biologically influenced mineralization is the process by which passive mineral precipitation is caused by the presence of cell surface organic matter such as extracellular polymeric substances associated with biofilms (Benzerara et al. 2011; Phillips et al. 2013). (3) Biologically induced mineralization is the chemical modification of an environment by biological activity that results in supersaturation and the precipitation of minerals (Lowenstam and Weiner 1989; Stocks-Fischer et al. 1999; De Muynck et al. 2010; Phillips et al. 2013).

Microbially induced calcite precipitation

Microbially induced calcite precipitation (MICP) refers to the formation of calcium carbonate from a supersaturated solution due to the presence of their microbial cells and biochemical activities (Bosak 2011). During MICP, organisms are able to secrete one or more metabolic products (CO32−) that react with ions (Ca2+) in the environment resulting in the subsequent precipitation of minerals. Previously, the formation of calcium carbonate precipitation was proposed to occur via different mechanisms such as photosynthesis (Thompson and Ferris 1990; McConnaughey and Whelan 1997), urea hydrolysis (Stocks-Fischer et al. 1999; De Muynck et al. 2010; Dhami et al. 2013a), sulfate reduction (Castanier et al. 1999; Warthmann et al. 2000; Hammes et al. 2003a), anaerobic sulfide oxidation (Warthmann et al. 2000), biofilm and extracellular polymeric substances (Kawaguchi and Decho 2002; Arias and Fernandez 2008). However, the precipitation of calcium carbonate by bacteria via urea hydrolysis is the most widely used method (Hammes and Verstraete 2002; DeJong et al. 2010; De Muynck et al. 2010).

More at link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4771655/

Active leak of sea-bed methane discovered in Antarctica for first time

by Bob Yirka , Phys.org

REPORT
antarctica
Credit: Pixabay/CC0 Public Domain

A team of researchers with Oregon State University has confirmed the first active leak of sea-bed methane in Antarctica. In their paper published in Proceedings of the Royal Society B, the group describes their trip to Cinder Cones located at McMurdo Sound situated in the Ross Sea, and why they believe it signals very serious repercussions for global warming.

Scientists believe that there is a large amount of methane sealed beneath the ocean floor off the coast of Antarctica. It is believed to have developed from algae decaying beneath the seafloor sediment. And it has likely been there for a very long time. As the planet has warmed, scientists have become concerned that the methane could be released if the waters above it were to warm. And if that were to occur, they fear it would release so much methane that there would be no recovering—the planet would warm beyond our means to survive.

The researchers note that the methane leak at the Cinder Cones is not in a part of the ocean that has been warming; thus, the reason for the leak is a mystery. Much more concerning is the reaction of undersea microbes. Prior research has shown that when other parts of the seafloor begin releasing methane, microbes move in and eat it, preventing it from making its way to the surface and into the atmosphere. Cinder Cones has been leaking for at least five years, they note, but as yet, methane-eating microbes have not moved in. Thus, the methane is almost certainly making its way into the atmosphere. The reason this is so concerning, they point out, is because it suggests that if other parts of the seafloor in Antarctica begin to seep methane due to warming, microbes may not move into the area quickly enough to prevent massive amounts of the gas from making its way into the atmosphere. They plan to continue monitoring seepage at Cinder Cones, noting that it could take as long as five more years for microbes to move in. But that research will have to wait, as the pandemic has put their plans on hold.

More at link: https://phys.org/news/2020-07-leak-sea-bed-methane-antarctica.html

News release by Oregon State University

Journal information: Proceedings of the Royal Society

............

NASA study suggests an Antarctic supervolcano could make the ice sheet ‘vulnerable’

NOVEMBER 9, 20171:27pm
5
STORYFUL3:24

Antarctic Glacier Melting Due to High Winds, Causing Potential Impact to Sea Levels.

Credit - Australian
Antarctic Division via Storyful

Antarctic Glacier Melting Due to High Winds, Causing Potential Impact to Sea Levels. Credit - Australian Antarctic Division via Storyfu

Jamie SeidelNews Corp Australia Network

ANTARCTICA is behaving oddly. Like its North Pole counterpart, it’s being affected by our changing climate. But not in ways science expects.

It has lakes. It has rivers. All of liquid, flowing water.

It’s just that they’re beneath the ice sheet. Not on top.

How did they get there?

A new NASA study is adding evidence to a theory that there is an enormous geothermal heat source sitting beneath the ice.

It’s called a mantle plume.

It’s positioned beneath a region named Marie Byrd Land.

It potentially explains a lot.

The amount of liquid water beneath an ice sheet has significant implications upon its stability.

The water acts as a lubricant. This allows glaciers to glide over bedrock easier.

And the presence of this geothermal heat source could explain why the thick West Antarctic ice sheet has had such a volatile history.

In an earlier era of rapid climate change, it collapsed unexpectedly quickly.

It could do so again.

https://www.news.com.au/technology/environment/natural-wonders/nasa-study-suggests-an-antarctic-supervolcano-could-make-the-ice-sheet-vulnerable/news-story/14ee668fa018e7f7d861ccbe63a3cd2f

.....
Also:  https://www.newsweek.com/antarctica-melting-below-mantle-plume-almost-hot-yellowstone-supervolcano-705086

Think Supercritical water:

https://www.nasa.gov/feature/jpl/hot-news-from-the-antarctic-underground

Catalytic Cracking Reaction of Heavy Oil in the Presence of Cerium Oxide Nanoparticles in Supercritical Water

Mehdi Dejhosseini†‡, Tsutomu Aida∥, Masaru Watanabe§, Seiichi Takami‡, Daisuke Hojo#, Nobuaki Aoki#, Toshihiko Arita‡, Atsushi Kishita⊥, and Tadafumi Adschiri*‡∥#
View Author Information
Cite this: Energy Fuels 2013, 27, 8, 4624–4631
Publication Date:July 19, 2013

https://doi.org/10.1021/ef400855k
Copyright 2013 American Chemical Society
RIGHTS & PERMISSIONS

SUBJECTS:Lipids,Oxides,Nanoparticles,
Abstract

Catalytic cracking of Canadian oil sand bitumen in supercritical water was performed to clarify the effect of CeO2 nanoparticles. The cracking was performed at 723 K to promote a redox reaction between the water, bitumen, and catalyst for the production of hydrogen and oxygen. As the catalyst, CeO2 with two different morphologies was employed because the redox reaction of CeO2 with water and organics is expected and its activity can be controlled by its structure. In this study, two roles of water were considered as well. Water is attractive as a high potential medium with low dielectric constant and density at near the critical point (374 °C, 22.1 MPa) that allows formation of highly crystalline smaller metal oxides particles. However, the chemical effects of water are investigated with heavy oil catalytic cracking. Transmission electron microscopy images indicated that CeO2 nanoparticles with cubic and octahedral shape were synthesized using a plug-flow reactor under hydrothermal conditions. The particles sizes were 8 and 50 nm for cubic and octahedral CeO2, respectively. At 773 K, it was found that the oxygen storage capacity (OSC) of the cerium oxide nanoparticles with cubic {100} facets was nearly 3.4 times higher than that of the cerium oxide nanoparticles with octahedral {111} facets. Heavy oil fractions of bitumen were cracked in a batch-type reactor at 723 K in order to produce as much light oil as possible, and the effect of the catalyst loading and reaction conditions on the conversion rate and coke formation were investigated. As a result, it was demonstrated that it is possible to obtain a high conversion rate by increasing the exposed surface area and reducing the particle size of the catalyst. The highest conversion was obtained in the presence of 20 mg loading of cubic CeO2 nanoparticles (8 nm) with reaction time of 1 h.

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Xiaodong Hao, Akira Yoko, Chunlin Chen, Kazutoshi Inoue, Mitsuhiro Saito, Gimyeong Seong, Seiichi Takami, Tadafumi Adschiri, Yuichi Ikuhara. Atomic-Scale Valence State Distribution inside Ultrafine CeO 2 Nanocubes and Its Size Dependence. Small 2018, 14 (42) , 1802915. https://doi.org/10.1002/smll.201802915
Morteza Hosseinpour, Shohreh Fatemi, Seyed Javad Ahmadi, Yoshito Oshima, Masato Morimoto, Makoto Akizuki. Isotope tracing study on hydrogen donating capability of supercritical water assisted by formic acid to upgrade heavy oil: Computer simulation vs. experiment. Fuel 2018, 225 , 161-173. https://doi.org/10.1016/j.fuel.2018.03.098
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Muhammad B.I. Chowdhury, Md. Zakir Hossain, Jahirul Mazumder, Anil K. Jhawar, Paul A. Charpentier. La-based catalysts to enhance hydrogen production during supercritical water gasification of glucose. Fuel 2018, 217 , 166-174. https://doi.org/10.1016/j.fuel.2017.12.105
Gimyeong Seong, Akira Yoko, Ryohei Inoue, Seiichi Takami, Tadafumi Adschiri. Selective chemical recovery from biomass under hydrothermal conditions using metal oxide nanocatalyst. The Journal of Supercritical Fluids 2018, 133 , 726-737. https://doi.org/10.1016/j.supflu.2017.09.032
Lien Thi Do, Chinh Nguyen-Huy, Eun Woo Shin. Different Metal Support Interactions over NiK/Mixed Oxide Catalysts and Their Effects on Catalytic Routes in Steam Catalytic Cracking of Vacuum Residue. ChemistrySelect 2018, 3 (6) , 1827-1835. https://doi.org/10.1002/slct.201702819
Akira Yoko, Tsutomu Aida, Nobuaki Aoki, Daisuke Hojo, Masanori Koshimizu, Satoshi Ohara, Gimyeong Seong, Seiichi Takami, Takanari Togashi, Takaaki Tomai, Takao Tsukada, Tadafumi Adschiri. Supercritical Hydrothermal Synthesis of Nanoparticles. 2018,,, 683-689. https://doi.org/10.1016/B978-0-444-64110-6.00060-3
Gimyeong Seong, Mehdi Dejhosseini, Tadafumi Adschiri. A kinetic study of catalytic hydrothermal reactions of acetaldehyde with cubic CeO2 nanoparticles. Applied Catalysis A: General 2018, 550 , 284-296. https://doi.org/10.1016/j.apcata.2017.11.023
Lien Thi Do, Chinh Nguyen-Huy, Eun Woo Shin. Effect of a CeyNi1−yO2−δ solid solution on the oxidative cracking of vacuum residue over NiK/CeO2. Reaction Kinetics, Mechanisms and Catalysis 2017, 122 (2) , 983-993. https://doi.org/10.1007/s11144-017-1252-5
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Link: https://pubs.acs.org/doi/10.1021/ef400855k