The authors explored microbial communities inside nodules from the northeastern equatorial Pacific. The nodules have a large connected pore space with a huge inner surface of 120 m2/g as analyzed by computer tomography and BET measurements. X-ray photoelectron spectroscopy (XPS) and electron microprobe analysis revealed a complex chemical fine structure.
The authors have used an enriched 57Fe tracer to show that aqueous Fe(II) exchanges with structural Fe(III) in hematite at room temperature, and that the amount of exchange is influenced by particle size, pH, and Fe(II) concentration.
Widespread iron oxide precipitation from groundwater in fine-grained red beds displays various patterns, including nodulation, banding and scallops and fingers. The authors here show that such patterns can autonomously emerge from a previously unrecognized Ostwald ripening mechanism and they capture rich information regarding ancient chemical and hydrologic environments.
Carbon is recycled via Earth's mantle at subduction zones. Laboratory experiments show that in the presence of water, carbon-rich liquids can form from the subducted crust at low temperatures, providing a supply of CO2 to surface volcanoes.
Ath Godelitsas's insight:
The author found that water strongly depresses the solidus for hydrous carbonate gabbro and limestone rocks, creating carbonatitic liquids that efficiently scavenge volatile elements, calcium and silicon, from the slab.
The dominant minerals in Earth’s lower mantle are thought to be Fe- and Al-bearing MgSiO3 bridgmanite and (Mg, Fe)O ferropericlase. Theoretical simulations, which depend on empirical evaluations of the effects of Fe incorporation into these minerals, support a pyrolitic lower mantle that contains a significant amount of ferropericlase, much like the Earth’s upper mantle. The authors here present first-principles computations combined with a lattice dynamics approach that include the effects of Fe2+ and Fe3+ incorporation.
Copper isotope range of the primitive (chondritic) meteorite groups. Inset: Box and whisker plot showing the range of Cu isotope compositions for the terrestrial samples used in constraining the BSE Cu isotope composition. Green box and dotted line represents the composition of BSE, light grey box and long dashes represent the composition of “chondritic bulk Earth” (CBE), dark grey box and short dashes represent the composition of “enstatite chondrite bulk Earth” (ECBE). Errors on the estimates are all 2 s.d.
Transmission electron microscopy (TEM) images showed that after initial absorption into the frayed edges, Cs migrated into the illite interlayer becoming incorporated within the mineral structure. Results from extended X-ray absorption fine structure spectroscopy (EXAFS) and density functional theory modelling confirmed that Cs was incorporated into the illite interlayer and revealed its bonding environment.
Faults weaken during earthquakes. Laboratory simulations of earthquake rupture show that the nanometric-scale fault gouge created during slip is inherently weak and flows by grain-boundary sliding, providing a mechanism to weaken faults.
Ath Godelitsas's insight:
High-speed friction experiments on a wide variety of rock types have shown that they all exhibit extreme weakening and that the sliding surface is nanometric and contains phases not present at the start.
The authors estimated that gallium was produced from 8 to 21% of alumina plants in 2011. The most important applications of gallium are NdFeB permanent magnets, integrated circuits and GaAs/GaP-based light-emitting diodes, demanding 22–37%, 16–27%, and 11–21% of primary metal production, respectively.
Yje authors have created three-dimensional simulations of ridge–flank hydrothermal circulation, flowing between and through seamounts, to determine what controls hydrogeological sustainability, flow rate and preferred flow direction in these systems.
The deep biosphere of the subseafloor basalts is recognized as a major scientific frontier in disciplines like biology, geology, and oceanography. Recently, the presence of fungi in these environments has involved a change of view regarding diversity and ecology. Here, the authors describe fossilized fungal communities in vugs in subseafloor basalts from a depth of 936.65 metres below seafloor at the Detroit Seamount, Pacific Ocean. These fungal communities are closely associated with botryoidal Mn oxides composed of todorokite.
Ath Godelitsas's insight:
Analyses of the Mn oxides by Electron Paramagnetic Resonance spectroscopy (EPR) indicate a biogenic signature. The authors suggest, based on mineralogical, morphological and EPR data, a biological origin of the botryoidal Mn oxides.
In 2009, scientists from Woods Hole Oceanographic Institution embarked on a NASA-funded mission to the Mid-Cayman Rise in the Caribbean, in search of a type of deep-sea hot-spring or hydrothermal vent that they believed held clues to the search for life on other planets. They were looking for a site with a venting process that produces a lot of hydrogen because of the potential it holds for the chemical, or abiotic, creation of organic molecules like methane – possible precursors to the prebiotic compounds from which life on Earth emerged. For more than a decade, the scientific community has postulated that in such an environment, methane and other organic compounds could be spontaneously produced by chemical reactions between hydrogen from the vent fluid and carbon dioxide (CO2). The theory made perfect sense, but showing that it happened in nature was challenging. Now we know why: an analysis of the vent fluid chemistry proves that for some organic compounds, it doesn’t happen that way. New research by geochemists at Woods Hole Oceanographic Institution, published June 8 in the Proceedings of the National Academy of Sciences, is the first to show that methane formation does not occur during the relatively quick fluid circulation process, despite extraordinarily high hydrogen contents in the waters. While the methane in the Von Damm vent system they studied was produced through chemical reactions (abiotically), it was produced on geologic time scales deep beneath the seafloor and independent of the venting process. Their research further reveals that another organic abiotic compound is formed during the vent circulation process at adjacent lower temperature, higher pH vents, but reaction rates are too slow to completely reduce the carbon all the way to methane.
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