Hydrothermal Activity Research Articles

Prebiotic membrane structures mimic the morphology of alleged early traces of life on Earth

Elucidating compositions of the first cell membranes requires experiments with molecules and chemical conditions representative of early Earth. The molecules used are described as ‘prebiotically plausible’, i.e., they could have formed through abiotic reactions before the emergence of biology. Similarly, the chemical properties of solutions in which these membranes are formed (e.g., pH, temperature, ionic strength) must represent early Earth environments. Here, using confocal and transmission electron microscopy combined with population morphometry, we show that prebiotically plausible molecules, in solutions representative of Hadean submarine alkaline hydrothermal vents, form microstructures with substantial morphological diversity. The microstructures hold the potential for use as analogues of prebiotic processes in the rock record. Additionally, many of the structures are morphologically similar to purported early microfossils, highlighting limitations of morphological interpretation in these studies. Detailed analyses of abiotic microstructures are essential for understanding the earliest life on Earth, and for interpretation of potential biosignatures from extra-terrestrial bodies.

The Ballynoe Stratiform Barite Deposit, Silvermines, County Tipperary, Ireland

The Ballynoe barite deposit is a conformable, mineralised horizon of Lower Carboniferous age overlying a diastem and mass faunal extinction demarking the transition from a quiet water environment to one of dynamic sedimentation. The geometry of the barite orebody correlates with the palaeotopography of the footwall, which acted as an important control over the lateral extent, thickness, and nature of the mineralisation. Sedimentary features within the barite horizon suggest that it was precipitated in the form of a cryptocrystalline mud which underwent major diagenetic modification resulting in extensive stylolitisation, recrystallisation, and remobilisation. There is abundant and compelling geological and isotopic evidence for early local exhalation from the presence of a hydrothermal vent fauna consisting of delicately pyritised worm tubes and haematised filaments of apparent microbial origin. The worm tubes are remarkably similar to examples from modern and ancient volcanic-hosted massive sulphide deposits, and the filamentous microfossils have similarities to modern Fe-oxidising bacteria. Strontium in the barite has an 87Sr/86Sr ratio indistinguishable from seawater between 350 and 344 Ma whilst oxygen isotopes from barite and chert suggest a diagenetic origin in equilibrium with such seawater around 60–70 °C. Fluid inclusion studies have shown that, in general, low temperature inclusions are very saline (20%–25%) whilst at higher homogenisation temperatures they are more dilute (9%–12%).

New Estimates of Nitrogen Fixation on Early Earth

Fixed nitrogen species generated by the early Earth’s atmosphere are thought to be critical to the emergence of life and the sustenance of early metabolisms. A previous study estimated nitrogen fixation in the Hadean Earth’s N2/CO2-dominated atmosphere; however, that previous study only considered a limited chemical network that produces NOx species (i.e., no HCN formation) via the thermochemical dissociation of N2 and CO2 in lightning flashes, followed by photochemistry. Here, we present an updated model of nitrogen fixation on Hadean Earth. We use the Chemical Equilibrium with Applications (CEA) thermochemical model to estimate lightning-induced NO and HCN formation and an updated version of KINETICS, the 1-D Caltech/JPL photochemical model, to assess the photochemical production of fixed nitrogen species that rain out into the Earth’s early ocean. Our updated photochemical model contains hydrocarbon and nitrile chemistry, and we use a Geant4 simulation platform to consider nitrogen fixation stimulated by solar energetic particle deposition throughout the atmosphere. We study the impact of a novel reaction pathway for generating HCN via HCN2, inspired by the experimental results which suggest that reactions with CH radicals (from CH4 photolysis) may facilitate the incorporation of N into the molecular structure of aerosols. When the HCN2 reactions are added, we find that the HCN rainout rate rises by a factor of five in our 1-bar case and is about the same in our 2- and 12-bar cases. Finally, we estimate the equilibrium concentration of fixed nitrogen species under a kinetic steady state in the Hadean ocean, considering loss by hydrothermal vent circulation, photoreduction, and hydrolysis. These results inform our understanding of environments that may have been relevant to the formation of life on Earth, as well as processes that could lead to the emergence of life elsewhere in the universe.

A new genus and one new species of the family Uristidae Hurley, 1963 (Amphipoda, Lysianassoidea) described from hydrothermal vent of the Okinawa Trough, NW pacific

A new genus of the family Uristidae Hurley, 1963 is proposed, Liuiuristis gen. nov., with new species L. thermalis sp. nov. as the type species based on specimens collected by the expedition to hydrothermal vents on the Okinawa Trough. The new genus is characterized by the shape of accessory flagellum liking cap, the outer plate of the maxilla 1 having 11 setal-teeth, the gnathopod 1 parachelate in female and subchelate in male, the rami of the uropod 3 without plumose setae and the telson not cleft. K2P divergences of the mitochondrial COI gene in taxa attributed to Liuiuristis gen. nov. is presented.

Exploration Vectors and Indicators Extracted by Factor Analysis and Association Rule Algorithms at the Lintan Carlin-Type Gold Deposit, Youjiang Basin, China

The Youjiang Basin in China is the world’s second-largest concentrated area of Carlin-type Au deposits after Nevada, USA, boasting cumulative Au reserves nearing 1000 t. This study examined the recently unearthed Lintan Carlin-type Au deposit within the Youjiang Basin. Factor analysis and association rule algorithms were used to identify exploration vectors and indicators essential for navigating this promising geological territory. In the Lintan mining area, the geological strata encompass the Triassic Bianyang, Niluo, and Xuman formations comprised clastic rocks, followed by the deeper Permian Wujiaping Formation with massive carbonate rocks. The orebodies are restricted to the F14 inverse fault, cutting through the Xuman Formation, with an additional F7 fault between the Wujiaping and Xuman formations. A total of 125 rock samples from the F14 fault and a representative cross-section were analyzed for 15 elements (Au, Ag, As, Bi, Cd, Co, Cu, Hg, Mo, Ni, Pb, Sb, Tl, W, and Zn). The elements were divided into four groups based on cluster and factor analysis. Group 1 (Co, Cu, Zn, Ni, Tl, W, and Bi) was mainly enriched in the Xuman, Niluo, and Bianyang formations controlled by sedimentary diagenesis. Group 2 (Au, As, Hg, and Sb) was concentrated in the F14 and F7 faults, representing Au mineralization. Group 3 (Pb, Ag, and Mo) was mostly enriched near the F14 and F7 faults, displaying a peripheral halo of Au mineralization, and was probability controlled by ore-forming hydrothermal activities. Group 4 (Cd and Mo) exhibited extreme enrichment along the periphery of the F7 fault. This pattern indicates the presence of a substantial hydrothermal alteration zone surrounding the fault, likely influenced by ore-forming hydrothermal processes. Additionally, Pb, Ag, Cd, Mo, and W are considered essential indicators for ore formation besides Au, As, Sb, Hg, and Tl. Twelve effective association rules were derived using the association rule algorithm, which can aid in discriminating Au mineralization. The spatial distributions of the 15 elements indicated that the F14 fault is the main ore-bearing fracture zone, while the F7 fault serves as the ore-conducting structure, channeling ore-forming fluids into the F14 fault. Faults between the Wujiaping and Xuman formations, along with their associated reverse faults, present potential prospecting targets both within and outside the Lintan Au deposit in the Youjiang Basin. Exploration geochemical data can be fully utilized by combining factor analysis and association rule algorithms, offering key guidance for prospecting Carlin-type gold and similar deposits.

Discovery of the first hydrothermal field along the 500-km-long Knipovich Ridge offshore Svalbard (the Jøtul field)

Oceanic spreading centers north of Iceland are characterized by ultraslow spreading rates, and related hydrothermal activity has been detected in the water column and at the seafloor along nearly all ridge segments. An exception is the 500-km-long Knipovich Ridge, from where, until now, no hydrothermal vents were known. Here we report the investigation of the first hydrothermal vent field of the Knipovich Ridge, which was discovered in July 2022 during expedition MSM109. The newly discovered hydrothermal field, named Jøtul hydrothermal field, is associated with the eastern bounding fault of the rift valley rather than with an axial volcanic ridge. Guided by physico-chemical anomalies in the water column, ROV investigations on the seafloor showed a wide variety of fluid escape sites, inactive and active mounds with abundant hydrothermal precipitates, and chemosynthetic organisms. Fluids with temperatures between 8 and 316 °C as well as precipitates were sampled at four vent sites. High methane, carbon dioxide, and ammonium concentrations, as well as high 87Sr/86Sr isotope ratios of the vent fluids indicate strong interaction between magma and sediments from the Svalbard continental margin. Such interactions are important for carbon mobilization at the seafloor and the carbon cycle in the ocean.

Genetic sex determination in three closely related hydrothermal vent gastropods, including one species with intersex individuals.

Molluscs have undergone many transitions between separate sexes and hermaphroditism, which is of interest for studying the evolution of sex determination and differentiation. Here we combined multi-locus genotypes obtained from RAD sequencing with anatomical observations of the gonads for three deep-sea hydrothermal vent gastropods of the genus Alviniconcha living in the southwest Pacific. We found that all three species (A. boucheti, A. strummeri, and A. kojimai) share the same male-heterogametic XY sex determination system, but that the gonads of XX A. kojimai individuals are invaded by a variable proportion of male reproductive tissue. The identification of Y-specific RAD loci (found only in A. boucheti) and the phylogenetic analysis of three sex-linked loci shared by all species suggested that X-Y recombination has evolved differently within each species. This situation of three species showing variation in gonadal development around a common sex determination system provides new insights into the reproductive mode of poorly known deep-sea species and opens up an opportunity to study the evolution of recombination suppression on sex chromosomes and its association with mixed or transitory sexual systems.

Experimental modelling of the growth of tubular ice brinicles from brine flows under sea ice

Abstract. We present laboratory experiments on the growth of a tubular ice structure surrounding a plume of cold brine that descends under gravity into water with a higher freezing point. Brinicles are geological analogues of these structures found under sea ice in the polar regions on Earth. Brinicles are hypothesized to exist in the oceans of other celestial bodies, and being environments rich in minerals, serve a potentially analogous role as an ecosystem on icy-ocean worlds to that of submarine hydrothermal vents on Earth.

Solvation Properties of Neutral Gold Species in Supercritical Water Studied By THz Spectroscopy

Supercritical water provides distinctly different solvation properties compared to what is known from liquid water. Despite its prevalence deep in the Earth’s crust and its role in chemosynthetic ecosystems in the vicinity of hydrothermal vents, molecular insights into its solvation mechanisms are still very scarce compared to what is known for liquid water. Recently, neutral metal particles have been detected in hydrothermal fluids and proposed to explain the transport of gold species to ore deposits on Earth. Using ab initio molecular dynamics, we elucidate the solvation properties of small gold species at supercritical conditions. The neutral metal clusters themselves contribute enormous THz intensity not because of their intramolecular vibrations, but due to their pronounced electronic polarization coupling to the dynamical supercritical solvent, leading to a continuum absorption up to about 1000 cm‐1 . On top, long‐lived interactions between the gold clusters and solvation water leads at these supercritical conditions to a sharp THz resonance that happens to be close to the one due to H‐bonding in liquid water at ambient conditions. The resulting distinct resonances can be used to analyse the solvation properties of neutral metal particles in supercritical aqueous solutions.

Solvation Properties of Neutral Gold Species in Supercritical Water Studied By THz Spectroscopy.

Supercritical water provides distinctly different solvation properties compared to what is known from liquid water. Despite its prevalence deep in the Earth's crust and its role in chemosynthetic ecosystems in the vicinity of hydrothermal vents, molecular insights into its solvation mechanisms are still very scarce compared to what is known for liquid water. Recently, neutral metal particles have been detected in hydrothermal fluids and proposed to explain the transport of gold species to ore deposits on Earth. Using ab initio molecular dynamics, we elucidate the solvation properties of small gold species at supercritical conditions. The neutral metal clusters themselves contribute enormous THz intensity not because of their intramolecular vibrations, but due to their pronounced electronic polarization coupling to the dynamical supercritical solvent, leading to a continuum absorption up to about 1000 cm-1 . On top, long-lived interactions between the gold clusters and solvation water leads at these supercritical conditions to a sharp THz resonance that happens to be close to the one due to H-bonding in liquid water at ambient conditions. The resulting distinct resonances can be used to analyse the solvation properties of neutral metal particles in supercritical aqueous solutions.

Genomic comparison of deep-sea hydrothermal genera related to Aeropyrum, Thermodiscus and Caldisphaera, and proposed emended description of the family Acidilobaceae

Deep-sea hydrothermal vents host archaeal and bacterial thermophilic communities, including taxonomically and functionally diverse Thermoproteota. Despite their prevalence in high-temperature submarine communities, Thermoproteota are chronically under-represented in genomic databases and issues have emerged regarding their nomenclature, particularly within the Aeropyrum–Thermodiscus–Caldisphaera. To resolve some of these problems, we identified 47 metagenome-assembled genomes (MAGs) within this clade, from 20 previously published deep-sea hydrothermal vent and submarine volcano metagenomes, and 24 MAGs from public databases. Using phylogenomic analysis, Genome Taxonomy Database Toolkit (GTDB-Tk) taxonomic assessment, 16S rRNA gene phylogeny, average amino acid identity (AAI) and functional gene patterns, we re-evaluated of the taxonomy of the Aeropyrum–Thermodiscus–Caldisphaera. At least nine genus-level clades were identified with two or more MAGs. In accordance with SeqCode requirements and recommendations, we propose names for three novel genera, viz. Tiamatella incendiivivens, Hestiella acidicharens and Calypsonella navitae. A fourth genus was also identified related to Thermodiscus maritimus, for which no available sequenced genome exists. We propose the novel species Thermodiscus eudorianus to describe our high-quality Thermodiscus MAG, which represents the type genome for the genus. All three novel genera and T. eudorianus are likely anaerobic heterotrophs, capable of fermenting protein-rich carbon sources, while some Tiamatella, Calypsonella and T. eudorianus may also reduce polysulfides, thiosulfate, sulfur and/or selenite, and the likely acidophile, Hestiella, may reduce nitrate and/or perchlorate. Based on phylogenomic evidence, we also propose the family Acidilobaceae be amended to include Caldisphaera, Aeropyrum, Thermodiscus and Stetteria and the novel genera described here.

Mafic veins in the mantle section of the Oman ophiolite: Petrological and geochronological insights from the Oman Drilling Project cores

The magmatic and tectonic evolution of the Oman ophiolite was investigated using the core samples obtained in the Oman Drilling Project. The core samples were recovered from three drilling sites (BA1B, BA3A, and BA4A) in the mantle section composed mainly of harzburgite and discordant dunite and wehrlite. A large number of mafic veins crosscut the structures of both mantle lithologies, indicating that they intruded after the formation of discordant dunites. The wehrlites include Fe3+-rich and TiO2-poor chromian spinel, suggesting that the discordant dunites and wehrlites were involved in hydrous, Ti-poor arc magmatism. The composition of plagioclase and clinopyroxene and rare-earth element (REE) patterns of clinopyroxene for the mafic veins suggest that the mafic veins were produced from mid-ocean ridge basalt (MORB)-like parental melts. On the other hand, early crystallization of clinopyroxene and Fe3+-rich and TiO2-poor chromian spinel in the mafic veins imply that the parental melts were also hydrous. Zircon UPb dating of the mafic veins yields the igneous age of about 91 Ma, which is younger than the V1 and V2 volcanic sequences. Depending on the distance from the mafic veins, the various REE patterns of clinopyroxene and Ca amphibole in the Oman harzburgites indicate local peridotite metasomatism during intrusion and percolation of late-stage melts that formed the mafic veins. Ca amphibole in the harzburgites and mafic veins lack significant enrichment in fluid-mobile elements, indicating that the hydrous phases were formed by fluids associated with hydrothermal activities in a spreading environment instead of slab-derived fluids. The mafic veins were likely produced in a spreading environment on a supra-subduction zone. As their formation took place after the arc magmatism that formed the Oman V2 lava sequence and discordant dunites, as a result of slab roll-back. This seafloor re-spreading on a supra-subduction zone after the V2 magmatism recorded in the mantle section might have been involved in the formation of the plume-related V3 lava sequence overlying the V2 lavas.

Directional hydrothermal hydrogenation of palmitic acid to alcohol over carbon-encapsulated highly dispersed Co catalyst

The directed conversion of fatty acids into fatty alcohols in water medium has recent received increasing attention. Here, a carbon-encapsulated catalyst (Co@C) is designed and used for the hydrothermal hydrogenation of palmitic acid (a model compound of microalgae-based bio-oils) to produce 1-hexadecanol, exhibiting ultra-high catalytic activity. The yield of 1-hexadecanol is as high as 95.1 % at 200 °C within 60 min. The characterization results indicate that a large number of highly dispersed CoO nanoparticles (CoO NPs) provide sufficient hydrogenation active centers for the Co@C catalyst. More importantly, under the protection of the carbon layer, the Co@C catalyst exhibits high hydrothermal stability, far superior to the conventional supported Co/AC catalyst. The catalyst uses inexpensive glucose and cobalt nitrate as raw materials, with a simple synthesis process, low cost, and easy large-scale industrial production. This work provides a new strategy for obtaining catalysts with hydrothermal stability and activity for production of alcohols.

New insights into the origin and depositional setting of the Haerdaban Pb[sbnd]Zn deposit, Chinese western Tianshan: Evidence from geology, chert geochemistry, and detrital zircon U[sbnd]Pb geochronology

The Haerdaban PbZn deposit (with an ore reserve of 10.93 Mt. at 1.0–25.65 % Zn and 0.7–12.29 % Pb) is hosted in weakly metamorphosed clastic‑carbonate rocks from the Proterozoic Haerdaban Group. It represents a significant addition of the sediment-hosted PbZn deposits in the Yili block, Chinese western Tianshan. Currently, there are ongoing debates regarding its genesis, with a particular focus on the crucial metallogenic mechanism (syngenetic sedimentary exhalation or epigenetic reworking) responsible for the primary sulfide mineralization. Mineralization at Haerdaban primarily occurs as banded to stratiform ore layers or lenses conformably sandwiched in their host rocks. Vein and stockwork ores occur locally below the stratiform ore layers. A syn-sedimentary fault trending SN was identified based on abrupt lateral changes in lithofacies and thickness of the stratigraphic units. The ore mineralogy is dominated by sphalerite, galena, quartz, and dolomite, with a small amount of pyrite, barite, and organic matter. Detrital zircon LA-ICP-MS UPb dating of the Haerdaban siltstones obtained a maximum depositional age of about 604 Ma. Their geochemical composition similar to the passive continental margin signatures, with rare earth element (REE) patterns enriched in LREE and negative Eu anomalies (Eu/Eu* = 0.50–1.14). Stratiform beds of chert that host disseminated ores have relatively high contents of hydrothermal components (e.g., Ba, Zn), with apparent positive Eu anomalies (Eu/Eu* = 7.38–49.34) and negligible negative Ce anomalies (Ce/Ce* = 0.85–0.98). They are thus interpreted to be hydrothermal sedimentary rocks (exhalites) deposited in a suboxic-anoxic environment proximal to the hydrothermal vents. Integrated geological and geochemical evidence indicates that the Haerdaban PbZn deposit is a typical vent-proximal sedimentary exhalative (SEDEX) deposit formed in a Neoproterozoic Sinian (Ediacaran) passive continental margin rift basin. Post-depositional metamorphism and deformation in the Paleozoic may have caused partial remobilization of primary ores but did not significantly alter the morphology of the orebodies. Furthermore, establishing a genetic model for the Haerdaban deposit has important implications for the exploration of similar deposits preserved in the equivalent stratigraphy within the Chinese western Tianshan region.

Hydrothermal alteration of accessory minerals (allanite and titanite) in the late Archean Closepet granitoid (Dharwar Craton, India): A TEM study

Allanite, a member of the epidote supergroup, is a widespread rare earth element (REE)-rich accessory mineral in the late Archean Closepet batholith (Dharwar craton, India). It is commonly associated with titanite. Previously recognized shear zones served as preferential paths for magma and later fluids. As a response to hydrothermal activity, allanite exhibits complex alteration textures, geochemical features, and breakdown products that vary across the batholith. In the central zone, allanite displays the largest variations. It has decomposed into secondary allanite, bastnäsite, chlorite, thorite, calcite, pyrite, and galena. In the southern zone, magmatic allanite core is preserved. The alteration products in the marginal regions are limited to secondary allanite, bastnäsite, chlorite, thorite, and synchysite. The breakdown products and textural features of allanite in the northern intrusions differ strongly from those in the other zones of the Closepet batholith and are limited to secondary allanite and chamosite. However, nanoscale element remobilization at the interface between allanite and titanite is evident. The observed texture in allanite indicates a complete dissolution–reprecipitation process. The chemical variations and differences in alteration products after allanite indicate that the fluid composition changed along the Closepet granitoid. The fluids that altered the allanite were most likely F-, Cl-, and CO2-rich and alkaline but eventually became acidic. When the chlorine-bearing fluids reached the northern zone, the concentrations or active contributions of CO2, F and H2S were very low. The alteration products (bastnäsite, chlorite, and thorite) indicate a rather low-temperature fluid.

Trace element (Be, Zn, Ga, Rb, Nb, Cs, Ta, W) partitioning between mica and Li-rich granitic melt: Experimental approach and implications for W mineralization

Mica is the most important carrier of rare alkalis (Li, Rb and Cs) and volatiles, and also a major host of rare metals such as Sn, W, Nb and Ta. Thus, the knowledge of trace element partitioning between mica and silicate melt is crucial to understand enrichment mechanisms of ore metals in evolved silicic systems. However, experimental data are scarce, mainly because the synthesis of large mica grains which can be analyzed with laser ablation techniques is challenging. To address this issue, we conducted two-step experiments, using a high-temperature step at 800 °C, and a low-temperature step at 600 °C with a temperature cycling interval of 30 °C, and variable run durations from 21 to 60 days. The experimental products, at 600 °C, 200 MPa, are mainly composed of mica and alkali feldspars. Ferroholmquistite (Fhlm; a Li-bearing amphibole) was also observed in the Li-bearing systems.Beryllium, Zn and Cs are highly incompatible in all run products with mineral/melt partitioning of mineral/meltDBe between 0.01 and 0.08, mineral/meltDZn between < 0.01 and 0.24 and mineral/meltDCs between <0.01 and 0.19. Gallium is mildly incompatible in mica and feldspars with mica/meltDGa, K-feld/meltDGa and Na-feld/meltDGa of 0.24 ∼ 0.35, 0.60 ∼ 0.67 and 0.69 ∼ 0.72, respectively, whereas Fhlm/meltDGa is nearly 1. Rubidium is characterized by a slight enrichment in mica and K-rich feldspar with respect to melt. Niobium and Ta are highly incompatible in feldspars, while they are compatible in ferroholmquistite. Li-mica crystallization would cause Nb/Ta fractionation with mica/meltDNb and mica/meltDTa of 4.46 and 0.88, respectively. Tungsten is preferentially incorporated in Li-rich mica with mica/meltDW > 22. The strong partitioning of W into Li-rich mica implies that minor Li-rich mica fractionation (>5 %) will strongly deplete W in the residual melt, thus inhibiting transfer to the magmatic fluid at the magmatic-hydrothermal transition. Based on the observed mineral/meltD value, a multi-stage quantitative fractionation model for the behavior of metals during the crystallization of Li-bearing granitic magmas was developed. The results suggest that crystal fractionation is an effective mechanism that could further enrich Be, Ga, Rb, Cs, Nb and Ta in residual melts. Li-rich mica and muscovite are more effective in causing Nb/Ta fractionation as compared with biotite. The very low Nb/Ta ratios found in natural granite may have resulted via extreme, i.e., >99 wt% of fractional crystallization, even if without the precipitation of columbite-group minerals or increasing hydrothermal activity. Due to the very high Li-mica/meltDW value, water saturation in the melt and subsequent magmatic fluid exsolution should occur before Li-mica starts to crystallize to avoid W sequestration in the magma. At 175 MPa, the efficiency of extracting W from Li-poor granitic system is at least 15 % higher than that from Li-rich granitic system. Li-poor granitic systems are thus expected to have a greater W-mineralization potential than Li-rich system, which is consistent with the fact that most parental magmas of large/giant W deposits are Li-poor in composition.

Hydrothermal activities contribute to the strong metal enrichments during early Cambrian: evidence from the comparison between black rock series in Tarim and South China

Hydrothermal activities contribute to the strong metal enrichments during early Cambrian: evidence from the comparison between black rock series in Tarim and South China

Impact‐Generated Fragmentation, Porosity, and Permeability Within the Chicxulub Impact Structure

AbstractLarge asteroid impacts have long been attributed to imparting long‐lived heat in the upper crust, as well as widespread fracturing and porosity. When an impact occurs on or near an ocean environment, displaced water rushes back filling the crater and percolating down into the fractured crust. The significant heat and fracturing from impact allow for extensive hydrothermal activity. Hydrothermal alteration has been observed at the 180 km Chicxulub impact structure in Yucatán, Mexico. Previous studies estimate widespread hydrothermal transport and activity within the Chicxulub structure, but these processes are largely dependent on the assumed post‐impact permeability distribution. In this work, we present an impact simulation that tracks fragmentation as well as the generation of porosity and permeability during the Chicxulub impact event. The generation of porosity during tensile failure results in final porosities (up to 40%) that are up to a factor of 4 higher than previous models and in better agreement with drill core data. We find that both fragmentation and porosity contribute to overall permeability of the Chicxulub structure. Estimated permeabilities (up to 10−14 m2) are greater than measured values from drill cores because of the contribution from large‐scale fragmentation, which cannot be resolved in cm‐diameter drill cores. The larger porosities and permeabilities computed in this work suggest that the volume of hydrothermal activity generated by Chicxulub were 10 times more than previously estimated for Chicxulub and 100 times more than the Yellowstone caldera.

Effect of Temperature on Calcium‐based Chemical Garden Growth

Hydrothermal vents maintain far‐from equilibrium conditions that may have provided the necessary settings for the origin of life. To understand reactions under these physicochemical conditions, scientists have turned to the classic demonstration experiment, chemical gardens. The self‐organization of precipitate tubes separates high and low pH environments similarly to the naturally occurring geological structures. Here, we report calcium‐based chemical gardens forming in solutions containing anions of silicate, carbonate, or a mixture of the two in 100 ºC and 23 °C environments. Under high temperature conditions, chemical gardens tend to have faster average growth velocities and form taller structures. We measure the composition of the precipitate tubes using Fourier transform infrared spectroscopy and and the formation of all polymorphs of calcium carbonate along with calcium silicates.

Sulfide mineralization in orogenic eclogites of the North Muya block (northeastern Transbaikalia): genesis and the first data on the isotopic composition of sulfur

   Subduction processes are accompanied by the sites of hydrothermal activity including large deposits of gold and transitional metals of island-arc or back-arc origin, whereas volcanic arcs host most part of the worldwide resources of metallic minerals. However, the role of suprasubduction metal transfer and the associated role of redox processes in their formation are still ambiguous and require direct studies of sulfide mineralization in high-pressure rocks, as well as their formation stages and sulfide preservation during progressive and peak metamorphism. In order to describe the behavior of chalcophile elements in the paleozones of continental subduction we performed preliminary mineralogical (SEM-EDX) and isotope (S) studies of sulfides in the North Muya block eclogites (northeastern Transbaikalia). Sulfide mineralization of pyrite-chalcopyrite-pyrrhotite composition has a metasomatic origin associated with the retrograde fluid transformation of initially “dry” eclogite assemblages during exhumation to lower- or mid-crust levels after or synchronously to the decompression and formation of plagioclase-diopside±amphibole symplectites (below 10-12 kbar). Extremely heterogeneous isotopic composition of pyrite sulfur (δ34SVCDT) was caused by various sources of fluids of presumably metasedimentary origin (from -8.2 to -6 %) in the paragneiss segments of the North Muya block. But they also could be predominantly buffered by hydrothermally altered metabasites (from +0.7 to +7.1 %). An alternative mechanism could be the participation of a single predominantly oxidized (sulfate-containing) fluid with the significant isotopic fractionation (up to ~15–20 %).