Evidence of an Impact Induced Hydrothermal System in the Auki Crater on Mars?

Geology and mineralogy of the Auki Crater, Tyrrhena Terra, Mars: A possible post impact-induced hydrothermal system

Authors:

Carozzo et al

Abstract:

A variety of hydrothermal environments have been documented in terrestrial impact structures. Due to both past water interactions and meteoritic bombardment on the surface of Mars, several authors have predicted various scenarios that include the formation of hydrothermal systems. Geological and mineralogical evidence of past hydrothermal activity have only recently been found on Mars. Here, we present a geological and mineralogical study of the Auki Crater using the spectral and visible imagery data acquired by the CRISM (Compact Reconnaissance Imaging Spectrometer for Mars), CTX (Context Camera) and HiRISE (High Resolution Imaging Science Experiment) instruments on board the NASA MRO mission.

The Auki Crater is a complex crater that is ∼38 km in diameter located in Tyrrhena Terra (96.8°E and 15.7°S) and shows a correlation between its mineralogy and morphology. The presence of minerals, such as smectite, silica, zeolite, serpentine, carbonate and chlorite, associated with morphological structures, such as mounds, polygonal terrains, fractures and veins, suggests that the Auki Crater may have hosted a post impact-induced hydrothermal system. Although the distribution of hydrated minerals in and around the central uplift and the stratigraphic relationships of some morphological units could also be explained by the excavation and exhumation of carbonate-rich bedrock units as a consequence of crater formation, we favor the hypothesis of impact-induced hydrothermal circulation within fractures and subsequent mineral deposition. The hydrothermal system could have been active for a relatively long period of time after the impact, thus producing a potential transient habitable environment.

Evidence of Glacial Meltwater/Volcanic Interaction From Rifting of Supercontinent Rodinia During Tonian/Crogenian NeoProterozoic

High temperature glacial meltwater-rock reaction in the Neoproterozoic: evidence from zircon in-situ oxygen isotopes in granitic gneiss from the Sulu orogen

Authors:

He et al

Abstract:

To seek the occurrence of negative δ18O magmas in the Neoproterozoic, we conducted in-situ zircon O isotope analysis and U-Pb dating for granitic gneisses from the northeastern Sulu orogen, east-central China. Zircon U-Pb dating yields protolith ages of 753±15 Ma to 780±13 Ma and metamorphic ages of 209±3 to 244±7 Ma. The Neoproterozoic cores with concordant U-Pb ages exhibit a wide δ18O range from -11.0 to 5.8‰, which is nearly the same as those for cores with discordant U-Pb ages. The Triassic rims of some samples have homogeneous δ18O values of around -10‰ whereas the rims of the other samples show a wider range from -9.8 to 5.0‰. The δ18O values as negative as -11.0‰ for zircons with concordant Neoproterozoic U-Pb ages are reported for the first time, representing the primary record of negative δ18O magma in the Neoproterozoic. The continental subduction-zone metamorphism in the Triassic did not erase the abnormal δ18O record in the protolith cores despite metamorphic dehydration and partial melting under high-pressure to ultrahigh-pressure conditions. A conservative estimate suggests that the hydrothermal fluid reacted with the rocks should have δ18O values lower than -9.2‰, corresponding to the meteoric water in cold paleoclimate or the meltwater of local continental glaciation. The spatial variation in the O isotope compositions of Neoproterozoic zircons is a manifestation of the O isotope heterogeneity in the extinct hydrothermal-magmatic system. The hydrothermal alteration during the Neoproterozoic was incongruent, which was lately recorded by the wide range of δ18O values in the metamorphic zircons of Triassic age. The extensive O isotope exchange between the surface water and the deep rock requires high temperature and high water-rock ratios in continental rifting zones. This is ascribed to Neoproterozoic splitting of the South China Block from the Rodinia supercontinent.

Rhyacian PaleoProterozoic Magnesite Deposits are NOT Deposited Under Hydrothermal Conditions

Genesis of a giant Paleoproterozoic strata-bound magnesite deposit: Constraints from Mg isotopes

Authors:

Dong et al

Abstract:

Giant strata-bound magnesite deposits are absent in modern and most Phanerozoic sedimentary environments but occur predominantly in Precambrian strata. These deposits may have formed directly through precipitation of evolved Mg-rich seawater in an evaporative shallow-marine setting or, alternatively, by epigenetic–hydrothermal replacement of the Mg-rich carbonate precursor. To test these hypotheses, we obtained the first Mg isotope data from the world’s largest strata-bound magnesite deposit belt, hosted by the ca. 2.1 Ga Dashiqiao Formation in Northeast China. The Mg isotope compositions (δ26Mg) of most magnesite ores in the Huaziyu deposit are heavier (–0.75 ± 0.26‰) than most Proterozoic sedimentary dolostones. The Mg isotope compositions and major and trace element data indicate that the magnesites are probably not of hydrothermal origin. Instead, a Mg-rich carbonate precursor precipitated from evaporating seawater in a semi-closed system. Diagenetic brines altered the Mg-rich carbonate precursor to magnesite. Subsequently, recrystallization during regional metamorphism produced coarsely crystalline and saddle magnesite. These interpretations are consistent with the geological features and other geochemical data (element concentrations and C and O isotopes) for the magnesite ores. Hence, we interpret the formation of the Huaziyu magnesite deposit to be dominated by evaporative sedimentation and brine diagenesis.

Reworking of atmospheric sulfur in a Paleoarchean hydrothermal system

Reworking of atmospheric sulfur in a Paleoarchean hydrothermal system at Londozi, Barberton Greenstone Belt, Swaziland

Authors:

Roerdink et al

Abstract:

Anomalous fractionation of the minor isotopes of sulfur (Δ33S, Δ36S) in Archean pyrite is thought to reflect photochemical reactions in an anoxic atmosphere, with most samples falling along a reference array with Δ36S/Δ33S ≈ −1. Small deviations from this array record microbial sulfate reduction or changes in atmospheric source reactions. Here, we argue that reworking of atmospheric sulfur with distinct minor sulfur isotope ratios (Δ36S/Δ33S ≠ −1) produced additional variability in sulfide Δ33S and Δ36S-values in a 3.52 Ga hydrothermal barite deposit at Londozi, Barberton Greenstone Belt, Swaziland. In situ measurement of the four stable sulfur isotopes in pyrite revealed Δ36S–Δ33S relationships and a Δ36S/Δ33S trend (−3.2 ± 0.4), which is significantly different from the co-variation between Δ36S and Δ33S in the co-existing barite that reflects ambient Paleoarchean seawater sulfate. This argues against biological or thermochemical sulfate reduction at the time of barite deposition, and requires incorporation of sulfide generated in a chemically distinct atmosphere before 3.52 Ga. We propose a model that combines reworking of this sulfur by hydrothermal leaching, deep mixing with juvenile sulfur and surface mixing with biogenic sulfide to explain the observed variation in δ34S, Δ33S and Δ36S. These interactions between abiotic and biological processes in the Londozi hydrothermal system complicate the interpretation of biosignatures based on deviations in Δ33S and Δ36S from the Archean reference array.

How to Test if Hydrothermal Vents Were the Origin of Life

Hydrothermal Conditions and the Origin of Cellular Life

Authors:

Deamer et al

Abstract:

The conditions and properties of hydrothermal vents and hydrothermal fields are compared in terms of their ability to support processes related to the origin of life. The two sites can be considered as alternative hypotheses, and from this comparison we propose a series of experimental tests to distinguish between them, focusing on those that involve concentration of solutes, self-assembly of membranous compartments, and synthesis of polymers.

Does a new Type of Hydrothermal Vent Explain how the Earth's Crust Cooled?

The first discovery of a new type of hydrothermal vent system in a decade helps explain the long observed disconnect between the theoretical rate at which the Earth's crust is cooling at seafloor spreading ridge flanks, and actual observations. It could also help scientists interpret the evidence for past global climates more accurately.

This discovery has been made by scientists at the National Oceanography Centre (NOC) and the University of Southampton using a combination of robot-subs and remotely operated vehicles operated by the NOC.

Dr Bramley Murton, who co-supervised this research, published today in Nature Communications, said "This will really improve our understanding of how the Earth's interior cools. Theory has long predicted that there must be more cooling in certain locations on the Earth's crust than we could account for using the known mechanisms....and this new class of hydrothermal vent system may account for that difference."

What makes these hydrothermal vent systems different is that the source of heat driving them comes from hot rock pushed towards the seabed by low angle faults, called tectonic spreading centres, rather than volcanic heat from magma chambers. Dr Murton has been involved in research that discovered tectonic seafloor spreading centres at a number of sites across the ocean floor.

link.

Implications of Quartez Embedded Biogenic Iron-Rich Filaments From Ediacaran NeoProterozoic China

Biogenic Iron-Rich Filaments in the Quartz Veins in the Uppermost Ediacaran Qigebulake Formation, Aksu Area, Northwestern Tarim Basin, China: Implications for Iron Oxidizers in Subseafloor Hydrothermal Systems

Authors:

Zhou et al

Abstract:

Fe-(oxyhydr)oxide-encrusted filamentous microstructures produced by microorganisms have been widely reported in various modern and ancient extreme environments; however, the iron-dependent microorganisms preserved in hydrothermal quartz veins have not been explored in detail because of limited materials available. In this study, abundant well-preserved filamentous microstructures were observed in the hydrothermal quartz veins of the uppermost dolostones of the terminal-Ediacaran Qigebulake Formation in the Aksu area, northwestern Tarim Basin, China. These filamentous microstructures were permineralized by goethite and hematite as revealed by Raman spectroscopy and completely entombed in chalcedony and quartz cements. Microscopically, they are characterized by biogenic filamentous morphologies (commonly 20–200 μm in length and 1–5 μm in diameter) and structures (curved, tubular sheath-like, segmented, and mat-like filaments), similar to the Fe-oxidizing bacteria (FeOB) living in modern and ancient hydrothermal vent fields. A previous study revealed that quartz-barite vein swarms were subseafloor channels of low-temperature, silica-rich, diffusive hydrothermal vents in the earliest Cambrian, which contributed silica to the deposition of the overlying bedded chert of the Yurtus Formation. In this context, this study suggests that the putative filamentous FeOB preserved in the quartz veins might have thrived in the low-temperature, silica- and Fe(II)-rich hydrothermal vent channels in subseafloor mixing zones and were rapidly fossilized by subsequent higher-temperature, silica-rich hydrothermal fluids in response to waning and waxing fluctuations of diffuse hydrothermal venting. In view of the occurrence in a relatively stable passive continental margin shelf environment in Tarim Block, the silica-rich submarine hydrothermal vent system may represent a new and important geological niche favorable for FeOB colonization, which is different from their traditional habitats reported in hydrothermal vent systems at oceanic spreading centers or volcanic seamounts. Thus, these newly recognized microfossils offer a new clue to explore the biological signatures and habitat diversity of microorganisms on Earth and beyond.

Hydrothermal Environments as Home for Early Life on Earth and Mars

Hydrothermal Microbial Ecosystems Were Flourishing, Diverse During PaleoArchean

Archean (3.33 Ga) microbe-sediment systems were diverse and flourished in a hydrothermal context

Authors:

Westall et al

Abstract:

Interacting, diverse microbe-sediment systems exist in natural environments today but have not yet been recognized in the oldest records of life on Earth (older than 3.3 Ga) because of lack of distinctive biomarker molecules and patchy preservation of microbial paleocommunities. In an in-situ outcrop- to microbial-scale study, we have differentiated probable phototrophic, chemolithotrophic, and chemo-organotrophic fossil microbial signatures in a nearshore volcanogenic sedimentary setting in 3.33 Ga rocks of the Josefsdal Chert, Barberton greenstone belt, South Africa, while demonstrating the importance of contemporaneous hydrothermal activity. Hydrothermal fluids, as a nutrient source, strongly controlled the development and distribution of the microbial communities and, as a silicifying agent, contributed to their rapid fossilization. We thus show that intricate microbe-sediment systems are deep-rooted in time and that at least some early life may indeed have been thermophilic.

A Possible Geological Explanation for Methanogenesis on Mars

Spectral reflectance characteristics of the Hamar Laghdad hydrothermal sequence, Morocco: Implications for the methane origin on Mars

Authors:

Sgavetti et al

Abstract:

We analyze and discuss reflectance spectra of carbonate rocks from the Hamar Laghdad area (Morocco), where evidences of interactions with hydrothermal, and, in some cases, methane enriched fluids derived from underlying volcanoclastic rocks, are reported in the literature. Deconvolution of the rock spectra into a sum of Gaussians, using MGM, resolved a number of both vibrational and electronic absorption features, mainly assigned to CO32−, Al–OH, and Fe2+, Fe3+, Cu, CF interaction processes, respectively. The associations of these absorption bands are exhaustive descriptions of the rock spectral properties. A spectral model of the Hamar Laghdad carbonate sequence was therefore delineated, based on the integration of these absorption band associations with XRF and Mössbauer analyses of the rock samples. The model involves: pure limestones and dolostones, limestone with iron carbonates, mixed carbonate and Al-silicate impure limestones, limestones with iron sulfides. The model points out the complexity of the spectral characteristics of rocks that underwent hydrothermal and partly methanogenic processes, but also suggests an alternative geologic scenario plausible for possible methanogenic activity in the Mars geologic past.

Evidence of Hydrothermal Fluid, Escaping CO2 & Black Shale Interaction From Rhyacian PaleoProterozoic China

Fluid evolution of the Paleoproterozoic Hujiayu copper deposit in the Zhongtiaoshan region: Evidence from fluid inclusions and carbon-oxygen isotopes

Authors:

Jiang et al

Abstract:

The Zhongtiaoshan region, located in the southern margin of the North China Craton, is the host to a number of metamorphosed sediment-hosted stratiform copper deposits. These deposits are hosted by dolomitic marble and silicic albitite of the mid-Paleoproterozoic Zhongtiao Group and contain economically significant copper and cobalt. The formation of these deposits is considered to be closely associated with the evolution of the Paleoproterozoic “Zhongtiao” rift. The Hujiayu deposit, the second largest Cu deposit of this type, is mainly hosted in silicic albitite and dolomitic marble in the upper part of the Bizigou Formation but locally extends into carbonaceous shales at the bottom of the Yujiashan Formation. Mineralization of the Hujiayu Cu deposit can be divided into an early stage (diagenetic stage) with disseminated to veinlet sulfides and a late stage (metamorphism stage) with coarse-vein sulfides. Mineral assemblages are similar for the two stages, with major minerals as chalcopyrite, pyrite, and pyrrhotite and main gangue minerals as dolomite and quartz. Sulfide veinlets formed in the early stage are thin and discrete, and have irregular boundaries with the host rocks; whereas the ore-bearing veins of the late stage are controlled by fractures.

Five types of fluid inclusions are recognized in the Hujiayu Cu deposit and they are: (1) pure vapor and vapor-rich inclusion (V-type), (2) pure CO2 inclusion (PC-type), (3) CO2-H2O inclusion (C-type), (4) liquid-rich inclusion (L-type), and (5) daughter mineral-bearing inclusion (S-type). Microthermometric analysis shows that the ore-forming fluids of the early mineralization stage are characterized by high salinity (22-40 wt.% NaCl equiv.) and moderate temperature (120-280 °C). The ore-forming fluids of the late mineralization stage are characterized by CO2 enrichment, high salinity, high temperature and underwent significant unmixing at a temperature interval of 240 °C to 480 °C. Compositions of the ore-forming fluids in the early and late stages are interpreted to be mainly basinal brine and metamorphic hydrothermal solution, respectively. Carbon and oxygen isotope compositions suggest possible carbon isotope exchange between the ore-forming fluids and organic-rich carbonaceous shales during the early stage. In the late mineralization stage, both degassing of CO2 and isotopic exchange with organic carbon may have contributed to the formation of the more negative δ13CV-PDB values of mineralized carbonates.

The early stage mineralization of the Hujiayu Cu deposit may have occurred via interaction of oxidized Cu-bearing brines from the red-bed in the lower segment of the Bizigou Formation with the overlying reductive carbonaceous shales. Late stage mineralization at Hujiayu was mainly triggered by CO2 escaping from metamorphic hydrothermal solutions.

Evidence of Subsurface Hydrothermal Activity From a Martian Meteorite?

A Conspicuous Clay Ovoid in Nakhla: Evidence for Subsurface Hydrothermal Alteration on Mars with Implications for Astrobiology

Authors:

Chatzitheodoridis et al

Abstract:

A conspicuous biomorphic ovoid structure has been discovered in the Nakhla martian meteorite, made of nanocrystalline iron-rich saponitic clay and amorphous material. The ovoid is indigenous to Nakhla and occurs within a late-formed amorphous mesostasis region of rhyolitic composition that is interstitial to two clinopyroxene grains with Al-rich rims, and contains acicular apatite crystals, olivine, sulfides, Ti-rich magnetite, and a new mineral of the rhoenite group. To infer the origin of the ovoid, a large set of analytical tools was employed, including scanning electron microscopy and backscattered electron imaging, wavelength-dispersive X-ray analysis, X-ray mapping, Raman spectroscopy, time-of-flight secondary ion mass spectrometry analysis, high-resolution transmission electron microscope imaging, and atomic force microscope topographic mapping. The concentric wall of the ovoid surrounds an originally hollow volume and exhibits internal layering of contrasting nanotextures but uniform chemical composition, and likely inherited its overall shape from a preexisting vesicle in the mesostasis glass. A final fibrous layer of Fe-rich phases blankets the interior surfaces of the ovoid wall structure. There is evidence that the parent rock of Nakhla has undergone a shock event from a nearby bolide impact that melted the rims of pyroxene and the interstitial matter and initiated an igneous hydrothermal system of rapidly cooling fluids, which were progressively mixed with fluids from the melted permafrost. Sharp temperature gradients were responsible for the crystallization of Al-rich clinopyroxene rims, rhoenite, acicular apatites, and the quenching of the mesostasis glass and the vesicle. During the formation of the ovoid structure, episodic fluid infiltration events resulted in the precipitation of saponite rinds around the vesicle walls, altered pyrrhotite to marcasite, and then isolated the ovoid wall structure from the rest of the system by depositing a layer of iron oxides/hydroxides. Carbonates, halite, and sulfates were deposited last within interstitial spaces and along fractures. Among three plausible competing hypotheses here, this particular abiotic scenario is considered to be the most reasonable explanation for the formation of the ovoid structure in Nakhla, and although compelling evidence for a biotic origin is lacking, it is evident that the martian subsurface contains niche environments where life could develop

Banded Iron Formations From North China

Neoarchean Algoma-type banded iron formations from Eastern Hebei, North China Craton: SHRIMP U-Pb age, origin and tectonic setting

Authors:

Han et al

Abstract:

Algoma-type BIF-hosted iron deposits occur in the Shirengou, Xingshan, Erma, Lingshan and Sijiaying areas of Eastern Hebei. The deposits are hosted in Archean rocks, and their formation was related to volcanic and sedimentary processes in small volcano-sedimentary basins. Supracrustal rocks of the Qianxi and Dantazi Groups were metamorphosed from granulite facies to amphibolites facies. Available data indicate that these BIF deposits mainly formed during Paleoarchean and Neoarchean times. The Paleoarchean BIF-hosted iron deposits are represented by the Xingshan deposit that yielded a SHRIMP U-Pb zircon age of 3389.5 ± 7.6 Ma. The other BIF-hosted iron deposits formed in the late Neoarchean, represented by the Shirengou, Shuichang, Lingshan, Erma and Sijiaying deposits that formed between 2605 Ma and 2503 Ma. The late Neoarchean BIF iron deposits are considered to have formed under a mantle plume environment. The Eu anomalies of the ore samples from Eastern Hebei show that the BIF ores formed in a hydrothermal related volcanic submarine environment, where submarine hydrothermal effluents associated with volcanic activities may have supplied both the iron and silica for the BIFs from Eastern Hebei.