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serpentinization of peridotites from the southern Mariana forearc

Progress in Natural Science:Materials International 2009年第10期19卷 1287-1295页

作者： Xiaomei Wang a,b,Zhigang Zenga,Junbing Chenc a Key Laboratory of Marine Geology and Environment,Institute of Oceanology,Chinese Academy of Sciences,7 Nanhai Road,Qingdao 266071,China b Graduate School of Chinese Academy of Sciences,19 Yuquan Road,Beijing 100049,China c Geological Brigade of Hydrogeology and Engineering Geology,Zhejiang Geological Prospecting Bureau,206 Baoshan Road,Ningbo 315012,China Key Laboratory of Marine Geology and Environment Institute of Oceanology Chinese Academy of Sciences 7 Nanhai Road Qingdao 266071 China Graduate School of Chinese Academy of Sciences 19 Yuquan Road Beijing 100049 China Geological Brigade of Hydrogeology and Engineering Geology Zhejiang Geological Prospecting Bureau 206 Baoshan Road Ningbo 315012 China

A detailed petrologic and mineralogic study was carried out on serpentinized peridotites dredged from the southern landward slopes of the Mariana Trench,in order to reveal the serpentinization process of these unusual rocks and to identify the sole presence of the mineral *** constituent minerals of these southern Mariana forearc peridotites are olivine,amphibole and spinel,as well as serpentine,chlorite and *** with serpentinite seamounts,the serpentinized peridotites from the southern Mariana forearc are characterized by the absence of magnetite and brucite,and the common presence of talc;besides,the serpentine mineral variety is simplex,only *** mineral chemistry and mineral phase relationships,we conclude that(1) the absence of magnetite in the serpentinized peridotites is due to incomplete serpentinization,other than magnetite,the iron end-member in olivine forms Ferich brucite and Fe-rich serpentine;(2) brucite is not stable with high silica activity,reacting with later SiO2-rich fluid and then forming lizardite,leading to a lack of brucite in these serpentinized peridotites;(3) the occurrence of talc is the result of later SiO2-rich fluid reactions with lizardite;and(4) the reason for the sole occurrence of lizardite is that the temperature condition of our study are awas nothig henough for the formation of antigorite(whichisstable at >500 °C).Despite the broad overlap of lizardite and chrysotile in growth temperature,differences in the modes of occurrence of lizardite and chrysotile,such as the scarcity of H2O,low porosity and permeability,as well as the actual situation of initial serpentinization in the study area,result in the absolute prevalence of lizardite over chrysotile in the area.

关键词： Peridotite serpentinization Mineral chemistry Lizardite Mariana

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The production of iron oxide during peridotite serpentinization:Influence of pyroxene

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Geoscience Frontiers 2017年第6期8卷 1311-1321页

作者： Ruifang Huang Chiou-Ting Lin Weidong Sun Xing Ding Wenhuan Zhan Jihao Zhu Key Laboratory of Mineralogy and Metallogeny Guangzhou Institute of GeochemistryChinese Academy of SciencesGuangzhou 510640PR China Key Laboratory of Marginal Sea Geology South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301PR China State Key Laboratory of Isotope Geochemistry Guangzhou Institute of GeochemistryChinese Academy of SciencesGuangzhou 510640PR China The Second Institute of Oceanography SOAHangzhou 310012PR China

serpentinization produces molecular hydrogen(H2)that can support communities of microorganisms in hydrothermal fields;H2 results from the oxidation of ferrous iron in olivine and pyroxene into ferric iron,and consequently iron oxide(magnetite or hematite)***,the mechanisms that control H2 and iron oxide formation are poorly *** this study,we performed serpentinization experiments at 311℃ and 3.0 kbar on olivine(with serpentinization process,which may have led to a decrease in iron oxide *** correlation between FeO content and SiO_2 or AI_2 O_3 content in olivine-and orthopyroxene-derived serpentine indicates that aluminum and silica greatly control the production of

关键词： serpentinization Iron oxide Peridotite Orthopyroxene Silica Aluminum

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serpentinization,abiogenic organic compounds,and deep life

Serpentinization,abiogenic organic compounds,and deep life

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中国科学院地质与地球物理研究所2014年度（第14届）...

作者： WANG XianBin OUYANG ZiYuan ZHUO ShengGuang ZHANG MingFeng ZHENG GuoDong WANG YongLi Lanzhou Center for Oil and Gas Resources Institute of Geology and GeophysicsChinese Academy of Sciences National Astronomical Observatories Chinese Academy of Sciences Northeastern University at Qinhuangdao

The hydrocarbons and other organic compounds generated through abiogenic or inorganic processes are closely related to two science subjects,i.e.,energy resources and life’s origin and evolution."The earth’s primordial abiogenic hydrocarbon theory"and"the serpentinization of abiogenic hydrocarbon theory"are the two mainstream theories in the field of related *** generally occurs in slow expanding mid-ocean ridges and continental ophiolites tectonic environment,*** abiogenic hydrocarbons and other organic compounds formed through the serpentinization of ultramafic rocks provide energy and raw materials to support chemosynthetic microbial communities,which probably was the most important hydration reaction for the origin and early evolution of *** superposition of biological and abiological processes creates big challenge to the identification of the abiogenic organic materials in serpentinite-hosted *** abiotic(inorganic)process can form oil and gas resource is a difficult question that has been explored continuously by scientific community for more than a century but has not yet been ***,some important progress has been *** prospecting practice of abiogenic hydrocarbons in commercial gases from the Songliao Basin,China,provides an important example for exploring abiogenic natural gas resources.

关键词： ultramafic rocks serpentinization abiogenic origin organic compound origin of life

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Magnetic Signature of serpentinization at Zedang in the South Tibetan Ophiolite Belt

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Acta Geologica Sinica(English Edition) 2020年第S1期94卷 28-28页

作者： LI Zhiyong XIONG Qing ZHENG Jianping Hubei Subsurface Multi-scale Imaging Key Laboratory Institute of Geophysics and GeomaticsChina University of GeosciencesWuhanHubei 430074 State Key Laboratory of Geological Processes and Mineral Resources China University of GeosciencesWuhanHubei 430074

Magnetic signature of serpentinized mantle peridotite has crucial importance in understanding the serpentinization process and interpreting the origin of strong magnetization anomalies at ultramafic-hosted hydrothermal settings. However, different groups of serpentinized peridotites from both ocean drillings and ophiolite complexes have shown considerable variations in the abundance of magnetite(Oufi et al., 2002;Bonnemains et al., 2016;Li et al., 2017). We examined the magnetic properties, petrography and mineral chemistry of variably serpentinized peridotites from Zedang ophiolite in the eastern Yarlung-Zangbo suture in south Tibet to evaluate the conditions of serpentinization and magnetite formation as well as magnetic sources in suture zones. The studied samples were 0–90% serpentinized with densities from 3.316 to 2.593 g cm–3 and show typical mesh textures of olivine replaced by serpentine on thin sections of core specimen. Serpentines were divided into type-1 Fe-poor serpentine mesh(1.84–2.88 wt% FeO) associated with magnetite in the early stage and type-2 Fe-rich serpentine cores(3.92–5.12 wt% FeO) with no formation of magnetite in the late serpentinization. Brucite vein appeared in central serpentine veins and show Mg/(Mg+Fe) values of 0.74–0.87 at ~50–70% of serpentinization. Pure magnetite was identified as the main magnetic carrier by thermomagnetic analyses, but minor Cr-magnetite(~0.8 mole fractions of Fe3O4) was also detected due to oxidation of early spinel. All the peridotite samples show a rapid increase of magnetic susceptibility from ~0.001 to ~0.03 SI before 40–50% of serpentinization and a following flat trend in values 0.02–0.03 SI at > 50% of serpentinization. This density-susceptibility relationship differs from the rapid production of magnetite above 60-70% of serpentinization for many abyssal peridotites(Oufi et al., 2002;Bach et al., 2006) and suggests that magnetite formation was coupled with hydration of olivine in the early serpentini

关键词： serpentinization rock magnetism Zedang ophiolite Yarlung-Zangbo suture

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The influence of silica on reaction rates and molecular hydrogen(H_(2))generation during olivine hydrothermal alteration

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Science China Earth Sciences 2024年第1期67卷 222-233页

作者： Ruifang HUANG Weidong SUN Xing DING Yusheng ZHAO Yibing LI Xiuqi SHANG CAS Key Laboratory of Ocean and Marginal Sea Geology South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China SUSTech Academy for Advanced Interdisciplinary Studies Southern University of Science and TechnologyShenzhen 518055China Center of Deep Sea Research Institute of OceanologyChinese Academy of SciencesQingdao 266071China State Key Laboratory of Isotope Geochemistry Guangzhou Institute of GeochemistryChinese Academy of SciencesGuangzhou 510640China Institue of Geology Chinese Academy of Geological SciencesBeijing 100037China

Hydrothermal alteration of olivine greatly influences geodynamics and the recycling of volatiles(such as water and carbon)in subduction *** is an important component of geological fluids,and its influence on the hydrothermal alteration of olivine remains poorly *** this study,we performed experiments at 300–515℃ and 3.0 kbar(1 bar=10^(5)Pa)by reacting well homogenized mixtures of olivine and silica powders with saline solutions(0.5 mol L^(−1)NaCl).Silica greatly influences the reaction pathways,reaction rates,and molecular hydrogen(H_(2))formation during olivine hydrothermal *** experiments at 300℃ and 3.0 kbar with mixtures of olivine and 10 wt%silica,olivine was replaced by serpentine and *** proportions of serpentine and talc were determined according to standard curves based on infrared spectroscopy *** 6.5%serpentine and 12%talc were produced after an experimental duration of 7 days,which had no change after a longer period(14 days).Compared to the kinetics in silica-free systems,the rates of olivine hydrothermal alteration in experiments with 10 wt%silica are much *** overall reaction is:4.5Forsterite+5.5SiO_(2),aq+4H_(2)O=Serpentine+*** the addition of more silica(20 wt%and 40 wt%),olivine was transformed into *** rates of reaction were much faster,e.g.,for experiments with olivine and 20 wt%silica,43%of talc was produced after 14 days,which increased to 77%for experiments with 40 wt%silica over the same *** overall reaction is:3Forsterite+5SiO_(2),aq+2H_(2)O=*** experiments at 400–505℃ and 3.0 kbar,the promoting effect of silica on olivine hydrothermal alteration was also observed,which is closely associated with a decrease in Gibbs free energies of olivine hydrothermal *** 300℃ and 3.0 kbar,silica decreased H_(2)formed during olivine hydrothermal alteration by around an order of magnitude,resulting in an increase in oxygen *** on measured H_(2),we calibrated ox

关键词： Olivine hydrothermal alteration Silica serpentinization Hydrogen Serpentine

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Crustal S-wave velocity structure across the northeastern South China Sea continental margin: implications for lithology and mantle exhumation

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Earth and Planetary Physics 2019年第4期3卷 314-329页

作者： WenAi Hou Chun-Feng Li XiaoLi Wan MingHui Zhao XueLin Qiu Institute of Marine Geology and Resources Zhejiang University Zhoushan Zhejiang 316021 China Laboratory for Marine Mineral Resources Qingdao National Laboratory for Marine Science and Technology Qingdao 266237 China State Key Laboratory of Marine Geology Tongji University Shanghai 200092 China South China Sea Institute of Oceanology Chinese Academy of Sciences Guangzhou 510301 China

The northeastern margin of the South China Sea (SCS), developed from continental rifting and breakup, is usually thought of as a non-volcanic margin. However, post-spreading volcanism is massive and lower crustal high-velocity anomalies are widespread, which complicate the nature of the margin here. To better understand crustal seismic velocities, lithology, and geophysical properties, we present an S-wave velocity (VS) model and a VP/VS model for the northeastern margin by using an existing P-wave velocity (VP) model as the starting model for 2-D kinematic S-wave forward ray tracing. The Mesozoic sedimentary sequence has lower VP/VS ratios than the Cenozoic sequence;in between is a main interface of P-S conversion. Two isolated high-velocity zones (HVZ) are found in the lower crust of the continental slope, showing S-wave velocities of 4.0–4.2 km/s and VP/VS ratios of 1.73–1.78. These values indicate a mafic composition, most likely of amphibolite facies. Also, a VP/VS versus VP plot indicates a magnesium-rich gabbro facies from post-spreading mantle melting at temperatures higher than normal. A third high-velocity zone (VP : 7.0–7.8 km/s;VP/VS: 1.85–1.96), 70-km wide and 4-km thick in the continent-ocean transition zone, is most likely to be a consequence of serpentinization of upwelled upper mantle. Seismic velocity structures and also gravity anomalies indicate that mantle upwelling/ serpentinization could be the most severe in the northeasternmost continent-ocean boundary of the SCS. Empirical relationships between seismic velocity and degree of serpentinization suggest that serpentinite content decreases with depth, from 43% in the lower crust to 37% into the mantle.

关键词： South China Sea continental margin crustal structure converted S-wave VP/VS ratio lithology serpentinization

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Geological Evidence does not Support a Shallow Origin for Diamonds in Ophiolite

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Acta Geologica Sinica(English Edition) 2020年第S1期94卷 70-72页

作者： YANG Jingsui LIAN Dongyang Paul T ROBINSON QIU Tian XIONG Fahui WU Weiwei School of Earth Sciences and Engineering Nanjing UniversityNanjing 210023China Center for Advanced Research on Mantle(CARMA) Institute of GeologyChinese Academy of Geological SciencesBeijing 100037China College of Marine Science and Technology China University of GeosciencesWuhan 430074China

Farré-de-Pablo et al.(2018)report a new occurrence of in situ microdiamonds enclosed in chromite from ophiolitic chromitite pods hosted in the Tehuitzingo serpentinite of southern *** discovery enlarges the number of occurrence of the ophiolite-hosted microdiamonds to 7 countries in the world,including India(Das,2015,2017),Albania(Xiong et al.,2017;Wu et al.,2017),Turkey(Lian et al.,2017),Myanmar(Chen et al.,2018),Russia(Yang et al.,2015),and China(Bai et al.,1993;Xu et al.,2009).The microdiamonds occur in ophiolitic podiform chromitites and peridotites,and are generally interpreted as UHP phases formed at pressures>4 GPa(Yang et al.,2014;Griffin et al.,2016;Das et al.,2017).However,Farré-de-Pablo et al.(2018)conclude that the Tehuitzingo diamonds were formed under low-temperature and low-pressure conditions during serpentinization,which challenges the current knowledge of diamond ***,we discuss several lines of evidence that do not support the authors’conclusion.

关键词： diamonds in ophiolite serpentinization chemical vapor deposition UHP crystallization

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Composition and Seismic Properties of the Oceanic Lithosphere: A Synthesis of Ophiolites and Core Samples of the IODP

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Acta Geologica Sinica(English Edition) 2020年第S1期94卷 89-90页

作者： ZHAO Jiabin WANG Qin State Key Laboratory for Mineral Deposits Research School of Earth Sciences and EngineeringNanjing UniversityNanjingJiangsu 210023

Our knowledge of the oceanic lithosphere largely comes from analogy with ophiolite complexes and the direct scientific drilling of the present-day oceanic crust(e.g.,Christensen and Salisbury,1975,1989;Smith and Vine,1989;Dilek and Furnes,2011,2014).In this study,we summarized previous experimental results on seismic properties of oceanic lower crust and upper mantle according to different tectonic *** results are used to highlight the compositional heterogeneity and the nature of the oceanic *** in different ophiolites reveal an ideal oceanic lithosphere profile with ideal petrologic units and seismic units(Dilek and Furnes,2011,2014).The lithospheric mantle beneath ocean basins is composed of tectonized peridotites,which include layered lherzolites and harzburgites and lenses of dunites with chromitites and nearly correspond to the seismic Layer *** overlying layered gabbros and mafic sheeted dike complex equal to the seismic Layer 3,as a result of crystallization from a magma *** transitional unit between the former two petrologic units consists of layered ultramafic and mafic rocks,corresponds to the petrological *** seismic Layer 2 and 1 are well defined by pillow lavas and massive flows,and the overlying abyssal sediments,*** these results with the refraction seismic profiles,the oceanic crust and upper mantle show different composition and *** Pwave velocities of the Layer 3 gabbros varies from 6.7 to 7.0 km s-1 and have low velocity gradients of<0.1 km *** the gradual increase of P-and S-wave velocities with depth can be attributed to the increasing proportion of mafic minerals from the top to the bottom,prehnite-pumpellyite facies alteration of basalts,greenschist-faces metamorphism to epidote-amphibolite facies metamorphism of gabbros will decrease the velocities of the Layer 2 and Layer 3(Christensen and Salisbury,1975,1989),because the P-wave velocities of chlorite and hornblende a

关键词： ophiolite seismic velocity oceanic crust serpentinization Moho

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Troodos: A Giant Serpentinite Diapir

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International Journal of Geosciences 2011年第2期2卷 98-101页

作者： Roelof Dirk Schuiling Institute of Geosciences

Troodos is a classical ophiolite complex. It is proposed that the serpentinized harzburgites that now form the top of the mountain and represent the originally lowest part of the ophiolite sequence rose as a diapir. This diapiric rise is caused by the pervasive serpentinization of a suboceanic harzburgite, due to rock-sea water interaction. The serpentinization caused a 44% expansion of the rocks. Contrary to salt diapirism, the driving force for this diapiric rise is not so much the difference in density, but the volume increase asscociated with the transformation of harzburgite into serpentinite. The overlying gabbros, sheeted dike complex and pillow lavas were pierced by this serpentinite diapir but barely deformed. Their interaction with sea water was li- mited to some pyroxenes in the gabbros being transformed to amphiboles, and epidotisation of some of the dikes in the sheeted dike complex. The location of steep faults in the Troodos massif is determined by the contrasting expansion behavior of different rock-types on both sides of the fault.

关键词： Ophiolites Seawater Interaction serpentinization (Lack of) Deformation Cyprus Olympic Flame

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