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Melting geodynamics reveals a subduction origin for the Purang ophiolite,Tibet,China

Acta Geochimica 2024年第4期43卷 754-773页

作者： Tao Ruan Zhong-Jie Bai Wei-Guang Zhu Shi-Ji Zheng State Key laboratory of {1. Deposit geochemistry Institute of GeochemistryChinese Academy of SciencesGuiyang 550081China University of Chinese Academy of Sciences Beijing 100049China

The debate regarding whether the Yarlung-Zangbo ophiolite(YZO)on the south of the Qinghai-Tibet Plateau,formed in a mid-ocean ridge(MOR)or a supra-subduction zone(SSZ)setting has remained *** we present petrological,mineralogical,and geochemical data associated with modeling melting geodynamics of the mantle peridotites from the Purang ophiolite in the western segment of the Yarlung-Zangbo Suture Zone(YZSZ)to explore its tectonic *** Purang lherzolites are characterized by the protogranular texture and have abyssal-peridotite-like mineral compositions,including low Cr^(#)(20-30)and TiO_(2) contents(1.t%)in spinel,high Al_(2)O_(3)(2.9wt%-4.4wt%)and CaO(1.9wt%-3.7wt%)contents in orthopyroxene and LREE-depletion in *** of these lherzolites can be modeled by~1.%dynamic melting of the DMM source with a small fraction of melt(~0.5%)entrapped within the source,a similar melting process to typical abyssal *** Purang harzburgites are characterized by the porphyroclastic texture and exhibit highly refractory mineral compositions such as high spinel Cr^(#)(40-68),low orthopyroxene Al_(2)O_(3)(1.1.t%)*** in these harzburgites are enriched in Sr(up to 6.0 ppm)and LREE[(Ce)N=0.02-0.4],but depleted in Ti(200 ppm,on average)and HREE[(Yb)Nore depleted samples tend to have higher clinopyroxene Sr and LREE *** observations indicate an open-system hydrous melting with a continuous influx of slab fluid at a subduction *** modeled results show that these harzburgites could be formed by 1.%-23%hydrous melting with the supply rate of slab fluid at 0.1.-1..The lower clinopyroxene V/Sc ratios in harzburgites than those in lherzolites suggest a high oxidation stage of the melting system of harzburgites,which is consistent with a hydrous melting environment for these *** is therefore concluded that the Purang ophiolite has experienced a transformat

关键词： Melting geodynamics SSZ peridotites MOR peridotites Clinopyroxene Purang ophiolite

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Metallogenesis of the Baidi Au-Sb deposit, southwest Guizhou Province, China: mineralogical and geochemical evidence from sulfur-bearing minerals

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Acta Geochimica 2024年第2期43卷 199-213页

作者： Jun Yan Yong Xia Qinping Tan Zhuojun Xie Guosong Ji State Keylaboratory of {1. Deposit geochemistry Institute of GeochemistryChineseAcademy of SciencesGuiyang 550081China Guizhou InstituteofTechnology Guiyang550003China No.1.2 GeologicalTeam Guizhou Bureau of Geologyand Mineral Exploration&DevelopmentZunyi563003China

The Baidi Au-Sb deposit, which contains 8 t of Au and 1.,979 Mt of Sb, is a typical and rare paragenetic deposit located in southwestern Guizhou Province, *** studies have focused on individual ores, but have not combined them to identify their paragenetic mechanism or metallogenic regularity. Therefore, we used field investigations, microscopic observations, and in situ analyses to identify the spatial distribution, mineral paragenesis, compositional evolution, and metallogenic material sources of the ore bodies. We also determined the Au and Sb paragenetic characteristics and the metallogenesis of the deposit. The main Au-bearing minerals in the deposit were early(Apy1.2) and late(Apy3) stage arsenopyrites, as well as pre-mineralization(Py1., mineralization(Py2–5), and late mineralization(Py6–7) stage pyrites. The main Sb-bearing minerals were stibnite(Snt), skinnerite, bournonite,and valentinite. The minerals formed in the order of Py1.Py2–3 + Apy1. Py4–5 + Apy2, Snt, and Py6–7 + *** δ34S values of the arsenopyrites and pyrites ranged from-5 to 5‰, while those of stibnite were mostly less than-5‰ in the later mineralization stages. Sulfur was provided by deep magmatic hydrothermal fluids, but sedimentary sulfur was added in the later stages. Moreover,the trace elemental contents fluctuated and eventually became similar to those of the sedimentary strata. By comprehensively considering the ores along with the geological characteristics of the deposit, we determined that deep magma provided the Au during ore formation. Later tectonic changes provided Sb from the sedimentary strata,which precipitated along fault expansion areas and produced Au and Sb paragenesis.

关键词： Au-Sb mineralization Arsenopyrite Pyrite Stibnite Metallogenetic process

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Rebuilding the theory of isotope fractionation for evaporation of silicate melts under vacuum condition

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Acta Geochimica 2024年第4期43卷 661-676页

作者： Jie Wang Yun Liu Research Center for Planetary Science College of Earth and Planetary SciencesChengdu University of TechnologyChengdu 610059China State Key laboratory of {1. Deposit geochemistry Institute of GeochemistryChinese Academy of SciencesGuiyang 550081China CAS Center for Excellence in Comparative Planetology Hefei 230026China

Isotope eff ects are pivotal in understanding silicate melt evaporation and planetary accretion *** on the Hertz-Knudsen equation,the current theory often fails to predict observed isotope fractionations of laboratory experiments due to its oversimplified ***,we point out that the Hertz-Knudsen-equation-based theory is incomplete for silicate melt evaporation cases and can only be used for situations where the vaporized species is identical to the one in the *** propose a new model designed for silicate melt evaporation under *** model considers multiple steps including mass transfer,chemical reaction,and *** derivations reveal a kinetic isotopic fractionation factor(KIFF orα)αour model=[m(^(1.species)/m(^(2)species)]^(0.5),where m(species)is the mass of the reactant of reaction/nucleation-limiting step or species of diffusion-limiting step and superscript 1.and 2 represent light and heavy isotopes,*** model can eff ectively reproduce most reported KIFFs of laboratory experiments for various elements,i.e.,Mg,Si,K,Rb,Fe,Ca,and ***,the KIFF-mixing model referring that an overall rate of evaporation can be determined by two steps jointly can account for the eff ects of low P_(H2)pressure,composition,and *** addition,we find that chemical reactions,diffusion,and nucleation can control the overall rate of evaporation of silicate melts by using the fitting slope in ln(−ln f)versus ln(t).Notably,our model allows for the theoretical calculations of parameters like activation energy(E_(a)),providing a novel approach to studying compositional and environmental eff ects on evaporation processes,and shedding light on the formation and evolution of the proto-solar and Earth-Moon systems.

关键词： Evaporation Kinetic isotopic fractionation Chemical kinetics Hertz-Knudsen equation CAIS

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Features of sampling stream sediments of large river valleys under cryolithogenesis conditions in the Balygychan-Sugoy trough,North-East of Russia

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Acta Geochimica 2024年第4期43卷 638-660页

作者： Artem S.Makshakov Raisa G.Kravtsova A.P.Vinogradov Institute of geochemistry Siberian Branch of the Russian Academy of SciencesFavorskiy Str 1AIrkutskRussia 664033

Comprehensive research has been implemented to raise the efficiency of the geochemical survey of stream sediments(SSs)that formed under the cryolithogenesis *** authors analysed the composition,structure and specific features of the formation of exogenous anomalous geochemical fields(AGFs)identified through SSs of large river valleys of IV *** our case,these were the valleys of Maly Ken,Ken and Tap *** rivers are located in the central and southern parts of the Balygychan-Sugoy trough enclosed in the Magadan region,North-East of *** authors proposed a new technique to sample loose alluvium of SSs in the large river valleys along the *** profiles were located across the *** AGFs of Au,Ag,Pb,Zn,Sn,Bi,Mo and W were *** between elements have been *** elements are the main indicator elements of Au-Ag,Ag-Pb,Sn-Ag,Mo-W and Sn-W mineralization occurring on the sites under *** results obtained were compared with the results of geochemical surveys of *** is concluded that the AGFs recognized along the profiles reflect the composition and structure of eroded and drained ore zones,uncover completely and precisely the pattern of element distribution in loose sediments of large water *** alluvium fractionore *** of this fraction in the river valleys of IV order does not cause any difficulty,for this kind of material is *** developed technique of alluvium sampling within large river valleys is efficient in searching for diverse mineralization at all stages of prognostic *** is applicable for geochemical survey of SSs performed at different scales both in the North-East of Russia,as well as other regions with similar climatic conditions,where the SSs are formed under the cryolithogenesis conditions.

关键词： Stream sediments Large river valleys Geochemical fields Mineralization Indicator elements Geochemical survey

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Geochemical Tracing of ore-forming Material Sources of Carlin-type Gold {1. in the Yunnan-Guizhou-Guangxi Triangle Area --A Case Study of the Application of the Combined Silicon Isotopes geochemistry and Siliceous Cathodoluminescence Analysis

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Acta Geologica Sinica(English Edition) 1999年第1期73卷 30-39页

作者： LIU Xianfan NI Shijun LU Qiuxia JIN Jingfu ZHU Laimin 1. open lab of ore deposits geochemistry Institute of Geochemistry Chinese Academy of Sciences Guiyang 550002 2. Chengdu Institute of Technology Chengdu 610059

Abstract This paper deals with characteristics of silicon isotope compositions and siliceous cathodoluminescence of host rocks, ores and hydrothermal silicified quartz of the Carlin-type ore deposits in the Yunnan-Guizhou-Guangxi triangle area. The study shows that primary silicified quartz is nonluminescent but quartz in host rocks and secondary silicified quartz are luminescent by the action of cathode rays. Correspondingly, silicon isotope compositions of host rocks, ores and hydro6thermal quartz veins are clearly distinguished. In strata from the Middle Triassic to the “Dachang” host bed, δ30Si of the host rocks ranges from 0.0% ?0.3%, while that of primary ore-forming silicified fluids from ?0.1. to ?0.4%; in the Upper Permian and Lower Carboniferous strata and Indosinian diabase host beds, δ30Si of the host rocks is from ?0.1. to ?0.2% and that of the primary silicified quartz veins from 0.3 % ?0.5 %. This pattern demonstrates the following geochemical mineralization process, primary ore-forming siliceous fluids migrated upwards quickly along the main passages of deep-seated faults from mantle to crust and entered secondary faults where gold deposits were eventually formed as a result of permeation and replacement of the siliceous ore-forming fluids into different ore-bearing strata. This gives important evidence for the fact that ore-forming fluids of this type of gold deposits were mainly derived from upper mantle differentiation and shows good prospects for deep gold deposits and geochemical background for large and superlarge gold deposits.

关键词： silicon isotope siliceous cathodoluminescence tracing of ore-forming material source Carlin-type gold deposit Yunnan-Guizhou-Guangxi triangle area

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On the Mechanism of Transformation fromPrimary ores into Oxidized ores in FinelyDisseminated Gold deposits

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Acta Geologica Sinica(English Edition) 1998年第3期72卷 291-298页

作者： LIU Xianfan NI Shijun JIN Jingfu LU Qiuxia ZHANG Xingchun open {1. of ore deposits geochemistry Institute of Geochemistry Chinese Academy of Sciences Guiyang Guizhou 550002 Chengdu Institute of Technology Chengdu Sichuan 610059

This paper, taking the finely disseminated gold deposits in southwestern Guizhou and northwestern Guangxi as examples, discusses the difference between the occurrence of primary {1.s and that of oxidized {1.s, analyzes the occurrence mechanism in terms of crystallochemistry and geochemistry, and especially studies the chemical model for supergene leaching transformation of clay minerals in the two types of {1.s. This study proposes a new idea for dressing and smelting technology for primary gold {1.s.

关键词： occurrence of gold ore clay minerals supergene leaching transformation chemical model

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Complexation of Si in Hydrothermal Systems

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Chinese Journal Of geochemistry 2001年第3期20卷 201-209页

作者：樊文苓王声远田弋夫陈紫新 open {1.. of ore Deposit geochemistry Institute of Geochemistry Chinese Academy of Sciences Guiyang China

The Au\|SiO\-2 and Sn\|SiO\-2 complexes have been experimentally calibrated at varying temperature, silica concentration and pH: Au\+++H\-3SiO\+-\-4AuH\-3SiO\-4lgK=-1.65436+961..21.T Sn\+\{4+\}+4H\-3SiO\+-\-4Sn(H\-3SiO\-4)\-4lgK\-\{200℃\}=42.73Compared with Au\|Cl, Au\|HS and Sn\|OH complexes, AuH\-3SiO\-4 and Sn(H\-3SiO\-4)\-4 complexes can be recognized as the dominant transport forms in Si\|bearing solutions under pH and Eh conditions of general interest. The decrease of SiO\-2 concentration and oxygen fugacity would reverse the direction of dissolution\|complexing reactions, resulting in the precipitation of gold and silica, as well as cassiterite and silica. This study illustrates the significance of SiO\-2\|complexation in hydrothermal solutions for gold, tin and other metallizations.

关键词：金矿化作用硅化作用硅酸水岩反应

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Trace Elements in Fluid Inclusions in the Carlin-Type Gold deposits, Southwestern Guizhou Province

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Chinese Journal Of geochemistry 2001年第3期20卷 233-239页

作者：苏文超胡瑞忠漆亮方维萱 open {1.. of ore Deposit geochemistry Institute of Geochemistry Chinese Academy of Sciences Guiyang China

Fluid inclusions in quartz from the Lannigou and Yata Carlin\|type gold deposits in southwestern Guizhou were analyzed by inductively coupled plasma\|mass spectrometry for their trace elements (Co, Ni, Cu, Pb, Zn, Pt, etc.). The results show that quartz fluid inclusions entrapped at different {1.\|forming stages contain higher Co, Ni, Cu, Pb and Zn. It has been found for the first time that the {1.\|forming fluids responsible for the Carlin\|type gold deposits are rich in Pt. From this it can be concluded that basic volcanic rocks seem to be one of the important sources of {1.\|forming materials for the Carlin\|type gold deposits.

关键词：示踪元素 ICP-MS 金矿床贵州成矿流体

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X-Ray Diffraction Characteristics of Ceshui Formation Coal in Lianyuan Coal Basin

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Chinese Journal Of geochemistry 1998年第2期17卷 170-174页

作者：毕华 open {1.. of ore Deposit geochemistry Institute of Geochemistry Chinese Academy of Sciences Guiyang

On the basis of X-ray diffraction analysis of Ceshui Formation coal and its roof mud-stone in the Lianyuan coal basin, it is concluded that telemagnatic metamorphism is the main factor leading to the metamorphism of the Ceshui Formation coal in the study region, which has a great impact on the chemical structure of the Ceshui coal series, and the dynamometa-morphism is of local and secondary importance.

关键词： X射线衍射分析煤化学结构岩浆变质作用动力变质作用

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Super-Enrichment of Dispersed Elements and Associated ore {1.

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Chinese Journal Of geochemistry 2004年第1期23卷 46-51页

作者：高振敏姚林波 open {1.. of ore Deposit geochemistry Institute of Geochemistry Chinese Academy of Sciences Guiyang 550002 China

Dispersed elements do not always occur as associated elements in the ore {1. of other elements. Instead, they can constitute independent ore {1.. The focus of this paper is placed on the mechanism of super-enrichment of the four dispersed elements Tl, Ge, Se, and Te under favorable geological conditions, where their enrichment coefficients are so high that their abundances can reach n×1.+3-n×1.+4, sometimes even up to n×1.+6 times (e.g. Te) those of the crust. As a result, they can form their independent ore {1.. Studies have shown that such independent ore {1. are mostly distributed in the southwestern part of China, most of which belong to low-temperature ore {1., ranging in age from Yanshanian to Himalayan (Cretaceous to Cenozoic), with a significant time gap with the host strata. Moreover, this paper also deals with the existing forms (as independent minerals, occurring isomorphously and being adsorbed) of the dispersed elements in those independent ore {1.. The discovery of independent ore {1. of dispersed elements is a great breakthrough in the study of dispersed element metallogenesis.

关键词：沉积物地质条件元素富集地壳喜马拉雅山

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