Origin of Listwanite in the Luobusa Ophiolite, Tibet, Implications for Chromite Stability in Hydrothermal Systems   总被引：1，自引：0，他引：1  

ZHANG Lan  YANG Jingsui  Paul T. ROBINSON  XIONG Fahui  CHEN Yanhong  LAI Shengmin  CHEN Mei 《《地质学报》英文版》2015,89(2):402-417

Listwanite from the Luobusa ophiolite,Tibet,forms a narrow,discontinuous band along the eastern part of the southern boundary fault. We undertook a detailed petrographic and geochemical study to understand the mineral transformation processes and the behaviour of major and trace elements during listwanite formation. Three alteration zones characterized by distinct mineral components and texture are recognized and,in order of increasing degree of alteration,these are: zoneIII is rich in serpentine minerals; zoneII is rich in talc and carbonates; and zoneI is mainly composed of carbonates and quartz. Geochemical data for the three alteration zones show significant modification of some major and trace elements in the protolith,although some oxides show linear correlations with Mg O. Gold mineralization is recognized in the Luobusa listwanite and may signify an important target for future mineral exploration. Gold enrichment occurs in both zoneI and zoneIIand is up to 0.91 g/t in one sample from zoneI. We show that CO2-rich hydrothermal fluids can modify both the occurrence and composition of chromite grains,indicating some degree of chromite mobility. Low-Cr anhedral grains are more easily altered than high-Cr varieties. The compositions of chromite and olivine grains in the listwanite suggest a dunite protolith.  相似文献   

Critical Controlling Factors of Shale Gas Enrichment and Accumulation, and Remaining Uncertainties     

JIANG Zhenxue  TANG Xianglu  LI Zhuo  JI Wenming  YANG Wei  YUAN Yuan  WANG Pengfei  and XIONG Fengyang 《《地质学报》英文版》2015,89(Z1):251-252

<正>Shale gas exploration have yielded remarkable achievements recently in China,and four national demonstration areas for shale gas exploration and production have been established respectively as FulingJiaoshiba,Changning-Weiyuan,Zhaotong and Yanchang.During recent few years,nearly 400 wells have been drilled including 143 exploratory wells(vertical wells)and  相似文献   

Zircon U-Pb Geochronology and Geochemical Characteristics of the Volcanic Host Rocks from the Tongyu VHMS Copper Deposit in the Western North Qinling Orogen and Their Geological Significance     

XIONG Xiao  ZHU Laimin  LI Ben  ZHANG Guowei  GONG Hujun  ZHENG Jun  JIANG Hang 《《地质学报》英文版》2015,89(6):1926-1946

Precise in situ zircon U-Pb dating and Lu–Hf isotopic measurement using an LA-ICP-MS system, whole-rock major and trace element geochemistry and Sr–Nd isotope geochemistry were conducted on the volcanic host rocks of the Tongyu copper deposit on the basis of further understanding of its geological characteristics. Three zircon samples from the volcanic host rocks yielded 206Pb/238 U weighted average ages ranging from 436±4 Ma to 440±5 Ma, which are statistically indistinguishable and coeval with the ca. 440 Ma northward subduction event of the Paleo-Qinling oceanic slab. The volcanic host rocks were products of magmatic differentiation that evolved from basalt to andesite to dacite to rhyolite, forming an integrated tholeiitic island arc volcanic rock suite. The primitive mantle-normalized trace element patterns for most samples show characteristics of island arc volcanic rocks, such as relative enrichment of LILE(e.g. Th, U, Pb and La) and depletion of HFSE(e.g. Nb, Ta, Ti, Zr and Hf). Discrimination diagrams of Ta/Yb vs Th/Yb, Ta vs Th, Yb vs Th/Ta, Ta/Hf vs Th/Hf, Hf/3 vs Th vs Nb/16, La vs La/Nb and Nb vs Nb/Th all suggest that both the volcanic host rocks from the Tongyu copper deposit and the volcanic rocks from the regional Xieyuguan Group were formed in an island arc environment related to subduction of an oceanic slab. Values of ISr(0.703457 to 0.708218) and εNd(t)(-2 to 5.8) indicate that the source materials of volcanic rocks from the Tongyu copper deposit and the Xieyuguan Group originated from the metasomatised mantle wedge with possible crustal material assimilation. Most of the volcanic rock samples show good agreement with the values of typical island arc volcanic rocks in the ISr-εNd(t) diagram. The involvement of crustal-derived material in the magma of the volcanic rocks from the Tongyu copper deposit was also reflected in the zircon εHf(t) values, which range from-3.08 to 10.7, and the existence of inherited ancient xenocrystic zircon cores(2616±39 Ma and 1297±22 Ma). The mineralization of the Tongyu copper deposit shows syn-volcanic characteristics such as layered orebodies interbedded with the volcanic rock strata, thus, the zircon U-Pb age of the volcanic host rocks can approximately represent the mineralization age of the Tongyu copper deposit. Both the Meigou pluton and the volcanic host rocks were formed during the ca. 440 Ma northward subduction of the Paleo-Qinling Ocean when high oxygen fugacity aqueous hydrothermal fluid released by dehydration of the slab and the overlying sediments fluxed into the mantle wedge, triggered partial melting of the mantle wedge, and activated and extracted Cu and other ore-forming elements. The magma and ore-bearing fluid upwelled and erupted, and consequently formed the island arc volcanic rock suite and the Tongyu VHMS-type copper deposit.  相似文献   

Formation and Evolution of a Paleosol across the Lower Silurian-Lower Permian Boundary in Zunyi District, Northern Guizhou, China and Its Paleoenvironment and Paleoclimate Implications     

XIONG Xiaohui  XIAO Jiafei  HU Ruizhong  WANG Jian  WANG Yi  WANG Xinsong  DENG Qi 《《地质学报》英文版》2015,89(6):2012-2029

This paper presents a set of bulk geochemical and mineralogical data from a paleoweathering profile located in Zunyi District, Northern Guizhou, China. It was formed at the top of the Hanjiadian Formation of the Lower Silurian. A truncated, argillic, gleyed, kryptic paleospodosol is recognized in the paleoweathering profile. Ratios of immobile elements (Ti/Zr, Ti/Al) and their binary (e.g., Nb vs. Zr/TiO2 and Th/Sc vs. Zr/Sc), triangular diagrams (La-Th-Sc, Th-Sc-Zr/10, Zr-Cr-Ga) reflect that the Gaojiayan paleosol is the product of in-situ weathering of gray-green silty mudstone of the underlying Hanjiadian Formation. Mass balance calculations indicate K enrichment and Na enrichment in the upper and lower portions of paleosol, respectively. These findings both are the results of transgression, which brings substantial concentrations of such elements as K, Na, and Sr. In particular, K enrichment is achieved by the illitization of kaolinite. The biological processes of terrestrial vascular plants also enhance K concentration, especially at the top of the paleosol. Na enrichment is a consequence of albitization and/or adsorption by clay minerals through cation exchange. The mass distributions and relative mass changes of rare earth elements (REEs) in the studied profile display characteristics of vertical zonation. Three peaks in total REEs content are observed, indicating two paleoclimatic or paleoenvironmental changes. Mineralogical characteristics indicate that the paleoclimate changed first from warm and humid to cold and dry and later, to dry and lightly warmer. The corresponding soil environment varies from weakly acidic to strongly alkaline and later, to weakly acidic. Mass translocation characteristics of REEs and several transition metals suggest that the Gaojiayan paleosol may have undergone top erosion.  相似文献   

The Study of Deep Mineral Association in Chromitites of the Hegenshan Ophiolite, Inner Mongolia, China     

HUANG Zhu  YANG Jingsui  ZHU Yongwang  XIONG Fahui  LIU Zhao  ZHANG Zhongming  XU Wei 《《地质学报》英文版》2015,89(Z2):30-31

<正>Previously reported in the Mesozonic Tibet and the early Paleozoic Polar Ural,Russia,diamond and other deep minerals are found in ophiolite mantle peridotite chromite that need to be reconsidered ophiolite and chromite traditional understanding of the causes of shallow.The ophiolitic chromitite can be divided two classes,the high-Cr chromitite and high-Al chromitite.  相似文献   

Podiform Chromitites and Mantle Peridotites of the Purang Ophiolite, Western Yarlung-Zangbo Suture Zone, Tibet: Implications for Partial Melting and Melt-Rock Interaction in Oceanic and Subduction-Related Settings     

GAO Jian  YANG Jingsui  XIONG Fahui 《《地质学报》英文版》2015,89(Z2):12-12

<正>The Purang ophiolite,which crops out over an area of about 650 km~2 in the western Yarlung-Zangbo suture zone,consists chiefly of mantle peridotite,pyroxenite and gabbro.The mantle peridotites are mostly harzburgite and minor lherzolite that locally host small pods of dunite.Some pyroxenite and gabbro veins of variable size occur  相似文献   

Composition and Textual Characterization of Platinum-group Mineral (PGM) in Chromites from Zedang Ophiolite in Tibet, China     

GUO Guolin  YANG Jingsui  PAUL T. Robinson  XIONG Fahui  XU Xiangzhen  LIU Xiaodong  LIJinyang  LIU Zhao 《《地质学报》英文版》2015,89(Z2):16-17

<正>1 Introduction Platinum-group elements(PGE)are mainly concentrated in some specific minerals known as PGMs,which commonly occur in podiform chromites of ophiolites.In-situ PGM assemblages in chromites can provide valuable information on the physico-chemical nature of the parental melt(s)from which chromitite  相似文献   

Diamond Discovered in Dangqiong Ophiolite, Western Yarlung-Zangbu Suture Zone, Tibet     

XIONG Fahui  YANG Jingsui  Robinson T.PAUL  XU Xiangzhen  BA Dengzhu  LI Yuan  LIJinyang  ZHANG Zhongming  RONG He 《《地质学报》英文版》2015,89(Z2):99-100

<正>The first diamonds from ophiolite were found in peridotite of Luobusa ophiolite along Yarlung Zangbu suture zone in Tibet,China(IGCAGS,1981),and then more and more diamonds found in harzgurgite(Bai et al.,1993;Yang et al.,2007a;Robinson et al.,2014;Xu et al.,  相似文献   

Diopside and Magnetite Exsolutions in Olivine from Lower Cr# Dunite in the Dongbo Ophiolite, Southern Tibet     

XIONG Fahui  YANG Jingsui  Robinson T PAUL  Dilek YILDIRIM  CHEN Yanhong  XUXiangzhen  LIU Zhao  TIAN Yazhou  ZHOU Wen  LAI Shengming  ZHANG Lan 《《地质学报》英文版》2015,89(Z2):101-101

<正>Diopside and magnetite exsolutions occur as oriented intergrowths within olivine of the lower Cr~#dunite in the Dongbo ophiolite,Tibet.The fresh lower Cr~#dunite has a mineral assemblage of olivine,spinel and diopside.The Fo content of its olivine is 90–92,which is lower than that of the higher Cr~#dunite lenses(Fo92-Fo94)without  相似文献   

The Lower Mantle Minerals in Ophiolite-hosted Diamond     

YANG Jingsui  WIRTH Richar  XIONG Fahui  TIAN Yazhou  HUANG Zhu  ROBINSON Paul T.  DILEK Yildirim 《《地质学报》英文版》2015,89(Z2):108-109

<正>Ophiolites are fragments of ancient ocean lithosphere emplaced on continental margins,in island arcs or in accretionary prisms,and have long been studied to better understand the evolution of ocean basins and collision of tectonic plates,the processes of mountain building and the occurrence of valuable ore bodies,such as podiform  相似文献