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Origin of Listwanite in the Luobusa Ophiolite, Tibet, Implications for Chromite Stability in Hydrothermal Systems
作者姓名:ZHANG Lan  YANG Jingsui  Paul T. ROBINSON  XIONG Fahui  CHEN Yanhong  LAI Shengmin  CHEN Mei
作者单位:1 School of the Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China.2 CARMA, State Key Laboratory for Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China
基金项目:We thank Ba Dengzhu for assistance with the field work, Rong He for the microprobe analyses and the China National Research Center for the geochemical analyses. This research was funded by National Natural Science Foundation of China (Grant No. 40930313) and the China Geological Survey (Grants No. 12120114061801; No.12120114057701; and No.12120114061501).
摘    要: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.

关 键 词:Listwanite  mineralogy  geochemistry  gold  mineralization  chromite  stability
收稿时间:1/1/2015 12:00:00 AM
修稿时间:2015/1/27 0:00:00

Origin of Listwanite in the Luobusa Ophiolite, Tibet, Implications for Chromite Stability in Hydrothermal Systems
Authors:ZHANG Lan  YANG Jingsui  Paul T ROBINSON  XIONG Fahui  CHEN Yanhong  LAI Shengmin and CHEN Mei
Institution:ZHANG Lan;YANG Jingsui;Paul T.ROBINSON;XIONG Fahui;CHEN Yanhong;LAI Shengmin;CHEN Mei;School of the Earth Sciences and Resources,China University of Geosciences;CARMA,State Key Laboratory for Continental Tectonics and Dynamics,Institute of Geology,Chinese Academy of Geological Sciences;
Abstract: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 MgO. 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 zoneII and 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.
Keywords:Listwanite  mineralogy  geochemistry  gold mineralization  chromite stability
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