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Origin of Listwanite in the Luobusa Ophiolite, Tibet, Implications for Chromite Stability in Hydrothermal Systems
Author(s) -
Lan ZHANG,
Jingsui YANG,
ROBINSON Paul T.,
Fahui XIONG,
Yanhong CHEN,
Shengmin LAI,
Mei CHEN
Publication year - 2015
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/1755-6724.12438
Subject(s) - chromite , protolith , ophiolite , geology , hydrothermal circulation , geochemistry , mineral , petrography , olivine , plagioclase , mineralogy , quartz , talc , metamorphic rock , chemistry , tectonics , paleontology , seismology , organic chemistry
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: zone III is rich in serpentine minerals; zone II is rich in talc and carbonates; and zone I 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 zone I and zone II and is up to 0.91 g/t in one sample from zone I . We show that CO 2 ‐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.