Origin And Related Mineralization Of Listwanite From Southeastern Boundary Of The Luobusa Ophiolite, Tibet

Listwanite from Luobusa ophiolite, Tibet, forms a narrow discontinuous band along the southern boundary fault by hydrothermal alteration of mantle peridotite. Our mineralogy and geochemistry studies aim to figure out the mineral transformation process and major, trace elements behaviors in the Luobusa listwanite system, which record different stage of peridotite carbonation. Four alteration zones characterized by distinct mineral textures are recognized: Perodotite Zone is least altered, Serpentinite Zone is rich in serpentine minerals; Talc-magnesite Zone is rich in talc and carbonate minerals; Quartz-magnesite Zone is mainly composed of carbonate minerals and quartz. Geochemistry data of three zones show significant modification, though some oxides show linear correlations trend with MgO. Chondrite-normalized REE patterns for peridotite, Talc-magnesite Zone and Serpentinite Zone, both show two U-shaped segments but great variations occur for Quartz-magnesite Zone listwanite. Au enrichment in Luobusa listwanite was previously unrecognized and may signify an important target for future mineral exploration. Quartz-magnesite Zone show Au enrichment and Au content can be 0.91 g/t. Based on detailed statistics study, we find that CO₂-rich hydrothermal fluids can modify chromite grains, both for their composition and occurrence, especially for those anhedral chromites with low chromium content, which indicate that chromium is mobile to some extent. Based on the field occurrence and regional geology, the Luobusa listwanite was most likely formed ¹9-10 Ma.