The prospects of chromitite in ophiolite of Yarlung Zangbo Suture Zone, Tibet

Abstract: Podiform chromitite is the main source of chromium, and is a kind of important strategic material of extreme shortage in China; therefore, the study of chromitite and peridotite has become the first way to solve the long-term dependence on imports. In this study, the authors focused on the main ultramafic body and chromitite from Yarlung Zangbo ophiolite belt. On the basis of field geological work, the authors summarized the sequence of ophiolite, mineral composition, geochemistry, Re-Os isotopic composition and other characteristics, so as to discuss the formation of chromite and mantle peridotite. Some conclusions have been reached: (1) The ophiolite in different segments of Yarlung Zangbo suture zone exhibits quite different rock assemblages, with different tectonic evolution backgrounds, which proves the heterogeneity of Tethys evolution; (2) There are two types of high aluminum and high chrome chromitie found in western YZSZ, and the mineral chemical characteristics of chrome spinel have recorded traces of different tectonic settings, mineralogy and geochemistry; (3) The mineralogy and geochemistry of mantle peridotites peridotite and chromite have both the features of deep mantle peridotite and the island arc mantle peridotite, suggesting multi-processes of rock/melt reaction and partial melting; (4) The podiform chromite formation experienced multiple stages, from the early subduction to the mantle transition zone; driven by plume / mantle convection, the materials migrated onto the top of the transition zone, where they condensed and consolidated, and reacted with harzburgite in the emplacement process under a subduction zone environment; (5) The diamond and other UHP minerals extensively exist in all of the Yarlung Zangbo suture zone, with the western part bearing similarity to Luobusha in that they both experienced the same tectonic setting and ore mineralization, thus having potential for further prospecting.