Deep origin of both the Kangjinla podiform chromite deposit and its host rock peridotite in southern Tibet

The Yarlung Zangbo ophiolites in southern Tibet are remnants of the Neo-Tethys oceanic lithosphere and are considered as the last suture zone representing the breakup and reconnection of Gondwana during Mesozoic. Recently, many unusual mantle minerals with the possible deep source (>300km) have been reported from podiform chromite deposit in the Luobusa ophiolite within the eastern Yarlung Zangbo suture zone, Tibet. This new finding has attracted high attention in geosciences field and arose many significant issues: does these deep mantle minerals also occur in other chromitite deposite in the region? Can we discover the similar mantle minerals from the mantle rocks associated with the chromitite? What is the origin of the chromitite and mantle rocks? This paper is to report the main features of the Kangjinla chromite deposit and its host rock peridotite in the Luobusa ultramafic body, southern Tibet, based on studies in mineralogy, petrology and geochemistry. The preliminary results include (1) The peridotite is the remnants of partial melted MOR mantle altered by SSZ fluids; (2) over 1000 diamond grains and many other unusual mantle minerals have been discovered in chromitite; (3) a great deal of diamond grains and unusual mantle minerals firstly discovered from peridotite, the host rocks of chromitite orebody. The results indicate the chromitite has a genetic relationship with the host rock peridotite.