Implications of unusual minerals in Zedang mantle peridotite, Tibet

Abstract: The mineral assemblage of such minerals as diamond and moissanite has been discovered in several mantle peridotites in Yarlung Zangbo ophiolite belt. The authors collected 526 kg harzburgite rocks from Zedang mantle peridotite for artificial heavy mineral research so as to further investigate the physical and chemical environment of these unusual minerals. Diamond, moissanite and more than 30 other mineral species were discovered, similar to the result of other mantle peridotite in the Yarlung Zangbo ophiolite belt. These unusual minerals show that high pressure, super-reduction conditions and numerous continental crust materials existed in mantle peridotite, suggesting that ancient crust might have experienced continental deep subduction or lithosphere delamination into mantle or even into mantle transition zone (410-660 km) at the early stage; subsequenty these crustal materials were modified in an environment of high pressure and super-reduction in the deep mantle, and surged upward to shallow crust by mantle plume or mantle convection process. Unusual minerals were trapped within the mantle peridotite in such a recycling process. It is of great significance to understend crust mantle exchange and deep mantle dynamics for comprehensive research on mineralogy of unusual mineral assemblages in mantle peridotite.