Feng Guang-ying1, Yang Jing-sui1, Liu Shen2, Niu Xiao-lu1, Xiong Fa-hui1, Liu Fei1
(1. CARMA, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China；
2. State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, Xi’an 710069, China)
Abstract: For the origin and tectonic setting, feature of Platinum-group elements (PGEs) from Cuobuzha peridotites in western Yarlung-Zangbo suture zone was reported in this study. The studied peridotite mainly consists of Cpx-harzburgite and harzburgite. The Cpx-harzburgite is characterized by higher PGEs content (22.31×10-9－36.12×10-9) than primitive mantle, and with a average of 29.60×10-9, whereas, the harzburgite has lower PGEs content (17.34×10-9－25.18×10-9) than the primitive mantle. Compared with magmatic ultramafic rocks, two types of rocks are characterized by higher Os and Ir, implying that they are residual mantle rocks after partial melting and melt extraction. In addition, the Cpx-harzburgites and some harzburgites are characterized by high Pd content, (Pd/Ir)m ratio, low Cu/Pd ratio, and left-leaning PGE model. Based on the above discussion, we suggest that the harzburgite are the residual mantle rocks resulted from higher degree of partial melting of the cpx-harzburgite. There may be residual sulfides which have not been totally melted into the silicate melt. At the same time, melt supersaturated in sulfur probably added to the peridotites by melt-rock reaction in the suprasubduction zone.
Keywords: western Yarlung-Zangbo suture zone; peridotite; Platinum group elements; Cuobuzha
ACTA MINERALOGICA SINICA Vol. 36, No. 3, 2016, Page 309-317
