Abstract
The Xigaze ophiolite, which lies in the middle section of the Yarlung Zangbo suture zone (YZSZ) of southern Tibet, is composed from the base upward of tectonized harzburgites with minor dunites, and a magmatic sequence of wehrlites, pyroxenites, troctolites and gabbros. Both abundant high-Cr, metallurgical and sparse, dunites occur within the harzburgites. The peridotites show abundant evidence of mantle melt extraction at various scales as indicated by the Fo values of olivine (92.4–93.5) in the harzburgites and 92.8–94.0 in the dunites. Whole-rock MgO contents are 41–50wt%, similar in composition to forearc peridotites. Most of the chromitites have high Cr# numbers (61–81), although there are systematic changes in olivine and chromian spinel compositions from harzburgites, to dunites to chromitites, reflecting variable partial melting and melt-rock reaction. The primitive mantle U-shaped rare earth element (REE) patterns of the harzburgites indicate refertilization of depleted peridotites by suprasubduction melts. The PGE abundances in the Xigaze rocks provide additional constraints on their geochemical evolution and show multiple episodes of melt extraction from the mantle source, giving it a subchondritic character. Compositional zoning of minerals likewise attest to modification by migrating melts, formed in a suprasubduction zone mantle wedge.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
