Zircon Shrimp U-Pb Geochronology?geochemistry Of The Early Palaeozoic Qingshuihe Granite With Pb-Zn Mineralization In Baoshan Block And Implications For Ore-forming Tectonic Setting

The Baoshan Block is one of the important branches of the Tethyan orogen of western Yunnan.The Qingshuihe granite is located in the north of Baoshan Block,include two-mica porphyritic granite and musconvite porphyritic.These rocks are high alumina content and strongly peraluminous,with Al₂O₃=12.57¹4.8 4wt.%,A/CNK ratios of 1.22¹.76,and CIPW normative corundum contents of 2.50⁵.62wt.%,are calc-alkaline.They are enriched in LILEs?e.g.,Rb,K?and Pd,depleted in HFSEs,they show similar chondrite-normalized REE pattern,with negative Eu anomalies??Eu=0.31⁰.54?.SHRIMP U-Pb ages of 473Ma⁴62Ma for two-mica porphyritic granite and 479Ma for musconvite porphyritic,they were emplaced in Early Palaeozoic.The geochemical signatures and analysis of Sr-Nd-Pb isotopes indicate that they are S-type granite in character and were derived from anatexis of ancient metasedimentary rocks,whild small amount of mantle-derived components were introduced into the magma sources for two-mica porphyritic granite.We propose these ca.492Ma⁴73Ma musconvite porphyritic granite can be derived from partial melting of ancient crustal materials caused by the compression.furthermore,these ca473Ma⁴60Ma two-mica porphyritic granite were formed in the tectonic setting of the thickened lithospheric delamination following the final amalgamation of outboard microcontients onto the East Gondwana margin.Trough the comparasion of two-mica porphyritic granite and musconvite porphyritic to Chain granitioid,Qingshuihe granite are commomly enrich in ore-forming elements?e.g.,Cu?W?Sn?Au?Zn?and mineralizer elements?e.g.,B?F?Ba?Bi?.