Platinum‐Group Element Geochemical Characteristics of the Picrites and High‐Ti Basalts in the Binchuan Area, Yunnan Province
作者： BAI Mei , ZHONG Hong , ZHU Weiguang , BAI Zhongjie , HE Defeng
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摘要: The Binchuan area of Yunnan is located in the western part Emeishan large igneous province margin Yangtze Block. In present study, Wuguiqing profile thickness about 1440 m mainly composed high-Ti basalts, with minor picrites lower and andesites, trachytes, rhyolites upper have relatively higher platinum-group element (PGE) contents (ΣPGE=16.3–28.2 ppb), high Cu/Zr Pd/Zr ratios, low S (5.03–16.9 ppm), indicating parental magma S-unsaturated generated by degree partial melting (ELIP) mantle source. slightly Cu/Pd ratios (11 000–24 000) relative to that primitive suggest 0.007% sulfides been retained PGE basalts exhibit a wider range (ΣPGE=0.517–30.8 ppb). samples middle parts are depleted eNd (260 Ma) ranging from −2.8 −2.2, suggesting crustal contamination during ascent triggered sulfur saturation segregation 0.446%–0.554% sulfides, sulfide process may also provide ore-forming material for magmatic Cu-Ni-PGE deposits close studied basalts. this show Pt-Pd type mantle-normalized patterns, Pd/Ir than (Pd/Ir=1), obvious differentiation between Ir-group elements (IPGE) Pd-group (PPGE) controlled olivine or chromites fractionation evolution. Pd/Pt most average ratio (Pd/Pt=0.55), showing happened Pt Pd. be relevant hosted discrete refractory Pt-alloy phase mantle; whereas probably associated Fe-Pt alloys, coprecipitating Ir-Ru-Os alloys. Some basalt negative Ru anomalies, possibly due removal laurite collected early crystallized chromites.
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