科研之友
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摘要
The granitoids in Saishitang Cu deposit of the West Qiling terrane consist of diorite porphyrite, quartz diorite, quartz diorite porphyrite, granite porphyry and quartz porphyry. Their magma sources and tectonic setting can provide vital constrains on the evolution of the Paleotethyan Ocean and regional metallogenesis. Geochemical analyses indicate that these granitoids belong to metaluminous calc-alkaline to high-K talc-alkaline rock series with similar geochemical charcacteristics of I-type granite. They have variable Mg-# values of 39 similar to 68, high (La/Yb)(N) ratios of 8.50 similar to 22.9 with LREE enrichment, HREE depletion and negative Eu anomalies (delta Eu = 0.28 similar to 0.78). They are enriched in LILE (Cs, Rb, K and Pb), depleted in HFSE (Nb, Ta and Ti), showing typical features of subduction-related arc granitoids. Zircon SHRIMP U-Pb dating of quartz diorite porphyrite and quartz porphyry yields concordant ages of 219.0 +/- 2.3Ma and 220.0 +/- 2.0Ma, repectively. Their epsilon H-f(t) values of magmatic zircons are -4.5 similar to -2.1 and -2.5 similar to +1.0, with conresponding t(DM2), ages of 1392 similar to 1544Ma and 1190 similar to 1415Ma, respectively. In combination with previous results on Triassic granitoids in the West Qinling terrane and A' nymaqen ophiolitic melange, we suggest that the coeval granitoids in the Saishitang Cu deposit and West Qinling terrane should be formed in continental margin arc environment by northward subduction of the Paleotethyan Ocean. They should mainly originate from the partial melting of Mesoproterozoic lower-crustal metabasic rocks and were contaminated by mantle-derived magmas.
- 出版日期2016-7
- 单位中国科学院大学; 中国地质科学院矿产资源研究所; 合肥工业大学
