地质通报2012，Vol.31Issue(9)：1420-1434,15.
冈底斯东段古新世朱拉岩体LA-ICP-MS锆石U-Pb定年和岩石地球化学特征
LA-ICP-MS zircon U-Pb dating and geochemical characteristics of Zhula intrusion in eastern Gangdise, Tibet
摘要
Abstract
Field investigation has found that Zhula intrusion consists of biotite monzogranite with abundant dioritic enclaves, and there exists gradually transitional relationship between the enclaves and their host rock. Zircon LA-ICP-MS U-Pb dating of 3 samples from the granite yielded the ages of 64,6±0.8Ma,64.3± 0.8Ma and 63.9±0,5Ma respectively, with a surface age of 776Ma of inherited zircon. A dioritic enclave samples yielded the age of 66.1±0.3Ma. The dioritic enclaves have rich Fe and high alkalinity as well as poor Si, Mg and Ca, thus belonging to aluminous, high-K cale-alkaline series; they have Nb/Ta ratio of 15.9, Sr/Y ratio of 3.69, LREE/ HREE ratio of 1.92, substantial negative Eu anomalies, higher LILE(Rb,K) and RHE(U,Th) concentrations, lower HFSE (Nb, Ta, Sr, Ti) concentrations relative to the primordial mantle, thus indicating that dioritic magma originated from partial melting of the mantle. The host rocks have rich Si, K, and poor P, belonging to meta-aluminous and aluminous and cale^alkaline to high-K cale-alkaline series, they have Nb/Ta ratio of 15.9, higher LILE(Rb, K), lower HFSE(Nb, Ta, Ba, P, Ti), similar to calc-alkaline rocks in island arc or active continental margin. The host rocks and enclaves might have been derived from the same magmatic processes- The enclave rocks originated from crystallization differentiation of mantle source magma assimilating and contaminating some crust materials, while the host rocks originated from crystallization differentiation of large quantities of crustal magma mixed with some mande sourced magma. In combination with previous research results, the authors hold that the petrogenesis might have been related to the northward subduction of the Yarlung Zangbo Ocean.关键词
花岗岩类/闪长质包体/LA-ICP-MS锆石U-Pb定年/岛弧/雅鲁藏布江大洋/冈底斯东段Key words
granitoid/ dioritic enclave/ LA-ICP-MS zircon U-Pb dating/ island arc/ Yarlung Zangbo Ocean/ eastern Gangdise分类
天文与地球科学引用本文复制引用
李奋其,刘伟,张士贞,王保弟..冈底斯东段古新世朱拉岩体LA-ICP-MS锆石U-Pb定年和岩石地球化学特征[J].地质通报,2012,31(9):1420-1434,15.基金项目
中国地质调查局项目《冈底斯成矿带基础地质综合研究》(编号:1212011086039) （编号:1212011086039）
