滇西南澜沧江带红豆山铜矿花岗斑岩地质地球化学特征及成岩时代

摘要

南澜沧江火山弧带红豆山花岗斑岩属于过铝质钾玄岩性S型花岗岩,SiO2含量为71.1%~74.4%,全碱含量高(K2O+Na2O=8.4%~9.4%),富钾(K2O/Na2O=3.9~5.0),铝饱和指数(A/CNK)为1.06~1.21;具轻稀土元素富集特征,负Eu异常(δEu=0.53~0.74);相对富集大离子亲石元素(LILE,如Rb、Ba、Th、U等),但亏损Sr、P、Ti等元素.地球化学特征表明,红豆山花岗斑岩具火山弧花岗岩与同碰撞花岗岩的特征,为活动大陆边缘弧的产物.红豆山花岗斑岩的LA-ICP-MS锆石U-Pb年龄为220.3±3.6Ma,形成于晚三叠世.红豆山花岗斑岩的地球化学特征和形成时代与小定西组基性火山岩非常相似,两者是同一期岩浆活动不同阶段的产物.%The Hongdoushan granite porphyry in the South Langcangjiang volcanic arc zone is a peraluminous and shoshonite S-type granitoid. The granite porphyry contains 71.1%~74.4% of SiO2, high total alkalis (K2O+Na2O=8.4%~9.4%), high K and high A/CNK of 1.06~1.21, and is characterized by enrichment of light rare earth elements with negative europium anomalies (δEu=0.53~0.74), relative enrichment of large ion lithophile elements (LILE) such as Rb, Ba, Th and U, and relative depletion of Sr, P and Ti. Geochemical features indicate that the Hongdoushan granite porphyry has characteristics of volcanic arc granite and syn-collision granite, and is epicontinental arc-volcanic rock. LA-ICP-MS zircon U-Pb dating age of the Hongdoushan granite porphyry is 220.3±3.6Ma, indicating that the rock was formed during Late Triassic. Geochemical features and formation age of the Hongdoushan granite porphyry is very similar to features of basic volcanic rock of Xiaodingxi Formation, which suggests that they are products of different stages of the same magmation.