摘要
为进一步丰富对东昆仑造山带成矿动力学背景的整体认识,针对加里东期花岗岩构造岩石和形成环境研究尚不够深入,选取位于东昆仑造山带西段,北昆仑岩浆弧的妥拉海沟地区花岗岩,开展了花岗岩成因研究,分析了其形成环境,为该地区构造演化历史提供了新资料。结果表明:妥拉海沟地区似斑状花岗闪长岩中获得的锆石U-Pb年龄为(406±2)Ma,形成于早泥盆世。地球化学分析结果体现了中-高钾钙碱性,多呈过铝质、少数呈偏铝质系列花岗岩特点,过碱指数为0.31~0.68,平均0.45;Nb、Zr、Y、Ce含量均较低;轻重稀土元素之比为5.09~13.14,稀土配分模式图显示出物源的复杂性;部分样品显示为正铕异常的右倾型曲线,显示了物源中地幔物质的参与;微量元素表现出明显的Ta、Sr、Sm、Ba、Nb、P、Ti等元素亏损,Ba、Th、K、Zr、Hf等元素富集;Sr-Nd同位素分析结果显示,I_(Sr)值为0.69464~0.72859,双阶段模式年龄t_(DM2)为1287~1789 Ma,ε_(Nd)(t)为-7.9~-1.72,兼具S型和Ⅰ型花岗岩特征,其物源为壳幔混合源。综合岩石地球化学特征及前人研究成果,妥拉海沟地区早泥盆世花岗岩属于后碰撞造山阶段的产物。
In order to further enrich the overall understanding of the metallogenic dynamic background of the East Kunlun orogenic belt,considering that the Caledonian granite tectonic rocks and formation environment are not deeply studied,the granite in the Tola Valley area located in the west part of the East Kunlun orogenic belt and the North Kunlun magmatic arc is selected to carry out detailed studies on the chronology,geochemical characteristics and Sr-Nd isotopes.The tectonic environment is discussed,which provides new data for the tectonic evolution history of this area.The results show that the zircon U-Pb age from the porphyritic granodiorite in the Tolahaigou area is(406±2)Ma,and the formation age is early Devonian.The geochemical analyses indicate that the granites are medium-to high-potassium calc-alkaline rocks,predominantly peraluminous with a few meta-aluminous members.The peralkali index range from 0.31 to 0.68,averaging at 0.45.Low contents of Nb,Zr,Y and Ce were observed in these rocks while the ratio of heavy rare earth elements to light rare earth elements ranges between 5.09 and 13.14 indicating complex source heterogeneity.Some samples exhibit right-leaning curves of positive europium anomalies,suggesting the involvement of mantle-derived materials in the source.The trace element data reveal significant deficiencies in Ta,Sr,Sm,Ba,Nb,P and Ti with enrichments in Ba,Th,K,Zr and Hf.Sr-Nd isotope analysis indicates I_(Sr)values ranging from 0.69464 to 0.72859,two-stage model ages t_(DM2)between 1287 Ma and 1789 Ma andε_(Nd)(t)values ranging from-7.9 to-1.72 indicating of a mixed crust-mantle source for both S-type andⅠ-type granites.According to the geochemical characteristics of the rocks and previous research findings,it can be inferred that the early Devonian granites in the Tuolahaigou area are products of post-collision orogeny.
作者
赵明福
董基恩
祁昌炜
魏有宁
董小军
ZHAO Mingfu;DONG Jien;QI Changwei;WEI Youning;DONG Xiaojun(Qinghai Geological Survey Bureau,Xining,Qinhai 810000,China;Technology Innovation Center for Exploration and Exploitation of Strategic Mineral Resource in Plateau Desert Region,Ministry of Natural Resources,Xining,Qinhai 810000,China)
出处
《中国锰业》
2024年第5期31-39,共9页
China Manganese Industry
基金
青海省科协中青年科技人才托举工程(编号:2023QHSKXRCTJ47)
青海省地质勘查基金项目(编号:青国土资[2018]260)。
