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引用本文:樊新祥,孔维琼,杨镇熙,赵吉昌,李昱星. 北祁连造山带西段车路沟岩体U-Pb年代学、地球化学特征及岩石成因[J]. 中国地质, 2020, 47(3): 755-766.
FAN Xinxiang,KONG Weiqiong,YANG Zhenxi,ZHAO Jichang,LI Yuxing. U-Pb chronology, geochemical characteristics and petrogenesis of the Chelugou pluton in the western part of North Qilian orogenic belt[J]. Geology in China, 2020, 47(3): 755-766(in Chinese with English abstract).
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北祁连造山带西段车路沟岩体U-Pb年代学、地球化学特征及岩石成因
樊新祥1, 孔维琼2, 杨镇熙1, 赵吉昌1, 李昱星1
1.甘肃省地质矿产勘查开发局第四地质矿产勘查院, 甘肃 酒泉 735000;2.兰州新区自然资源局, 甘肃 兰州 730000
摘要:
车路沟岩体位于北祁连造山带最西端,岩石类型以英云闪长玢岩和闪长玢岩为主。本次对英云闪长玢岩进行U-Pb年代学研究,获得加权平均年龄为(462.1±3.8)Ma,表明岩体形成于中奥陶世。岩石地球化学分析结果显示,英云闪长玢岩中SiO2含量60.37%~66.73%,Al2O3含量15.65%~16.45%,Na2O/K2O值7.47~9.96,A/CNK为0.90~1.00,属中酸性岩系列,显示相对富钠、低钾的特征,A/CNK=0.90~1.00,属于准铝质低钾钙碱性系列;稀土总量较低(33.40×10-6~39.27×10-6),LREE/HREE值为3.95~6.51,在稀土元素配分图解上呈现出右倾特征;δEu值1.23~1.49之间,呈现Eu呈正异常特征;在微量元素原始地幔标准化图解上,显示富集Ba、Sr,亏损Nb、Ti、Yb高场强元素的特征。对车路沟岩体地质、地球化学特征与产出背景的全面分析,认为其为奥陶纪祁连洋持续向华北板块俯冲,诱使俯冲洋壳部分熔融形成的埃达克岩。
关键词:  车路沟岩体  锆石U-Pb  洋壳俯冲  北祁连造山带  埃达克岩
DOI:10.12029/gc20200314
分类号:P597;P588.1
基金项目:中国地质调查局项目“祁连成矿带肃南—大柴旦地区地质矿产调查”(DD20160012)资助。
U-Pb chronology, geochemical characteristics and petrogenesis of the Chelugou pluton in the western part of North Qilian orogenic belt
FAN Xinxiang1, KONG Weiqiong2, YANG Zhenxi1, ZHAO Jichang1, LI Yuxing1
1.Fourth Institute of Geological and Mineral Exploration of Gansu Bureau of Geology and Mineral Resources, Jiuquan 735000, Gansu, China;2.Lanzhou New Area Natural Resource Bureau, Lanzhou 730000, Gansu, China
Abstract:
Located at the westernmost end of the North Qilian orogenic belt, the Chelugou pluton consists predominantly of quartz diorite porphyry and diorite porphyry. Zircon LA-ICP-MS U-Pb dating of the Chelugou quartz diorite porphyry yielded an age of (462.1±3.8) Ma. Rocks from the Chelugou pluton show intermediate-felsic, metaluminous and low calc-alkaline features, with relatively low SiO2 (61.44%-67.63%), Al2O3 (15.09%-16.7%) and A/CNK values (0.90-1.00), and high Na2O/K2O ratios (7.47-9.96). They have relatively low rare earth element content (33.40×10-6-39.27×10-6) and are characterized by positive Eu anomaly and high LREE/HREE ratios (3.95-6.51), similar to features of typical adakites. All of the rocks are also enriched in Ba, Sr and depleted in HFSEs (e.g., Nb, Ti and Yb). By comprehensively synthesizing geochemical compositions and geological setting for magma rocks within the study area,the authors hold that the Chelugou granitoids were derived from partial melting of subducted oceanic plate related to the northward subduction of the Qilian Ocean underneath the North China Block in Ordovician.
Key words:  Chelugou pluton  zircon U-Pb  subduction of oceanic crust  Qilian Mountain orogenic belt  adakite