摘要
选取福建省西南部紫金山中粗粒花岗岩、石壁寨西部含斑细粒二长花岗岩和东部斑状含黑云母二长花岗岩作为研究对象,利用LA-ICP-MS法对三个岩体的锆石进行了U-Pb、Lu-Hf和微量元素分析,获得了3个岩体的岩浆结晶分别为156.5±2.7Ma(晚侏罗世),166.2±8.1Ma(中侏罗世)和154.1±1.4Ma(晚侏罗世)。锆石的Lu-Hf同位素分析结果表明,锆石的两阶段Hf模式年龄(tDM2)分别为1.6~2.2Ga、1.7~2.0Ga和1.7~1.9Ga。锆石Hf同位素初始值ε_(Hf)(t)均为负,分别为-14.88^-8.40、-11.9^-7.8和-10.9^-7.4。锆石的ε_(Hf)(t)、Hf同位素地壳模式年龄分布范围较小,暗示岩体岩浆来源具有较为均一锆石Hf同位素组成。中侏罗世(166.2±8.1Ma)期间,古太平洋板块与欧亚板块发生碰撞,导致洋壳俯冲至陆壳之下,陆壳并发生了小规模的部分熔融,形成了石壁寨西部岩体;碰撞结束后,在晚侏罗世(145~156Ma)期发生由挤压向拉张环境的转换,闽西南岩石圈伸展减薄、壳源物质发生广泛的熔融作用,形成了大规模的紫金山岩体和石壁寨东部岩体。本文的研究成果,为研究闽西南花岗岩体的来源和区域构造演化提供了新的资料证据。
Medium-coarse grained granite of the Zijinshan pluton, fine grained monzogranite in west of Shibizhai, and porphyritic biotite monzogranite in east of Shibizhai were selected to conduct U-Pb, Lu-Hf and trace elements analysis. LA-ICP-MS dating of zircons from three rock bodies yielded three magma crystallization ages of 156.5±2.7Ma （late Jurassic）, 166.2±8.1Ma （middle Jurassic） and 154.1±1.4Ma （late Jurassic） for three rock bodies, respectively. Zircon Lu-Hf isotope analysis results show that zircon Hf isotope twostage model ages （t DM2） are 1. 6-2.2Ga, 1.7-2.0Ga and 1.7-1.9Ga. Zircon Hf isotope initial values （εHf（t）） are negative. --14. 88--8.40, --11.9--7.8 and --10.9--7.4. The zircon εHf（t） and Hf isotope crustal model ages vary in a small range, implying that magma source was of much uniform zircon Hf isotope composition. During the Middle Jurassic （166.2 ± 8.1Ma）, paleo-Pacific plate collided with Eurasian plate, resulting in that oceanic crust subducted beneath the continental crust and partial melting of small-scale continental crust formed the pluton in the west of Shibizhai during the time. Upon completion of the collision in the Late Jurassic （145 - 156Ma）, tectonic environment converted from extrusion to extension, triggering lithospheric extension and thinning, extensive melting of crust-derived substance, and finally giving rise to the formation of the Zijinshan pluton and the Shibizhaidong pluton. The result of this study will provide new data evidence for studying granite source and regional tectonic evolution in southwestern Fujian Province.
作者
谢其锋
蔡元峰
董云鹏
黎敦朋
林荣锋
XIE Qifeng CAI Yuanfeng DONG Yunpeng LI Dunpeng LIN Rongfeng(College of Zijin Mining, Fuzhou University, Fuzhou, 350116, Fujian, China State Key Laboratory for Mineral Deposits Research, School of Earth Science an Engineering, Nanjing University, Nanjing , 210046, Jiangsu, China State Key laboratory of Continental Dynamics, Department of Geology , Northwest University, Xi＇ an, 71 O069, Shaanxi, China Zijin Mining Group Co. Ltd. , Longyan, 364200, Fujian,China)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2017年第10期2212-2230,共19页
Acta Geologica Sinica
基金
南京大学内生金属矿床成矿机制研究国家重点实验室项目(20-15-05)
福州大学2017年国家级大学生创新训练计划项目(201710386031)资助成果
