摘要
龙泉岩体是浙南地区少有的加里东期花岗质岩体。岩石学、地球化学和年代学研究显示,龙泉岩体由花岗岩-二长花岗岩组合(花岗岩类)和英云闪长岩-奥长花岗岩-花岗闪长岩组合(TTG)组成,两类岩石组分普遍富集大离子亲石元素Rb、Ba、Th、U、K,亏损高场强元素Nb、Ta、P、Ti,显示岛弧岩浆岩的特征。TTG岩石的地球化学特征显示属于典型的高压型TTG,其岩浆来源于受俯冲板片流体作用的基性下地壳的重熔作用,而花岗岩类岩石则主要源于古老地壳沉积物的部分熔融,两者均未受地幔的明显混染。锆石SHRIMP U-Pb和锆石LA-ICP-MS U-Pb测年结果表明龙泉岩体的形成时间为443±3~410±3 Ma,结合岩石地球化学特征,指示晚至泥盆纪早期,龙泉地区还存在着洋壳的俯冲作用。
The Longquan pluton is a rare Caledonian granitic rock mass in southern Zhejiang.Studies on the Longquan pluton using petrology,geochemistry,and chronology were conducted in this paper,which reveal that it is composed of granite-monzogranite assemblage(granitoid)and tonalite-trondhjemite-granodiorite assemblage(TTG).The two types of rocks are generally enriched in large ion lithophile elements Rb,Ba,Th,U and K,and depleted in high field strength elements Nb,Ta,P and Ti,showing the characteristics of island arc magmatic rocks.The geochemical characteristics of the TTG rocks show that they belong to the typical high-pressure type TTG,and its magma originated from the remelting of the basic lower crust under the action of subducted slab fluid.While the granitoids were mainly derived from partial melting of ancient crustal sediments.Neither of them was significantly contaminated by mantle.The zircon SHRIMP U-Pb and LA-ICP-MS U-Pb dating results show that the Longquan pluton was formed between 443±3 Ma~410±3 Ma.Combined with its petrological and geochemical characteristics,it is indicated that the subduction of oceanic crust had still existed in the Longquan area until early Devonian.
作者
刘远栋
苏小浪
程海艳
张建芳
李翔
刘风龙
LIU Yuandong;SU Xiaolang;CHENG Haiyan;ZHANG Jianfang;LI Xiang;LIU Fenglong(Zhejiang Institute of Geological Survey,Hangzhou 311203,Zhejiang,China;Hangzhou Jintian Engineering Design Consulting Co.Ltd,Hangzhou 311203,Zhejiang,China)
出处
《地质力学学报》
CSCD
北大核心
2022年第2期237-256,共20页
Journal of Geomechanics
基金
浙江省级基础性公益性战略性地质工作专项资金项目(〔省资〕2018006)
中国地质调查局地质调查项目(12120114043101)。
