浙江治岭头地区霏细岩锆石U-Pb年龄、地球化学特征及形成背景  

Zircon U-Pb age,geochemical characteristics and formation setting of felsite in Zhilingtou area,Zhejiang Province

作　　者：华杰雄 刘汉仑 HUA Jiexiong;LIU Hanlun(Zhejiang Suichang Gold Mine Co.Ltd.,Lishui 323300,Zhejiang,China;Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China)

机构地区：[1]浙江省遂昌金矿有限公司,浙江丽水323300 [2]中国地质科学院矿产资源研究所,北京100037

出　　处：《世界地质》2022年第1期26-37,共12页World Geology

基　　金：中国地质调查局地质调查二级项目(DD20201173)。

摘　　要：通过对浙江治岭头地区的霏细岩进行较为系统的LA-ICP-MS锆石U-Pb定年及全岩地球化学分析,探讨了晚白垩世华南地区的构造演化。定年结果显示霏细岩年龄为(98.31±0.92)Ma,为燕山期岩浆侵入活动的产物。岩石为高钾钙碱性偏铝质系列,富SiO_(2)(68.17%~72.90%)、Al_(2)O_(3)(13.58%~16.07%)和K_(2)O(4.75%~5.34%),而贫Fe_(2)O_(3)(1.17%~1.37%)、MgO(0.15%~0.22%)和CaO(1.03%~1.62%)。稀土元素配分曲线呈右倾型,Eu具有明显的负异常,ω(∑REE)=(206.57~222.54)×10^(-6),LREE/HREE为18.17~19.10,(La/Yb)_(N)值为23.56~25.49,δEu=0.61~0.65。Rb、Th、U、K表现为相对富集,而Nb、Ta、P、Zr、Hf表现为相对亏损。微量元素配分曲线显示富集大离子亲石元素(LILEs)和轻稀土元素(LREEs),亏损高场强元素(HFSEs)及重稀土元素(HREEs),类似于I型花岗岩的特征。结合岩石成因、构造环境判别及区域构造演化过程,认为治岭头地区霏细岩的形成与古太平洋的俯冲作用密切相关,该地区晚侏罗世-晚白垩世早期由古太平洋板块俯冲消减作用为主导,结合同时期伸展构造,并伴有大量的玄武岩浆底侵上涌,导致了大量的花岗质岩浆产生,随着地幔组分逐渐参与形成了区内发育的霏细岩。A systematic zircon LA-ICP-MS U-Pb dating and whole rock geochemical analysis were carried out for the felsite in Zhilingtou area,Zhejiang Province,and the tectonic evolution of South China in the Late Cretaceous was discussed.The dating results show that the intrusive age of the felsite is(98.31±0.92)Ma,which is the product of Yanshanian magmatic event.The rocks belong to high potassium,calc-alkaline,metaluminous series,and are rich in SiO_(2)(68.17%~72.90%),Al_(2)O_(3)(13.58%~16.07%)and K_(2)O(4.75%~5.34%),but poor in Fe_(2)O_(3)(1.17%~1.37%),MgO(0.15%~0.22%)and CaO(1.03%~1.62%).The REE distribution curve is right inclined with obviously negative Eu anomalies.Theirω(ΣREE)=(206.57~222.54)×10^(-6),LREE/HREE=18.17~19.10,(La/Yb)_(N)=23.56~25.49,andδEu=0.61~0.65.Rb,Th,U and K are relatively enriched,while Nb,Ta,P,Zr and Hf are relatively depleted.The trace element distribution patterns show the enrichment of large ion lithophile elements(LILEs)and light rare earth elements(LREEs),but depletion of high field strength elements(HFSEs)and heavy rare earth elements(HREEs),which are similar to the characteristics of I-type granites.Combined with the petrogenesis,tectonic environment discrimination and regional tectonic evolution processes,the formation of the felsite in Zhilingtou area is closely related to the subduction of the Paleo-Pacific Ocean.The area was dominated by the subduction of the Paleo-Pacific plate from the Late Jurassic to early Late Cretaceous,combined with the extensional structure of the same period,accompanied by a large number of basaltic magma underplating and upwelling,resulting in the generation of a large number of granitic magma,and with the gradual participation of mantle components,felsite in this area was formed.

关 键 词：霏细岩 锆石U-PB定年 地球化学特征 构造背景 治岭头地区 

分 类 号：P595[天文地球—地球化学] P597[天文地球—地质学]