摘要
在我国华南地区广泛发育了白垩纪岩浆活动,形成了大面积的花岗岩和多期侵位的中基性和酸性脉岩。其中中基性脉岩被认为是华南白垩纪多期伸展作用的标志之一。本文对采自福建沿海石狮地区的石狮和东埔两地的花岗岩和侵入的中基性脉岩进行了锆石U-Pb年代学和Hf同位素以及岩石元素地球化学研究。石狮地区的花岗岩和花岗闪长岩为中钾-高钾钙碱性、弱过铝质岩石,2个锆石U-Pb年龄分别为105.3±1.0Ma和105.1±0.5Ma,2个花岗岩的锆石εHf(t)为-0.9^+2.0;侵入的脉岩为辉绿岩和闪长岩,属于准铝质中钾-高钾钙碱性岩石,2个闪长岩的锆石U-Pb年龄分别89.5±1.5Ma和96.1±1.2Ma,脉岩的εHf(t)为+1.3^+5.0。石狮地区花岗岩和脉岩显示轻重稀土中等分馏和弱的Eu异常,花岗岩稀土总量明显低于脉岩,岩石大离子亲石元素富集、高场强元素亏损,显示岛弧岩浆岩的地球化学特征;微量元素判别(Ta/Hf-Th/Hf,Zr-Zr/Y)表明石狮地区的岩脉产于大陆边缘裂谷环境或板内构造环境,脉岩应是古太平洋俯冲的大陆边缘背景之上,俯冲结束后转入大陆边缘伸展作用的标志。福建沿海厦门-石狮-晋江地区的伸展作用发生在87~96Ma,与华南区域上多期伸展作用中~90Ma的伸展作用吻合。
The Cretaceous magmatism have been widely taken place in South China,and have created large scale distribution of granitoids and intruded mafic,intermediate and acid dikes,in which the mafic dikes are representative or response to the Cretaceous crustal extension tectonic activity in South China. This paper carried out the research of zircon U-Pb geochronology and Hf isotopes,and elemental geochemistry on the samples collected from the localities of Shishi and Dongfu from Shishi area,coastal Fujian Province.The granite and granodiorite are mediate- to high-K potassic calc-alkaline,and peraluminous,with U-Pb ages of 105. 3 ± 1. 0Ma and105. 1 ± 0. 5Ma. Their zircon εHf（ t） range from- 0. 9 to ＋ 2. 0. The dikes are diabase and diorites,showing metaluminous,mediateto high-K potassic calc-alkaline features. Two diorites yield zircon U-Pb ages of 89. 5 ± 1. 5Ma and 96. 1 ± 1. 2Ma. The εHf（ t） of diorite are in the rage of ＋ 1. 3 to ＋ 5. 0. Both granitoids and dikes in the Shishi area show medium scale fractionation of light rare earth elements（ REE） relative to heavy REE,and less Eu anomaly. The total REE of granitoids are less than that of the dikes. The rocks show significant enrichment of large ion lithosphile element（ LILE） and depletion of high field stretch element（ HFSE）,which is the distinct characteristic of rocks from arc-related magmatism. The discrimination geochemical diagrams（ Ta / Hf-Th / Hf,Zr-Zr / Y）suggest that the dikes from this study generated from the tectonic settings of continental margin rift or within plate environments. The dikes maybe intruded within the tectonic transition from continental subduction-related tectonic to continental extension settings,which is the index for the extension. The extension should have occurred during 87 ～ 96 Ma in the coastal Fujian Province,including Xiamen,Shishi,and Jinjiang areas,which is consistent to the regional ～ 90 Ma extension,in the multi-stage extension in the Cretaceous evolution in the whole South China.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2015年第5期1433-1447,共15页
Acta Petrologica Sinica
基金
深部探测技术与实验研究专项课题(SinoProbe-04-02)
科技部国际合作基金(2011DFA22460)
111计划(B07011)联合资助
关键词
花岗岩
脉岩
U-PB年代学
地球化学
石狮
福建沿海
Granitoids Dikes U-Pb geochronology Geochemistry Shishi Coastal area of Fujian Province
