摘要
滁州冶山地区研究程度较低,前人研究认为金牛岩体属于冶山岩体的边缘相,本次对金牛岩体开展独立研究。金牛侵入岩锆石U-Pb定年结果为(129±2)Ma,属于早白垩世早期。锆石原位Hf同位素分析显示,具有较均一的负εHf(t)值(-2.82^-6.52)和较古老的地壳模式年龄tDMC(1360~1600 Ma)。金牛岩体为碱性(σ:5.08~5.74)、准铝质(A/CNK:0.803~0.844)岩石,具有较强的轻重稀土元素分异、无明显-弱负Eu异常、相对富集轻稀土元素、大离子亲石元素,明显亏损重稀土元素和高强场元素的特点,综合对比冶山岩体,认为金牛岩体与冶山岩体同期不同源。结合区域构造演化特征及岩石地球化学、Hf同位素特征,金牛岩体很可能为来源于富集岩石圈地幔的富水底侵基性岩浆与古老下地壳部分熔融形成的岩浆混合的产物,其源动力与太平洋板块的俯冲有关。
The research on Lower Yangtze block in Yeshan area of Chuzhou is very insufficient.Previous researchers held that Jinniu rock mass belongs to marginal facies of Yeshan pluton.In this paper,the authors studied Jinniu pluton.Zircon U-Pb dating indicates that The Jinniu pluton of Yeshan area of Lower Yangtze block was formed at129±2Ma,suggesting a product of Early Cretaceous.Zircon Hf isotopic composition has relatively uniform negativeεHf(t)values(-2.82--6.52)and old Hf isotopic crustal model ages(1360-1600Ma).The Jinniu pluton is alkaline(σ:5.08-5.74)),metaluminous rock body(A/CNK:0.803-0.844),which is characterized by relatively strong differentiation between light and heavy rare earth elements,indistinct negative Eu anomalies,enrichment of LREE and LILE,and depletion of HREE and HFSE.Comprehensive comparative study of the Yeshan rock mas shows that the Jinniu rock mass and Yeshan rock mass belong to two different sources of the same period.Regional tectonic evolution characteristics and geochemistry of rocks and Hf isotope characteristics indicate that the source of the Jinniu rock mass seems to have been a mixed product of underplating water-rich basic magma from enriched lithospheric mantle and partially melted ancient lower crust due to the subduction of Paleo-Pacific Plate.
作者
陈俊
王辉
王丽娟
关俊朋
CHEN Jun;WANG Hui;WANG Lijuan;GUAN Junpeng(Geological Survey of Jiangsu Province, Nanjing 210018, Jiangsu, China)
出处
《中国地质》
CAS
CSCD
北大核心
2018年第1期110-128,共19页
Geology in China
基金
中国地质调查局项目(12120114045701
12120114007101)资助~~
