摘要
为探讨湖南省衡阳市将军庙花岗岩的成因,在野外地质调查的基础上,对其进行了岩石地球化学、锆石U-Pb定年及Sr-Nd-Hf同位素分析测试。结果显示,将军庙花岗岩的SHRIMP锆石U-Pb加权平均年龄为(229.1±2.8)Ma(n=8)。岩石以富硅、富碱、高钾钙碱性、过铝质为特征,且富集轻稀土元素和大离子亲石元素(Rb、Th、U、K),亏损重稀土元素、高场强元素(Nb、Ta、Ti)和Ba、Sr等。全岩Sr-Nd同位素显示其具有较高的Sr初始比值(0.7025~0.7189)、低的Nd初始比值(-9.0^-9.4),t(DM2)较老(1.7~1.8 Ga)。锆石εHf(t)为-0.2^-2.9,tDM2为1.3~1.4 Ga,加权平均值为1.35 Ga。结果表明,将军庙岩体具壳源花岗岩的特点,形成于后碰撞期或碰撞晚期的构造环境,源于中元古代结晶基底的部分熔融。结合区域大地构造背景,认为将军庙岩体形成于秦岭-大别和松马两条印支期缝合带碰撞结束后的印支晚期伸展构造背景,是板内挤压加厚的地壳减压熔融作用的产物。
Based on field geological investigation,a study on the whole-rock element geochemistry,zircon U-Pb geochronology,and Sr-Nd-Hf isotopes of the Jiangjunmiao granitic pluton in Hengyang City,Hunan Province has been carried in this paper in order out to discuss petrogenesis of the Jiangjunmiao granitic pluton.The results show that the Jiangjunmiao granite has a weighted mean age of(229.1±2.8)Ma on the basis of SHRIMP zircon U-Pb dating results.It is characterized with high silicon,high potassium,metaluminous,as well as enriched LREE and LILE(Rb,Th,U,K),but depleted HREE,HFSE(Nb,Ta,Ti),Ba,and Sr.Sr-Nd isotopic study shows that bulk samples of the granite have relatively high initial 87Sr/86Sr ratios(0.7025~0.7189),lowεNd(t)values(-9.0^-9.4)and old two-stage model ages of Nd isotopes(1.7~1.8 Ga).The zirconεHf(t)values vary from-0.2 to-2.9 and two-stage model ages of Hf isotopes vary from 1.3Ga to 1.4Ga with the weighted average age of 1.35Ga.Geochemical studies indicate that the Jiangjunmiao granitic pluton is characterized with the typical crust-sourced peraluminous granite,derived from the partial melting of the Mesoproterozoic crystalline basement under the post-collision or late collision tectonic setting.Combining with the regional tectonic setting,it is believed that the Jiangjunmiao granitic pluton was formed by the de-compressional partial melting of the intraplate compressional thickened crust under the late Indosinian extensional tectonic setting after the collision of the Songma and Qinling-Dabie two Indosinian sutures.
作者
李湘玉
易立文
陈迪
文春华
唐分配
张晓阳
安江华
邓蕾
LI Xiang-yu;YI Li-wen;CHEN Di;WEN Chun-hua;TANG Fen-pei;ZHANG Xiao-yang;AN Jiang-hua;DENG Lei(Hunan Institute of Geological Survey,Changsha 410116,China;College of Resources and Environmental Sciences,Hunan Normal University,Changsha 410081,China;Hunan Key Laboratory of Geospatial Big Data Mining and Application,Changsha 410081,China)
出处
《矿物岩石地球化学通报》
CAS
CSCD
北大核心
2020年第4期726-740,共15页
Bulletin of Mineralogy, Petrology and Geochemistry
基金
湖南省青年基金项目(2018JJ3269)
湖南省重点领域研发计划项目(2019SK2261)。
