安徽铜陵沙滩脚岩体年代学及地球化学特征

GEOCHRONOLOGY AND GEOCHEMISTRY OF SHATANJIAO GRANODIORITE FROM TONGLING,ANHUI PROVINCE

沙滩脚岩体位于铜陵矿集区东南部,主体为花岗闪长岩,锆石LA-ICP-MS U-Pb同位素测年结果表明,岩石侵位时代为141.4 Ma±1.1 Ma,属早白垩世,与铜陵地区其它岩体形成年代范围一致。沙滩脚花岗闪长岩的w（SiO2）在62.06%~65.53%之间、w（Al2O3）为16.05%~17.06%,Na2O/K2O比值均大于1（1.24~2.34）,其属于高钾钙碱性系列。岩石稀土元素含量高,富集轻稀土和大离子亲石元素,亏损高场强元素,同时具有高Sr、低Y从而高Sr/Y比值（47.43~137.50）的特征,类似埃达克质岩石,暗示其岩浆形成于较高的压力下,为加厚的下地壳部分熔融的产物。

The precise zircon LA-ICP-MS U-Pb dating of Shatanjiao granodiorite in the southeast Tongling area gives a mean age of 141.4 Ma±1.1 Ma,belonging to early Cretaceous and having the same e ages of other plutons in Tongling area.Analysis of major and trace elements of Shatanjiao granodiorite shows that it belongs to high-K calc-alkaline series characterized by high SiO2（62.06%～65.53%） and Al2O3（16.05%~17.06%） contents,enriched in LREE and LILE,depleted in high field strength elements such as Ta and Nb as well as high Sr,low Y and high Sr/Y ratios（47.43~137.50）.These features are similar to those of adakitic magmas and imply that the Shatanjiao granodiorite was derived from partial melting of thickened lower crust under the condition of higher pressure.