铜陵狮子山地区胡村岩体年代学及地球化学特征

Geochronology and Geochemistry of the Hucun Granodiorite in the Shizishan Area,Tongling

铜陵地区燕山期岩浆热液活动与大规模成矿作用有密切联系.本文开展了锆石年代学和地球化学的研究,以探讨胡村花岗闪长岩体与铜矿床之间的成因联系.结果显示花岗闪长岩体锆石U-Pb年龄为139.6±2.2 Ma;主量元素含量为：SiO260.00％～65.26％,Al2 O3 15.2％～17.15％,全碱（K2O＋Na2O） 6.94％～7.85％,落入高钾钙碱性系列;微量元素结果表明,大离子亲石元素相对相邻元素富集,亏损高场强元素;轻重稀土元素分馏明显,轻稀土元素富集,具轻微Eu负异常.这些结果说明胡村花岗闪长岩体的岩石地球化学特征、形成时代、构造环境等都与狮子山矿田内具有代表性的岩体相似,认为花岗闪长岩成岩物质主要来自上地幔,同时还有地壳物质的混入,具有壳幔混合特征.

Magmatic hydrothermal activities in the period of Yanshan are closely linked with the large-scale mineralization in the Tongling area.Geochronology and geochemistry studies were employed to investigate the genetic relationships between the Hucun granodiorite and the copper deposits in this article.The results showed that the mean zircon U-Pb age the granodiorite is 139.6±2.2 Ma,and that the major elements contents are：SiO2 60.00％～65.26％,A12O3 15.2％～17.15％,the （Alk） （K2O＋Na2O） 6.94％-7.85％,indicating a high K calc-alkaline series,while the trace elements results indicated that large lithophile ions are relatively enriched,high field strength elements are depleted,and the REE fractionation is severity with enriching of light REEs and a slight negative EU anomalies.Given the mineralization similarity of the Hucun granodiorite and the Hucun copper deposit,we believed that the Hucun granodiorite were formed by mixing of the differentiated mantle magma and the crustal magma.