甘肃公婆泉铜矿床含矿斑岩体地球化学特征、锆石U-Pb年龄及Hf同位素特征研究

[摘 要]甘肃公婆泉铜矿是我国西北地区一个非常重要的斑岩型铜矿床。矿体主要产在花岗闪长斑岩和英安斑岩体内。在斑岩的地球化学特征上，这两种斑岩的主量元素表现为低铝、高钾、高碱，微量元素以富集大离子亲石元素（LILE），如Rb、Ba、Th、Sr等元素，亏损高场强元素（HFSE），如Nb、Ta等元素为特征，具有较为明显的Eu负异常。锆石Hf同位素研究显示，本区花岗闪长斑岩的锆石?Hf (t)值为4.7 ~ 8.2，单阶段Hf模式年龄（tDM1）为714 ~ 857 Ma，平均为791 Ma；二阶段模式年龄（tDM2）的变化范围为887 ~ 1113 Ma，平均为1003 Ma，显示幔源特征。利用LA-ICP-MS锆石U-Pb年代学方法，测得花岗闪长斑岩的年龄为453.2 + 6.5 Ma，为晚奥陶世，代表了公婆泉铜矿花岗闪长斑岩的成岩结晶时代。花岗闪长斑岩的结晶时间为晚奥陶世，因此认为，公婆泉铜矿的成矿时代为晚奥陶世。

Geochemical Characteristics, Zircon U-Pb ages and Hf Isotopic Characteristics of the Ore-bearing Porphyry in the Gongpoquan Copper Deposit

Abstract: The Gongpoquan copper deposit is a very important copper deposit in northwest China. The ore bodies in this deposit are mainly hosted within granodiorite porphyry and dacite porphyry. The two kinds of ore-bearing porphyry are characterized by low values of Al, high values of K2O, high abundance of LILE, such as Rb, Ba , Th, and Sr, and low abundances of HFSE, such as Nb, and Ta. The chondrite-normalized REE patterns show strong negative Eu anomalies. The granodiorite porphyry is dated 453.2 + 6.5 Ma by the zircon LA-ICP-MS U-Pb method. The zircon Hf isotope study shows the Hf(t) values of the granodiorite porphyry are 4.7 ~ 8.2 , tDM1 714 ~ 857 Ma, tDM2 887 ~ 1113 Ma , Hf model age of the first stage (tDM1) is 791Ma and the age of the second stage (tDM2) is 1003Ma. In this study, the age of the granodiorite porphyry is the late Ordovician. It is suggested that the mineralogenetic age of the Gongpoquan copper deposit is the late Ordovician.