中条山铜矿峪变石英二长斑岩的锆石U-Pb年龄和Hf同位素特征及其地质意义

Zircon U-Pb geochronology and Hf isotope geochemistry of metamorphic quartz-monzonite porphyry from Tongkuangyu area,Zhongtiao Mountain and its geological implications

中条山铜矿峪斑岩型矿床的成矿斑岩形成时代一直存在争议。本文通过对铜矿峪矿床中变石英二长斑岩的U-Pb年代学研究发现:铜矿峪变石英二长斑岩的36颗锆石的上交点年龄为2121±10Ma,207Pb/206Pb年龄从2065Ma到2196Ma,加权平均年龄为2117±13Ma,这与铜矿峪矿床的Re-Os同位素年龄(2108Ma)在误差范围内一致,暗示了成岩成矿的一致性。锆石的Hf同位素特征显示,样品的εHf(t)值介于-7.79～0.39,显示出斑岩的形成与古老地壳的部分熔融有关。同时,铜矿峪变石英二长斑岩的形成时代与华北地区的一些A型花岗岩,双峰式火山岩等与伸展有关的火成岩的形成时代大体一致,同时也与中条裂谷的活动一致,说明铜矿峪变石英二长斑岩形成于一个伸展的动力学背景下。因此,本文认为铜矿峪矿床是与大陆伸展环境的斑岩型矿床。

The formation time of the metamorphic quartz-monzonite porphyry associated with the Tongkuangyu porphyry copper deposit is still controversy. A set of zircon U-Pb geochronology and in-stiu Hf isotopic date was presented in this study for the metamorphic quartz-monzonite porphyry. The result show that the discordia upper intercept age 2121 ± 10Ma and 207 Pb / 206 Pb age range from 2065Ma to 2196Ma,have a weighted average age 2117 ± 13Ma. This age （ 2117 ± 13Ma） is accounted as the formation time of the metamorphic quartz-monzonite porphyry from Tongluangyu porphyry copper deposit,and is approximately consistent with the extension of the North China Craton （ NCC） ,especially the activity of Zhongtiao rift which is located in the southern part of NCC. In addition,zircons Hf isotopic characteristics （ ε Hf （ t） range from - 7. 79 to 0. 39） indicate that the old crustal materials played an important role in the petrogenesis. So,we conclude that the Tongkuangyu porphyry Cu deposit is a typical porphyry Cu deposit formed in inner continental settings,which genetic with the large-scale extension of the NCC.