铜陵地区中生代侵入岩LA-ICP-MS锆石U-Pb年代学及Cu-Au成矿指示意义  

Zircon U-Pb geochronology of the Mesozoic intrusive rocks in the Tongling region:Implications for copper-gold mineralization

作　　者：谢建成[1,2] 杨晓勇[2] 杜建国[3] 孙卫东[2,4] 

机构地区：[1]合肥工业大学资源与环境工程学院,合肥230009 [2]中国科学技术大学地球和空问科学学院,合肥230026 [3]安徽省地质调查研究院,合肥230011 [4]中国科学院广州地球化学研究所,广州510640

出　　处：《岩石学报》2008年第8期1782-1800,共19页Acta Petrologica Sinica

基　　金：中国科学院知识创新工程重大项目“中国东南部中生代成矿地球动力学和找矿勘查示范(KZCX1-Y)”;安徽省优秀青年科技基金资助项目(08040106907);安徽国土资源厅“铜陵深部找矿”专题资助

摘　　要：安徽铜陵地区是我国著名的 Cu-Au 多金属产地之一,金属成矿与燕山期岩浆作用关系密切。本次对铜陵地区石英(二长)闪长岩和花岗闪长岩系统地进行了 LA-ICP-MS 锆石年代学研究。高质量锆石 U-Pb 同位素^(206)Pb/^(238)U 加权平均年龄结果表明铜陵地区中酸性侵入岩的成岩序列可能为花岗闪长岩(141Ma)→辉石(二长)闪长岩(139Ma)→石英(二长)闪长岩(135Ma,136Ma,137Ma)。对比已有的高精度锆石 U-Pb 同位素年龄,我们认为铜陵地区岩体侵入后可能有个快速冷却的过程。铜陵地区与 Cu-Au 矿床有关的最主要侵入岩 LA-ICP-MS 锆石数据给出两组年龄:130～132Ma 和138～140Ma。据高精度锆石 U-Pb 数据和一些矿床的 Re-Os 年龄,结合锆石元素地球化学资料,本文得出铜陵地区主要表现出两次成矿事件:早期成矿事件是与高 Ce 异常流体密切相关的铜金成矿事件(辉钼矿 Re-Os 年龄138～140Ma);晚期成矿事件可能与低 Ce 异常流体密切相关的铁硫成矿事件(黄铁矿 Re-Os 年龄约126Ma)。Tongling region is one of the most important non-ferrous metal producers where the formation of Cu-Au deposits and other poly-metal deposits has close genetic relations with Mesozoic intrusions. In this study, LA-ICP-MS zircon chronology of three-type Mesozoic intrusives （i. e., quartz diorite--monzonite and granodiorite assemblies related with Cu-Au-S-Fe ore-forming ） was systematically investigated in Tongling region. The results of high precise zircon U-Pb ages possibly present the sequences of the intrusive evolutions in Tongling region as follows： granodiorite （141 Ma） → pyroxene diorite-pyroxene monzodiorite （139Ma） → quartz diorite--quartz monzodiorite （135Ma, 136Ma, 137Ma）. These high-precision zircon U-Pb ages manifest that the intrusive rocks possibly experienced immediately after crystallization. Laser ablation ICP-MS zircon U-Pb dating yielded two groups of ages （ c. a. 130 - 132 Ma and 138 - 140 Ma） for the intrusive rocks, which are the most important magmatic events in Tongling area related to Cu-Au mineralization. Combined the high-precision zircon U-Pb dates, Re-Os age of some ore deposit and zircon trace element measurements, two events of ore-forming periods are obtained ： one is the ore-forming event with high Ce abnormality （ molybdenite Re-Os age of 138 - 140Ma） , which is closely related to those of copper and gold ore deposits; another is probably ore-forming event with low Ce abnormality （ pyrite Re-Os age of about 126 Ma） closely related to those of iron and sulfur ore deposits in the Tongling region.

关 键 词：中生代侵入岩 LA—ICP—MS锆石年代学 铜金成矿 铜陵地区 

分 类 号：P597.3[天文地球—地球化学] P618.41[天文地球—地质学]