Zircon SHRIMP U-Pb dating of ores from the Tongjing gold deposit in Yinan County has yielded two concordant ages of (2 500 + 15) Ma (MSWD=5.0)and (128.6±3.6) Ma (MSWD=0.89). The upper intersection age of (2 500±15) Ma is made up of seven measuring points, while the concordia curve age of (128.6 + 3.6) Ma is made up of five measuring points. It is considered that the former can represent the formation age of late Archean adamellite, whereas the latter might represent the age of magmatic crystallization at late Yanshani-an stage. The authors have thus reached the conclusion that the Tongjing gold deposit was formed at 120 Ma. On the basis of analyzing regional ore-forming regularity, it is thought that there was an gold ore-forming event in 120 ～ 100 Ma in Luxi area, and the formation of gold deposits had close relationship with magmatic activities in Mesozoic.%通过对山东省沂南铜井金矿矿石中的锆石进行SHRIMP U-Pb同位素年龄测定,获得了2组谐和年龄,其中7个测点构成的谐和线上交点年龄数值为(2 500±15)Ma(MSWD=5.0),有5个测点构成的谐和线年龄数值为(128.6±3.6)Ma(MSWD=0.89).研究认为,前者基本代表了新太古代二长花岗岩的形成年龄,而后者则代表了燕山晚期岩浆结晶的年龄,从而推断铜井金矿的形成时代在120 Ma左右.从区域成矿规律分析,鲁西地区存在有120～100Ma的金矿成矿事件,金矿的形成与中生代岩浆活动关系密切.
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