胶东晚中生代三期成矿岩体和3. 5 Ga锆石的发现及成矿动力学背景

胶东地区在晚中生代发生了大规模岩浆活动和"爆发式"成矿作用。为了深入研究岩浆活动的时代及其对成矿的影响,本文在对胶东晚中生代花岗岩类侵入岩及大规模成矿作用进行综合分析基础上,选择福山邢家山钼钨矿区、栖霞香夼铅锌矿区和福山王家庄铜矿区,对成矿岩体进行锆石U-Pb同位素年龄测试。测试结果表明,幸福山斑状二长花岗岩体(邢家山矿区)和香夼花岗闪长斑岩体的SHRIMP锆石U-Pb同位素年龄分别为159.3±1.6Ma和130.4±1.2Ma,养虎山石英闪长玢岩体(王家庄矿区)的LA-ICP-MS锆石U-Pb年龄为116.1±5.1Ma和119.8±1.8Ma,由此确定了三期岩浆活动及与之相对应的三期成矿事件。在晚侏罗世幸福山岩体中测得了前寒武纪残余锆石的年龄信息,三组年龄分别为3548±12Ma、2472.9～2400Ma和2192～1725Ma,指示岩浆物质来源于前寒武纪结晶基底的再循环作用。3548±12Ma是胶东地区迄今为止获得的最大年龄值,指示胶东地区存在古太古代早期的古老结晶基底。综合分析认为,胶东晚侏罗世岩浆活动和160Ma±的成矿事件是华北克拉通与扬子克拉通碰撞造山后续过程的产物,形成于挤压构造背景;早白垩世早期的岩浆活动及130Ma±成矿事件与太平洋板块俯冲有关,形成于挤压向伸展转化背景;早白垩世中晚期岩浆活动形成于拉张环境,与华北克拉通破坏和岩石圈伸展减薄有关,由此产生的胶东热隆-伸展构造体系,为115Ma±的金、银及有色金属等热液矿床大规模爆发式成矿提供了有利成矿条件。

The discovery of Three- stage Late Mesozoic metallogenic granitic bodies and 3. 5 Ga zircon in the Jiaodong Terrane and their metallogenetic geodynamical setting

The extensive magmatism and explosive mineralization occurred in the Jiaodong terrane in Late Mesozoic. In order to investigate the age of magmatic activity and its impact for mineralization, we carried out zircon U- Pb isotopic dating for samples from Xingjiashan molybdenum- tungsten deposit, Xiangkuang lead- zinc deposit and Wangjiazhuang copper deposit, based on comprehensive analysis of Late Mesozoic granitoid and mineralization in the Jiaodong terrane. The dating yields the zircon SHRIMP U- Pb isotopic age of 159. 3±1. 6 Ma and 130. 4±1. 2 Ma respectively for porphyritic granite in Xinffushan and granodiorite porphyry in Xiangkuang, and 116. 1±5. 1 Ma and 119. 8±1. 8 Ma for quartz diorite porphyrite in Yanghushan. Therefore three stages of magmatism and relative metallogenic events have been determined. Age of residual Precambrian zircons was also obtained for the Late Jurassic granitoid: 3548±12Ma, 2472. 9~2400Ma and 2192~1725Ma, which indicate that the Late Jurassic granitoid derived from recycling of the Precambrian crystalline basement. 3548±12Ma is the oldest one obtained so far, indicating the existence of early Paleoarchean ancient crystalline basement in the Jiaodong area. Comprehensive analyses suggest that the magmatism and mineralization at 160Ma± should be the products after the collision between North China craton and Yangtze craton in the compressive tectonic settings. The early Early Jurassic magmatic activity and metallogenic events of 130 Ma± are related to the subduction of the Pacific Plate and formed in a transitional environment from compressional orogeny to extensional structure. Middle to late Early Cretaceous magmatism formed in an extensional seting, likely related to destruction of the North China Craton and lithospheric thinning, which provided preferential condition for large- scale hydrothermal mineralization of Au, Ag and non-ferrous metals at 115 Ma±.