吉林省云峰岩体年代学、地球化学特征及其形成构造背景

Geochronology,geochemical characteristics and tectonic setting of the Yunfeng rock mass in Jilin Province

云峰岩体分布于吉林省东部重要的有色金属、贵金属鸭绿江断裂成矿带内,主要岩性为钾长花岗岩类。对云峰岩体进行岩石学、地球化学、年代学、及锆石U—Pb测年研究:LA-ICP-MS锆石U—Pb年龄资料表明,岩石侵位年龄为(120.9±1.8)Ma,属于早白垩世(晚于鸭绿江断裂活动时间)。云峰钾长花岗岩富SiO_(2)、K_(2)O、贫Al_(2)O_(3),富集Rb等大离子亲石元素,亏损P、Ti、Sr等元素,亏损重稀土元素,Eu亏损明显,属于典型非造山带A型花岗岩。岩浆来源较浅且以壳源物质为主,表明地层可能受太平洋板块向西俯冲欧亚板块碰撞影响,具有强烈的碰撞伸展构造背景,断裂带附近局部发生地壳伸展—减薄的构造过程,岩浆沿已形成的断裂通道上升并冷凝成岩。

The Yunfeng rock mass is located in the Yalu River fault metallogenic belt of important non-ferrous metal and precious metal,eastern part of Jilin Province.The petrology,geochemistry,geochronology,and zircon U-Pb dating of the Yunfeng pluton are studied.The main lithology is K-feldspar granite.LA-ICP-MS zircon U-Pb dating of the rock,concordant age of(120.9±1.8)Ma,indicates that the rock mass was formed in Early Cretaceous(later than the activity time of the Yalu River fault).The Yunfeng K-feldspar granite is rich in SiO_(2),K_(2)O,poor in Al_(2)O_(3),enriched in Rb and other large ion lithophile elements,depleted in P,Ti,Sr and other elements,depleted in heavy rare earth elements,and obviously depleted in Eu,which belongs to typical non-orogenic A-type granite.The magma source is shallow and dominated by crust-derived materials,indicating that the strata may be affected by the collision of the Pacific plate subducting westward to the Eurasian plate,with a strong collision extensional tectonic background.The tectonic process of crustal extension-thinning occurs locally near the fault zone,and the magma rises and condenses along the formed fault channel.