山东鲁东碰撞造山型金矿成矿作用探讨

摘要

The mineralization during collision orogenesis is an important part of continental dynamic study. Mapping of the tectonic phases ( 1: 500000 ) was used to study the dispersion, convergence, collision and orogeny of the continental block in Shandong Province. Duringthe mapping of tectonic phases in Shandong Province, we found thatthere are two important Mesozoic collision events in Eastern Shandong Province--Indosinian and Yanshanniancollision. Indosinian collision orogeny was resulted from the subduction of the Yangtze plate beneath North China plate, which led to the formation of the Sulu high pressure-ultra-high pressure metamorphic belt, synorogenic granites and post-orogenic high-alkali syenites; the Yanshannian collision orogeny originated from the transformation of central Asia-Tethyan tectonic region to the coastal Pacific tectonic plate, and the subduction of the Pacific plate, which is demonstrated as three phases of orogeny and extensions in Eastern Shandong Province. Four sets of granitoids associated with orogenesis can be discerned, I. E. , the Linglong gneissic granites of early orogenic period ( J3) , the Guojialing granodiorite-granite of the middle orogenic period ( K1 ) , the Weideshan diorite-granodorite-granite of the late orogenic period, and in the Laoshan A-type granites of the post-orogenic. SHRIMP U-Pb age of the Guojialing orogenic granodiorite-granite assemblage in middle orogenic period is 130 ～ 126 Ma, which is closely related to gold mineralization. The ore-forming age of the gold deposits in Eastern Shandong is 120 ～ 115 Ma, which basically represents the main ore forming period. Poly-metallic mineralization is closely related to the Weideshan diorite-granodiorite-granite of late orogenic period which is a period of superimposed gold mineralization in the region. Tectonic-magmatic events and gold mineralization are controlled by the interaction of Tethys, Paleo-Asian Ocean and the Pacific tectonic regions. Dynamic background of the gold mineralization was the transition of Mesozoic tectonic regime and lithospheric thinning, which was resulted from the collision bewteen North China plate and Yangtze plate and subduction of the Pacific plate.%碰撞造山成矿作用是大陆动力学研究的重要内容,大地构造相编图是研究山东大陆块体离散、会聚、碰撞、造山的大陆动力学过程的主要载体和具体表达形式.作者在编制1:50万山东省大地构造相图时发现,鲁东地区中生代有两次重要的碰撞造山事件——印支和燕山碰撞造山作用.印支造山作用主要表现为扬子板块向华北板块俯冲,形成苏鲁高压-超高压变质带及同造山花岗岩及后造山高碱正长岩；燕山造山作用的大陆动力学环境起源于中亚-特提斯构造域向滨太平洋构造域转化和太平洋板块的俯冲,在鲁东地区表现为三次造山和三次伸展,可分为造山早期玲珑片麻状花岗岩组合(J3)、造山中期郭家岭花岗闪长岩-花岗岩组合(K1)、造山晚期伟德山闪长岩-花岗闪长岩-花岗岩组合和后造山A型崂山晶洞过碱性碱长花岗岩-正长花岗岩组合.造山中期郭家岭花岗闪长岩-花岗岩组合SHRIMP U-Pb年龄集中在130～126 Ma,与金矿的定位关系密切,而鲁东金矿形成的年龄集中在120～115 Ma,基本代表了主成矿期的年龄.多金属矿则与造山晚期伟德山闪长岩-花岗闪长岩-花岗岩组合有关,也是区内金矿的叠加成矿期.鲁东地区构造-岩浆事件和金矿成矿作用受控于特提斯、古亚洲洋和太平洋三大构造域的相互作用,金矿形成的动力学背景是中生代构造体制转折和岩石圈减薄,起因为华北板块与扬子板块碰撞及太平洋板块的俯冲机制有关.