胶东金矿陆内构造岩浆核杂岩隆起-拆离带蚀变成矿

Mineralization of tectono-magmatic upheaval-hydrothermal alteration in the detachment zone,Jiaodong Peninsula

胶东金矿是全球级别的大型金矿床,与世界范围内绿岩带型金矿明显不同,矿床以中生代强烈活化改造绿岩带的壳源深熔花岗岩为成矿岩体,具有地台构造活化的独特成矿特征。前人注重板块俯冲、造山作用等构造环境研究,但这里需要强调的是,胶东金矿在陆内构造环境中形成。本文特别注重岩浆侵入作用及其热液交代蚀变成矿的这一特殊过程。研究开展野外观测,依据五条1∶5万长达220km的实测剖面,编制了胶东莱州—招远地区1∶25万构造蚀变岩相成矿图,并由此提出"胶东陆内构造岩浆核杂岩隆起-拆离带蚀变"的成矿模式。此模式认为,在东亚区域反钟向剪切构造体制下,构造应力场首先引起莫霍面的变化和起伏,形成了北东向和斜列展布的地幔隆起和凹陷。这一壳幔结构的变化控制了中生代交代重熔岩浆发育的区带。例如,胶西北莫霍面凹陷区带,发育北北东分布的玲珑杂岩体。花岗岩的成岩构造测量与分析显示,形成了"玲珑花岗杂岩核"及其岩浆穹隆构造。在胶东群等变质岩与花岗岩的接触带叠加了区域剪切断裂破碎带,断裂破碎带的构造测量表明,它们在岩浆固结期或更晚发育了上盘下滑的正断层活动。就是在这些剪切拆离带,形成了多期次、多方向构造破碎且同步发生了大规模的岩浆期后热液交代蚀变成矿作用。在胶东西北部宽达1.5km或更宽的断裂破碎同步叠加的热液交代蚀变作用,形成了巨大的"玲珑-焦家式"石英脉-蚀变岩金矿床。这一"陆内岩浆核杂岩隆起-拆离带"成矿模式不仅对胶东金矿成矿研究具有推动作用,而且可以指导多层次深部外围找矿。

The Jiaodong gold mine has a world-class large gold deposit.Different from the greenstone-belt type gold mine,it contains ore-forming anatexis granite of crust origin as a result of Mesozoic activation and transformation;and underwent an unique mineralization brought by platform tectono-magmatic activation.Previous researchers lay emphasis on the study of plate subduction and orogeny,but here they also need to consider the intra-continental tectonic environment and magmatic intrusion,as well as the special process of the late stress-relaxation induced hydrothermal metasomatic metallogenesis of Jiaodong gold deposit.Selecting five 1∶50000 geological-sections of 220 km in total length,we carried out field observations and completed the 1∶250000tectonical lithofacies metallogenic map of the Jiaodong Laizhou-Zhaoyuan region.Here we present the metallogenic model of＂mineralization of tectono-magmatic upheaval-hydrothermal alteration in detachment zone＂.In this model,in the counterclockwise shearing structures of East Asia region,Moho fluctuation induced by the tectonic stress field first brought about the North-East mantlebulge and mantleshrinkage,where Moho distribution controlled the concentrated development zone of Mesozoic metasomatism molten magma.Next,as shown by the diagenetic structural measurement and analysis of granites,the tectonic magmatic dome formed with the Linglong granite body at its core,and regional shear fracture zone developed in the contact zone between metamorphic rocks and granites in Jiaodong groups.In later times,the shear zone developed normal faulting from the sliding of the hanging wall,and a large-scale post-magmatic hydrothermal replacement-alteration occurred at the shear detachment zone,as illustrated by the structural measurement of fracture zone.In the final step,in a 1.5km wide or wider fractured rock zone,superimposed hydrothermal metasomatic alteration formed the huge Linglong-Jiaojia-type quartz vein-altered rock type gold mine.This new metallogenetic model not only has a role in promoting studies on the metallogenesis of the Jiaodong gold mine,it can also guide the deep peripheral mine explorations.