华北克拉通南缘早白垩世区域大规模岩浆-热液成矿系统

Early Cretaceous Regional-Scale Magmatic-Hydrothermal Metallogenic System at the Southern Margin of the North China Carton

华北克拉通南缘在中生代发生了大规模的成矿作用,主要的矿床类型有脉状金矿床(石英脉型、构造蚀变岩型)、斑岩型钼矿床、脉状银铅锌矿床.对于这些矿床的成因和成矿动力学背景,目前还存在不少争议.但近年来越来越多的成矿年代学证据表明,这些矿床均主要形成于早白垩世,且与区域上广泛发育的岩浆活动具有高度的时空一致性.在归纳总结华北克拉通南缘主要矿床类型地质特征和时空分布的基础上,简述各类矿床的成矿物质来源以及它们之间的成因联系,指出这些不同类型的矿床组成了一个巨型的岩浆-热液成矿系统.华北克拉通南缘成矿作用与其邻近的东秦岭-大别成矿带的成矿作用具有一致性,均受中国东部早白垩世大规模伸展作用控制,是统一的地球动力学背景下的产物.结合地球物理的资料认为,早白垩世岩石圈伸展及其导致的岩浆作用最可能与晚中生代古太平洋板块向东亚大陆边缘俯冲作用有关.上涌的岩浆热液在合适的构造体制下,与上地壳的岩石和流体发生交代和流体混合,最终在浅部形成大规模的岩浆-热液成矿系统.

The southern margin of the North China Craton has a large-scale ore-forming event during the Mesozoic,and includes three major deposit types of lode gold(as either quartz veins or disseminated ores),porphyry Mo,and quartz vein-type Ag-PbZn deposits.Ore genesis and geodynamic setting for these deposits,however,are still in a matter of debate.Geochronological studies in recent years have revealed that all of these deposits were formed during the Early Cretaceous,and show close spatialtemporal relationship with regional large-scale magmatism.In this study,we make a summary of geological features and regionally spatial-temporal distributioin of the major deposit types,and discuss their probable metal sources and possible genetic links between different deposit types.We suggest that these different types of deposits formed a giant regional magmatichydrothermal metallogenic system.Moreover,the mineralization event at the southern margin of the North China Craton has ages and geological features consistent with those deposits in the neighboring eastern Qinling-Dabie metallogenic belt.Theywere formed in the same geodynamic setting,which was controlled by the Early Cretaceous large-scale extensional events of the East China.In combination with geophysical data,such an extensional and magmatic event at a lithospheric scale was mostly likely related to the subduction of the Paleo-Pacific Plate underneath the East Asia continent.Upwelling of the magmas and the related hydrothermal fluids were extensively interacted with upper crustal rocks and shallow-derived fluids,and formed a regional scale magmatic-hydrothermal matallogenic system at the priority structures of upper crustal level.