中国东北部陆缘内生金矿床成因类型、成矿时代及地球动力学背景

Genetic Types,Metallogenic Epoch and Geodynamic Settings of Endogenetic Gold Deposits in the Continental Margin,Northeast China

中国东北部陆缘是我国内生金矿床较为发育的地区之一,以成矿作用复杂、蕴藏丰富的金资源量倍受国内外地质学家关注。通过对该区内生金矿的地质和成矿年代的系统研究,初步将该区内生金矿床划分为中温热液金矿床、接触交代-热液金矿床、斑岩型/类斑岩型金铜矿床和浅成低温热液金矿床4种主要成因类型和3个重要成矿期(170～160 Ma、130～110 Ma和110～90 Ma)。结合同位素地球化学特征,进一步确定中温热液金矿床的成矿物质主要来自下地壳源,成矿作用与中生代燕山早期古太平洋板块俯冲作用引发的中国东部大陆边缘岩石圈减薄及拆沉的动力学过程密切相关;接触交代-热液金矿床的成矿物质来源于年轻地壳,成矿作用与古太平洋板块俯冲引起的岩石圈减薄拆沉的伸展构造背景下的岩浆接触交代作用更为密切;而斑岩型/类斑岩型金铜矿床和浅成低温热液金矿床的成矿物质来源为壳幔混合源,其成矿发生在古太平洋板块向亚洲大陆正北向俯冲转入Izanagi-Farallon板块西向俯冲的构造转换期。

Numberous endogenetic gold deposits are found in the epicontinental region in Northeast China,and they have attracted more attention and research efforts from both domestic and international economic geologists.These deposits are featured by the characteristic of complex and obviously multistage mineralization.Based on systematic study on geological features and metallogenic epoch of these endogenetic gold deposits in the area,the present paper has divided the gold deposits into four main types： mesothermal,contact-metamorphic,porphyry gold-copper and epithermal gold deposits.They were formed in three important ore-forming epochs at 170-160 Ma,130-110 Ma and 110-90 Ma.Based on isotope geochemistry,we concluded that that the metallogenic material of the mesothermal gold deposit was derived from the lower crustal source and its mineralization was closely related to lithospheric thinning and delamination of the continental margin,a processes triggered by the subduction of the Paleo-Pacific plate in the Early Mesozoic Yanshanian orogeny.The metallogenic material of the contact-metamorphic gold deposit was derived from the younger crust and the mineralization was relevant to contact metasomatism of magmatic process under extensional setting of the lithospheric thinning and delamination,which caused by the subduction of Paleo-Pacific plate.However,metallogenic material of porphyry gold-copper deposit and epithermal gold deposit manifested as crust-mantle mixture.Their mineralization occurred in the tectonic transition period from Asian continent subducted by the Paleo-Pacific plate towards the due north to the Izanagi-Farallon plate subduction toward west.