Minerogenetic Series And Ore-forming Processes Of Metal Deposits In The Liaodong Rift

Liaodong area, always paid attention to by researchers, is a nature geologic studying location due to long history, complex actions, various rocks and rich ore resources. It is generally divided into three parts in tectonic location—Archean North-liaoning granite-greenstone belt(Liaobei Block), Archean South-liaoning granite-greenstone belt(Liaonan block) and intermediate Paleoproterozoic Liaodong Rift composed of a set of thick volcanic sedimentary strata usually referred as to Liaohe group.The Liaodong Rift of NEE strike,400km long and150km wide, one of the most intact Paleoproterozoic rifts in China and even in the world, is located in east parts of the Eastern Block of the North China Cration, also a part of the Jiao-Liao-Ji Belt., including Haicheng, Dashiqiao,Gaixian,Fengcheng,Huanren counties and so on. There are plenty of important ore resources inclusive of magnesite, talc, jade, boron, gold, silver, copper, molybdenum, lead and zinc in the Liaodong Rift, the famous ore production base of North China. Metallogenic features of the Liaodong Rift are summed up of long ore history, special ore species, multiple ore deposit types, large ore scale and manifest ore beds. Intricate and chronic geologic processes blurred original ore appearance and added new ore likeness, so as not to correctly and perfectly recognize ore-forming processes and definite mineralization age nowadays.Research contents of the paper involve four aspects—tectonic history, minerogenetic series, ore-forming processes and divisions of ore belt of the Liaodong Rift by means of lithology, tectonics, geochemistry, geochronology and ore geology on the basis of field investigation, laboratory analysis, acquired data and the author’s recognition. And the main conclusions are as follows:(1) Tectonic history of the Liaodong Rift is newly divided into four phases,that is respectively, preliminary formation-early Liaoji granite emplacement, extensional subsidence-Liaohe group sedimentation, returning extinction-metamorphism, later Liaoji granite emplacement and reactive reconstructing-structure and magmas in relation to subduction. (2) Minerogenetic series of metal deposits in the Liaodong Rift are divided into minerogenetic series of Paleoproterozoic rift-formation age、Mesozoic rift-reactivation age and Paleoproterozoic-Mesozoic superimposed age. The former, in light of ore-bearing layers of Liaohe group upward, are subdivided into volcanic syndepositional-metamorphic Cu-Co deposit and carbonate syndepositional-metamorphic Pb-Zn deposit. The second are subdivided into four sub-Seriers of porphyry Mo、skarn multimetal、hydrothermal-vein Au and subvolcanic Au deposits. The last consists of disseminated Au、siliceous-potassium Au and siliceous-rock Au deposits.(3)Three ore-forming processes of Paleoproterozoic rift-fomation age、Mesozoic rift-reactivation age and Paleo-proterozoic-Mesozoic superimposed age are built according to minerogenetic series division. Ore-material sources, ore-fluid features and ore-forming processes of key metallic ore deposits are discussed on the basis of S, Pb, REE, D-O and fluid inclusion geochemical parameters. For the first time Qingchengzi lead-zinc deposits are considered in connection with peripheral gold-silver deposits, ore-forming processes of Huanren contact-type polymetallic deposit and Wanbaoyuan disseminated-type molybdenium deposit are simply researched and gold-silver deposits of superimposed ore-forming process are originally produced in ore deposit or ore embryo and finally superimposed and formed by main Mesozoic magmas activities.(4)Ore resources in the Liaodong Rift are divided into two NW striking ore belts of the south Wulong-baiyun gold ore belt and the north Wanbao-Huanren copper-lead-zinc polymetallic ore belt. The former is subdivided into the Wulong-Baiyun,the Xiuyan-Dagushan and the Xinfang-Maoling sub-belts, The latter is subdivided into the Huanrenerrpengdianzi, the Wulidianzi-Xiangyang and the Wanbao-Zhangjiabaozi copper-lead-zinc sub-belts.10million tons of Cu,20million tons of Pb-Zn and500tons of Au are expected to be found in the Liaodong Rift in future.