Ore-forming Factors And Metallogenic Prediction Of Banmiaozi Gold Deposit Jilin Province

The Banmiaozi gold deposit is located in Baishan City,southern Jilin Province.The Laoling metallogenic belt,in the eastern part of the northern margin of the North China plate.The Mesozoic tectonic evolution experienced collisional orogeny and post-collisional extension related to the closure of the Paleo-Asian Ocean,as well as active continental margin and intracontinental extension environment related to the subduction of the Paleo-Pacific Ocean.Because of the superimposition of the Paleo-Asian Ocean and Paleo-Pacific Plates,the mineralization in Northeast China is relatively complex and intense.The intracontinental extensional environment caused by subduction provides favorable conditions for the formation of porphyry copper-molybdenum deposits and epithermal deposits.The Banmiaozi gold deposit was formed under this condition.By studying the diorite porphyry body,ore-hosting strata,structure and geochemical characteristics of the deposit in Banmiaozi gold deposit area,this paper discusses the metallogenic elements,genesis of the deposit,restricts the metallogenic age,determines the prospecting criteria,establishes the metallogenic model and conducts deep prospecting prediction research.The main results are as follows:(1)The ore-hosting strata of Banmiaozi gold deposit are mainly marble of Zhenzhumen Formation of Paleoproterozoic Laoling Group,hematite quartz sandstone developed at the bottom of Diaoyutai Formation of Neoproterozoic Qingbaikou System and silicified structural breccia zone between them.The regional F102 thrust nappe fault and F100 detachment normal fault are important ore-controlling,ore-guiding and ore-hosting structures.(2)The geochemical composition of diorite porphyry exposed in the mining area shows obvious adakitic rock characteristics.Magma originates from partial melting of the dismantled and subsided crust and metasomatism with mantle peridotite.The emplacement age of diorite porphyry is 133.3±0.9 Ma,and its formation age is Early Cretaceous.The tectonic setting is in a strong extensional background related to the subduction of the Paleo-Pacific Plate,and the hydrothermal zircon age in the porphyritic zircon is 130.6±1.0 Ma,which limits the metallogenic age of Banmiaozi gold deposit.(3)The analysis of H and O isotopes of barite minerals in Banmiaozi gold deposit shows that the ore-forming fluids originate from the mixing of formation water,metamorphic water and magmatic water.The analysis of S isotopes of pyrite and barite minerals shows that the mineralization materials in stage II are related to magmatic activity,and the mineralization materials in stage III are derived from oceanic water and marine evaporite.(4)Banmiaozi gold deposit belongs to epithermal deposit,which is related to magmatic activity of Yanshanian,especially early Cretaceous.(5)Based on the metallogenic elements of Banmiaozi gold deposit,the prospecting indicators are determined as follows: marble of Zhenzhumen Formation,hematite quartz sandstone developed at the bottom of Diaoyutai Formation,silicified structural breccia belt,adakitic dioritic porphyry,silicified structural breccia belt in the early stage of overthrust fault transformation,etc.And the paper established the metallogenic model i and predice the deep metallogenic.