The Mineralization Characteristics And Prospecting And Evaluation Marks Of The Breccia-pipe-type Gold Deposit In Jinchang,Dongning County,Heilongjiang Province

Jinchang deposit which is a super large gold deposit found by the first squad of the chinese people's armed police force gold units is Located in the Dongning county,Heilongjiang province,It is in the geotectonic location of the transition area between Taipingling uplift and LaoHeishan fault.The stratums in the mining area are less exposed while the fracture structures that present as an "M" word are extraordinarily growing.There are five period magma intrusion activities and formed a broad distribution of magmatic rocks in the mining area.There are three mineralization types:breccia-pipe type,veinlet-disseminated type and filled-controlled-vein type.The scale of the breccia-pipe-type mineralization is the biggest which account for 44% of the total resources of the deposits.There is a lack of systematic comparison of breccia pipes within the mining area and the summary of prospecting evaluation marks of the breccia barrel type mineralization is also imperfect,therefore,the article carried out a systematic classified research and forming reason research about the breccia pipes in order to provide theoretical support for the ore exploration.The breccia pipes mainly distributed in the contact zone of yanshanian granite and indo-chinese epoch diorite and near the intersection of all kinds of fault,they mainly present oval or suborbicular in the plane while shaped tubular or funnel in the section.According to the differences of the gold-bearing nature and the mineral composition the breccia pipe can be divided into three types: Au-Cu±Mo-type breccia pipe,Au-type breccia pipe,lean-ore-type breccia pipe.The former's ore mineral in which the Au and Cu have reached industrial grade give priority to pyrite and chalcopyrite,followed by molybdenite,hematite,magnetite,galena,sphalerite and natural gold.The middle's ore mineral in which the Au have reached industrial grade give priority to pyrite,followed by chalcopyrite,galena,sphalerite,arsenopyrite and natural gold.The latter's oremineral is poor which give priority to pyrite followed by galena and sphalerite.It have no industrial value.The protogenetic fluid inclusions in the quartz that contained in the cement of breccia-pipe-type ore are very rich.There are 4 types fluid inclusions as follow:S-type,V-type,SL-type and VL-type.Fluid inclusions microscopic temperature measurement and Hydrogen and oxygen isotopic composition of the ore-forming fluid indicate that the ore-forming fluid of the breccia-pipe-type ore body is a mixture of lava,volatile,high temperature and high salinity solution.In the late ore-forming there is a little bit atmospheric precipitation mixed in.The characteristic of sulfur isotopic composition show taht the sulfur belongs to magmatic sulfur that mainly comes from the mantle and a small amount from the earth's crust.Combined with the feature of lead isotope composition,we can speculate that the ore-forming material mainly comes from the mantle and a little from the earth's crust.Isotopic dating results indicate that the metallogenic age of breccia-pipe-type deposit is about 102.9±2.7 Ma,so,I consider that the formation of the breccia-pipe-type deposit mainly related to the granite porphyry intrusion activities(109 ± 2.4Ma)happened in the late yanshan,the later diorite porphyrite intrusion activities(97.5±1.1Ma)made a superimposed mineralization.The distribution of breccia barrel is close contact with the intersection of different magmatic rock,the intersection of fracture structure,mineralized alteration zone and the ring structure interpreted by remote sensing.At the same time,the orebody shows clear low resistance and high polarization characteristics.In addition,the three types of breccia barrel have some differences in the following several aspects: Ore mineral composition,pyrite typomorphic features,fluid inclusions microscopic measuring temperature and soil geochemical characteristics.All of these provide the basis for the summary of prospecting and evaluation marks of breccia barrel.