Geology, Geochemistry And Metallogenic Model Of Carlin-type Gold Deposits In Southeast Yunnan Province, China

Southeast Yunnan province is a part of Dian-Qian-Gui gold-triangle, one of the famous concentration area of carlin-type gold deposits,and presently the systematic research is still insufficient for it.Guided by theory of plate tectonics,regional metallogenics,geochemistry, metallogenic prognosis,prospecting systematic engineering,based on more than ten years of gold-prospecting practice in Southeastern Yunnan area,the author has collected a large number of geological and geochemical data,analyzed different sub-types of the carlin-type gold deposits,and pay attention to the temporal and spatial distribution of gold and tin-tungsten,copper lead,zinc and silver,antimony arsenic mercury(Ba).Furthermore,took the mineralization,metallogenic law, forming within this area as the main line,the author has conducted systematic studies about its geological and geochemical characteristics, metallogenesis,metallogenesis law and metallogenic prognosis.The main achievements and cognitions are as follows:1.Combined with its existing studies,a redefinition of Carlin-type gold deposits is put forward that is(ultra) fine,disseminated, meso-epithermal gold deposits with concentrated zoning distribution.2.Regional metallogery geological setting of Dian-Qian-Gui gold-triangle was systematically discussed with geology,geophysics, geochemistry and remote sense data,the existence of Youjiang valley(mantle swell) was also be confirmed,and it was demonstrated that the source material of Carlin-type gold deposits in Dian-Qian-Gui gold-triangle is mainly relative to the basic igneous rock and volcaniclastic turbidite deposition which accompanied with the Emei mantle plume activity happened nearby the rift valley and regional discordogenic fault.The regional structure movement and acidity and the basic magmatic activity accompanying were the most important heat source.3.It is demonstrated that the formation and evolution of Nanpanjiang basin is the result of the differential subsidence on the weak district caused by the effusion and horizontal stretching of basalt which originated from the collision of Indian,Eurasian and Pacific plates and then the mantle thriving.It is pointed out that,from the regional geochemistry standpoint,the Youjiang Rift activity begins as early as Cambrian Period at least,and splits gradually form western Guangxi to southeastern Yunnan and southwestern Guizhou.4.A brief introduction about the geological characteristics of carlin-type gold deposit in Southeast Yunnan province is given in the paper.On the basis of its yielding features,host rocks etc.,the Karlin gold ore in southeast Yunnan region could be divided into fine clastic rock-impure carbonatite type,unconformity type,basic rock type and red clay type.Discussed the relationship between Carlin-type gold deposits and gold-bearing construction,magmatic rocks,tectonic,and took the typical gold deposits in this studying area for example,the author presented the geochemical characteristic of the major elements,trace elements,REE,fluid inclusion,isotopes and pyrite single mineral and so on.5.As for the mineralization of Carlin-type gold deposit in Southeastern Yunnan province,it is indicated that crust-mantle inhomogeneity and their interactions→pre-metallogenesis→metallogenesis→post-metallogenesis is a series of natural "Beneficiation" Process and they contacted and promoted with each other. "pre-metallogenesis" concept,the possibility and its implications for mineralization of epithermal-mesothermal ore deposits(such as carlin-type gold deposit etc.) were put forward in the paper.Furthermore, from the geochemical point of view,the author discussed the mechanism of ore-forming transfer and sedimentation.6.Using the theory of metallogenic series,the author discussed the space-time relationship between gold deposit and tungsten,tin,copper, lead,zinc,silver,antimony,arsenic,mercury and other minerals,and put forward there are some major metallogenic series combination in Southeast Yunnan including:(1) the pre-metallogenesis series related to the evolution of northern Vietnam oldland and Nanpanjiang basin;(2) the epithermal-mesothermal minerogentic series related to the Emei mantle column activity;(3) the superimpositiom and transformation minerogentic series related to the Yanshanian granitic magma activity and regional tectonic movement.7.As for the genesis of Carlin-type gold deposit in Southeastern Yunnan,three conclusion are summarized:(1) Crust-mantle inhomogeneity and distribution and redividsion of the elements from original evolution to present are the basic factors of special distribution difference of different ore(2) Pre-metallogenesis is the key factor of the unconformity type gold deposit mainly forming along the Caledonian unconformity surface;(3) Driving heating power came from the northward thrust overriding of Vietnam oldland and strike-slip of a few macroplate,and associated with fault-fold zone,cut-layer fracture structure and the intensive tension zone formed by magmatic intrusion and shrinkage at the external magmatic-body are determinate for the formation of Carlin-type gold deposit and other endogenetic deposit in Dian-Qian-Gui gold-triangle even in southeastern Yunnan province.What's more,the author formerly summed up the metallogenic laws and metallogenic model of Carlin-type gold deposit in Southeastern Yunnan region.8.As for the gold prospect of the region,guided by theory of metallogenic series,regional metallogenics,metallogenic prognosis,the author made some pertinence investigation,and then focus on the application of research results at geology prospecting and engineering approval in deep ditch and external edge of Manlonggou gold deposit.At the same time,The author predicted the ore-forming targets at the outskirts of Gejiu deposit and deep part of one gold deposit in Qiubei, and put forward that in addition to Youjiang rift,there are still have others ascending passageway for the gold and other siderophile elements in Dian-Qian-Gui gold-triangle.Therefore,it is good prospect to look for large,superlarge primary gold deposit in southeastern Yunnan even in Dian-Qian-Gui gold-triangle area.