Research On Origin Between High-Arsenic Coal And Carlin-type Gold Deposit In Southwestern Of Guizhou Province

High-arsenic coal mostly lies in the "Golden Triangle Area" of Carlin-type gold deposits in Xingyi,Anlong,Xingren,ect.counties and cities in southwestern of Guizhou,among Yunnan,Guizhou as well as Guangxi.High-arsenic coal deposit Longtan formation in the Upper Permian,the main regional stratium is limestone of Maokou formation,clay,sandstone,limestone as well as coal of Longtan formation, Chert limestone of Changxing formation,siliceous shales of Dalong formation and fine sandstone of Yelang formation in Triassic System,a large number of Carlin-type gold deposits also occur in the Longtan formation.In southwestern of Guizhou province,often appear out Carlin-type gold deposits(mineral occurrence) near high-arsenic coal mine,and even coexistence between high-arsenic coal and gold bodies,which forms an unique geological phenomenon between exogenous deposits and endogenous deposits background.In this paper,through a study deeply from the regional geological background,geological features,related features,mineralization and geochemical characteristics,coexistence,origin relationship between high-arsenic coal and Carlin-type gold deposits in southwestern of Guizhou province,show out the following conclusions:1.A large number of high-arsenic coal and Carlin-type gold deposits are strictly controlled by sedimentary layer in southwestern of Guizhou province.Coal-bearing rocks as well as ore-bearing rocks of Carlin-type gold deposits are located between the Emei Mountain basalt("Dachang layer") and the lower Triassic series.It is a sedimentary of Longtan stage.2.In appearance,high-arsenic coal and non-high-arsenic coal are unable to be distinguished.Content of high-pyrite is high with high As,pyrite vein is development, and the pyrite crystal is coarse,and in the contrary,to the sample of low As content, pyrite content is less-sustained bulk distribution pyrite crystal is small tablets.It shows a closer relationship between mineralization mine of As and mineralization of pyrite.3.Not all are high-arsenic coal,even with a high-arsenic coal mine,and only one or several beds is a high-arsenic coal in western of Guizhou.4.Arsenic and arsenic minerals such as arsenopyrite are not detected in all forms of pyrite(pyrite strawberry-shaped,star disperse,banded, idiomorphism-hypidiomorphic granular,interstitial disseminated,a ring-structure and other shapes) and other minerals as well as organic matter,therefore arsenic does not exist in the form of independent mineral.5.Arsenic and Aurum are together intergrowth,there be always aurum and other metal deposits(mineral occurrence) near by high-arsenic coal deposit;Arsenic and Aurum of the Emeishan basalt underlying of high-arsenic coal-bearing rocks is significantly higher compared to the content of the world average,and they can provide a wealth of arsenic and gold source for the future high-arsenic coal and Carlin-type gold deposits.6.REE,Mineral inclusions,Stable isotope geochemistry revealed:gold, mercury,thallium ore is in a homology with arsenic of Longtan coal,the Longtan coal shale as well as Emeishan basalt is inheritance in composition of the REE.7.Emei mantle plume activity is the prerequisite formed high-arsenic coal and Carlin-type gold deposits in southwestern of Guizhou province,it provided material source of high-arsenic coal and Carlin-type gold deposits,under magmatic activity of the Emei mantle plume in the Late Permian epoch-Middle Triassic epoch,the source bed of arsenic,gold and other minerals ore are formed by a large-scale eruption of magma material,which is deposited by hydrothermal solution sediment process and halmyrolysis.8.The sedimentary environment of the southwestern Guizhou was rebuilt by Emei mantle plume activities.Emeishan basaltic magma eruption of the numerous intermittent mineralization dynamic process leads to form high-arsenic coal,gold and other ore deposit in southwestern Guizhou province.The mineralization process of high-arsenic coal and gold deposits is actually As,Au activation→migration→aggregation.9.The Emei mantle plume activity of Yanshan period changed the macro structure condition of the southwestern Guizhou,it makes the ore-bearing hydrothermal solution change from the relatively closed system to a semi-enclosed-open system changes,which lead to from high-arsenic coal and gold deposits through accumulating arsenic,gold and other minerals.By studying and discussion,high-arsenic coal and gold ore-forming process is as follows:the southwestern Guizhou locates special tectonic position of the verge of Tethys-Himalaya tectonic domain and Dying Pacific tectonic domain binding sites, Emei mantle's plume activity continued a long time,under the Hercynian Soochow campaign role,the most strongly in Guizhou,a larger phenomenon of mantle plume formation of activities shaped a more occlusion,platform facies and platform marginal slope the transition zone sedimentary environment along Xingyi,Anlong, Xingren,Zhenfeng in southwestern of Guizhou;At the same time,Emei mantle's plume activity of the Late Permian early Emeishan basaltic magma eruption,which is the base of the peak period of activity,along with underwater volcanic hydrothermal activity,a large number of As,Au,and other trace elements were very homogeneous dispersion state enter the special environment of sedimentary basins,with the ancient sea-level changes,entered and sedimented in the Longtan Formation Group.As,Au, and other trace elements of diagenesis of the coal were very homogeneous dispersion state;But in Emei mantle's plume activity of Yanshan Age under again,as Emei mantle's plume activity formation of regional geothermal anomaly,a large number of As,Au,and other minerals extraction by deep groundwater seepage from the constant cycle of the Emeishan basalt and coal strata into hot water,as strong tectonic movement,the relatively closed system balance has been damaged,and the water along the fold activation,such as tectonic fault with weak migration,when the hot water through the seam,As,Au,and other minerals were a large number of enrichment under deposition role in the local pyrite Lot,as a result of the mineralization of high-arsenic coal formation and the surrounding gold deposits (mineral occurrence) and other unusual element.In addition,aggregate out high-arsenic coal,Carlin-type gold mineralization models in this paper.In short,basaltic magma eruption of Mount Emei of Emei mantle's plume activity provides a source of ore-forming matter and unusual geothermal background forming high-arsenic coal,Carlin-type gold deposits of western,Guizhou,it promoted the ore-bearing hot water cycle and migration,and the late again Emei mantle's plume activity mineralization dynamic role,which lead to form high-arsenic coal,Carlin-type gold deposits.