The Analysis Of The Relations Between The Geochemical Characteristics Of The Ag-Pb-Zn Polymetallic Deposit Wallrock And Its Mineralization In Keshiketengqi Bairendaba,Inner Mongolia

This paper is to analyze the geological characteristics of the western slope of the southern section of Daxinganling Bairendaba Ag-Pb-Zn deposit,with an emphasis on the study of geochemical characteristics of the wallrock,aiming to discuss the diagenetic mechanism of the wallrock,and in addition,its relations with the deposit as well as the diagenetic mineralization mechanism between the two.The conclusions are as follows:1.The content of the major elements in metamorphic rock of the Lower Proterozoic Baoyintu group in the mine changes greatly;less SiO2 is contained in diorite;the content of alkali is balanced and sodium is relatively rich.The average of A/CNK is 1.02 and A/NK 2.24.Therefore,it can be deduced to be calc-alkaline metaluminous-peraluminous igneous rock;Mafic dikes can be divided into two parts:alkaline gabbro and sub-alkaline gabbro.Both are characterized by very poor SiO2,poor alkali,rich iron,magnesium and sodium as well as weak unsaturated aluminum.But the latter is richer in magnesium and has pile of crystal effect;northern granite is rich in SiO2 and alkali,relatively abundance in potassium.A/CNK value is about 1.Hence,it might be alkaline quasi aluminum magmatite with high content in potassium and calcium.2.In the mine of Lower Proterozoic Baoyintu group,metamorphic rock,diorite,mafic dikes and northern granite are relatively rich in LILEs but obviously poor in HFSEs,and the beads graph overall turns right;the first three have lower ?REE,moderate negative Eu anomaly,while the last one has higher ?REE and obviously positive Eu anomaly;Baoyintu group metamorphic rock has an uneven pattern:relatively rich in light REE.While diorite,northern granite and sub-alkaline gabbro have such a pattern:the light REE obviously turns right while the heavy REE is relatively flat,with sub-alkaline gabbro more flatter.The alkaline gabbro has "geese"shaped REE pattern,for the distinction between the light REE and the heavy REE is not obvious.As for the content of transition element,only sub-alkaline gabbro is high,but the rest are low.3.As for diagenetic mechanism,the Lower Proterozoic Baoyintu group metamorphic rock was formed by an acidic magmatic event in the Proterozoic(1005?1286Ma),and subsequently accompanied by a mixture of the regional sedimentary clastic rocks and experienced the multi-stage regional tectonic deformation and metamorphism.The Late Carboniferous intrusive rocks were not only formed by the island arc where the crust of the Paleo-Asian oceanic subducted to Siberian plate in the Late Carboniferous but also the product when in the active continental margin background,the oceanic plate continued to subduct to keep the interior of the continent.In the north of the mine,Late Jurassic granite is a S-type granite and has the characteristics of Adakite.It was formed during the Paleoasian closed post-orogenic background when crustal thickening caused by orogenic collision led to the partial melting together of the crust materials containing iron and magnesium.4.As for mineralization mechanism,there does not exist a direct connection between the formation of the deposit and Lower Proterozoic Baoyintu group metamorphic rock as well as the northern granite in terms of time and space.The latter two may provide some material basis for the mineralization.And the tectono-magmatic event of the Late Carboniferous rocks mainly provided space,place,and some minerals for mineralization.