Dachang Tin Devonian Geological Research

Tongkeng tin mine (polymetal) of DaChang in Guangxi is located in the north of Dan pond fold in the southwest margin of southern Pangea, which is the world's ultra-large type tin polymetallic deposit. It also plays an important role in tin industry in the world. Devonian is the main ore-controlling strata, which has a few stratigraphic horizon with the stratiform deposit related to the volcano-hot water deposition of the seabed. Vein-type orebody related to magmation of Yan Mountain in the advanced stage is mainly in the Devonian.In the past, the research mainly concerned granite, deposit control action and regularity of ore formation. but devonian stratum and its deposit control action have not been specially researched. The master's thesis did a preliminary research of the devonian stratum on the Devonian, which combined with school project "stratum and the study of regularity of ore-control and mineralization prediction of the Dachang tin devonian stratum".Is there volcano rock in Dachang tin ore devonian stratum? This involves cause of Dachang tin polymetallic deposit, and has drawn a lot attention of geologists. With a intensive study on Dachang tin ore during a period of two years time, plenty of basic volcano rock and sub subvolcano rock have been found in devonian ore rock stratum, including layered rock ore and top/bottom of wall rock. The ore rock stratums, grain layer, fine granularity, strip originally developed for mutual layered mud limestone, carbon shale, skarns. According to the findings and referencing to the previous studies, a wide range of devonian stratum and the field geological investigation and research work of indoor comprehensive are conducted, including actual survey of devonian stratum section and collection of various kind of samples in order to microspecimen identification and chemical analysis of petrology and geochemistry characteristic of devonian stratum. On the basis of analysis result and previous research achievements of regional stratum of extenics, the detailed division of various group and section in devonian stratum the contrast of volcanic rocks founded and Guangxi's devonian volcanic rocks. Based on the comprehensive study of devonian stratum and summary of Dachang tin ore formation, results are mainly follows: (1)Plenty of basic volcano rock and subvolcano rock were found in devonian ore rock stratum. Volcanic rocks showed layered output, and mainly types included tuff, tuffite, altered basaltic andesite and so on; subvolcanic rocks showed vein output.(2) According to the rock stratigraphy method, devonian ore rock stratum was divided;based on the organization of previous research, according to volcanic rock were founded, luofu Fm of Devonian was subdivided two layers and liujiang Fm of Devonian was subdivided three layers.(3) With chemical analysis on samples, researches are carried out in the geochemistry characteristics in Devonian, and conclusion is that neutral-basic volcanic rock belonged to calcium alkali series in Devonian period stratum in Dachang.(4) East wall is a period of magmatic activity of multi-stage deep tectonic. Haixi is deposition (homozygous) fracture in the early stage to control volcano-hot water deposition of the seabed and jets-hot water deposition from the south and north to sub sea basin. In the north west yanshan period, to show the compresso-shear; to control invasion of sub-tuff, diorite and granite-porphyry and superimposed deformation mineralization.(5) Dachang tin ore was the cause of formation volcano jets-hot water deposition was put forward. In the existing copper mining area, there are at least one submarine, early hercynian volcanic sedimentary mineralization, and submarine sedimentation-exhalation hot water sedimentary mineralization, besides traditional granite metallogenesis at an advanced stage of Yan Mountain.