| Dachang of Guangxi nandan is a world-famous super tin polymetallic deposit in China. Also the tin industry has a great influence to the world. The complex geological conditions and the metallogenic conditions attracted numerous geological researchers studying in the region. There is so many statment of the DaChang metallogeny. Yu-Chuan Chen academicians mines and fields by studying the pattern forming, and established Dachang tin-polymetallic ore belt metallogenic series and metallogenic model. Xilin Li, Xu-Sun Ye, etc. discussed the primary tin ore deposit, the geological characteristics and the metallogeny, demonstrating the granite and metallogenic evolution is the formation of tin-polymetallic deposits in the major controlling factors. Cai Hongyuan, Liang-qi Lei, Huai-yang Zhou, Guo-Lin Zhang, Hanfa, Zong-Ting Liao, De-Xian Qin, etc. belive that it's a syngenetic mineral deposit with volcanic blowpiping and related to Granite hydrothermal then. These studies focused primarily on geological studies of granite and mineral deposits, has not yet been systematic research on the formation.This paper combined to "The study of Dachang Devonian controlling tin ore's mineralization" and "The east of Dachang east rock wall's metallogenic regularity and prediction" project, on the basis of the previous research results, the writer Researched and explorationed the stratigraphy, rock characteristics, rock geochemistry and rock facies and palaeogeography in the area.The researcharea stayed in Danchi fold belt.It is affluent in minerals,but geological features is very complex. For a long time, researchers focus on igneous rocks, intrusive rocks.So the formation's analyse is trifle. As a pointcut,we made new division of the formation combined with the new discovery during research process. Main accomplishments include the following:(1) After drilling core samples and testing the tunnel plots, we summed up a more systematic stratigraphic division of Dachang district. This division mainly focuses on the following:According to the Devonian Period slide River Group chert output characteristics, it is divided into three layers; through the identification of the Devonian Period in the Unification Luo group of samples,they have been re-classified; The skarn is carried out a systematic study on Devonian; we make histograms on the basis of the information on various aspects of Devonian.(2) In the middle and upper Devonian Commission found basic, neutral volcanic rock, and the sub-basalt veins was found near the "East Rock Wall". Volcanic basalt, altered andesitic basalt, tuff-based; times basalt pulse outputs from north to south, and parallel with the "east rock wall" outputs.(3) Through the study sample of stratigraphy and intrusive rocks in the area, reach the geochemistry feature about constant element, trace elements and REE of various geological periods. Made on the vertical curves of the various elements, combined with the sedimentary characteristics of each period for comparison.(4) through the various studies of Lithology and output, combined with the theory of our predecessors experience, given Summary to palaeogeography phase of Devonian of integration of Dachang District.(5) Proposed the "east rock wall" should be the same as the Devonian sedimentary faults, substantially isotonic in the early Hercynian, for the same deposition (with students) fault, controlling the formation of the deposition and mineralization; Indo-Yanshanian north-west to the folding,Hin-twisting pressure, controlling the transformation of invasive activity and superimposed mineralization in the Devonian strata.(6) Proposed the "East Rock Wall" ore-controlling mode of Dachang tin, and Carved out the target areas with prospecting potential in the research division. |
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