Research On The Geological-Geochemical Characteristics And Metallogenic Prognosis In The Shuangpengxi Deposit Area, Tongren, Qinghai Province

Based on the summary of regional geological background and main deposit types of Shuangpengxi deposit, the author choses Shuangpengxi gold-copper deposit and Dehelongwa copper-gold deposit as a key point, and gave a deposit geochemistry and prospecting geochemistry research on them. A systematic and further study of geological features of deposit, metallogenic regularity, geochemical characteristics and ore genesis on Shuangpengxi deposit was given in the paper by multi-interdisciplinary knowledge such as petrology, structural geology, mineral deposit geology, ore deposit geochemistry, isotope geochemistry, fluid inclusion geochemistry, exploration geochemistry and mathematical geology. Given a comprehensive summary of metallogenic regularity, the author had developed some researches on prospecting prognosis. Major conclusions of this paper are following.Firstly, the paper summarized and studied the regional tectonic setting and regional geological features of Shuangpengxi deposit, and gave a summary and research on the geological feature, ore feature, orebody feature, structure, and construction and wall rock alteration characteristics of its deposits and related rock-mass.Secondly, the paper conducted an analysis for major elements, REE and trace elements of intrusive rock and volcanic rock in Shuangpengxi deposit, and gave a further research into the tectonic setting in which the two rocks were formed. The results showed that the granitoid intrusive rocks in this region were gabbro diorite, grano diorite, diorite, granite respectively. So it was concluded that the main was land-land collision granite with some of arc granite feature. The volcanic rocks in this region were basalt, basalt-andesite and andesite. With graphic analysis, it was thought that source of the volcanic rock was of diversity. Some was from the volcanic arc basalt and the other was from the oceanic basalt.It showed that the ore-forming material source in Shuangpengxi deposit should be mixed source, with some REE and trace elements from magma and sulfur and lead isotopes from the crust-mantle mixed source, through an analysis of ore petrochemistry, rare earth element, trace element, dispersed element and sulfur and lead isotopes in the deposit and a comparison with the geochemical characteristics of volcanic rocks and granite intrusive rocks in this region.Thirdly, it was the first time to research on the fluid inclusion of ore in Shuangpengxi deposit. The study showed that the gas fluid inclusion was predominent. As for the liquid composition, the most amout of cation were Na⁺,K⁺,Ca²⁺, while the most amout of anion were SO₄^2-,Cl^- and the second was F^-. The gas composition mainly was H₂O and CO₂ then H₂,CH₄,N₂,C₂H₂,C₂H₆,O₂ and CO respectively It showed that the ore-forming fluid was a kind of mixed fuild with meteonic water through the study on the gas-liquid characteristic parameter of inclusion. It also was a kind of fluid of medium-high temperature, low salinity, moderate density and medium pressure by homogenization temperature for the fluid inclusion and analysis on some important parameters.Fourthly, it was concluded that the deposit was characteristics of multiore-controlling factors, multisource ore-forming materials and multiore-forming periods on the summary and research of its ore-controlled factors, ore-forming material sources, and the source of ore-forming fluid.Fifthly, the paper gave a summary and study on the geological characteristics, ore-controlling factors and metallogenic regularity of Shuangpengxi gold-copper deposit and Dehelongwa copper-gold deposit. It showed that Lower-Permian Daguanshan group and Lower-Triassic Longwuhe group were source beds, and the west-north fault was the host stuctures of ore-controlling.The volcanic rocks and granitoid intrusive rocks were not only an important source of metallogenic materials, but also an important condition for the forming of metallogenic fluids and metallogenic structure. On the basis of the deposit geological geochemistry characteristics and exploration geochemistry characteristics, the stratigraphic, tectonic, magmatic rocks, wall rock alteration, geochemical and other prospecting criteria were determined.At last, given a 1:25000 primary halo geochemical exploration for Shuangpengxi gold-copper deposit and a 1:5000 secondary halo geochemical exploration for Dehelongwa copper-gold deposit, the paper established the right synthesis prospecting model by application of geostatistical analysis to determine the background value.On the study of geological characteristics, metallogenic regularities, genesis of deposit, and geochemistry of deposit, the author gave an initial exploration for the deposit by exploration geochemistry and delineated 3 prospect areas of A-type, 2 prospect areas of B-type and 2 prospect areas of C-type, which had a great significance for carrying out mining exploration work in future.