| The main content in this paper is the basic geological characteristics of Dachang gold deposit, respectively with the primary halo of ore deposit, gold occurrence state and gold ore quartz veins silica source as the focus for research; on this basis, combined with previous data and knowledge, give a comprehensive analysis on the genetic type of the deposit.First, make full use of drilling production of gold and other elements of primary halo data for statistical analysis, obtained the gold mineralization material sources mainly is Triassic Changmahe group sandstone slate strata. According to the regional abnormal mineralization to draw the geochemistry contour diagrams, on this basis, reveal the total element geochemical primary halo zoning and deep prospecting rule from top to bottom is:(Sb、Hg)1,2,3-(Au、As)1,2,3-(Pb.Zn、Cu)1,2-3-(W、Sn、Bi、Mo)1,2,3. Based on the trace elements of primary halo characteristics of spatial distribution and the single drilling primary halo zoning, we think that this area have at least three times on an axially "pulse" fluid activity, and in some areas are superimposed on each other, leading to the axial element zoning tends complex. Simultaneous analysis the erosion status of the district formation of the ore field, Dachang area denudation degree is shallow, and has great potential for prospecting; Jiageilongwa area general denudation degree is medium, the shallow and deep prospecting foreground is valued; Zhajiatongna area local denudation degree is deep.Secondly, use laboratory analysis and testing technology, through the high power microscope, electron probe microanalyzer, environmental scanning electron microscope system and spectroscopy to study the occurrence state of gold, obtained the occurrence of gold in minerals mainly are arsenopyrite and pyrite, followed by quartz and iron dolomite. It is proved that the occurrence states of gold in this area mainly are two kinds of forms. The first is as microscopic, submicroscopic form exists in the form of pyrite, arsenopyrite and other arsenic sulfide lattice defects, ring and microscopic holes; the second is possible exist isomorphous alternative form occur in the gold-bearing mineral arsenopyrite and pyrite.Studied on ore quartz vein feature, period and its causes of formation or the relationship with the periphery area granite, think that ore silica source mainly related to the deep magmatic hydrothermal evolution. The east part of Zharijia granite formed during Indosinian period, and has a similar age with the area of Kunlun orogenic movement and Dachang gold deposits, which illustrate the Kunlun Orogeny, magmatic activity, and gold mineralization dynamics coupling relationship.On the above analysis of the basic geological characteristics of the deposit, combined with early stage and other aspects relevant to understanding, the genetic type of the deposit is discussed, think that the formation of Dachang area gold deposit is related to the Indo-end of the Kunlun orogenic movement; from the point of view of dynamics is the large type orogenic gold deposit, genus orogenic gold deposit as shallow sub-categories; mineralization analysis should be mainly to atmospheric precipitation, and affected by the magmatic hydrothermal fluid and metamorphic hydrothermal fluid of mixed hydrothermal reaction type gold deposit. |
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