Study Of Orebody Space Location Regularity And Prospecting Direction Of Axi Gold Deposit In Xinjiang Province

Axi gold deposit lies in the Tulasu volcanic fault-basin on the west side of West Tianshan Mountain, North Xinjiang. Late Paleozoic volcanic rocks are widely distributed in this basin, and together with these newly discovered gold deposits or ore occurrences, constitute the gold metallogenic series related to the early Carboniferous volcanic rocks. Axi gold deposit is the largest epithermal gold deposit in the Tulasu basin or even in the West Tianshan Mountain, who was formed in Late Paleozoic and was closely related to the volcanic rocks, volcanic apparatus and fracture F2. This deposit includes7epithermal hydrothermal ore bodies and1sedimentary origin one, and it suffered certain denudation and transformation.Based on field geologic survey in Axi mining area as well as its peripheral gold deposit Tawuerbieke and Abiyindi, by studying regional metallogenic background and geological characteristics of deposit and comparing to previous research results, this paper places emphasis on (1)the ore-controlling characteristics of volcanic apparatus and fault structure,(2)morphology and spatial distribution of the orebodies,(3)orebody quality parameters,(4)lateral trending,(5) characteristics of denudation and alteration, and space location of Axi-Tawuerbieke-Abiyindi regional gold deposit. Finally, the paper draws the orebody space location regularity, and furthermore the future prospecting direction in this mining area has been discussed. The main results are as following:(1) Axi gold deposit occurred in fissure type volcanic apparatus, so there is not any annular type volcanic apparatus as well as the metallogenic belt on the east ring mentioned by the predecessors. Three deep fault systems (NS, NW and NE in direction) have controlled the spatial distribution of different types of volcanic apparatus and gold deposit. Central volcanic eruption occurs at the NW and NE trending faults crossing where Tawuerbieke-Abiyindi porphyry gold deposit is, and fissure eruption occurs in the NS-trending fault F2where Axi epithermal gold deposit is. Fracture F2not only controls the fissure eruption, but also lays a foundation of construction space for Axi orebodies and metallogenic material.(2) F2fracture mechanic property along different directions controls the output spatial features of Axi orebodies. It has secondary fractures of horsetail shape on its northern and southern ends, which represents some disappearance of the stress, and therefore the main fault limits these Axi orebodies in the reverse "S" of fault systems; its tensional nature makes Axi orebodies outline a wedge shape with bigger head and smaller end and thin out to the depth; its strike-slip nature in horizontal direction causes the concavities and convexities of structural surface, which controls the special occurrence of the ore shoot. The stress condition limits the orebodies in its upper part, and controls these branch orebodies to appear at the elevation of1300m above, especially where the main orebody enlarges and its occurrence changes greatly.(3) The spatial patterns of Axi orebodies vary regularly both in the plane and vertical profile. The deposit shows inverse S-shaped on the plane with cauda-liked minor orebodies paralleled both in the north and south ends, while on cross section it appears like a wedgy carrot with bigger head and smaller end, and along both strike and tendency it has enlargement and systolic characteristics. The thickness of orebody rapidly decreases between1300m and1250m level, and the orebody shows large and thick as the main part of wedgy carrot above1300m, and long and thin as the root of the carrot below1250m. The mineralization intensity in north ore section is higher than in the south part, and the rich ore-column occurs in northern exploration line38～48.(4) By studying on the grade and thickness with analysis on the forms and mineralization of ore body, this paper holds that the mineralization intensity in north ore section is higher than in the south and that the deposit pitches N. The northern orebody shows larger scale and stronger mineralization, and have relatively deeper mineralization depth, especially between exploration line16～56. The characteristics of lateral trending reflects in two aspects the lateral trending of the deposit and that of ore column, the former with a pitch angle of10°～15°while the latter with a much larger pitch angle of70°～80°. The deposit is buried deeper gradually to the north, and the deepest level has been obtained by pyrite pyroelectricity.(5) By study of the morphology and occurrence of the orebodies and geological features, this paper establishes a corrosion model of Axi gold deposit, and points out that Axi deposit suffered the first balanceable corrosion and the second discrepant corrosion. As a result, the southern deposit is denudated to the middle and lower of the original deposit (at a detachment rate of40.75%), more strongly than the northern part with a denudation to the central or middle-upper part (at a rate of25%). This erosion and reworks also caused the deposit to pitch N.(6) By comprehensive study on the regional spatial distribution, metallogenic features and genetic connection of Axi-Tawuerbieke-Abiyindi epithermal gold deposit and porphyry gold deposit both related to volcanism, the ore-controlling characteristics of volcanic apparatus and fault structure, and the occurrence and erosion of Axi deposit, this paper also establishes a space positioning pattern of Axi-Tawuerbieke-Abiyindi gold deposit. This pattern points out the time and space relationship between Axi epithermal deposit and Tawuerbieke-Abiyindi porphyry gold deposit as well as eruption of central type and fissure type. It also holds that the gold mineralization in this area has a vertical zoning (from upper to lower):quartz vein typeâ†'altered rock typeâ†'porphyry type.Finally, based on all the geological research results, the space location regularity and the prospecting situation, this paper puts forward that the key point of the following prospecting in Axi mining area should be put to the northern ore section at line16～56, especially line24～44, and900to1200m level, while attentions should be paid to new mineralization as porphyry type in deep and new branch orebody on the hanging wall of the main orebody above1300m.