Study On Mineralization Regularity In Hongtugou-Chuancigou Gold Deposit Of North Qilian

The North Qilian orogenic belt is located between the Alashan block of western North China Craton and Middle Qilian-Qaidam massif,which is one of the most characteristic continental orogenic belt.This research object Hongtugou-Chuancigou gold deposit(H-C gold deposit)is located in the middle of the North Qilian orogenic belt.The unique geological background makes a polymetallic metallogenic condition.The H-C gold deposit is rich in placer gold resources but lack in rock gold resources.The author carried out the macro-micro structural analysis of the work area,and systemic mineralography,petrography,geochemistry.Through field geological work and laboratory analysis,we achieved the following work.(1)By studying the typical ore body and surface engineering of H-C gold deposit,combined with the multielement analysis of geological body section,we discover the the main mineralization and alteration characteristics,the association of Au element and other elements.(2)With the remote sensing geological interpretation,we reveal the macroscopic tectonic pattern within the mining area,and extract the mineralization and alteration information.Combining with the geological observations and anomalies of the mining area,we recognize the ductile shear zone and have further understanding on the mineralization of volcanic rock.(3)By calculating the thermoelectric property of pyrites,we infer to the metallogenic temperature and the orebody denudation depth of H-C gold deposit.(4)By studying the special annular serpentinite in the working area,we refer that the original rock is dolomite marble and under the silicon-rich hydrothermal solution in acidic magmatite leading the formation of zonal serpentined marble.Based on the electron microprobe study,we reveal the serpentine+calcite+garnet+apatite+vesuvianite+diopside+chlorite mineral assemblage,which suggest the existence of skarn.(5)By using zircon SHRIMP U-Pb isotope,we find that H-C gold deposit has three main magmatic activities:Proterozoic,early Paleozoic and Mesozoic thermal events.(6)Compared with the other gold deposits with the same output characteristics of North Qilian orogenic belt,we summarize the metallogenic regularity and refer mesozoic thermal events for the H-C gold mineralization period.The ore source layer is mafic and ultramafic rocks.Because of the erosion,the orebody has been erosed to the upper position and lower orebody may be extended.The main prospecting marks is ultra-mafic rocks with the broken alteration.