Application Study Of Geochemical Deep-Penetrating Technology For Gold Exploration

Deep-penetrating geochemistry is a kind of new geochemical technique for prospecting buried ore-body in overburden area. Through studying the theory of deep-penetrating geochemical migration mechanisms and summarizing the technology of leaching of mobile forms of gold, and after test of method effectiveness, this technology has been employed for prospecting the deposit buried under the grassy marshland in the South Gansu Province, where is the favorable area of gold formation, but the conventional geological and geochemical prospecting methods are ineffective to evaluate the effectiveness of this technology.The study area was divided by the regional fault of Minxian-Lixian-Hezuo-Xiahe, Northern Qingling fold zone in the north, and middle section of Triassic rift geosynclines in Western Qingling in the south. It has been recognized widely that the high percolation environment of the regional fault of Minxian-Lixian-Hezuo-Xiahe was favorable for metallogenesis because the fault reached the deep crust, which caused deep ore solution moving up, accumulating and depositing in the flanking area of the fault. The investigation and evaluation of gold resources done in Xiahe-Hezuo Region has identified many good clues for potential exploration.The surface conditions of study area impede the lateral movement of ultra-fine gold. Although some good clues have been identified in the periphery of rock-mass contact zone, the prospecting result through the conventional geological, geophysical and geochemical methods was not notable because the sections of key anomaly are the area with the thick overburden, the gentle terrain, the shortage of bedrock, and undeveloped drainage system.On the basis of study of the theory, the leaching experiment of partial extraction of mobile gold in the soil and profiling survey on the known buried ore bodies in Shiqingdong Gold Mine and Zhongqu Gold Mine have been carried out. It has been employed the partial extraction technology provided by Institute of Geophysical and Geochemical Exploration in Langfang to leach 5 phases'gold of soil sample, among which 3 phases'gold including water extractive, organic and free natural phase gold were determined. All of 3 phase's gold shows the mobile gold anomalies on the top soil of buried gold body.Subsequently, the method of deep-penetrating geochemical area survey for gold prospecting in the grassy marshland is designed according to the landscape condition, by which the area survey of scale 1:20000 has been completed at the basic grid of 200×200m. The soil samples were collected from the lowest part of soil A horizon or the upper part of B at the depth of 30-40cm. The contents of 3 phase's gold were analyzed, and the geochemical maps of 3 phase's gold were made. The anomalies of gold by the deferent indications show their consistency of a certain extent.The experiment and application of deep-penetrating geochemical survey and verification of a few anomalies revealed that this method is effective for identifying the anomalies. It will be the evidences for the further study, and important for guiding exploration and evaluation of the buried or semi-buried deposit in this region.