Geochemical Characteristics Of Tuwu-Yandongporphyry Copper Ore Belt In Eastern Tianshan, Xinjiang And Study On Geochemical Exploration In Gobi Desert Regions

Mineral prospecting at cover of gobi desert regions is the theme of this paper, which is financial supported by "The study and comprehensive analysis of metallogenic setting at gobi desert regions in Tianshan mountion". Tuwu-Yandong porphyry copper ore belt in eastern Tianshan was a part of Paleo-Asia metallogenic domain and discovery of that was a breakthrough on copper exploration for the past decades. Complicated tectonic evolution and widely distributed volcanic and intrusive rock worked favorably for exploration of copper deposits. Nevertheless, only some small deposits were found for lack of innovation on exploration theory and method before1990s. The covered areas account for31percent in eastern Tianshan, but there were only4percent of deposits found in gobi desert regions. We should make more geochemical and geophysical deep penetration experiments to overcome the unclear of underlying lithology, weak and small changes of geochemical and geophysical anomaly.Based on the factors offered above, we analysed the characteristics of regional geochemical anomalies and measured the geological-geochemical-geophysical section. Associated with field investigate and laboratory experiment, the conclusion was listed as follows:(1) The geochemical anomalies spread from east to west, which were consistent with tectonic line. Anomalies of Cu, Pb, Zn,(Au, As), V, Ti, Fe, Mn,(Co, Cr, Ni), P, Sr were all related to Tuwu-Yandong porphyry ore belt. High background of Fe, V, Co, Cr, Ni had relevance for Devonian and Carboniferous volcanic rock. Tectonic deformation and magma activity resulted in further enrichment of Cu, Pb, Zn, Au, As, P, Sr. Different geochemical characteristics of deposits may reflect different metallogenic model in the same metallogenic belt.(2) Cu content was the highest in Carboniferous Qi’eshan Group with the largest variation coefficient. Devonian volcanic rock also showed high Cu content but with lowest variation coefficient. Factor analysis underscored that Cu-Mo anomaly could indicate mineralization.(3) Both of ere elements content and magnetic intensity of coarse detritus changed small in the same regions, but magnetic intensity in northern covering area was much higher than that in southern covering area and We can make use of this to distinguish the underlying lithology.(4) Results of magnetic susceptibility, which can reflect the hydrothermal activity, showed that mining district had higher magnetic susceptibility than Carboniferous strata and gobi desert regions.(5) Results of detritus measurement indicated that Cu, V, Mo, Ni, Co, Cr, As, Na, Mg, Fe, Ti, S content was higher in weak cemented layer with higher variation coefficient and most elements enriched in fine detritus with high content of clay. Exchangeable and adsorptive Cu, Pb, Zn can improve the anomaly contrast and make the anomaly more evident.(6) Geomorphological environment was the basic factor to consider for geochemical exploration. In the environment of torso mountain and eolian deposit, we would better collect coarse detritus samples and fine samples which were suitable in the environment of alluvial-diluvial sediments.