Chemical Speciation Of Au And Its Exploration Significance Of The Yangshan Deposit, Gansu Province

Yangshan Deposit, located at the borderline of Chuan, Shan, Gan province, is one of themost largest Carlin-like gold deposits. It not only has the typical Carlin gold depositcharacteristics, but also the orogenic.The researchers study Yangshan deposit for itscomplicated mineralization and abundant gold. The paper stydies on the rock geochemistry,stratigraphic geochemistry and metallogenic element phase state based on the systematicgeological field observations.The results show that regional rock geochemistry is characterized evidently by enrichmentof Pb, As, Bi, Sb, W,Au and CaO, strong depletion of Cr, Mn, Na2O, MgO and SiO2. Devonianis the enrichment of trace elements, and maybe the source beds. Because its Au, Sb, As, Bi andW have high differentiation, large enrichment coefficient and obvious preconcentration. Au, Sb,As, Bi, W is the typical trace element combination in regional rock which combine decision atenrichment coefficient greater than1.5and the results of factor analysis.Based on the analysis of trace elements of ore and rock in mining area, Au, As, Sb, Bi, W,Hg show strong enrichment and high differentiation in Yangshan gold deposit. Au has a goodmetallogenic potential which differential coefficient and enrichment coefficient are3.08and1579.27respectively. By contrast Different kinds of ore, Au, As, Sb, Hg are significantenrichment. Among the average content of Au, quartz vein type is the highest(23.13×10-6). Thesecond is altered granitic porphyry type(8.48×10-6). Mo, Pb and the rest elements have nodifference with Sanhekou formation. The characteristics above indicate that Au, As, Sb, Bi, Hg,W are ore-forming elements association of Yangshan gold deposit.The phase analysis results show that Au of the rock in the mining area is mainlydistributed in the sulfide bound fraction and residual fraction. The sulfide bound fractionaccounts for44.5%～48.35%in the ores,13.31%～25.01%in the non ores.The proportion ofsulfide bound fraction in the ores is higher than that in the non ores. The sulfide bound and carbonate bound fractions account for26.19%～49.22%in the ores,64.93%～76.31%in thenon ores. The proportion of sulfide bound and carbonate bound fractions in the ores are muchlower than that in the non ores. Based on the phase behavior of Au in the rock, we can get theore potentiality of the original rock, then find the gold orebody.The phase analysis results show that Au of the soil in No.17exploration line of Anba oreblock has obvious phase distribution regularity. Maximum point of the free form proportion, orthe Minimum point of the mobile forms proportion is consistent with the gold orebodyposition.We can guide the gold exploration based on the phase distribution regularity.The phase analysis results show that Au of the stream sediment in the mining area ismainly distributed in the free form. The proportion of the free form of the mining area,anomaly area, non mining area and non anomaly area were decreased one by one. The freeform accounts for4.72%in the non anomaly area,43.30%in the anomaly area. The sulfidebound fraction accounts for61.14%in the non anomaly area,9.48%in the anomaly area. Sowe can outline the anomaly based on the phase distribution behavior ofAu.