Geological characteristics and prospecting potential analysis of Duolong porphyry-epithermal copper （gold） ore district in Tibet

On the basis of summarizing the geological characteristics of the Duolong ore district, this paper conducts a potential analysis of the depth and margin areas of the mine, in order to provide ideas for ore exploration prediction. Duolong porphyry-epithermal copper （gold） ore district is located in the northwest of the Bangongco-Nujiang Metallogenic Belt in Tibet. It is mainly composed of Tiegelongnan giant porphyry-epithermal copper （gold） deposit; Naruo large porphyry-cryptoexplosive breccia copper （gold） deposit; Duobuza, Bolong, and Duobuzaxi large porphyry copper （gold） deposits, and Gaerqin, Dibaonamugang high sulfidation-epithermal copper （gold） ore occurrences. A total of over 15 million tons of copper have been discovered in the Duolong ore district, with over 250 tons of associated gold and 3 900 tons of associated silver. Duolong ore district was formed in a continental margin arc environment of the northward subducting of Bangongco-Nujiang Ocean Basin in the early Cretaceous （120 Ma）. The material source is a mixed of crust and mantle, and the ore-forming magmatic rocks are mainly the moderately acidic diorite porphyry-granodiorite porphyry-granite porphyry series, with arc magmatic characteristics. The rollback of subducting plates is the main dynamic mechanism for the formation and emplacement of deep magma in the Duolong ore district. The coverage of andesitic volcanic rocks （110 Ma） after mineralization plays an important role in the preservation of the deposit. The F2 reverse fault in Duobuza ore area divides the ore body into upper and lower parts, and the lower part of the ore body is the key direction for prospecting. The deep drilling in the Tiegelongnan ore area exposes a reverse fault, the ore body on the hanging wall overlies the “red layer”, the foot wall is the direction for the missing half of ore body. The extensive development of “lithocaps” indicating epithermal mineralization system, the enrichment of elements such as Au, Ag, As, Sb, Bi, Cu, etc. and the good combined anomalies of Au, As, Sb, Hg, etc. in the Gaerqin ore area show the potential for epithermal deposits. The development of high sulfidation epithermal alteration （kaolinite, dickite, alunite, etc.） and mineral assemblages （covlite, digenite, bornite, etc.） in Dibaonamugang ore area and well intergrated geophysical, geochemical, and remote sensing anomalies make it a focus of future mineral exploration. The transformation effect of thrust faults on deposits in the area is a key focus of future research and has important guiding significance for further exploration and evaluation.