Integrated anomaly model and metallogenic prediction of the Duolong porphyry copper-gold ore concentration area in northern Tibet

Located in the northern margin of the Tibetan Plateau, the Duolong Cu-Au ore concentration area has typical geological setting and metallogenic dynamic background, which is quite unique in porphyry copper deposits of Tibet. The effective geological exploration model for Duolong is of great significance. This paper focused on metallogenic system and exploration model in this area. Several important results were obtained through detailed field and laboratory studies: ① Copper and gold ore bodies are preserved in altered (feldspathic) quartz sandstone and volcanic rocks of Jurassic Quse Formation and Sewa Formation. Three alteration zones exist from the center of ore-bearing porphyry outwards, i.e., potassium- silicified and sericitized zone, sericitized zone, and pyritized-hornfelsic zone. ②The spacial layout of mineralization in this area finds expression in "three ore belts and five ore fields". The three belts are distributed in en echelon shape, i.e., Naruo- Sena- Gaerqin Cu- Au belt, Duobuza- Bolong- Tiegelongnan Cu-Au-Mo belt, and Dibaonamugang Cu-Au belt, whereas the five blocks are ore zones located in the three belts, i. e., Naruo- Saijiao- Rongna, Gaerqin, Dibaonamugang, Duolong- Duobuza and Tiegelongnan ore fields. ③ The model of "four effective approaches to exploration" has been summarized: (1) Iron caps, malachites and porphyry intrusions are direct indicators for porphyry coppe depositsr; (2) Low magnetic anomalies reflect the granodiorite porphyry ore rock indirectly; (3) High-polarization areas directly reflect sulfide zones surrounding both sides of the ore body, and indirectly reflect the copper ore body wrapped in the pyrite zone; (4) Copper and gold geochemical anomalies indicate regional enrichment of ore-forming elements. The application of this model to Naruo and Rongna areas led to the effective discovery of the deep-buried porphyry copper deposit. The exploration breakthrough in the Duolong area has been achieved on the basis of this exploration model.