Geological exploration of the Rongna porphyry copper deposit in the Duolong ore concentration area, northern Tibet

The Rongna copper deposit is a major exploring breakthrough of Chinalco Resources Corporation in recent years. The Rongna deposit is located in northern island arc of Bangong Co-Nujiang suture zone. Based on geological data of regional geological and mineral survey, 1:50000 magnetic anomaly, and distribution pattern of global porphyry copper deposits, the authors delineated the exploring potential zone in Duolong. According to 1:50000 stream sediment survey and other exploring achievements, Rongna and Naruo deposits were chosen as major exploring targets. Induced polarization survey was conducted as an effective method for delineating the drilling area by summarizing alteration, mineralization and exploration modes of global porphyry copper deposits. Two different geophysical anomaly patterns are generally displayed for the buried porphyry system in plan view:(1) the center of buried porphyry system generally develops the low resistance, moderate polarization, and negative magnetic anomaly, and (2) the pyrite shell surrounding porphyry system forms medium to high resistance, medium to high polarization, and positive magnetic anomaly. The authors infer that medium-high polarization and positive-magnetic anomaly developed surrounding the periphery of the Rongna deposit was triggered by pyrite shell correlated with propylitization belt, whereas the medium polarization and negative magnetic anomaly is located at the center of the mineralization zone. Bonanza grade copper mineralization was achieved after operating reasonable drilling. The exploring procedure of Rongna from the theoretical thinking, geophysical and geochemical anomaly analysis at different scales for effective investment and drilling operation reflects the combination art of scientific research and industrial production.