藏北多龙矿集区荣那斑岩铜矿找矿突破的实践

摘要

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.%荣那铜矿是中铝矿产资源有限公司近年在斑岩型铜矿找矿方面取得的一项重大突破。矿床产于班公湖—怒江缝合带北侧岛弧带中。公司在找矿初期重视基础地质研究，加强对地调和矿调成果的二次解剖，借鉴国内外斑岩铜矿区域分布规律，结合1∶5万磁法异常，明确多龙矿集区重点找矿方向；根据前期勘查成果，结合1∶5万水系沉积物测量成果，确定荣那、拿若为重点验证区。通过总结国外斑岩铜矿蚀变模式、矿化模式和勘查模式，选择有效的激电勘查方法圈定重点验证地段。结合隐伏斑岩体系矿化中心为中低阻、负磁异常、中等极化率，外围发育黄铁矿化壳形成近似环状中高阻、正磁异常、中高极化率异常，最终确定外围正磁、中高极化环形异常系荣那矿床与青磐岩化带有关的黄铁矿化壳引起，负磁、中等极化率异常为矿化中心部位，通过选择合理网度进行钻探验证实现找矿突破。荣那矿床勘查过程中的理论思考，区域−矿田物化探异常的综合分析、有效方法的投入和验证工程的部署充分体现了科学研究与生产的有机结合。