西藏铁格隆南-多不杂矿床对冲储矿机制——地球物理勘查的证据

铁格隆南和多不杂矿床是西藏多龙整装勘查区的2个主要矿床,目前控制铜资源量1400万吨。2个矿床空间距离仅6～7 km,它们之间的构造关系和深部资源潜力仍不明确。笔者在铁格隆南和多不杂矿区实施音频大地电磁测深,识别出多条逆冲推覆断层。通过恢复原始矿体的形态,进一步确认了被荣那沟断层错失的另一半矿体,预测铁格隆南矿床铜资源量可能达到2000万吨以上。在多不杂识别出被推覆构造错失的矿体,推测多不杂铜资源量400～500万吨。本次勘查地球物理工作构建了铁格隆南-多不杂对冲断层储矿格架,提出美日切错组安山岩和逆冲推覆断层对矿体的保存具有双重作用,建议优先对铁格隆南荣那沟断层下盘物探异常实施深钻验证。

Mechanism of Tiegelongnan-Duobuza ramp style ore-controlling structure, Tibet: Evidence from geophysical exploration

The Duolong ore district in Tibet is one of the largest porphyry copper ore concentration areas in China. As important deposits in Duolong, the Tiegelongnan and the Duobuza deposits contain nearly 14 million tons of copper resources currently. Although researchers all believe that these deep and peripheral areas still have great prospecting potential, the structural spatial relationship between the two deposits (6~7 km apart from each other) is still unclear. The Audio-frequency Magnetotellurics(AMT)was employed in the Tiegelongnan and Duobuza mining areas. Based on thrust fault discovery, the orebody which was displaced by the Rongna valley fault was further confirmed. It is inferred that the original ore bed is in an ellipsoid form, and therefore the copper resources of the Tiegelongnan deposit may reach more than 20 million tons. The missing orebody in Duobuza was identified at the footwall of the thrust fault, and it is initially held that the amount of copper is between 4 and 5 million tons. Based on the exploration geophysical work, the authors constructed the ore-controlling framework of Tiegelong-nan-Duobuza ramp style thrust faults and reached the conclusion that the volcanic cover and the thrust faults have exerted a dual effect on preservation of the orebody. The authors suggest giving priority to carrying out deep drilling at the footwall of the Rongna valley fault to verify geophysical anomalies.