三江北段纳日贡玛黑云母花岗斑岩LA-ICP-MS锆石U-Pb定年及其地质意义

西南三江北段是青海省重要的斑岩型铜钼矿成矿带，纳日贡玛铜钼矿是近年来在三江北段发现的与侵入岩有关的斑岩型铜钼矿。利用锆石U-Pb方法测得纳日贡玛黑云花岗斑岩的形成年龄为41.53Ma ±0.24Ma，属于喜马拉雅早期。纳日贡玛斑岩型铜钼矿的成矿时代主要在40.86~40.80Ma之间。在多期热液叠加、多期成矿作用中，纳日贡玛斑岩型铜钼矿的热液应是纳日贡玛黑云花岗斑岩（41.53Ma ±0.24Ma）和纳日贡玛斜长花岗斑岩（41.00Ma ±0.18Ma）共同提供的。由于该区有较多的中酸性岩体存在，因而确定这些侵入体的形成年龄，对于在该区寻找同时代的斑岩型铜钼矿有重要的理论意义和现实意义。

LA-ICP-MS zircon U-Pb dating of Narigongma biotite granite porphyry in northern Sanjiang region and its geological significance

Narigongma biotite granite porphyry in northern Sanjiang region is an important porphyry type copper-molybdenum mineralization belt in Qinghai Province, and the Narigongma copper-molybdenum deposit is an intrusion-related porphyry type ore deposit recently discovered in northern Sanjiang region. The authors obtained the zircon U-Pb age of 41.53±0.24Ma for Narigongma biotite granite porphyry, which should belong to early Himalayan period. The main metallogenic age is between 40.86 and 40.8 Ma. In multi-phase hydrothermal superimposition and mineralization, the hydrothermal solution of the Narigongma porphyry copper-molybdenum deposit must have been derived from biotite granitite porphyry of 41.53±0.24 Ma and plagioclase granite porphyry of 41.0±0.18Ma. In virtue of existence of many intermediate-acid intrusive rocks, the age determination of these intrusive is not only of theoretical importance but also of practical significance in search for porphyry type copper-molybdenum deposits of the same epoch.