西藏玉龙铜矿床成矿斑岩的厘定及地质意义

Recognition of the ore_ forming porphyry in the Yulong Cu deposit and its geological significance

位于青藏高原东缘的玉龙铜矿是我国最大的斑岩铜矿之一,其形成一致认为与矿区中心产出的二长花岗质复式斑岩体有关,但成矿与复式岩体的确切关系并不清楚。本文通过详细的野外地质填图,特别是矿床8号勘探线12个钻孔的重新编录,在复式岩体中识别出一套花岗斑岩岩枝,岩枝中不规则状石英-钾长石脉广泛发育,同时还见有单向固结结构、粗晶及细晶结构,这些特征表明该岩浆中的流体曾经发生过饱和。同时结合矿床高品位(>0.6%,质量分数)铜矿化紧密围绕花岗斑岩分布、含矿脉体自花岗斑岩向外围逐渐由高温石英-钾长石A脉过渡为中低温石英-硫化物脉、热液蚀变自花岗斑岩向外由高温钾硅酸盐化过渡为中低温石英-绢云母化的规律,最终确定这套花岗斑岩为玉龙矿床的成矿斑岩。玉龙铜矿成矿斑岩的厘定,较好地解释了矿床矿化类型及金属的分布规律,为进一步深入理解矿床形成过程提供了帮助。

The Yulong porphyry Cu-Mo deposit in eastern Tibet is one of the largest copper deposits in China. The formation of the deposit has been regarded to be related to a monzogranilic composite intrusion in the center of the deposit, but the genetic relationship between mineralization and the composite intrusion remains poorly constrained. Based on field geological mapping and drill hole logging along No. 8 section, the authors identified a suite of granite porphyry stocks from the composite pluton. The stocks include abundant quartz-feldspar A-type veins, and some quartz shows unidirectional solidification texture and pegmatite/aplite texture. These character- istics indicate that the magma was once water-saturated. Additionally, high-grade （ 〉0.6 % ） copper mineraliza- tion is distributed closely around the granite stocks, with high-temperature A-type veins within the stock, and meso-temperature quartz-sulfide D-type veins far away from the stock. Hydrothermal alteration surrounding the deposits is generally characterized by concentric zones from an inner potassic zone outward to phyllic and argillic alteration zones, and an outer propylitic and skarn zone. The potassic alteration zone well overlaps the granite porphyry stocks. Based on above observation, the authors hold that the granite porphyry stocks are ore-forming intrusions at Yulong.