鲁尔玛斑岩型铜(金)矿为冈底斯成矿带西段新发现的斑岩型矿点,目前已发现赋存于石英二长斑岩体中的斑岩型铜矿体1条,赋存于构造破碎带中的热液型脉状金(铜)矿体1条、热液型脉状铜矿体1条。以鲁尔玛含矿斑岩为中心,依次发育钾硅酸盐化、绢英岩化、青磐岩化,表现出斑岩型矿床的典型蚀变分带模式。其中,热液脉体从早到晚被可划分为:钾硅酸盐化脉(A脉)、石英-金属硫化物脉(B脉)以及石英-绿帘石-碳酸盐化脉(D脉)。这一新的发现,证实冈底斯成矿带西段具有斑岩型铜(金)矿床的找矿潜力,有望将冈底斯斑岩型铜矿带向西延伸近200km,同时也表明拉萨地体南缘的冈底斯成矿带斑岩型铜成矿作用最晚应该开始于晚三叠世。鲁尔玛斑岩型铜(金)矿点的发现,对深入理解冈底斯斑岩铜(金)矿带的成矿作用,完善冈底斯成矿带的成矿理论,更好地评价冈底斯西段找矿潜力,指导该地区的找矿突破,均具有重要意义。
Previously, almost all the porphyry copper-gold deposits in the Gangdise metallogenic belt are located at the eastern section of the Gangdise metallogenic belt, and their mineralization ages are younger than the late Triassic epoch. This paper discusses Luerma, the newly discovered late Triassic porphyry copper-gold ore-spot in the western Gangdise metallogenic belt. Zircon U-Pb dating and molybdenite Re-Os dating indicate that Luerma copper-gold occurrence is with a 212 Ma mineralization age, implying it is related to the subduction process of the Indian ocean plate northward to the Gangdise plate in the late Triassic epoch. The Luerma copper-gold ore-spot developed typical porphyry hydrothermal alteration zones, which can be divided into a potassium-silicification zone, asericitization zone, a clayization zone, and a propylitization-propylitization zone from ore-bearing quartz monzonite porphyry to wall rocks, respectively. By so far, three ore bodies are determined in Luerma copper-gold occurrence:one porphyry copper orebody occured in quartz monzonite porphyry, one hydrothermal vein gold-copper orebody and one hydrothermal vein-typed copper orebody occured in structural fracture zones respectively. Moreover, three main types of hydrothermal veins have been identified based on their mineral assemblages,cutting relationship and alteration features: the potassium-silicification vein (A-typed vein), the medium-term quartz-polymetallic sulfides vein (B-typed vein), and the epidote-carbonatation (D-typed vein), respectively. The discovery of Luerma ore-spot suggests that the western part of the Gangdise metallogenic belt is potential for porphyritic copper-gold deposits.