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多龙矿集区是班公湖-怒江成矿带最重要的组成部分,其成矿规模巨大、时间跨度较长、成矿过程复杂,因而人们对该区成岩成矿地质背景及岩石成因等问题一直争议不断,值得进一步明确.通过研究矿集区中部拿若斑岩型铜(金)矿与成矿相关的花岗闪长斑岩LA-ICP-MS锆石U-Pb年龄、全岩地球化学特征及Hf同位素组成,并与区域邻近矿床进行详细地对比研究,查明了多龙地区与成矿相关的岩浆岩形成构造背景、岩石成因及深部动力学过程.测试结果表明拿若铜(金)矿形成时代为早白垩世120Ma左右,与多龙地区其他矿床形成时代一致.这些岩浆岩均相对富集轻稀土(LREE)与大离子亲石元素(LILE:Rb,Ba,K等);亏损重稀土(HREE)与高场强元素(HFSE:Nb,Ta,Zr,Hf等).原位锆石ε_(Hf)(t)均为正值,为1.38~7.37,Hf同位素两阶段模式年龄t_(DM2)为707~1 086Ma,表明多龙矿集区斑岩-浅成低温热液型铜(金)矿形成与早白垩世班公湖-怒江特提斯洋北向俯冲有关.当俯冲洋壳到达地壳50~70km深度时发生不同程度相变,从而导致角闪石等矿物脱水产生的熔体交代楔形地幔,进而诱发幔源物质部分熔融产生弧岩浆,其形成环境类似于南美安第斯成矿带洋陆俯冲背景之下的陆缘弧环境.
The Duolong ore district is the most important part of the Bangong Lake - Nujiang metallogenic belt. Its metallogenic scale is huge, its time span is long, and its metallogenic process is complicated. Therefore, people are interested in the geological background of diagenesis and mineralogy and the genesis of rocks The issue has been controversial and deserves further clarification.Based on the LA-ICP-MS zircon U-Pb age of granite diorite porphyry associated with ore-forming porphyry copper (Au) deposit in the central part of the ore district, Geochemical characteristics and Hf isotopic compositions of the ore bodies and a detailed comparative study with the adjacent ore deposits in the area to find out the tectonic setting, rock genesis and deep kinetic process of the magmatic rocks related to metallogenesis in the Duolong area.The results show that taking the copper (Gold) deposits formed during the Early Cretaceous period of about 120 Ma, consistent with the formation of other deposits in the Duolong area. These magmatic rocks are relatively rich in LREE and LILE (LILE: Rb, Ba, K, etc.) ), Depleted HREE and HFSE: Nb, Ta, Zr and Hf etc. The in-situ zircon ε_ (Hf) (t) are all positive values ranging from 1.38 to 7.37 and Hf isotopes The stage model age t_ (DM2) is 707 ~ 1 086Ma, indicating that the porphyry-epithermal copper ore is formed in the Duolong ore district The Early Cretaceous Bangong Lake - Tethys Ocean northward subduction of the Nujiang River is related to the subduction of the Tethyan ocean.When the subducted oceanic crust reaches the depth of 50 ~ 70km, different degrees of phase transition occur, resulting in the hydration of hornblende and other mineral melt wedge-shaped mantle, and thus Induced partial melting of the mantle source to produce arc magma which is formed in a land-arc environment similar to that of the Andean metallogenic belt in the South American Andean continent.