摘要
滇西北格咱弧是三江地区著名的铜钼(钨)多金属复合斑岩成矿带,但金矿勘查进展较为有限。前人研究表明,甭哥金矿床与格咱弧南缘的侵入岩密切相关,但找矿方向尚不明确。锆石U-Pb测年结果显示,甭哥正长岩的成岩年龄为214.8±1.1 Ma,属于印支期岩浆活动的产物。岩石地球化学分析表明,甭哥正长岩具有低Al_(2)O_(3)、高K_(2)O和MgO的特征,属于钾玄岩系列;其Mg#值较高,富集轻稀土元素和大离子亲石元素,相对亏损重稀土元素和高场强元素,表明其源于受俯冲板片交代作用影响的富集地幔。通过对比格咱地区印支期、燕山期中酸性侵入岩以及滇西地区喜山期富碱斑岩,结果表明,甭哥正长岩具有微弱的Eu、Zr负异常和较高的P、Hf正异常,与滇西富碱斑岩相似,推测其后期可能受到喜山期地幔流体的影响。岩石地球化学剖面测量结果显示,甭哥矿区内煌斑岩、正长岩、角岩、砂板岩、硅质砂板岩及硅质岩中Cu、Pb、Zn、Au、Ag、W、Sn、Mo 8种元素含量依次降低,其中正长岩中这些元素含量均高于围岩,且Cu、Au、W、Mo含量为格咱弧水系沉积物的2~3倍,据此认为正长岩为含矿围岩。根据组合异常并结合地质特征,圈定了4个找矿靶区,为后续勘查工作提供了重要参考。
The Geza arc in NW Yunnan represents a prominent Cu-Mo(W)polymetallic epithermal mineralized belt within the Sanjiang region.However,limited advancement has been achieved in Au exploration.Previous studies have identified that the Bengge deposit is associated with intrusive rocks at the southern margin of the Geza arc.Nonetheless,research on exploration directions remains limited.Zircon U-Pb dating of the syenite from the Bengge gold deposit yielded an age of 214.8±1.1 Ma,suggestive of an Indosinian magmatic activity product.Geochemical analyses indicated that the syenite was characterized by low Al_(2)O_(3) and high K_(2)O and MgO contents,belonging to the potassic trachyte series.These rocks exhibit high Mg#,enriched light rare earth elements(LREEs),and large ion lithophile elements(LILEs),alongside relatively depleted heavy rare earth elements(HREEs)and high field strength elements(HFSEs).This suggests that the Bengge syenite originated from an enriched mantle modified by subduction slab metasomatism.The Bengge syenite displays weak negative Eu and Zr anomalies and pronounced positive P and Hf anomalies,consistent with the alkali-rich porphyries of western Yunnan.Based on prior dating results,it is speculated that the Himalayan mantle fluid may have been influenced it in the later stage.Additionally,a geochemical profile analysis was conducted to extract primary halo information for eight elements(Cu,Pb,Zn,Au,Ag,W,Sn,and Mo)in the Bengge deposit.The results demonstrated that the abundance of these elements decreases sequentially in the lamprophyre,syenite,hornfels,sandstone,siliceous sandstone,and siliceous rock.Notably,the syenite exhibits higher abundances of these elements than the surrounding rocks,with Cu,Au,W,and Mo concentrations being 2-3 times higher than those in the Geza arc stream sediments.It is inferred that the ore-forming materials are primarily concentrated in the syenite.Based on the integrated anomaly patterns and geological characteristics,four exploration targets were delineated,offering insights for future exploration efforts.
作者
杜斌
段召艳
董涛
杨富成
毕晓路
肖高强
吴俊
余海军
DU Bin;DUAN Zhaoyan;DONG Tao;YANG Fucheng;BI Xiaolu;XIAO Gaoqiang;WU Jun;YU Haijun(Kunming University of Science and Technology,Kunming 650093,Yunnan,China;Yunnan Geological Survey Institute,Kunming 650216,Yunnan,China;Key Laboratory of Sanjiang Metallogenesis and Resource Exploration and Utilization,Ministry of Natural Resources,Kunming 650051,Yunnan,China;Yunnan Key Laboratory of Sanjiang Metallogeny and Resources Exploration and Utilization,Kunming 650051,Yunnan,China;Yunnan Institute of Land Resources Planning and Design,Kunming 650216,Yunnan,China)
出处
《大地构造与成矿学》
北大核心
2025年第4期813-827,I0003,共16页
Geotectonica et Metallogenia
基金
云南省基础研究计划项目(202401BC070019、202301AT070019)
中国地质调查地调项目(121201004000160901-40)
国家自然科学基金项目(42173026、U2344217)
云南省科技计划项目(202305AT350004-3)联合资助。
关键词
正长岩
地球化学
岩石剖面
找矿靶区
甭哥金矿
滇西北
syenite
geochemistry
rock section
prospecting target area
Bengge gold deposit
NW Yunnan
