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    藏北多龙斑岩铜金矿集区综合信息找矿模型研究

    Integrated anomaly model and metallogenic prediction of the Duolong porphyry copper-gold ore concentration area in northern Tibet

    • 摘要: 藏北多龙矿集区产出环境和成矿动力学背景在青藏高原斑岩铜矿中独具特色,目前已经发现了多龙、多不杂、拿若、荣那等超大型—大型斑岩铜(金)矿,其有效找矿模式亟待研究总结。典型矿床的综合信息找矿模型研究对于进一步开展矿体定位预测具有重要意义。研究认为多龙矿集区铜金矿体产于花岗闪长斑岩体内及岩体边部的黄铁绢英岩化和青磐岩化变质(长石)石英砂岩及火山岩中。自含矿斑岩体中心向外存在中心对称分布的3个蚀变带,依次为弱钾化带、绢英岩化带和黄铁矿化?角岩化带。根据地、物、化、遥异常套合特征,划分出“三带五田”。“三带”为呈北西向雁列状排列的拿若—色那—尕尔勤铜金矿带、多不杂—波龙—铁格隆南铜金钼矿带和地堡那木岗铜金矿带;“五田”为拿若—赛角—荣那矿田、尕尔勤矿田、地堡那木岗矿田、波龙—多不杂矿田和铁格隆南矿田,并分别厘定了各矿田的基本组成与矿床地质特征。通过地、物、化综合异常分析,建立了“四位一体”找矿模式。指出铁帽、孔雀石化和蚀变花岗闪长斑岩体为地表寻找斑岩铜矿的直接标志;低磁异常间接反映遭受蚀变的花岗闪长斑岩体成矿母岩;激电高极化异常直接反映斑岩型铜矿体两翼的黄铁矿化带,间接反映硫化物带包裹着铜矿体;Cu、Au元素高异常反映成矿元素的区域富集。以此为基础,对拿若、荣那矿区掩埋矿体运用了“四位一体”找矿模式,发现隐伏斑岩型铜矿床。

       

      Abstract: Located in the northern margin of the Tibetan Plateau, the Duolong Cu-Au ore concentration area has typical geological setting and metallogenic dynamic background, which is quite unique in porphyry copper deposits of Tibet. The effective geological exploration model for Duolong is of great significance. This paper focused on metallogenic system and exploration model in this area. Several important results were obtained through detailed field and laboratory studies: ① Copper and gold ore bodies are preserved in altered (feldspathic) quartz sandstone and volcanic rocks of Jurassic Quse Formation and Sewa Formation. Three alteration zones exist from the center of ore-bearing porphyry outwards, i.e., potassium- silicified and sericitized zone, sericitized zone, and pyritized-hornfelsic zone. ②The spacial layout of mineralization in this area finds expression in "three ore belts and five ore fields". The three belts are distributed in en echelon shape, i.e., Naruo- Sena- Gaerqin Cu- Au belt, Duobuza- Bolong- Tiegelongnan Cu-Au-Mo belt, and Dibaonamugang Cu-Au belt, whereas the five blocks are ore zones located in the three belts, i. e., Naruo- Saijiao- Rongna, Gaerqin, Dibaonamugang, Duolong- Duobuza and Tiegelongnan ore fields. ③ The model of "four effective approaches to exploration" has been summarized: (1) Iron caps, malachites and porphyry intrusions are direct indicators for porphyry coppe depositsr; (2) Low magnetic anomalies reflect the granodiorite porphyry ore rock indirectly; (3) High-polarization areas directly reflect sulfide zones surrounding both sides of the ore body, and indirectly reflect the copper ore body wrapped in the pyrite zone; (4) Copper and gold geochemical anomalies indicate regional enrichment of ore-forming elements. The application of this model to Naruo and Rongna areas led to the effective discovery of the deep-buried porphyry copper deposit. The exploration breakthrough in the Duolong area has been achieved on the basis of this exploration model.

       

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