西藏多龙矿集区岩浆岩成因与成矿作用关系研究

发布时间：2018-04-22 17:05

  本文选题：斑岩铜金矿 + 岩浆岩成因　； 参考：《岩石学报》2017年10期

【摘要】：西藏多龙矿集区(包括多不杂、波龙、拿若和铁格隆南(荣那)四个大型-超大型斑岩型-浅成低温热液型铜金矿床)位于班公湖-怒江缝合带西段,目前已探明铜的资源量超过1600万吨,金大于200吨。班公湖-怒江缝合带的找矿勘查工作现在正处于起步阶段,本文以多龙矿集区为例,系统讨论了该矿集区与成矿作用相关的岩浆岩的成因、成岩与成矿作用的相互关系并初步提出了针对该缝合带斑岩铜金矿床的找矿勘查步骤和标志。全岩地球化学、Sr-Nd-Hf同位素、造岩矿物化学成分等实验结果表明多龙地区与成矿作用相关的岩浆岩形成于壳幔混合作用并伴有俯冲沉积物的加入,岩浆在演化过程中还经历了一定程度的结晶分异作用和基性岩浆的注入并最终侵位至地壳浅部或喷发出地表。研究表明成矿物质主要来自于地幔源区,随后金属元素在富水(≥4%H_2O)和较高氧逸度(ΔNNO0.5)的岩浆环境下运移至地壳上部(距地表2.5~7.5km)岩浆房中,由于成矿物质(Cu、Au和H_2O)在中酸性岩浆中的溶解度随温度压力降低而降低,因此侵位较浅的岩浆房更容易发生含矿流体的出溶并最终形成斑岩铜金矿。研究提出班公湖-怒江缝合带斑岩型铜金矿的找矿勘查工作可按以下步骤和找矿标志来进行:(1)通过Nd、Hf同位素填图确认地幔组分相对较多的侵入岩分布区为成矿远景区,该区域岩石学特征可能表现为暗色包体(MMEs)大量发育;(2)通过角闪石、锆石等矿物开展氧逸度填图进一步圈定重点找矿勘查区,岩浆岩中角闪石的发育往往预示着较好的成矿潜力;(3)在重点找矿勘查区内通过岩浆磁铁矿中V、Ti含量对斑岩体的含矿性进行快速判定,具有较低V、Ti含量的斑岩体通常为含矿性较好的斑岩体。此外,富水(角闪石发育)、含矿质(黄铜矿呈他形晶粒状产出)、侵位浅(气相包裹体与多相包裹体共同产出)、并有蚀变矿物(次生黑云母、绿泥石)发育的中酸性岩体也可指示较好的成矿潜力。
[Abstract]:The Dulong ore concentration area in Tibet (including Dobonghu, Polong, Naro and Tigrongnan (Ronna), four large, super-large porphyry and epithermal hydrothermal copper-gold deposits) is located in the western section of the Bangong Lake-Nujiang suture zone. At present, the amount of proven copper resources is more than 16 million tons, and gold is more than 200 tons. The prospecting and exploration of the Bangonghu-Nujiang suture zone is now in its infancy. Taking the Dulong ore accumulation area as an example, the genesis of the magmatic rocks related to the mineralization in the ore concentration area is discussed systematically in this paper. The interrelation between diagenesis and metallogenesis and the prospecting steps and marks for porphyry copper-gold deposit in this suture zone are put forward preliminarily. The experimental results of Sr-Nd-Hf isotopes and petrogenic mineral chemical compositions indicate that magmatic rocks related to mineralization in the Dulong area were formed in crust-mantle mixing with the addition of subduction sediments. The magma also experienced some crystallization differentiation and the injection of basic magma during the evolution process and finally emplaced to the shallow part of the crust or erupt out of the earth's surface. The results show that the ore-forming material mainly comes from the mantle source region, and then the metallic elements migrate to the magma chamber of the upper crust (2.5 ~ 7.5km from the surface) under the magmatic environment of rich water (鈮，

本文编号：1788129