川西江浪穹隆在大地构造上位于松潘-甘孜造山带东南缘.环穹窿腰部分布着一系列产状、矿床特征相似的铜多金属矿床——里伍式铜矿床,包括里伍、中咀、笋叶林、柏香林、挖金钩、黑牛洞等矿床.这些矿床的矿体主要呈似层状产出于中元古代里伍群中,其成因模式目前尚不明确.本研究选择里伍和黑牛洞铜矿中的含矿石英-电气石脉作为重点研究对象,对其中的代表性电气石单矿物进行了电子探针分析及LA-MC-ICPMS原位硼同位素测试,据此制约矿床的成矿物质来源.背散射及显微图像特征揭示两矿床的含矿电气石具有单一的流体来源;电子探针分析结果表明这些电气石在类型上均属镁电气石;硼同位素测试结果显示两矿床的电气石δ11B值分别为-15.47‰±0.83‰～-13.06‰±0.77‰(n=10)及-13.19‰±0.57‰～-5.91‰±0.67‰(n=16),与花岗岩的δ11B值区间非常一致,表明这两个矿床属(区内燕山期)岩浆期后热液矿床.通过对比研究,本文进一步提出在松潘-甘孜造山带内很可能存在一条NE-SW向的铜多金属成矿带,即松潘-甘孜铜多金属构造成矿带.本次研究不仅可以丰富层状型矿床成矿理论,而且对指导该造山带中其他穹窿体的找矿具有较为重要的实际意义.%Jianglang Dome is located in the southwestern Songpan-Ganzi Orogen (SGO) in western Sichuan.A series of copper polymetallic deposits such as Liwu, Zhongzui, Sunyelin, Baixianglin, Wajingou and Heiniudong occur around the waist of the dome.All of these deposits occur as stratiform in the Mesoproterozoic strata of the Liwu Group.But their genesis is still unknown.With ore-bearing quartztourmaline from the Liwu and Heiniudong ore deposits as study objects, this paper performed boron isotopic analyses using LA-MC-ICPMS and electron microprobe methods to understand the origin of ore-forming material of the deposits.The BSE and micrographic images reveal that these tourmalines were possibly derived from a single hydrothermal source, and electronic probe results indicate these tourmalines can be grouped into magnesium tourmaline.Boron isotopic results suggest that δ11B values of tourmaline from two deposits are-15.47‰ ± 0.83‰ to-13.06‰ ±0.77‰(n=10) and-13.19‰ ±0.57‰ to-5.91‰ ± 0.67‰(n=16), respectively, both of which are consistent to that of granite, indicating that the two deposits belong to post-magmatic hydrothermal deposits.Comparison study further shows that an NE-SW trending metallogenic belt, i.e.the Songpan-Ganzi copper polymetallic metallogenic belt(SGCPMB), occurs likely within the Songpan-Ganzi orogenic belt.In summary, this study will not only be beneficial to supplement the metallogenic theory of stratiform deposits, but also significant for the copper exploration in other domes in the SGO area in future.
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