狼山-渣尔泰地区铜铅锌多金属成矿带成矿物质来源：硫化物微区原位S-Pb同位素及微量元素示踪

Langshan-Zhaertai district in Inner Mongolia endowed the Huogeqi, Dongshengmiao, Tanyaokou and Jiashengpan large–giant Cu-P-Zn deposits, which are the most important base metal resources in northern China. Previous studies regarded they are SEDEX deposits associated with Proterzoic rift sedimentary sequences. However, many mine geological features of these deposits are consistent with those of epigenetic hydrothermal deposits. We have studied these deposits in detail, including mine geology, ore fluid features and mineralization physical-chemical conditions, mineralization ages, and mechanism of mineralization. The results show that metamorphic grade of the host rocks, mineralization ages, ore-forming elements association of these deposits are systematic different. Cu-Pb-Zn source rocks formed with the development of the Proterozoic rift. Ore metals were remobilized by later regional metamorphic fluids and precipitated in faults. This model should be tested by sources of base metal studies. It will contribute to revealing base metals mineralization mechanism. Because multistage mineralization took place in these deposits, contaminations cannot be avoided using the traditional bulk analysis for isotope and trace element. Sulfide sulfur, lead isotope and trace elements analysis in situ is an ideal method for understanding mineralization process in this area.

内蒙古狼山-渣尔泰地区产出霍各乞、东升庙、甲胜盘、炭窑口等大型-超大型铜铅锌矿床，是我国北方重要的有色金属矿产资源基地。前人认为这些矿床为与元古代裂谷沉积岩系有关的SEDEX矿床，但矿床的许多地质特征符合外生热液成矿特征。申请人从矿床地质特征、成矿流体性质、成矿时代和成矿机理等方面进行了深入研究，发现它们赋矿地层的变质程度、成矿时代、成矿元素组合均存在系统差异，早期裂谷沉积作用可能对Cu、Pb、Zn进行了预富集，后期变质流体使成矿物质重新活化迁移并重新就位。本申请拟通过硫化物原位硫铅同位素和微量元素测试，示踪成矿物质来源，探讨变质流体与贱金属成矿的关系，深入揭示贱金属元素的迁移沉淀机制。由于该区存在多期叠加成矿作用，传统的化学溶样分析方法无法避免不同期次矿物的混杂，给数据解释带来不确定性，而精确地原位分析方法可以弥补该项不足，为细致研究该区成矿作用过程提供可靠依据。

霍各乞矿床赋存于角闪岩相变质岩中，黄铜矿产于石英岩和云母片岩而方铅矿和闪锌矿产于炭质板岩。甲胜盘矿床主要产于渣尔泰山群阿古鲁沟组含炭质白云质泥灰岩，仅见铅锌矿化。东升庙矿床铜铅锌金属硫化物常沿糜棱岩片理、细粒块状黄铁矿或者构造裂隙产出，黄铜矿主要呈团块状或细脉状，黄铁矿呈自形粒状并具有核幔结构，磁黄铁矿呈自形粒状或者他形粒状及脉状，闪锌矿和方铅矿呈脉状。. 甲胜盘矿床成矿期石英脉样品中的白云母39Ar/40Ar坪年龄为387.7±2.0 Ma，等时线年龄为388.0±2.9 Ma，铅锌矿石中的白云母39Ar/40Ar坪年龄为373.2±1.9 Ma，等时线年龄为372.9±2.6 Ma（图7）。成矿后花岗岩（截断矿体）的锆石U-Pb年龄为278.0±2.3 Ma（图8）。甲胜盘铅锌成矿作用发生于泥盆纪，与宝音图群变质时代（400 Ma）接近，表明成矿作用的发生与华北板块与南蒙微陆块拼合有关。. 原位铅同位素测试结果显示，甲胜盘和东升庙硫同位素组成较为相似，而霍各乞矿床显著较低。甲胜盘、霍各乞和东升庙矿床具有明显不用的铅同位素组成，霍各乞铅同位素模式年龄为860 Ma，甲胜盘铅同位素模式年龄为1600 Ma，东升庙铅同位素模式年龄为2020 Ma。. 原位硫同位素及成岩成矿时代研究结果显示，甲胜盘、霍各乞和东升庙矿床具有明显不同的微量元素和同位素组成。早期细粒硫化物微量元素含量高，明显遭受后期热液影响，导致硫化物含量显著降低，成矿期硫化物除As等少数元素含量显著增加外，成矿元素含量极低，早期硫化物被淋滤、交代、重结晶，释放大量成矿元素，为这些矿床的形成提供了物质来源。. 这3个矿床产于同一成矿带并具有相似的成矿特点，但是其成岩成矿时代、硫铅同位素及微量元素组成明显不同，表明这些矿床具有明显不要同的成矿物质来源和成矿背景。