阿尔泰南缘造山-变质环境中的金铜叠加成矿作用

The southern margin of the Altaides had undergone intensive NW-SE compression since the Late Devonian to the Early Permian, which resulted in syn-orogenic metamorphism, deformation and hydrothermal mineralization. This was another important mineralizing epoch after the Early Devonian VMS mineralization. The Low Devonian Kangbutiebao Formation (D1k), distributed in the southern Altaides, is an important host for volcanic massive sulfide Pb-Zn(Cu) mineralization. Not only had VMS ores undergone deformation and metamorphism, but gold-copper-bearing sulfide-quartz veins formed during orogeny or post-orogeny. These quartz veins can be divided into two groups. The first group of quartz (Q1) occurs as lentoid or streaked quartz veins which are parallel to the foliated structure of the biotite-chlorite or garnet-chlorite schist. These quartz veins are synorogenic and contemporaneous with early regional metamorphism, and may be gold-bearing veins, such as at the Sarekoubu gold deposit. The second group (Q2) is chalcopyrite- bearing quartz veins which cut across chlorite schist and banded sulfides at small angles, which may represent a much younger, metamorphic-related overprinting event. This proposal focus on temporal and spatial patterns between gold (copper) and lead-zinc mineralization in southern Altaides, ore-forming mechanism, overprints on ore system, as well as ore-forming chronology, so as to deepen the research on tectonic-fluid-metallogeny during orogeny in Carboniferous and Permian. The research contents which will be carried on includes three aspects. Firstly, lode gold and bedded lead-zinc mineralization in the Sarekoubu-Tiemuerte area will be concerned, which covers temporal and spatial distribution of gold and lead-zinc ore bodies, fluid inclusions of bedded lead-zinc ores and vein gold ores, overprints of lode gold, as well as chronology of mineralization and alteration. Secondly, deformation and metamorphism, overprints on lead-zinc deposit, evolution of CO2-rich inclusions in the Abagong-Talate Pb-Zn deposits will be studied, which includes textures and structures metamorphic ores, fluid inclusions in sphalerite of massive sulfide and hydrothermal vein ores, carbonic inclusions in vein quartz, as well as chronology of ores and altered rocks. And the last, late gold-copper mineralization in the The late copper-bearing sulfide quartz veins in the Mengku and Abagong iron deposits will also be studied, which contains CO2-rich fluid inclusions in the late copper-bearing sulfide quartz veins, gold-copper overprints on iron ore bodies, as well as fluid inclusions in quartz porphyroclast of mylonite and vein quartz. The distinguishing features and new ideas of this proposal can be concluded: 1) the temporal and spatial characteristics of gold and copper deposits related with orogrny and metamorphism; and 2)emphasizing preservation, decomposition, and overprints of structral ores and their fluid inclusions.

通过研究阿尔泰山南缘造山-变质环境中的金铜矿化时空分布规律及其对海相火山成矿系统的叠加-改造成矿作用，以及相应的流体活动形迹和成矿作用年代学，为深化阿尔泰成矿带的海相火山成矿系统和造山-变质成矿系统之间的成因联系和区域找矿提供理论依据。将开展的研究内容有：1）萨热阔布脉状金矿化与层状锌铅矿化的时空分布及成因关系；2）阿巴宫-塔拉特铅锌矿床的变形变质、叠加成矿作用和富CO2流体演化； 3）蒙库铁矿-阿巴宫铁矿区含铜硫化物石英脉的流体及成因。拟解决的关键科学问题有：1）获得不同尺度与造山-变质有关的金铜矿化叠加改造证据；2）查明海相火山成矿系统中原始流体、被改造的流体以及晚期叠加成矿流体的识别标志，及其相应的成矿意义；3）理清与造山-变质有关的构造-流体-成矿作用年代学。项目特色和创新点：深化与造山-变质有关的金铜叠加成矿作用及流体演化研究，追溯构造矿石及其流体包裹体的保存-破坏和改造特征。

以阿尔泰山南缘造山-变质环境中的金铜矿化时空分布规律以及对海相火山成矿系统的叠加-改造成矿作用为重点研究对象，开展变形变质、叠加成矿、流体活动形迹和成矿作用年代学研究，为深化阿尔泰成矿带的海相火山成矿系统和造山-变质成矿系统之间的成因联系和区域找矿提供理论依据。获得的主要成果有：1）获得了不同尺度与造山-变质有关的金铜矿化叠加改造证据，包括铁木尔特VMS矿床叠加于铅锌矿体之上的脉状金矿化，大东沟、乌拉斯沟、塔拉特等铜矿床中的晚期含铜石英脉，以及显微镜下各种变形变质证据；2）在前一个基金项目研究基础上，进一步查明阿尔泰山南缘萨热阔布-恰夏金(铜)石英脉、塔拉特铅锌矿床中黄铁矿-黄铜矿石英脉、铁木尔特叠加的脉状金矿化、乌拉斯沟铜矿化石英脉等的富CO2流体均为造山-变质成因,脉状金铜矿化主要形成于三叠纪时期的碰撞造山及其后伸张时期。金铜矿化则发生于220~370℃、110~330MPa的中高温中深条件； 3）对邻区阿舍勒铜锌矿床、克因布拉克晚期切层硫化物石英脉的研究表明，其原生包裹体也具有富CO2、中低盐度的变质流体特征；4）获得了一批黄铜矿的铜同位素数据，萨热阔布金矿的δ65Cu为-0.28‰~0.12‰，铁木尔特铅锌矿床叠加的金矿化δ65Cu为-0.14‰~-0.02‰，阿舍勒脉状铜矿化的δ65Cu为0.232‰~0.583‰，萨尔塑克细脉浸染状铜矿化的δ65Cu为0.388‰~0.805‰，克因布拉克浸染状铜矿化的δ65Cu为-0.021‰~0.369‰。这些数据都比较集中，与VMS矿床和矽卡岩矿床δ65Cu变化范围很大的特征不同，可能反映了这些金铜矿化的成因与造山-变质作用有关；5）理清了与造山-变质有关的构造-流体-成矿作用年代学，萨热阔布金矿主成矿阶段黄铁矿Rb-Sr同位素等时线年龄为237±53 Ma；黄铁矿-黄铜矿石英脉的包裹体Ar-Ar同位素坪年龄217.0±3.3 Ma和208±7.9Ma、等时线年龄218.0±6.3Ma和216.9±6.9Ma，表明金成矿时代为晚三叠世。与前人研究的热液黑云母40Ar-39Ar激光剥蚀年龄的研究结果相近。总之, 综合研究表明阿尔泰南缘造山-变质环境中存在晚三叠世的金铜叠加成矿作用，富CO2流体在其中起了重要作用。