CAJ | 학술논문

利用 LA-ICP-MS 技术,对湘中锡矿山煌斑岩中的锆石进行 U-Pb 同位素定年。研究表明,该煌斑岩中的锆石呈半自形或半浑圆状,为捕获锆石。锆石阴极发光图像显示有典型的振荡环带和韵律结构,部分还可见扇形分带,其形貌和地球化学特征均显示为岩浆成因。锆石U-Pb同位素年龄主要集中在830 Ma和800 Ma附近,少量为~730 Ma,与江南古陆前寒武纪浅变质岩的年龄十分吻合,揭示湘中盆地深部确实存在新元古界基底,这为示踪湘中锑矿的成矿物质来源和判别湘中地区大地构造环境提供了新的依据。锡矿山煌斑岩形成于一种拉张伸展的构造环境中,其侵位深度为5 km以上。
이용 LA-ICP-MS 기술,대상중석광산황반암중적고석진행 U-Pb 동위소정년。연구표명,해황반암중적고석정반자형혹반혼원상,위포획고석。고석음겁발광도상현시유전형적진탕배대화운률결구,부분환가견선형분대,기형모화지구화학특정균현시위암장성인。고석U-Pb동위소년령주요집중재830 Ma화800 Ma부근,소량위~730 Ma,여강남고륙전한무기천변질암적년령십분문합,게시상중분지심부학실존재신원고계기저,저위시종상중제광적성광물질래원화판별상중지구대지구조배경제공료신적의거。석광산황반암형성우일충랍장신전적구조배경중,기침위심도위5 km이상。
The giant Xikuangshan deposit, located in the Xiangzhong Basin, Central Hunan, is the largest antimony deposit in the world. In spite of numerous detailed geological investigations and geochemical researches have been carried out, the sources and tectonic background of the giant ore deposit is unclear. The lamprophyre dyke occurring in the eastern part of the mining district probably can shed light on these issues. LA-ICP-MS U-Pb isotopic dating has been conducted on zircon grains collected from the lamprophyre dyke in the Xikuangshan mining district. The zircon grains are usually subhedral or sub-rounded, and exhibit typical oscillatory or sector zoning under cathodoluminescence. Both its the morphology and geochemical signatures (Th/U ratio and REE chondrite-normalized distribution pattern) of these zircon grains reveals that they are predominately of magmatic origin, and were probably captured from the wall rocks during magma ascending. The zircon U-Pb ages mainly vary in the range of 830 Ma to 800 Ma, which coincide well with the ages of the Neoproterozoic Lengjiaxi Group and Banxi Group occurred in the adjacent Xufeng Range, implying the possible existence of underlying Precambrian clastic basement in the Xiangzhong Basin. The inferred Precambrian basement lays foundation for the further understanding for tracing the ore-forming metal of the giant Xikuangshan deposit and determining the tectonic nature of the Xiangzhong Basin. The Neoproterozoic basement underlying in the Xiangzhong Basin might have provided Sb for the giant ore accumulation in the Xikuangshan mining district. Tectonically, the Xiangzhong Basin should belong to the Yangtze Block rather than the Cathaysian Block as was previously considered. The lamprophyre in the Xikuangshan mining district formed under the geodynamic setting of crustal extension, and emplaced at a depth of at least 5 kilometers.