新元古界铁建造的成因与构造背景:以中天山沙垄铁矿为例

新元古界 铁建造 成矿机制 中天山 新疆
雷如雄 2014-01 项目
The Neoproterozoic iron formations embrace occurrences from all continents,they are spatialy and temporally associated with glacial rocks or volcanic rocks, considered to be one of the important indicators for rise of the oxygen level in the ocean. So it is of great sciencitific significance to study Neoproterozoic iron formations for understanding the Neoproterozioc snowball Earth event and the break-up of Rodinia supercontinent and revealing Neoproterozoic crustal accretion process, the global climate, environment and life evolution. Previous studies have shown that, the Northern Xinjiang occurs three set of Cryogenian glacial rocks and numerous Neoproterozoic bimodal magmatic rocks and preserves significant imprints of the Neoproterozoic Snowball Earth and breakup of Rodinia supercontinent. However,till now there is no study on the Neoproterozoic iron formations in the Northern Xinjiang.This applying project chooses the Shalong iron deposit in the Central Tianshan,Northern Xinjiang as research object which lies in the key preriod of the Neoproterozoic break-up of Rodinia supercontinent and snowball Earth event. We plan on studying high-quality zircon U-Pb geochronology, geochemistry,Sr-Nd-Hf-O isotope and ore deposit geology, to exactly constrain the epoch, origin, depostional environment and tectonic setting of this deposit. Then combined with the comparative study of the global Neoproterozoic iron formations, the study will discuss and reveal the Neoproterozoic tectonic affility, the tectonic evolution and the relationship with the evolution of Rodinia supercontinent of the Central Tianshan as well as the Northern Xinjiang.
新元古代铁建造在全球各古大陆均有不同程度的分布,常与冰碛岩或裂谷火山岩系在时空上密切相关,其形成是大洋氧逸度显著升高的重要标志之一。因而,新元古界铁建造已成为理解新古元代雪球地球事件和Rodinia超大陆裂解过程的重要研究对象,同时对于揭示新元古代地壳增生过程、气候、环境和生命演化等具有重要研究意义。前人研究表明,北疆地区发育三套成冰纪冰碛岩和大量双峰式岩浆岩,雪球地球和Rodinia超大陆裂解事件在该区响应强烈。然而,目前尚无针对该区新元古界铁建造的详细研究。本项目选择处于新元古代Rodinia超大陆裂解和雪球地球事件关健时期的中天山沙垄铁矿为研究对象,开展精细的锆石年代学、地球化学、同位素和矿床学综合研究,在确定沙垄铁矿的精确年龄、沉积环境和大地构造背景的基础上,与邻区及全球新元古宙铁建造进行综合对比,探讨和揭示中天山和北疆地区新元古代的构造属性、构造背景及其与全球超大陆演化的关系。