Petrogenetic and geodynamic investigation of Archean anorthosite-bearing layered intrusion and greenstone belt associations: implications for the early evolution of the Earth

太古代含斜长岩层状侵入体和绿岩带组合的岩石成因和地球动力学研究：对地球早期演化的影响

• 批准号: RGPIN-2014-04906
• 负责人: Polat, Ali
• 金额: $ 2.7万
• 依托单位: University of Windsor
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=633708
• 关键词: Petrogenetic; geodynamic; investigation; Archean; anorthosite

The geological models proposed to explain the origin of Archean anorthosite-bearing layered complex and greenstone associations in the Superior Province of Canada require re-evaluation within the context of new high-precision geochemical data. Over the next five years, I plan to study the field, petrographic and geochemical characteristics of Archean anorthosite-bearing layered complex and greenstone associations in the Superior Province, to constrain their petrogenesis, geodynamic setting and geological significance. The anorthosite-bearing layered complex and greenstone associations to be studied include the Neoarchean Bad Vermilion Lake (Ontario) and Doré Lake (Quebec) complexes. I will systematically sample each lithological unit in these associations and analyze them for major and trace elements and isotopes (Sm-Nd, Th-U-Pb, Lu-Hf, O), to improve our understanding the petrogenetic origin of these rocks. The geochemical characteristics of each rock type in the layered complexes and spatially associated volcanic rocks are expected to reflect petrological processes responsible for the compositional and isotopic variations in these rocks and their sources. Trace elements and Nd, Pb, Hf and O isotopes are sensitive to petrogenetic processes and thus can be used to distinguish different processes. These petrological processes can then be linked to the regional scale Neoarchean geodynamic processes in the Superior Province, and the geochemistry of these rocks can be used to understand their significance for Archean Earth evolution. Zircon grains from anorthosites, gabbros and felsic volcanic rocks will be dated using U-Pb isotopes, and these grains will also be analyzed for Hf isotopes. Three hypotheses will be tested: (1) anorthosite-bearing layered intrusions and greenstone belts are genetically related and represent relict Archean oceanic crust formed at either divergent or convergent plate margins; (2) they are genetically related and represent fragments of an oceanic plateau derived from a mantle plume; and (3) anorthosite-bearing layered intrusions are unique to the Archean and originated through non-uniformitarian geologic processes. The results of this project will have the following significance: (1) enhance our knowledge on the petrogenetic origin of Archean layered anorthosites and associated mafic to ultramafic intrusive rocks; and (2) the Canadian resource industry will benefit from this research program given that anorthosites and associated ultramafic rocks have high potential for chromite, vanadium, copper, nickel, and PGE (Platinum Group Elements) mineral deposits.

为解释加拿大苏必利尔省太古宙斜长岩层状杂岩和绿岩组合的成因而提出的地质模型需要在新的高精度地球化学数据的背景下重新评估。在未来五年中，我计划研究优势省太古界斜长岩层状杂岩和绿岩组合的野外、岩石学和地球化学特征，以约束它们的岩石成因、地球动力学背景和地质意义。待研究的斜长岩层状杂岩和绿岩组合包括新太古代巴德朱利昂湖(安大略省)和多雷湖(魁北克)杂岩。我将系统地对这些组合中的每个岩性单位进行采样，并对其进行主量元素和微量元素及同位素(Sm-ND、Th-U-Pb、Lu-Hf、O)的分析，以加深对这些岩石成因的认识。层状杂岩和空间伴生火山岩中每种岩石类型的地球化学特征有望反映导致这些岩石及其源区成分和同位素变化的岩石学过程。微量元素和Nd、Pb、Hf、O同位素对成岩过程敏感，可用来区分不同的成岩过程。这些岩石学过程可以与苏必利尔省的区域尺度的新太古代地球动力学过程联系起来，这些岩石的地球化学可以用来理解它们对太古宙地球演化的意义。来自斜长岩、辉长岩和长英质火山岩的锆石颗粒将使用U-Pb同位素测定年龄，这些颗粒还将被分析Hf同位素。将检验三个假说：(1)含斜长岩的层状侵入体和绿岩带具有成因联系，代表在发散或会聚的板块边缘形成的太古宙残余洋壳；(2)它们具有成因联系，代表来自地幔热柱的大洋高原的碎片；(3)含斜长岩的层状侵入体是太古宙独有的，起源于非均一主义地质过程。该项目的成果将具有以下意义：(1)加强我们对太古宙层状斜长岩及其相关的镁铁质至超镁铁质侵入岩的岩石成因的认识；(2)鉴于斜长岩及其相关的超镁铁质岩石具有很高的铬铁矿、钒、铜、镍和铂族元素(PGE)矿藏的潜力，加拿大资源行业将从这一研究计划中受益。