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

为解释加拿大苏伯利尔省太古宙含斜长岩层状复合体和绿岩组合的起源而提出的地质模型需要在新的高精度地球化学数据背景下进行重新评价。在接下来的5年里，我计划研究苏伯利斯省太古宙含斜长岩层状杂岩和绿岩组合的场域、岩石学和地球化学特征，研究它们的岩石成因、地球动力学背景和地质意义。拟研究的含斜长岩层状杂岩和绿岩组合包括新太古代的巴德朱米尔湖杂岩（加拿大安大略省）和多洛伊湖杂岩（加拿大魁北克省）。我将系统地对这些组合中的每个岩性单元进行采样，并分析它们的主要和微量元素和同位素（Sm-Nd, Th-U-Pb, Lu-Hf， O），以提高我们对这些岩石成因的理解。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将反映这些岩石及其来源的组成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，可用于区分不同的成岩过程。这些岩石学过程可以与苏必利尔省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特征可以用来了解它们对太古代地球演化的意义。利用U-Pb同位素对斜长岩、辉长岩和长英质火山岩中的锆石颗粒进行定年，并对这些颗粒进行Hf同位素分析。本文将验证三种假设：(1)含斜长岩的层状侵入体与绿岩带在成因上有联系，代表了形成于发散或收敛板块边缘的太古宙洋壳残余；(2)它们在遗传学上是相关的，代表了源自地幔柱的海洋高原碎片；(3)含斜长岩的层状侵入体是太古宙特有的，起源于非均变地质过程。本项目的研究成果具有以下重要意义：(1)增强了我们对太古宙层状斜长岩及其伴生基性-超基性侵入岩成因的认识；(2)加拿大资源行业将从该研究项目中受益，因为斜长岩和伴生的超镁铁质岩石具有很高的铬铁矿、钒、铜、镍和PGE（铂族元素）矿床的潜力。

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.