Geochemistry of pyroxene-phyric komatiites in the Southern Superior Province; Implications for Archean geodynamics

苏必利尔南部省辉石斑状科马提岩的地球化学；

• 批准号: RGPIN-2017-05362
• 负责人: Hollings, Peter
• 金额: $ 1.68万
• 依托单位: Lakehead University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=755036
• 关键词: Geochemistry; pyroxene; phyric; komatiites; Southern

Despite decades of research the nature of Archean plate tectonic processes remains the subject of considerable debate. The current discussion focuses on whether these processes were vertical or horizontal. This study of Archean pyroxene spinifex komatiites will help to resolve these questions by providing an improved model for Archean crustal evolution and the formation of the southern Superior margin during continental growth at ~2.7 Ga. By combining geochemical and isotopic studies of komatiites and associated siliceous high-magnesian basalts in well-mapped and geochronologically well-constrained greenstone belts along the length of the margin from Lake of the Woods to the Abitibi, it will be possible to evaluate the nature of Archean tectonic processes and compare them with those of the Phanerozoic. This study will examine the occurrences of subductionstyle lithologies (e.g. boninites and adakites) and a spectrum of komatiitic rocks types ranging from classic Al-depleted and Al-undepleted types recognized in the Abitibi and Wawa areas to more unusual types found in the Shebandowan and Lake of the Woods areas, as well as in the Abitibi greenstone belt. These unusual, generally pyroxene spinifex-bearing rock types are compositionally and texturally similar to occurrences in the Yilgarn which has traditionally been considered very distinct from the southern Superior. However, the common association of various komatiitic rocks and boninites indicates that, to some extent, they share a similar geodynamic history that may represent a key feature of the Neoarchean crustal growth processes. By assessing the geochemistry of pyroxene-phyric komatiites and associated rocks in the southern Superior Province we will be able to test these models in the world's largest Archean craton.Whole rock geochemistry, radiogenic isotopes and mineral chemistry will be used to investigate the nature and origin of the pyroxene-phyric komatiites on the southern margin of the Superior Province. The combination of methodologies and the integrated study of komatiites and associated rock types across the Superior Province to probe the nature of Archean subduction zones is truly innovative. Results from this research will help to enhance the international reputation of Canadian science. Improved understanding of the tectonic processes that distinguish the rare, highly mineralized greenstone belts of the Superior Province from the numerous less prospective examples will promote mineral exploration in Canada. In the longer term, the results will contribute to the debate about the nature of Archean plate tectonics and greenstone belt formation and will provide a platform for a comprehensive, long-term study of the relationship between igneous petrogenesis and ore deposit genesis.

尽管经过了数十年的研究，太古代板块构造过程的本质仍然是一个颇有争议的话题。当前的讨论集中在这些过程是垂直的还是水平的。这项对太古代辉石三齿稗科马提岩的研究将有助于解决这些问题，为太古代地壳演化和约 2.7 Ga 大陆生长过程中南上缘的形成提供改进的模型。通过结合科马提岩和相关硅质高位岩的地球化学和同位素研究-沿从伍兹湖到阿比蒂比边缘的长度，在地图绘制良好且地质年代学上受到良好约束的绿岩带中存在镁质玄武岩，评估太古代构造过程的性质并将其与显生宙的构造过程进行比较将成为可能。这项研究将研究俯冲型岩性（例如栉泥岩和埃达克岩）的出现情况以及一系列科马提岩类型，范围从阿比蒂比和瓦瓦地区发现的经典贫铝和未贫铝类型到谢班多万和湖中发现的更不寻常的类型伍兹地区以及阿比蒂比绿岩带。这些不寻常的、通常含有辉石的三齿稗岩石类型在成分和结构上与伊尔加恩 (Yilgarn) 中的矿点相似，传统上认为伊尔加恩 (Yilgarn) 与南部苏必利尔 (Superior) 非常不同。然而，各种科马提岩和桠岩的共同组合表明，在某种程度上，它们具有相似的地球动力学历史，这可能代表了新太古代地壳生长过程的关键特征。通过评估苏必利尔省南部辉石-斑状科马提岩和相关岩石的地球化学，我们将能够在世界上最大的太古宙克拉通中测试这些模型。全岩石地球化学、放射性同位素和矿物化学将用于研究其性质和起源苏必利尔省南缘的辉石斑状科马提岩。将方法论与对整个苏必利尔省的科马提岩和相关岩石类型的综合研究相结合来探索太古代俯冲带的性质是真正的创新。这项研究的结果将有助于提高加拿大科学的国际声誉。更好地了解将苏必利尔省稀有的、高度矿化的绿岩带与众多前景较差的例子区分开来的构造过程，将促进加拿大的矿产勘探。从长远来看，该成果将有助于引发关于太古代板块构造和绿岩带形成本质的争论，并为全面、长期研究火成岩与矿床成因关系提供平台。