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

尽管经过了几十年的研究，太古宙板块构造过程的性质仍然存在相当大的争议。目前的讨论集中在这些过程是垂直的还是水平的。对太古宙辉石尖粒科马长岩的研究将有助于解决这些问题，为大陆生长~2.7 Ga时太古宙地壳演化和南上缘形成提供一个改进的模型。通过对从森林湖到阿比提比边缘的绿岩带中科马铁矿及其伴生的硅质高镁玄武岩的地球化学和同位素研究，将有可能评价太古宙构造过程的性质，并将其与显生宙的构造过程进行比较。***本研究将考察俯冲式岩性（如博长岩和埃达克岩）的产状和科马提岩类型的谱，从阿比提比和瓦瓦地区的经典贫铝和未贫铝类型到在谢班道万和伍德湖地区以及阿比提比绿岩带发现的更不寻常的类型。这些不寻常的，通常是辉石质含尖晶石的岩石类型在成分和结构上与伊尔加恩（Yilgarn）的产状相似，而伊尔加恩传统上被认为与南苏伯利尔山非常不同。然而，各种科马提岩与博长岩的共同组合表明，它们在某种程度上具有相似的地球动力学历史，这可能是新太古代地壳生长过程的一个关键特征。通过评估苏必利尔省南部辉石岩-辉石岩和伴生岩石的地球化学，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。***将利用全岩石地球化学、放射性同位素和矿物化学对苏必利尔省南缘辉石质斑岩的性质和成因进行研究。通过对苏必利尔省科马地岩及其伴生岩石类型的综合研究和方法的结合，探索太古宙俯冲带的性质，这是真正的创新。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、高矿化绿岩带与众多不太有前景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，这些结果将有助于对太古宙板块构造和绿岩带形成性质的争论，并将为全面、长期研究火成岩成因与矿床成因之间的关系提供平台。

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.