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

尽管经过几十年的研究，太古宙板块构造过程的性质仍然是相当大的争论主题。目前的讨论集中在这些过程是垂直的还是水平的。对太古宙辉石尖晶石科马提岩的研究将有助于解决这些问题，为研究~2.7Ga大陆生长过程中太古宙地壳演化和南部优势边缘的形成提供了一种改进的模式。通过结合科马提岩和相关的硅质高镁玄武岩的地球化学和同位素研究，可以评估太古宙构造作用的性质，并将其与显生宙的构造作用进行比较。 这项研究将考察俯冲式岩性(例如，玻安岩和埃达克岩)的产状，以及从Abitibi和Wawa地区发现的经典贫铝和非贫铝类型到伍兹地区Shebanowan和Lake以及Abitibi绿岩带中发现的更不寻常的类型的一系列科马提质岩石类型。这些不寻常的、通常含有辉石的尖晶石岩石类型在成分和结构上与传统上被认为与南部Superior非常不同的Yilgarn的产状相似。然而，各种科马提质岩石和玻安岩的共同组合表明，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一个关键特征。通过评估南部苏必利尔省辉石-黄铜质科马提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。 利用全岩地球化学、放射性同位素和矿物化学等方法，对优胜省南缘辉石-千粒状科马提岩的性质和成因进行了研究。在苏必利尔省范围内对科马提岩和相关岩石类型进行综合研究，探索太古宙俯冲带的性质，将方法学与综合研究相结合，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，这些结果将有助于关于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和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.