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: $ 1.6万
• 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: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=653767
• 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 subduction–style 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.

尽管经过了几十年的研究，太古代板块构造过程的性质仍然是一个相当有争议的话题。目前的讨论集中在这些过程是纵向的还是横向的。通过对太古代辉石类刺铁岩的研究，将有助于解决这些问题，为太古代地壳演化和南部上级边缘在~ 2.7Ga大陆生长过程中的形成提供一个改进的模式。通过对从伍兹湖到阿比提比的边缘地带沿着已绘制好地图且地质年代学上已严格限定的绿岩带中的科马提岩和相关硅质高镁玄武岩进行地球化学和同位素研究，将有可能评估太古代构造过程的性质，并将其与古生代构造过程进行比较。* 这项研究将审查俯冲型岩性（如玻安岩和埃达克岩）的出现情况和一系列科马提岩类型，从Abitibi和Wawa地区发现的典型的铝贫化和铝未贫化类型到Shebandowan和伍兹湖地区以及Abitibi绿岩带发现的更不寻常类型。这些不寻常的，一般辉石spinifex轴承岩石类型的成分和纹理类似于发生在Yilgarn传统上被认为是非常不同的南部上级。然而，各种科马提岩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，这可能是新太古代地壳生长过程的一个关键特征。通过评估南部上级省的辉石-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检验这些模型。利用全岩地球化学、放射性同位素和矿物化学研究上级省南缘辉斑状科马提岩的性质和成因。将各种方法结合起来，对整个上级省的科马提岩和相关岩石类型进行综合研究，以探索太古代俯冲带的性质，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。提高对构造过程的理解，将上级省罕见的、高度矿化的绿岩带与众多前景不太好的例子区分开来，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代板块构造和绿岩带形成的性质进行辩论，并将为全面、长期研究火成岩成因与矿床存款成因之间的关系提供一个平台。