Sudbury Igneous Complex: The Ultimate Test of the Null Hypothesis

9725158沼泽为什么一些大的火成岩几乎是一致的，而其他外表相似的物体却不是，这长期以来一直是一个谜。有两组，一组最初含有大晶体(斑晶)，另一组最初不含斑晶。前者倾向于成分和质地的一致性。晶体的形核和生长似乎是由上下部向内扩展的凝固锋(SF)控制的，它抑制了晶体的分馏。Null假说认为，最初没有斑晶的片状岩浆经历了很小的分化。我们在一个厚(330米)的辉绿岩岩床上测试了这个假设，发现它是成立的。要想成为一个普遍的、基本的概念，它必须在一个大的身体上进行测试。萨德伯里火成岩复合体(SIC)是检验Null假说和洞察无斑晶体系凝固动力学的理想大体。通过使用贯穿整个身体的一系列钻芯对碳化硅进行晶体尺寸分布(CSD)的综合研究，将跟踪凝固的历史。为此，鹰桥有限公司允许从SIC无限制地访问其持有的大量核心资产。这项工作将极大地促进和补充萨德伯里的其他研究，并将从根本上有助于理解大型岩浆系统。

9725158 Marsh It has long been a mystery why some large bodies of igneous rock are nearly uniform and other outwardly similar bodies are not. There are two groups, those initially containing large crystals (phenocrysts) and those initially free of phenocrysts. The former tend toward compositional and textural uniformity. Crystal nucleation and growth seem to be controlled by upper and lower inward propagating solidification fronts (SF) that stifle crystal fractionation. The Null Hypothesis says that sheet-like magmas initially free of phenocrysts undergo little differentiation. We have tested this hypothesis on a thick (330 m) diabase sill and find it holds. To be a general, fundamental concept it must be tested on a large body. The Sudbury Igneous Complex (SIC) is an ideal large body to both test the Null Hypothesis and also to gain insight into the solidification dynamics of phenocryst free systems. The history of solidification will be tracked by making a comprehensive study doing Crystal Size Distributions (CSDs) of the SIC using a series of drill cores through the entire body. For this purpose, Falconbridge Limited has allowed unlimited access to their vast holdings of core from the SIC. This work will contribute substantially to and complement other studies of Sudbury, and will contribute fundamentally to the understanding of large magmatic systems.