Igneous Petrology of the New Skaergaard Stratigraphic Reference Column

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Igneous Petrology of the New Skaergaard Stratigraphic Reference ColumnEAR-0208075PI: Lesher The PI and his colleagues have established a new high-resolution reference column of the layered series of the Skaergaard intrusion from drill core from the Platinova exploration program in 1989-90 and surface samples collected and located by GPS during the summer of 2000. This was done as a collaboration between U.S. and Danish scientists, and students. Skaergaard differentiation has been highly controversial and the divergence of opinions is likely to remain unless new fundamental observations are brought to bear on the problems. The primary objective of this proposal is to document the petrology and geochemistry of this stratigraphically controlled suite of previously collected drill core and surface samples using well established petrographical and analytical tools. This composite stratigraphic column will provide a basis for rigorous hypothesis testing of the mechanisms of Skaergaard evolution that have eluded petrologists in the absence of good stratigraphic control. The main product will be a detailed mineralogical and chemical stratigraphy at a sampling interval of 10 m and less. Observations will be linked to the analysis of the physical factors that govern the behavior of the crystallizing magma and its liquid line of descent. This will provide the foundation for evaluating the roles of crystal sedimentation, in-situ crystallization, compaction, and infiltration metasomatism at Skaergaard and other layered igneous intrusions.