Collaborative Research: RUI: Magmatic Evolution of the Mid-Continent Rift System: Constraints From the Layered and Felsic Series of the Duluth Complex

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9903003WirthThe aim of this project is to constrain the magmatic and chemicalevolution of the Midcontinent Rift System (MRS). We will accomplish thiswith an integrated major- and trace-element, Sm-Nd and Lu-Hf isotopic, andU-Pb geochronological examination of two important components of the Duluthand Beaver Bay intrusive complexes of the MRS in northeast Minnesota: (1)layered mafic intrusions; and (2) large granophyric (hypabyssal granitic)bodies that have been intruded into the upper levels of the complexes. This portion of the MRS rift is critical for detailed study because (1)much of the entire upper crustal section, including complete volcanicsequences and shallow magma chambers, is exposed which will allow us toexamine the genetic relationships between the intrusive and extrusiveunits; and (2) this region contains numerous felsic units that arevolumetrically important in both the volcanic sequences and in theintrusive complexes. The genesis and timing of these felsic units is stillnot completely understood and will be a major focus of this proposal. Constraints on the petrogenesis, evolution, and ages of the layered maficand granophyric intrusions will help refine an integrated model for theevolution of the Midcontinent Rift System.