Collaborative Research: Magmatic Evolution of the Midcontinent Rift System: Constraints From the Layered and Felsic Series of the Duluth Complex

这个项目的目的是限制中大陆裂谷系统(MRS)的岩浆和化学演化。我们将通过对明尼苏达州东北部MRS的Duluthand Beaver Bay侵入杂岩的两个重要组成部分进行综合的主元素和微量元素、Sm-ND和Lu-Hf同位素和Du-Pb年代学研究来实现这一点：(1)层状镁铁质侵入体；(2)侵入杂岩上部的大型花岗质(浅成花岗岩)岩体。MRS裂谷的这一部分对于详细研究至关重要，因为(1)整个地壳上部的大部分都暴露了出来，包括完整的火山序列和浅层岩浆室，这将使我们能够检查侵入单元和挤压单元之间的成因关系；以及(2)这一区域包含许多在火山序列和侵入杂岩中具有重要体积意义的长英质单元。这些长英质单位的成因和时间仍未完全弄清楚，这将是本提案的一个主要焦点。对层状花岗岩和花岗斑岩体的岩石成因、演化和时代的制约，将有助于完善中大陆裂谷系统演化的完整模式。

9903266VervoortThe 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.