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

[903266 . vervoort]该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duluth和Beaver Bay侵入杂岩的两个重要组成部分进行综合主微量元素、Sm-Nd和Lu-Hf同位素和u- pb年代学检查来实现这一目标：(1)层状基性侵入；(2)侵入杂岩上部的大型花岗岩体（浅浅花岗岩体）。MRS裂谷的这一部分对于详细研究是至关重要的，因为：(1)整个上地壳剖面的大部分，包括完整的火山层序和浅层岩浆房，都暴露出来，这将使我们能够研究侵入单元和挤压单元之间的成因关系；(2)该地区含有大量长英质单元，它们在火山层序和侵入杂岩中都具有重要的体积意义。这些长质单位的起源和时间仍然没有被完全理解，这将是本提案的主要焦点。对层状基性和花岗岩体的岩石成因、演化和年龄的限制将有助于完善中大陆裂谷系统演化的综合模型。

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.