RUI: Mechanisms of Hybridization in Silicic Magma Chambers Affected by Mafic Injections and Their Imprint on Granite: The Vinalhaven Magmatic Complex, coastal Maine

WIEBE/HawkinsEAR-0003260/0003555该项目的目标是研究将镁铁质岩浆注入浅层硅质岩浆室如何影响花岗岩中保存的岩石的化学和同位素组成。Vinalaven岩体是这项研究的理想环境，因为硅质岩浆室的镁铁质输入在供给器中保存良好，并作为镁铁质和混合中硅质岩石的层状沉积物保存下来。这些岩石提供了一个空间和时间框架，使我们能够评估单个镁铁质补充物入口点近端和远端以及上覆的“均质”花岗岩中杂化的岩石学、地球化学性质和同位素特征。我们的工作将集中于通过对选定矿物的微量分析，使用激光烧蚀ICPMS和ID-TIMS来研究颗粒内的微量元素和同位素变化。我们还将使用高精度的U-Pb年代学来限制Vinalaven岩浆室的活动寿命，并试图将保存下来的岩浆记录与保存下来的与成因有关的火山岩的喷发记录联系起来。在第一年，这个项目将与9名本科生组成一个凯克地质联盟项目，他们将进行为期4周的野外工作。这项研究直接关系到花岗岩的成因和侵位。我们认为，对矿物分带的研究可能会表明，相邻的晶体具有非常不同的结晶历史。这一信息，结合花岗岩的常见同位素变异性和不同岩浆多次补充的野外证据，有力地表明，花岗岩的整体化学和同位素组成既不是单一岩浆源的记录，也不等同于从洞室喷发的火山液体。

Wiebe/HawkinsEAR-0003260/0003555The goal of this project is to investigate how the injection of mafic magma into a shallow silicic magma chamber affects the chemical and isotopic composition of rocks preserved in granite plutons. The Vinalhaven pluton is an ideal setting for this study because mafic input to a silicic magma chamber is well preserved in feeders and as layered deposits of mafic and hybrid intermediate to silicic rocks. These rocks provide a spatial and temporal framework that will permit us to evaluate the petrographic, geochemical, and isotopic signature of hybridization both proximal and distal to the point of entry of the individual mafic replenishments, as well as in the overlying "homogeneous" granite. Our work will focus on intragrain trace element and isotopic variations through microanalysis of selected minerals, using laser ablation ICPMS and ID-TIMS. We will also employ high-precision U-Pb geochronology to constrain the active lifetime of the Vinalhaven magma chamber and attempt to link the preserved magmatic record to the preserved eruptive record of genetically related volcanic rocks. In the first year, this project will incorporate a Keck Geology Consortium Project with nine undergraduates who will undertake 4 weeks of field work. This research bears directly on the origin and emplacement of granite. We believe that studies of mineral zoning are likely to show that adjacent crystals have very different histories of crystallization. This information, combined with the common isotopic variability of a granite and field evidence for multiple replenishments of diverse magmas, strongly suggests that the bulk chemical and isotopic compositions of granite are neither the records of a single magma source nor equivalent to volcanic liquids erupted from the chamber.