A Study of Trapped Liquid Variations and Coupled Chemical Trends in the Keweenawan Beaver Bay Gabbro Complex, Minnesota

这项建议旨在开发一种技术，利用背向散射扫描电子显微镜成像、诺曼斯基干涉衬度显微镜和电子探针导线，从明尼苏达州比弗湾辉长岩复合体的岩石中区分累积成分和累积成分。从这项研究中，捕获的积云间液体丰度(即原始孔隙度)将通过所有堆积成分的总和来估计，其方式类似于砂岩中原始孔隙度的估计。为了研究全岩化学成分与堆积相的丰度和组成之间的关系，还建议对全岩和矿物分离中的常量元素、稀土元素和其他微量元素的变化进行重点研究。我们还希望了解捕获液体数量的变化与液体组成之间的关系，并测试德卢斯杂岩中存在成分均匀的捕获液体的假设是否适用于比弗湾辉长岩。比弗湾辉长岩相对较小的规模、良好的曝光率、完整的地层层序和极端的富铁分异趋势，使其非常适合于本文提出的研究类型。这项研究获得的数据还将有助于表征母岩浆成分(S)，描述岩石中的结晶序列，并了解杂岩中强烈富铁结晶趋势的过程。

This proposal is to develop techniques for distinguishing cumulate from intercumulate components in rocks from the Beaver Bay gabbro complex, Minnesota, using backscatter SEM imaging, Normanski interference-contrast microscopy, and electron micro- probe traverse. From this study the trapped intercumulus liquid abundance (i.e., original porosity) will be estimated through summation of all intercumulate components, in a manner analogous to original porosity estimates in sandstones. A major study of major element, REE, and other trace element variations in whole-rocks and in mineral separates is also proposed in order to examine the relationships between whole-rock chemical composition and abundance and composition of the cumulate phases. We also wish to understand the relationship between the variation in the amount of trapped liquid and the composition of the liquid, and to test whether the hypothesis involving a compositionally uniform trapped liquid in the Duluth complex applies to Beaver Bay gabbro. The relatively small size, excellent exposure, complete stratigraphic sequence, and extreme iron-enrichment differentia- tion trend of the Beaver Bay gabbro make it well suited for the kind of study proposed here. The data obtained from this study will also lead to the characterization of the parent magma composition(s), a description of the crystallization sequences in the rocks, and an understanding of the processes to strong iron- enrichment crystallization trends in the complex.