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首页> 外文学位 >Characterization of heavy minerals in the Superior, Green Bay, and Lake Michigan glacial lobes and reconnaissance kimberlitic garnet search in northern Wisconsin.
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Characterization of heavy minerals in the Superior, Green Bay, and Lake Michigan glacial lobes and reconnaissance kimberlitic garnet search in northern Wisconsin.

机译：威斯康星州北部苏必利尔，绿湾和密歇根湖冰川叶的重矿物特征及侦察金伯利特石榴石的搜寻。

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摘要

Glacial till has been sampled all along the late Wisconsinan glacial margin in Wisconsin and Illinois. Heavy minerals extracted from the fine sand fractions of all till samples were grain counted to examine potential differences in the heavy mineral suites between and within the Superior, Green Bay, and Lake Michigan Lobes. Results of this work indicate that the three major glacial lobes can be distinguished by their heavy mineral populations. Heavy mineral suites in both the Superior and Green Bay Lobe tills contain large amounts of pyroxene and magnetic minerals and small amounts of garnet and epidote group minerals, whereas Lake Michigan Lobe tills contain significantly less pyroxene and magnetic minerals and relatively large amounts of garnet, epidote group minerals, accessory minerals (zircon, rutile, tourmaline, sphene, and monazite), and hornblende. Unusually high abundances of opaque heavy minerals in the Superior Lobe tills serve to separate them from all Green Bay Lobe tills. Differences in the abundances of various heavy minerals also exist within each glacial lobe, but these differences are much smaller than differences between the major lobes.; Heavy minerals were also extracted from the combined fine and medium sand fractions of eight samples of glaciofluvial sediment collected along the late Wisconsinan margin of the Superior and northern Green Bay Lobes. Potential kimberlitic garnets as well as regional garnets representative of each color group present then were selected and their chemistries determined by electron microprobe analysis. One garnet picked from northern Green Bay Lobe outwash was found to be chemically similar to G5 (magnesian almandine) garnets found in kimberlite and lamproite, but a possible crustal source can not be ruled out. No other possible kimberlitic garnets were found in this limited reconnaissance study. The regional garnets divided chemically into two distinct groups: iron-rich purple and pink garnets, and red and orange garnets containing larger amounts of manganese, calcium, or both.
机译：在威斯康星州和伊利诺伊州的威斯康星州晚期冰川边缘一直采样到冰盖。从所有样品的细砂级分中提取的重矿物进行谷物计数，以检查上级，绿湾和密歇根湖裂片之间及其内部的重矿物组之间的潜在差异。这项工作的结果表明，三个主要的冰川叶可以通过其大量的矿物质来区分。 Superior和Green Bay Lob耕地中的重矿物套房均包含大量的辉石和磁性矿物以及少量的石榴石和附子类矿物，而密歇根湖Loess耕种中的辉石和磁性矿物显着较少，而石榴石，Epidote则相对较多组矿物，辅助矿物（锆石，金红石，电气石，蝶粉和独居石）和角闪石。上等叶耕种中异常大量的不透明重矿物将它们与所有绿湾中耕种分开。每个冰川叶中也存在各种重矿物质丰度的差异，但这些差异远小于主要叶片之间的差异。还从沿Superior和Green Bay Lobes的威斯康星州晚期边缘收集的八份冰川河床沉积物的细砂和中砂组合物中提取了重矿物。然后选择潜在的金伯利岩石榴石以及代表每个颜色组的区域石榴石，并通过电子探针分析确定其化学性质。发现从北部格林贝洛贝溶石中选出的一种石榴石在化学上类似于金伯利岩和堇青石中发现的G5（镁铝金刚砂）石榴石，但不能排除可能的地壳来源。在这项有限的侦查研究中，没有发现其他可能的金伯利岩石榴石。区域性石榴石在化学上分为两个不同的组：富含铁的紫色和粉红色石榴石，以及含有大量锰，钙或两者的红色和橙色石榴石。

著录项

  • 作者

    Hoffman, Steven Michael.;

  • 作者单位

    The Ohio State University.;

  • 授予单位 The Ohio State University.;
  • 学科 Geology.; Mineralogy.
  • 学位 Ph.D.
  • 年度 1998
  • 页码 143 p.
  • 总页数 143
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地质学;矿物学;
  • 关键词

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