Jane Matheney

Publication Date

1989

Document Type

Dissertation/Thesis

First Advisor

Berg, Jonathan H.

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Geology

LCSH

Igneous rocks--Antarctica; Geochemistry--Antarctica

Abstract

The Cenozoic volcanic rocks of the Transantarctic Mountains (TAM) provide a plethora of xenoliths which allows for a viewing of the lower crust. Ninety lower- crustal xenoliths from the TAM were analyzed for major and trace elements and 20 for rare-earth elements. Typical mineralogy consists of two-pyroxene-plagioclase (dominant) and clinopyroxene-piagioclase (subordinate) xenoliths. The mineralogy and textures exhibited by the xenoliths allow for their classification as granu- 1i tes. Many of the xenoliths exhibit "1iquid-1ike" chemical characteristics that are atypical for the lower crust. Previous studies of other xenolith suites have established a basaltic cumulate composition for the lower crust. Contrary to those findings, the composition of these xenoliths shows the lower crust in the TAM to be comprised of a "1iquid-1ike" basaltic andesite composition, based on a weighted average. Since many of the xenoliths appear "liquid-like" rather than cumulate, it is useful to characterize and classify these inclusions in terms of magmatic affinities. Based on an average major-element composition and using definitions for orogenic andesites, the xenoliths from this study are classified as having a basic, medium-k, calc-alkaline orogenic andesite affinity. The lower-crustal xenoliths from the TAM exhibit continental as well as oceanic-isi and arc signatures. Due to the "liquid-like" characteristics and andesitic composition of the 1ower-crustal xenoliths, a mechanism of emplacement of this material into the lower crust probably involves tectonic underplating rather than the magmatic underplating that is typically associated with a basaltic cumulate 1ower-crustal composition.

Comments

Includes bibliographical references (pages 145-159)

Extent

viii, 159 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

Download

Share

COinS