Masters Theses

Date of Award

6-1986

Degree Type

Thesis

Degree Name

Master of Science

Major

Geology

Major Professor

L. A. Taylor

Committee Members

Harry Y. McSween, Theodore C. Labotka

Abstract

Today, "new" lunar samples are effectively provided by breccia "pull-apart" endeavors. These clasts are of various lithologies and permit the reconstruction of the breccia in time and space - the provenance. For this reason a consortium was gathered in June 1983 with the purpose of examining all of the large slab surfaces of lunar breccia 14321, these.samples included a newly sawn slab off of subsample ,37. In addition, recently discovered rock types require reevaluation of the general evolution of the early lunar crust.

A new petrogenetic model for polymict breccia 14321 is given based on the analyses of 12 new breccia clasts procured during the breccia "pull-apart" efforts of the current 14321 consortium. Using both petrographic and whole-rock chemistry data of these clasts, three distinct lithologies are defined: 1) microbreccia type-1 (MBT-l), 2) microbreccia type-2 (MBT-2), and 3) 14321 matrix breccia.

Microbreccia type-1 is dominated by highland material (78-99%). Mixing model calculations show that this highland component consists of 38-80% KREEP, 11-50% Mg-suite lithologies, and 5-17% granite. Microbreccia type-2 is also dominated by highland material (67-78%); however, the mixing calculations suggest that the KREEP component is consistently higher in this lithology than in MBT-1, varying from 75% to 81%. The other highland lithologies are correspondingly reduced with an Mg-suite component of only 7-17% and a granite component of only 0-2%.

In contrast to the two microbreccia lithologies, the 14321 matrix material contains an abundance of mare basalt (60-80%). The highland component has three constituents 19-29% KREEP, 7-8% Mg-suite, and 4-9% ferroan anorthosite (FAN). The occurrence of FAN in the 14321 matrix, although possibly an aberration of the mixing model, is important because this lithology has not been previously reported in 14321 and is scarce at Apollo 14. The presence of FAN in 14321 lends support to theories that at least a thin layer of this crustal component existed in the Apollo 14 region.

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