Bruce Ramsey

Date of Award

1972

Document Type

Thesis

Degree Name

Bachelor of Science (BS)

Department

Geology

First Advisor

Dr. Frank R. Karner

Abstract

A trend-surface modal analysis of the Tunk Lake granitic pluton was performed using a program for the IBM 30/40 computer (Appendix 1) by Heiner and Geller (MIRL Report No. 9) and data from Karner (1968). The quartz, total mafics, oligoclase, perthite, and albite in perthite percentages were analyzed.

All the trends show a southwest-northeast alignment, with the perthite, albite-in-perthite, and total mafic values increasing towards the margin of the pluton and quartz and oligoclase values decreasing outward to the margin. There is an area in the northwest part of the pluton which is an area of high values for total mafics, perthite, and albite-in-perthite, and an area of low values for quartz and oligoclase.

For the sixth-degree surfaces, the total mafics accounted for 49 percent of the total variation, quartz for 40 percent, oligoclase for 71 percent, perthite for 67 percent, and albite-in-perthite for 75 percent. The difference in the percentages points to two different types of trend. The quartz and total mafics trends are not as distinct as the oligoclase, perthite, and albite in perthite trends. This is a reflection of different processes involved in the formation of the pluton resulting in different trends. Water vapor pressure and cooling temperature govern the trends of oligoclase, perthite, and ablite-in-perthite and magma differentiation and movement govern the trends of quartz and total mafics.

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