Petrology and contact relationships, SW portion PC Mullen Creek mafic complex, Medicine Bow Mts., Wy.
Date
1983
Authors
Edwards, Jeffrey Scott, author
McCallum, M. E. (Malcolm E.), 1934-, advisor
Burns, L. K., committee member
Warren, C. Gerry, committee member
Journal Title
Journal ISSN
Volume Title
Abstract
Geologic mapping and thin section petrography of rock units in and adjacent to the southwestern portion of the Mullen Creek mafic complex reveals the presence of a roof zone of a Precambrian layered basic intrusion that invaded a metavolcanic sequence (predominantly hornblende gneiss). This portion of the mafic complex consists of variably metamorphosed interlayered rocks that originally ranged from pyroxenite to anorthosite but were dominantly gabbro and leucogabbro. Most of these rocks underwent regional medium-grade metamorphism to form amphibolite facies assemblages in which hornblende has replaced pyroxene, labradorite has remained stable and relict igneous textures are preserved. A later episode of retrogressive low-grade metamorphism has produced locally abundant fractures, veinlets and minerals typical of the greenschist facies such as chlorite, epidote, talc, serpentine and saussurite.
Description
Zip file contains supplementary plates 1 and 2.
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Subject
southern Wyoming
Petrology -- Medicine Bow Mountains (Colo. and Wyo.)
Medicine Bow Mountains
Prospect Mountain granite
Big Creek shear zone
layered mafic intrusion
Mullen Creek-Nash Fork shear zone
Mullen Creek mafic complex
northern Colorado
hornblende gneiss