Deformations of Sheared Marginal Granites and the Forceful Emplacement of the Tungstonia Pluton, Kern Mountains, Nevada
Abstract
Marginal granites of the Tungstonia Pluton of the Kern Mountains, Eastern Nevada, are foliated with poles to foliation that are nearly parallel to those of foliations developed in surrounding dolostones. Thus, the dolostones and marginal granites appear to have deformed during forceful magma emplacement. Previous studies of the foliated dolostones indicate that penetrative strains in the surrounding country rock were accommodated by high temperature creep within a narrow (<400m) zone that corresponds to a narrow contact metamorphic aureole. The foliated granites within the Tungstonia Pluton are interpreted to be the first-crystallized plutonic rocks, which were then subjected to stresses of the intrusion event soon after crystallization.
Microstructures of the foliated granites are under investigation by optical microscopy, in order to determine their intragranular strains and the mechanisms by which these rocks deformed. Quartz grains are highly sheared with locally large aspect ratios and micas show alignment. Quartz grains also show evidence of dynamic recrystallization. In contrast, most feldspar grains appear undeformed, and only occasional feldspar grains show deformation microstructures. Quartz grain shapes will be used to estimate their intragranular strains and alignments of quartz c-axes (and mica grains) will be used to evaluate strain patterns and conditions of deformation. These rocks represent a continuum of solid-state deformation surrounding the central intruding melt of the pluton, with shear in dolomites throughout the history of magma injection, and later shear of cooled and crystallized granite as the melt body was reduced in size but was still buoyant.
Citation
Hager, Travis Flint (2016). Deformations of Sheared Marginal Granites and the Forceful Emplacement of the Tungstonia Pluton, Kern Mountains, Nevada. Undergraduate Research Scholars Program. Available electronically from https : / /hdl .handle .net /1969 .1 /164396.