Abstract

The Jurassic Notch Peak stock intruded Upper Cambrian limestones and calcareous argillites of the Big Horse Limestone Member of the Orr Formation in west-central Utah. Previous petrologic and stable-isotope studies showed that the argillites interacted with more than two rock volumes of externally derived H2O, whereas the limestones were impervious to the infiltrating fluid. Thirty-four major, minor, and trace elements were analyzed in argillites and limestones to determine whether the substantial influx of H2O from the crystallizing pluton caused a change in the composition of the host rocks. The variability in the chemistry of the major elements is dominated by variability inherited from the protolith and by loss of CO2. The limestone samples were essentially unaffected by metamorphism because they underwent a small amount of recrystallization. The argillite samples, however, were nearly completely decarbonated during metamorphism. The ranges in major-element composition were unaffected by the great loss of CO2. There is no significant difference in the major-element chemistry with metamorphic grade, including the abundances of alkali elements. The variance in the major-element chemistry can be explained accurately by three sedimentary components: calcite, quartz + feldspar, and mica. The siliciclastic components were probably sorted independently in the sedimentary environment because of differences in grain shape. The abundances of all trace elements, except Sr, are strongly correlated with geochemically similar major elements. Sr shows very poor correlation with Ca in argillite samples and has enhanced abundances in some high-grade samples. The anomalous samples also contain high abundances of Ba, Rb, and K, and a cluster analysis groups Sr with these elements. The poor correlations among Sr and the other elements are caused by its dual affinity for alkali feldspar and calcite. The high abundance of feldspar in some high-grade samples indicates that feldspar components migrated over a volume of about 2 L during recrystallization of coarse-grained vesuvianite-and garnet-bearing samples. The results of the study indicate that there was no detectable, systematic change in composition with metamorphic grade. There is no evidence for large-scale migration of major or trace elements, despite the apparent substantial infiltration of H2O during metamorphism.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not currently have access to this article.