Strongly peraluminous granitic rocks (SPG), defined by an aluminum saturation index greater than 1.1, become abundant in the rock record in the Neoarchean. This study identifies three different varieties of Neoarchean SPG in the Archean Wyoming Province, USA. These include calcic SPG, represented by the Webb Canyon Gneiss and Bitch Creek Gneiss of the Teton Range; calc-alkalic to alkali calcic suites composed entirely of SPG, including the Rocky Ridge garnet granite gneiss of the northern Laramie Mountains and the Bear Mountain granite in the Black Hills; and calc-alkalic to alkali-calcic suites that include both weakly and strongly peraluminous granitic rocks, such as the Mount Owen batholith, Wyoming batholith, and Bears Ears intrusion. Although the petrogenesis of all the SPG suites involves partial melting of crustal sources, the composition of those sources, the melting conditions, and the tectonic settings vary.The calcic suites originate by dehydration melting or water excess melting of hornblendeplagioclase rocks at relatively high temperature. The suites composed entirely of SPG form by partial melting of metasedimentary rocks by reactions involving muscovite at lower temperatures. Suites with both weakly and strongly peraluminous granite may form by partial This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America.The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.
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