Petrography and petrogenetic history of a quartz monzonite intrusive, Swisshelm Mountains, Cochise County, Arizona
AuthorDiery, Hassan Deeb, 1934-
KeywordsGeology -- Arizona -- Cochise County.
Petrology -- Arizona -- Cochise County.
Swisshelm Mountains (Ariz.)
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PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractThe Swisshelm Quartz Monsonite covers about two square miles on the western slope of the Swisshelm Mountains, Cochise County, Arizona. Field observation and petrographic study indicate that the quartz monsonite was derived by differentiation and late-stage alkali metasomation of probably a quartz dioritic magma rich in alkali and volatile constituents. The high concentration of the volatiles is believed to be of great importance in the development of the different facies and rock types. Four different facies of the Swisshelm Quartz Monsonite have been distinguished as (1) the normal facies, (2) the altered facies, (3) the fine-grained facies, and (4) the contact facies. Also, several aplite dikes, local beryl-bearing pegmatite patches, and numerous quartz veins are present and attributed to late magmatic differentiation. Inclusions of an early and late magmatic facies are sparcely disseminated through the quartz monsonite. The Swisshelm Quartz Monsonite magma has intruded and metamorphosed the Upper Paleozoic sediments of the Mace Group as well as the Lower Cretaceous sediments of the Bisbee Group. The metamorphism is of a contact metasomatic type to which the mineralogical and textural changes in the country rocks have been attributed.