Collaborative Research: Contrasts in the Petrologic, Chemical, and Isotopic Evolution of Two Archean Mid-Crustal Environments: Processes Controlling Crustal Growth

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This proposal seeks funds to support a collaborative petrologic, structural, chemical, and isotopic investigation of the growth and development of continental crust as recorded in rocks of the middle crust (roughly 125-25 km). The middle crust is a dynamic environment through which Earth materials are cycled both mechanically and chemically. Supracrustal rocks may be transported to mid-crustal levels through tectonic processes; juvenile additions to the crust may be emplaced from the mantle; fluid fluxes may initiate melting, possibly to produce charnockites, or leach LIL elements; melting in the middle crust may extract large volumes of melt through vapor-absent melting. Artifacts of many of these processes have been recognized in two distinct blocks of Archean crustal rocks in the northern Madison Range, SW Montana. Our integrated study of this segment of Archean continental crust will lead to a more comprehensive understanding of the geochemical processes that contribute to the growth and development of continental crust, as well as to the specifics of the tectonic and magmatic cycles controlling crustal evolution in the northern Wyoming Province.