Proterozoic evolution of the Zuni Mountains, western New Mexico: Relationship to the Jemez lineament and implications for a complex cooling history
Diana Strickland, Matthew T. Heizler, Jane Selverstone, and Karl E. Karlstrom

Abstract:

Exposures of Proterozoic crystalline rocks in the southwestern United States record the accretion of juvenile crust to the Archean/ earliest Paleoproterozoic craton province along northeast-striking structural zones. The Jemez lineament of New Mexico and Arizona, an alignment of late Cenozoic volcanic centers, has been proposed as a tectonic boundary between two accreted Paleoproterozoic terranes. The Zuni Mountains of western New Mexico offer a unique opportunity to view the crystalline basement of the lineament. The most voluminous rocks within the range are calc-alkaline granitoids and related volcanic rocks that are consistent with Paleoproterozoic arc development. Geochemical data from ultramafi c rocks within the central Zuni Mountains are consistent with an oceanic origin for these rocks, supporting the existence of a terrane boundary. However, shear zones in the Zuni Mountains record normal-sense, upper greenschist/lower amphibolite-grade deformation that occurred ca. 1430 Ma (indicated by 40Ar-39Ar data), rather than a Paleoproterozoic accretionary history. The Zuni Mountains also contain an undeformed, megacrystic granite that may be ca. 1.4 Ga. Northwest-striking diabase dikes in the Zuni Mountains record subsequent magmatism ca. 1.1 Ga. The Zuni Mountains were later uplifted during the Ancestral Rockies and Laramide orogenies. The long-lived tectonic and magmatic history recorded within the Zuni Mountains is evidence that the Jemez lineament is a crustal-scale zone of weakness, and is consistent with episodic reactivation of a Paleoproterozoic accretionary boundary.


Citation:

  1. Strickland, Diana; Heizler, Matthew T.; Selverstone, Jane; Karlstrom, Karl E., 2003, Proterozoic evolution of the Zuni Mountains, western New Mexico: Relationship to the Jemez lineament and implications for a complex cooling history, in: Geology of the Zuni Plateau, Lucas, Spencer G.; Semken, Steven C.; Berglof, William R.; Ulmer-Scholle, Dana S., New Mexico Geological Society, Guidebook, 54th Field Conference, pp. 109-117.

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