Tectonic implications of postcontractional magmatism of the Alisitos arc segment of the Peninsular Ranges, Baja California, Mexico

Paul H. Wetmore, Scott S. Hughes, Ciprian Stremtan, Mihai N. Ducea, Helge Alsleben

Research output: Chapter in Book/Report/Conference proceedingChapter

7 Scopus citations

Abstract

The Alisitos arc segment is the southernmost and only part of the western Peninsular Ranges batholith accreted during the Cretaceous. Collision-related deformation is concentrated along the northern and eastern margins of the arc segment. While shortening within the Alisitos arc produced similar amounts of crustal thickening throughout the arc, suppression of parts of the lower crust of the Alisitos arc due to throw across the terrane-bounding faults varies substantially. Geobarometric change across the Main Mártir thrust suggests that ∼15 km of additional crust was thrust onto the central Alisitos arc. Geochemical and geochronologic data from intrusive rocks of the Alisitos arc indicate arc magmatism was active before, during, and after collision. The data suggest that all Peninsular Ranges batholith intrusive rocks within the Alisitos arc were derived from a broadly similar primitive source, lacking interaction with evolved continental lithologies. Postcollisional intrusions from the central Alisitos arc adjacent to the Main Mártir thrust yield trace elemental signatures suggesting melt derivation at depths where garnet would be a stable residual phase. The spatial and temporal coincidence of these intrusions with the Main Mártir thrust suggests that the increased pressure of anatexis inferred for the depth of generation of these melts was generated by displacement on this fault. Further, close temporal and spatial characteristics, and similar geochemical characteristics between the central Alisitos arc intrusions and La Posta intrusions east of the Main Mártir thrust suggest that the Alisitos arc intrusions represent precursors to the much larger flare-up event. This observation supports models suggesting collision as a cause of magmatic flare-ups in arcs.

Original languageEnglish (US)
Title of host publicationMemoir of the Geological Society of America
PublisherGeological Society of America
Pages669-690
Number of pages22
ISBN (Print)9780813712116
DOIs
StatePublished - Jan 1 2014

Publication series

NameMemoir of the Geological Society of America
Volume211
ISSN (Print)0072-1069

ASJC Scopus subject areas

  • Geology

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    Wetmore, P. H., Hughes, S. S., Stremtan, C., Ducea, M. N., & Alsleben, H. (2014). Tectonic implications of postcontractional magmatism of the Alisitos arc segment of the Peninsular Ranges, Baja California, Mexico. In Memoir of the Geological Society of America (pp. 669-690). (Memoir of the Geological Society of America; Vol. 211). Geological Society of America. https://doi.org/10.1130/2014.1211(21)