Document Type
Article
Publication Date
3-2018
Publication Title
Geochemistry, Geophysics, Geosystems
Abstract
Meter‐scale AUV bathymetric mapping and ROV sampling of the entire 47 km‐long Alarcon Rise between the Pescadero and Tamayo transforms show that the shallowest inflated portion of the segment hosts all four active hydrothermal vent fields and the youngest, hottest, and highest effusion rate lava flows. This shallowest inflated part is located ∼1/3 of the way between the Tamayo and Pescadero transforms and is paved by a 16 km2 channelized flow that erupted from 9 km of en echelon fissures and is larger than historic flows on the East Pacific Rise or on the Gorda and Juan de Fuca Ridges. Starting ∼5 km south of the Pescadero transform, 6.5 km of the Alarcon Rise is characterized by faulted ridges and domes of fractionated lavas ranging from basaltic andesite to rhyolite with up to 77.3 wt % SiO2. These are the first known rhyolites from the submarine global mid‐ocean ridge system. Silicic lavas range from >11.7 ka, to as young as 1.1 ka. A basalt‐to‐basaltic andesite sequence and an andesite‐to‐dacite‐to‐rhyolite sequence are consistent with crystal fractionation but some intermediate basaltic andesite and andesite formed by mixing basalt with dacite or rhyolite. Magmatism occurred along the bounding Tamayo and Pescadero transforms as extensive channelized flows. The flows erupted from ring faults surrounding uplifted sediment hills inferred to overlie sills. The transforms are transtensional to accommodate magma migration from the adjacent Alarcon Rise.
Recommended Citation
Clague, David A.; Caress, David W.; Dreyer, Brian M.; Lundsten, Lonny; Paduan, Jennifer B.; Portner, Ryan A.; Spelz‐Madero, Ronald; Bowles, Julie A.; Castillo, Paterno R.; Guardado‐France, Rigoberto; Le Saout, Morgane; Martin, Julie F.; Santa Rosa‐del Río, Miguel A.; and Zierenberg, Robert A., "Geology of the Alarcon Rise, Southern Gulf of California" (2018). School of Natural Sciences Faculty Publications and Presentations. 43.
https://digitalcommons.csumb.edu/sns_fac/43
Comments
© 2018. The Authors.
This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial‐NoDerivatives License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.
Published in Geochemistry, Geophysics, Geosystems by American Geophysical Union. Available via doi: 10.1002/2017GC007348.