Abstract
Isla Tortuga is a morphologically young volcanic island in the Guaymas Basin. It formed as a result of extensional tectonics in the Gulf of California, and is characterized by two stages of basaltic volcanism with poor age constraints. The oldest volcanic sequence is located on the southern side of the volcano while the youngest lavas are found in northern Isla Tortuga. The most recent eruption produced a lava lake within the caldera. Additionally, Isla Tortuga hosts pyroclastic deposits at the northeastern side of the volcano. We conducted a five-day field expedition to collect samples for whole-rock geochemical analysis of major and trace element compositions and Ar-Ar radiometric dating. Meanwhile, the International Ocean Discovery Program (IODP) Expedition 385 drilled approximately four kilometers of core in total across eight different sites in the Guaymas Basin. Expedition scientists discovered sills intruding the Quaternary biogenic and terrigenous sediments in the recovered core strata. These sills have similar petrographic and geochemical compositions to the volcanic units on Isla Tortuga. A compilation and comparative analysis of the existing petrographic and geochemical data of major element compositions of Isla Tortuga volcanic units and the sills in the Guaymas Basin is ongoing, aiming to establish a petrological correlation of Isla Tortuga with the sills in the Guaymas Basin to evaluate the possibility of a common magma source. We also aim to integrate the results of the Ar-Ar whole-rock dating to propose a temporal and spatial model for the magmatic plumbing system in the Guaymas Basin.