Outcrops of the Santa Rosalía area thus offer the opportunity to understand the magmatic evolution of the Guaymas rift, which has been the focus of numerous oceanographic expeditions. (starting at 6 Ma) before transtensional pull-apart basins to the north and south ruptured the continental crust. This area represents the western margin of the Guaymas basin, the most magmatically robust segment of the Gulf of California rift, where seafloor spreading occurred in isolation for 3–4 m.y. We report on volcanic rocks of all three suites, which surround and underlie the Santa Rosalía sedimentary rift basin. The bajaites correlate spatially with a fossil slab imaged under central Baja and are inferred to record postsubduction melting of the slab and subduction-modified mantle by asthenospheric upwelling associated with rifting or slab breakoff. 24–12 Ma), to rift magmatism, related to the opening of the Gulf of California (4%) and adakite (>56% SiO2 and MgO <3%). Volcanic rocks of central Baja California record the transition from calcalkaline arc magmatism, due to subduction of the Farallon plate (ca. The Gulf of California is an archetype of continental rupture through transtensional rifting, and exploitation of a thermally weakened arc to produce a rift.
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