Ignimbrite flare‐up and deformation in the southern Sierra Madre Occidental, western Mexico: Implications for the late subduction history of the Farallon plate

摘要: geologic mapping, and structural data for the southern part of SMO demonstrating that most this volcanic province was built in two episodes ignimbrite flare-up Oligocene (31.5–28 Ma) early Miocene (23.5–20 time, extensional deformation occurred mostly before transfer Baja California to Pacific plate. Extensive successions, with 40 Ar/ 39 Ar ages clustering at � 23 21 Ma, cover SMO, thus correlating age ignimbrites exposed central Mexico. Grabens a 020� N-S orientation developed east almost concurrently episode. Half grabens NNW striking listric normal fault systems formed end middle as far 150 km from present coast. A belt left-lateral transpressional structures along boundary during same period. We link these magmatic tectonic events evolution dynamics Farallon North America plates Miocene. Particularly, we propose first detachment lower plate time produced transient thermal event partial melting crust via mafic underplating. Middle extension would be related second event, resulting slowing subduction preceded final capture Magdalena microplate by 12.5 Ma. Transpression southernmost inland projection MagdalenaCocos may explained difference rate temporal convergence between eve INDEX TERMS: 5480 Planetology: Solid Surface Planets: Volcanism (8450); 8150 Tectonophysics: Evolution Earth: Plate boundary—general (3040); 8109 Continental tectonics—extensional (0905); KEYWORDS: flare-up, Sierra Madre Occidental, western Mexico, tectonics, slab