The Cerro Mencenares volcanic center, Baja California Sur: source and tectonic control on postsubduction magmatism within the Gulf Rift

At the end of active subduction along the North American plate (12.5 Ma), in the Baja California peninsula arc magmatism was replaced mainly by alkali-rich high-Mg basaltic andesites and andesites with peculiar and unusually high K/Rb, Sr/Rb, and LREE/HREE ratios defined "bajaite' by Rogers et al. (1985) and "Baja alkalic suite' by Sawlan (1991). Two interesting features of this magmatic change are represented by: 1) emplacement of transitional, high-K calc-alkaline andesites that preceded, in places, the Baja alkalic suite magmatism and 2) subduction unrelated medium-K calc-alkaline magmatism in Baja California Sur, active in areas within the Gulf of California Rift. A previously unknown example of this calc-alkaline activity was studied in the area of Cerro Mencenares located north of Loreto, Baja California Sur. -from Authors