Regional orientation of tectonic stress and the stress expressed by post-subduction high-magnesium volcanism in northern Baja California, Mexico: Tectonics and volcanism of San Borja volcanic field

• Published in: Journal of volcanology and geothermal research Vol. 192; no. 1; pp. 97 - 115
• Main Authors: Negrete-Aranda, Raquel, Cañón-Tapia, Edgardo, Brandle, Jose Luis, Ortega-Rivera, M. Amabel, Lee, James K.W., Spelz, Ronald M., Hinojosa-Corona, Alejandro
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier B.V 20.04.2010; Elsevier
• Subjects: Baja California; Crystalline rocks; Earth sciences; Earth, ocean, space; Exact sciences and technology; Igneous and metamorphic rocks petrology, volcanic processes, magmas; post-subduction high-magnesium volcanism; San Borja volcanic field; tectonic stress; volcanic alignments; Mexico; Baja California; Baja California Mexico; tectonic stress; volcanic alignments; post-subduction high-magnesium volcanism; San Borja volcanic field; Baja California; Neogene; volcanic centers; upper Tertiary; North America; spatial distribution; volcanism; magmatism; cones; lava flows; tectonics; Cenozoic; direction; satellites; stress; geochronology; mesas; andesites; Quaternary; volcanic rocks; Tertiary; magnesium; concentration; igneous rocks; preferred orientation; scoria; vents; pyroclastics; subduction; volcanic fields; tectonic setting; Miocene; Phanerozoic; slope angle; Pleistocene
• ISSN: 0377-0273; 1872-6097
• DOI: 10.1016/j.jvolgeores.2010.02.014

Because of its long-lived (Late Miocene to Pleistocene) post-subduction volcanic activity and location, the San Borja volcanic field (SBVF) is a key area for understanding the physical mechanisms controlling the spatial distribution of post-subduction volcanism on the Peninsula of Baja California. In this paper, we study the distribution and general characteristics of individual eruptive centers in the SBVF, aiming to provide insight into the changing physical nature of post-subduction magmatism and the control on vent location in a very unique tectonic setting. Volcanic activity has built more than 227 high-magnesium andesites (HMA) monogenetic scoria cones and thick lava flows capping large mesas during the last 12.5 Ma. The average (mean) eruptive center in the SBVF has a height of 85 m, a basal diameter of 452 m and a slope angle of 30°. Our volcanic alignment analysis of this field is based on field data, satellite images, and a quantitative method for detecting volcanic center alignments. The morphologic data, together with new 40Ar/ 39Ar geochronology data have been used to refine our alignment analysis and to better delineate the temporal evolution of post-subduction volcanic activity in this field. The available ages vary from 3.53 ± 0.18 to 10 ± 0.23 Ma suggesting that the long-lived HMA volcanism occurred almost continuously (with some concentration of pulses) throughout Late Miocene and extending to the Pleistocene and even into the Quaternary, replacing the arc-related activity of the Comondú arc which vanished in this area around 12.5 Ma. Alignment analysis confirms a NW–SE direction as the preferred orientation of volcanic alignments and shows that vent elongations do not display a strong parallelism in any particular direction, marking the absence of matches between lineaments defined by multiple vents and orientations of vent elongation. The results of the volcanic alignment analysis allowed us to infer the direction of the maximum instantaneous extension ( S 1_local) at SBVF from Late Miocene to Quaternary. We compared this value to the direction of maximum instantaneous extension for the Baja California Peninsula at a regional scale ( S 1_regional), which can be estimated from regional tectonic reconstruction. The comparison of S 1_regional and S 1_local allows us to quantify the influence of tectonic stresses in controlling the localization of monogenetic volcanism at the SBVF.