Synextensional Pliocene–Pleistocene Eruptive Activity in the Camargo Volcanic Field, Chihuahua, México

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The Camargo volcanic field is the largest mafic alkalic volcanic field in the Mexican Basin and Range province, and the relationship between volcanism and normal faulting is especially strong. The Camargo volcanic field lies in the northern part of the province, midway between the Sierra Madre Occidental and Trans-Pecos Texas. It is formed by Pliocene–Pleistocene (4.7–0.09 Ma) intraplate mafic alkalic volcanic rocks, some of which contain peridotite, pyroxenite, and granulite xenoliths. The volcanic field covers ∼3000 km2 and has an estimated volume of ∼120 km3 erupted from >300 recognized vents. Twenty-six new 40Ar/39Ar age determinations for the Camargo volcanic field and its environs show that volcanic activity began in the southwest part of the field and shifted toward the northeast at ∼15 mm/yr. The average magmatic eruption rate during growth of the field was ∼0.026 km3/k.y.

The Camargo volcanic field lies within an accommodation zone with west-dipping faults and east-tilted blocks to the north and east-dipping faults and west-tilted blocks to the south. These faults are expressed in the volcanic field by a N30°W-trending graben with scarps up to ∼100 m high through its central part. Volcanism and faulting were at least in part coeval, and younger volcanic products commonly drape fault scarps that cut earlier lavas. Normal faulting is bracketed between 4.7 and 2.1 Ma and may have also migrated northeastward. Estimated vertical slip rates on four Pliocene faults range from 0.03 mm/yr, a likely long-term rate, to 1.67 mm/yr, interpreted as a short-term rate operative during periods of active faulting. Northwest-striking normal faults that cut alluvial-fan deposits and Pleistocene lavas in the northern Camargo volcanic field and geomorphic evidence for recent uplift to the south of the volcanic field suggest that the region is still extending.

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Geological Society of America Bulletin, v. 115, no. 3, p. 298–313