Calderas of the Sierra Madre Occidental volcanic field western Mexico

The data base on the mineral content, geomorphology, and extent of caldera in the Sierra Madre Occidental volcanic field is surveyed. Caldera identified from Landsat imagery and confirmed by field studies have generally had high structural levels and are therefore the youngest calderas and sometimes overlap. Detectable margins have been vertical and abrupt, while other structures indicate collapse during eruption and accumulation of thick, intracaldera facies. Calderas which collapsed are generally filled with sedimentation. Mineral deposits hosted by the caldera include tin, silver, gold, and iron, and a spatial relationship has been characterized between the Ocampa caldera structure and mineralized precaldera rocks. The survey has confirmed the locations of several dozen caldera, while the volume of silicic rocks surveyed indicates the presence of several hundred caldera in the Sierra Madre.