IntroductionThe Mascota field contains calc-alkaline andesitic and minette cinder cones and lava domes and is part of the Jalisco tectonic block about 50 km east of Puerto Vallarta.
Mascota is the youngest of a group of potassic volcanic fields in extensional grabens of the Jalisco block south of the Río Ameca. Most volcanism in the Mascota volcanic field is confined to two NNW-SSE-trending grabens cutting Cretaceous ash-flow tuffs.
The oldest eruptions (2.4 - 0.5 million years ago) for the southern part of the field, while the younger eruptions (less than 500,000 years old) are in the north.
The volcanic field is known for its unusual diversity of volcanic rocks. It contains the Earth's youngest known minettes (70-80,000 years old). Minettes are a variety of igneous rock with phenocrysts of biotite, and with or without phenocrysts of hornblende, augite with a high diopside content, and olivine.
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