Geology of Nevado de Toluca Volcano and surrounding areas, central Mexico

Abstract

Nevado de Toluca is an andesitic-dacitic stratovolcano of Pliocene-Holocene age located in central Mexico. The volcano is built on a complex sequence of metamorphic and sedimentary formations of Jurassic-Cretaceous age, rhyolitic ignimbrites of late Eocene age, and massive andesitic lava flows of late Miocene. In the northwest corner of the map area, on top of this basement sequence, a complex andesitic-dacitic stratovolcano, San Antonio, and a series of andesitic-dacitic domes and cones of Pliocene‐ early Pleistocene age were also built. The first andesitic-dacitic emissions of Nevado de Toluca occurred 2.6 Ma and continued during late Pleistocene‐Holocene time contemporarily with basaltic to dacitic emissions of the Chichinautzin Volcanic Field in the eastern parts of the map area. Volcanism in the area has been controlled by the interplay of three fault systems active since late Miocene. These systems, from older to younger, are the Taxco-Queretaro Fault System (NNW‐SSE), the San Antonio Fault System (NE‐SW), and the Tenango Fault System (E‐W). Nevado de Toluca was built at the intersection of these three fault systems, which have influenced its volcanic history as evidenced by at least three sector collapses and several large explosive eruptions. The Pliocene to Holocene volcanism at Nevado de Toluca and the late Pleistocene‐Holocene activity at Chichinautzin Volcanic Field, together with the regional tectonic activity and recent seismic swarms, suggest that the Tenango Fault System represents an active segment within the Trans-Mexican Volcanic Belt. The potential reactivation of either this fault system or Nevado de Toluca Volcano would pose earthquake and/or volcanic hazards to more than 25 million inhabitants in the vicinity, including large cities such as Toluca and Mexico.