K-Ar dating on eastern Mexican volcanic rocks - Relations between the andesitic and the alkaline provinces

Abstract:

Eastern Mexico is characterized by two large magmatic provinces: the trans-Mexican volcanic belt, mainly of Miocene and Quaternary andesitic rocks, and the eastern alkaline province (oversaturated alkalic and subsaturated nephelinitic-type volcanic rocks) which appears to be Oligocene to Quaternary in age. Twenty-eight K-Ar analyses show the respective positions and the relationships between the two magmatic types: 1. (1) The data indicate that the trans-Mexican andesitic zone has had various important periods of volcanic activity since the Early Miocene: the major activity seems to have taken place about 20-15 m.y. and 9-6 m.y. ago. Ages of 3-0 m.y. are concentrated in the neovolcanic belt, the southern part (high volcanoes of Quaternary age), apparently more recent than the northern part (Atotonilco lavas). 2. (2) In the eastern alkaline province, the volcanism occurred from the Late Oligocene, with various phases, until the most recent volcanic episode. Activity has moved southwards from Tamaulipas to the Veracruz region. 3. (3) Alkaline basaltic lavas ("traps"), which occur in the fault zone of the Altiplano border, show a progression of the rifting, between 9 and 3 m.y. ago, from northern Hidalgo to Veracruz. 4. (4) The periods of alkaline magmatism were not contemporaneous with andesitic phases. The two types occur independently, the andesitic one having an east-west direction and the alkaline one a north-south orientation and north-south migrations. 5. (5) Such patterns lead to a crossing and interference of the two Pliocene and Quaternary fields of magmatism. It appears that the relations between the andesitic and the alkalic provinces is not in agreement with a classical scheme recognized in the Circum-Pacific. © 1979.

Año de publicación:

1979

Keywords:

Fuente:

scopus