Alkaline lavas and intrusions are extensively developed along the eastern Mexican coastal plain. A series of traps, mostly of alkali basalt parentage, occur in a faulted zone that limits the altiplano on the east. The essentially alkaline association is present along the entire Gulf Coast, and could be a southward prolongation of the Trans-Pecos province of Texas.In southern Central America, alkaline intrusive and extrusive rocks have been discovered along the Caribbean coast.This study defines the situation in time and space of the alkaline-type associations with respect to the better known andesitic series.

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