Three suites of mid-Tertiary volcanic rocks are recognized in the state of Chihuahua in northwestern Mexico: (1) a dominantly silicic calc-alkalic suite that includes moderate-K and high-K. facies, (2) a ferroaugite rhyolite suite, and (3) a mildly alkalic basaltic suite. Subduction-related calc-alkalic volcanism was predominant until ∼28 m.y. ago when it was replaced by basaltic volcanism. The source of the basaltic magmas in western Chihuahua was enriched in lithophile elements relative to that of the calc-alkalic magmas. The ferroaugite rhyolites, which are restricted to eastern Chihuahua, appeared ∼32 m.y. ago. They are genetically unrelated to the calc-alkalic suite and are interpreted to represent a westward expansion of alkalic volcanism from west Texas.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not have access to this content, please speak to your institutional administrator if you feel you should have access.