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Cenozoic Magmatism in the Trans-Pecos Province: Relation to the Rio Grande Rift

2011; American Geophysical Union; Linguagem: Inglês

10.1029/sp014p0382

2771-6929

Daniel S. Barker,

earthquake and tectonic studies

An early Cenozoic belt of alkalic rocks adjoins the Rio Grande rift on the southeast, in Trans-Pecos Texas. The customary assumption that alkalic magmatism is associated with rifting suggests that the two provinces are genetically linked. However, alkalic magmatism in the Trans-Pecos province began and ended before magmatism in the Rio Grande rift, starting long before normal faulting and even before the "Laramide" compressional regime had ended. The alkalic belt of the Trans-Pecos province is the easternmost extreme of a gradational series that starts on the west with contemporaneous calcalkalic rocks. The gradation is tentatively attributed to decreasing H2O to CO2 ratios in the upper mantle inland from the destructive plate margin. The Trans-Pecos alkalic belt ends at the Rio Grande rift, after continuing north-northwestward for several hundred kilometers as a chain of closely spaced plutons and volcanic centers.