Isotope systematics of volcanics from the south-central Rio Grande rift and the western Mexican volcanic belt: Implications for magmatic tectonic evolution of Cenozoic extensional regimes in western North America
A diverse suite of volcanic rocks from New Mexico were analyzed for lead, neodymium, strontium, and oxygen isotopic composition. Samples range in age from late Eocene to Recent, and in composition from basaltic to rhyolitic. Results indicate that initial Eocene-Miocene calcalkaline volcanism tapped sources primarily within the lower crust and continental lithospheric mantle, whereas late Miocene-Recent basaltic volcanism may have tapped an asthenospheric source. Comparisons with published data for the northern Rio Grande rift and the Basin and Range shows that Miocene-Recent volcanism in these adjacent provinces is, in contrast, largely derived from continental lithosphere. This indicates that the south-central portion of the Rio Grande rift is distinct from the Basin and Range province, and implies that the greater degree of extension in the south-central rift compared with the north has resulted in tapping of deeper mantle sources. Lead isotopic data were obtained in this study for Quaternary alkaline and calc-alkaline volcanics of the western Mexican Volcanic Belt. Both suites have typical continental-arc trace element patterns, and it appears that the trace element signature is primarily carried in the incompatible-element enriched alkaline component. The presence of unusual extrusive minettes in this region is probably related to tensional stress within the Tepic-Zacoalco and Colima rift zones which allowed them to reach the surface with little modification.
- Research Organization:
- Washington Univ., Seattle, WA (USA)
- OSTI ID:
- 6742337
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Calc-Alkaline magmatism associated with lithospheric extension in the Eocene and Miocene of the Pacific Northwest, U. S. A
Patterns of geochemical change in north Basin and Range volcanic rocks
Related Subjects
NEW MEXICO
RIO GRANDE RIFT
GEOCHEMISTRY
AGE ESTIMATION
CONTINENTAL CRUST
EARTH MANTLE
ELEMENTS
GEOLOGIC HISTORY
ISOTOPE RATIO
LEAD
NEODYMIUM
ORIGIN
OXYGEN
RESERVOIR ROCK
STRONTIUM
TECTONICS
TRACE AMOUNTS
VOLCANIC REGIONS
VOLCANISM
ALKALINE EARTH METALS
CHEMISTRY
EARTH CRUST
FEDERAL REGION VI
METALS
NONMETALS
NORTH AMERICA
RARE EARTHS
USA
580000* - Geosciences