The questa magmatic system: Petrologic, chemical and isotopic variations in cogenetic volcanic and plutonic rocks of the latir volcanic field and associated intrusives, northern New Mexico
Thesis/Dissertation
·
OSTI ID:5022769
Field, chemical and isotopic data demonstrate that nearly all igneous rocks at Questa resulted from interactions between mantle-derived parental magmas and the crust. Strontium, neodymium and lead isotope ratios of early andesites to rhyolites (28 to 26 Ma) indicate that these magmas assimilated > 25% lower crust. Injection of basaltic magmas extensively modified the strontium and neodymium but not the lead isotope compositions of the lower crust. Eruption of comendite magmas and the peralkaline Amalia Tuff 26 Ma is correlated with inception of regional extension. Lead isotope ratios identify different sources for the metaluminous granites and the peralkaline rocks. 26 Ma metaluminous granite to granodiorite intrusions have chemical and isotopic compositions to those of the precaldera intermediate-composition rocks, and are interpreted as representing the solidified equivalents of the precaldera magmatic episode. However, both conventional and ion-microprobe isotopic data prohibit significant assimilation of crustal rocks at the level of exposure, suggesting that the plutons were emplaced a relatively crystal-rich mushes which did not have sufficient heat to assimilate country rocks. This suggest that in some cases plutonic rocks are better than volcanic rocks in representing the isotopic compositions of their source regions, because the assimilation potential of crystal-rich magmas is significantly less than that of largely liquid magmas.
- Research Organization:
- Stanford Univ., CA (USA)
- OSTI ID:
- 5022769
- Country of Publication:
- United States
- Language:
- English
Similar Records
Isotopic zonations in silicic magma chambers: conventional and ion-microprobe data from the late-Oligocene Questa caldera, northern New Mexico
Neodymium, strontium, and lead isotopes in the Maloin Ranch Pluton, Wyoming: Implications for the origin of evolved rocks at anorthosite margins
Jim River and Hodzana plutons, Alaska: the role of assimilation in the petrogenesis of syenite and granite
Conference
·
Mon Dec 31 23:00:00 EST 1984
· Geol. Soc. Am., Abstr. Programs; (United States)
·
OSTI ID:6461055
Neodymium, strontium, and lead isotopes in the Maloin Ranch Pluton, Wyoming: Implications for the origin of evolved rocks at anorthosite margins
Journal Article
·
Thu Aug 01 00:00:00 EDT 1991
· Geochimica et Cosmochimica Acta; (United States)
·
OSTI ID:6967762
Jim River and Hodzana plutons, Alaska: the role of assimilation in the petrogenesis of syenite and granite
Conference
·
Mon Dec 31 23:00:00 EST 1984
· Geol. Soc. Am., Abstr. Programs; (United States)
·
OSTI ID:6595425
Related Subjects
58 GEOSCIENCES
580000* -- Geosciences
ALKALINE EARTH ISOTOPES
CALCULATION METHODS
DATA
DATA ANALYSIS
EXPERIMENTAL DATA
FEDERAL REGION VI
IGNEOUS ROCKS
INFORMATION
ISOTOPES
LEAD ISOTOPES
MEASURING INSTRUMENTS
MEASURING METHODS
MULTI-PARAMETER ANALYSIS
NEODYMIUM ISOTOPES
NEW MEXICO
NORTH AMERICA
NUMERICAL DATA
ROCKS
STRONTIUM ISOTOPES
USA
VOLCANIC ROCKS
580000* -- Geosciences
ALKALINE EARTH ISOTOPES
CALCULATION METHODS
DATA
DATA ANALYSIS
EXPERIMENTAL DATA
FEDERAL REGION VI
IGNEOUS ROCKS
INFORMATION
ISOTOPES
LEAD ISOTOPES
MEASURING INSTRUMENTS
MEASURING METHODS
MULTI-PARAMETER ANALYSIS
NEODYMIUM ISOTOPES
NEW MEXICO
NORTH AMERICA
NUMERICAL DATA
ROCKS
STRONTIUM ISOTOPES
USA
VOLCANIC ROCKS