Major and trace element compositions and Sr, Nd, and Pb isotopic ratios of late Cenozic mafic lavas from the northern basin and range
During the late Cenozoic mafic lavas were emplaced contemporaneously with Basin and Range extension near Battle Mountains, Nevada. They display wide ranges in major and trace elements contents and Sr, Nd, and Pb ratios. The temporal and compositional characteristics of the basalts indicate the effects of crustal contamination on the compositions of the younger lavas has decreased relative to the older lavas. Assimilation and fractional crystallization (AFC) modeling suggests their compositional heterogeneity cannot be attributed solely to crustal contamination. Regional variations in the trace element ratios (Rb/La and Ba/Zr) and Sr, Nd and Pb isotopic compositions of mafic lavas from the western US indicate they were derived from a heterogeneous lithospheric mantle. The variation in the basalts' isotopic ratios likely reflects their derivation from a heterogeneous mantle source region. Plots of [sup 87]Sr/[sup 86]Sr versus [sup 207]Pb/[sup 204]Pb or [sup 207]Pb/[sup 207]Pb illustrates the compositional characteristics of their source regions. The Snake River Plain and southern Sierran Province basalts display elevated [sup 87]Sr/[sup 86]Sr and varied Pb isotopic ratios indicating they were derived from a heterogeneous ancient lithospheric source with high time integrated Rb/Sr and U/Pb ratios. The low [sup 87]Sr/[sup 86]Sr and Pb isotopic ratios of the Colorado Plateau-Eastern Transition Zone basalts were derived from a heterogeneous ancient lithospheric source with low time integrated Rb/Sr and U/Pb ratios. Basalts from the Basin and Range, Oregon Plateau, and northern Sierran Province display a positive correlation between their [sup 87]Sr/[sup 86]Sr versus [sup 208]Pb/[sup 204]Pb or [sup 207]Pb/[sup 204]Pb ratios, which appears to reflect two component mixing between accreted depleted oceanic-type mantle and an enriched mantle component.
- Research Organization:
- Rice Univ., Houston, TX (United States)
- OSTI ID:
- 5608103
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
540210* -- Environment
Terrestrial-- Basic Studies-- (1990-)
58 GEOSCIENCES
580000 -- Geosciences
ABUNDANCE
ALKALI METALS
ALKALINE EARTH ISOTOPES
BASALT
BETA DECAY RADIOISOTOPES
CENOZOIC ERA
COLORADO PLATEAU
DEVELOPED COUNTRIES
EARTH MANTLE
ELECTRON CAPTURE RADIOISOTOPES
ELEMENT ABUNDANCE
ELEMENTS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
GEOCHEMICAL SURVEYS
GEOLOGIC AGES
HEAVY NUCLEI
HOURS LIVING RADIOISOTOPES
IGNEOUS ROCKS
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPE RATIO
ISOTOPES
LANTHANUM
LAVA
LEAD 207
LEAD ISOTOPES
METALS
MILLISEC LIVING RADIOISOTOPES
MOUNTAINS
NEVADA
NORTH AMERICA
NUCLEI
OREGON
RADIOISOTOPES
RARE EARTHS
ROCKS
RUBIDIUM
SECONDS LIVING RADIOISOTOPES
SNAKE RIVER PLAIN
STABLE ISOTOPES
STRONTIUM 86
STRONTIUM 87
STRONTIUM ISOTOPES
SURVEYS
TRACE AMOUNTS
USA
VOLCANIC ROCKS