Petrogenesis of Late Cenozoic volcanic rocks from the Raton-Clayton volcanic field, northeastern New Mexico and southeastern Colorado

Conference · Thu Apr 01 04:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5022872

Zhu, J; Stormer, J C; Wright, J E ^[1]; Middlefeldt, D D ^[2]

---

1. Rice Univ., Houston, TX (United States). Dept. of Geology and Geophysics
2. NASA-JSC, Houston, TX (United States)

The Raton-Clayton volcanic field, located in the eastern flank of the Rio Grande rift on the Great Plains, is at the northeastern end of the Jemez lineament. A broad variety of late Cenozoic volcanic rocks ranging from rhyodacites through basalts to basanites and nephelinites, with well established ages, provides a good probe of magma sources at different depths down to the mantle. New Sr, Nd and Pb isotopic data on late Cenozoic volcanic rocks from the Raton-Clayton volcanic field yield significant variations. [sup 87]Sr/[sup 86]Sr ratios vary from 0.70397--0.70499, [var epsilon][sub Nd] values range from [minus]3.7--2.4, [sup 206]Pb/[sup 204]Pb ratios are in the range of 17.43--18.48, [sup 207]Pb/[sup 204]Pb from 15.45--15.54 and [sup 208]Pb/[sup 204]Pb from 37.27--38.05. The mafic feldspathoidal rocks, believed to be derived from the enriched mantle reservoir with little crustal contamination, show relatively homogeneous [sup 87]Sr/[sup 86]Sr (ca. 0.7041) and [var epsilon][sub Nd] (ca. 2). A positive trend of Pb isotopic ratios, however, suggests possible mantle heterogeneity in Pb isotopic composition beneath the continent. Isotopic data from basaltic lavas display well defined variation trends, bringing to light the role of crustal components in the magmatic process. A strong signature of upper crustal involvement is indicated in the formation of tholeiitic basalts with dicktytaxitic texture, while isotope data from alkali olivine basalts and Capulin trachybasalts suggest lower crust contaminations of these rocks. An apparent isotopic variation trend of the dicktytaxitic basalts is well correlated with geographic location from south to north. Significant discrepancies in isotopic compositions of more silicic rocks compared with those of similar rocks from the Taos Plateau volcanic field to the west, may indicate either large differences in lower crustal composition or different mechanisms in generating these magmas.

• OSTI ID: 5022872
• Report Number(s): CONF-9305259--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:5
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ALKALINE EARTH ISOTOPES
COLORADO
DEVELOPED COUNTRIES
GEOLOGIC DEPOSITS
GEOLOGY
IGNEOUS ROCKS
ISOTOPE RATIO
ISOTOPES
LEAD ISOTOPES
MAGMA
NEW MEXICO
NORTH AMERICA
PETROCHEMISTRY
PETROGENESIS
PETROLOGY
ROCKS
STRONTIUM ISOTOPES
USA
VOLCANIC ROCKS