ISSN:
1432-0967
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
Notes:
Abstract Major and trace-element whole rock data, Nd and Sr isotopic data, and microprobe data have been collected from a suite of basanites, olivine nephelinites, and olivine melilite nephelinites from the Raton-Clayton volcanic field, New Mexico. Most of the lavas have geochemical characteristics that suggest they are primary upper mantle derived melts. The previously unreported occurrence of Type I and Type II ultramafic xenoliths in some of the lava flows supports this conclusion. All the lavas are strongly enriched in light REE, Sr, Ba, U, Th, and P2O5. 87Sr/86Sr ratios are 0.70394 to 0.70412 and 143Nd/144Nd ratios are equal to an epsilon value of +1.4; the data fall within the Nd-Sr correlation field. Trace-element modeling indicates that the lavas were last in equilibrium with a light-REE enriched mantle with a (La/Yb)N of two to nine. However, the Nd isotopic data indicate a source with a time integrated, chondritic normalized, Sm/Nd ratio of 1.01. To account for this discrepancy a metasomatic enrichment of the source is proposed. The timing of the enrichment event can only be constrained to less than 1 AE ago, and the isotopic composition of the premetasomatized source and the metasomatizing agent cannot be specified. However, geochemical constraints suggest a CO2-rich fluid enriched in incompatible elements as the likely metasomatizing agent
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00371284
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