Spatial, temporal, and petrogenetic relationships of basaltic and lamprophyric dikes and sills of the Raton Basin, southern Colorado and northern New Mexico

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Alkali basalts and lamprophyres commonly occur as sheet intrusions along the flanks of continental rifts. The Raton Basin, on the eastern shoulder of the Rio Grande rift, is host to numerous basaltic and lamprophyric dikes and sills. Structural analysis of petrofabrics indicates a dominantly westward flow of magma in the basaltic and lamprophyric E-W trending dikes. Elevated light rare earth element concentrations (LREE) suggests that both of these magmas were sourced from an enriched portion of the mantle, most likely the sub-continental lithospheric mantle (SCLM). New 40Ar/39Ar ages show significant overlap in the emplacement of basalts and lamprophyres between 2̃7-20 Ma. These observations are interpreted to reflect a similar source and storage history in a crustal level magma chamber to the east of the basin. It is proposed that the magma chamber in which the basalts and lamprophyres evolved is located near the present exposure of the Raton-Clayton volcanic field.