Late Cenozoic basalts of southwestern New Mexico
Jerry M. Hoffer


Chemical analyses of 208 basaltic rocks from 13 occurrences in southern New Mexico show the existence of two differing basalt types. The group I basalt occurrences contain both alkalic and tholeiitic varieties with low SiO2 and high MgO and TiO2 concentrations. Group II basalts are 100% tholeiitic and contain high SiO2 and low MgO and TiO2 concentrations. Differences in Y, Zr, Rb, Sr and Ba concentrations also exist between the two groups. Spatially, the group I basalts occur in the center of the area and are flanked on the west and east by the group II basalts; this distribution is roughly parallel to the proposed boundaries of the Rio Grande rift.


  1. Hoffer, Jerry M., 1988, Late Cenozoic basalts of southwestern New Mexico, in: Cretaceous and Laramide tectonic evolution of southwestern New Mexico, Mack, G. H.; Lawton, T. F.; Lucas, S. G., New Mexico Geological Society, Guidebook, 39th Field Conference, pp. 119-122.

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