New data reflect on the thermal antiquity of the Socorro magma body locale, Rio Grande Rift, New Mexico

New heat flow data and recent relative Vs (Delta Vs/Vs) studies suggest differential crustal warming from prolonged intrusions in the Socorro magma body area. Heat flow above the Socorro magma body, relative to the adjacent Colorado Plateau and Datil-Mogollon region, indicates that similar to 8 times more heat has been introduced into the crust than contained in a basaltic Socorro magma body. A combination of relative Vs contours and heat flow data suggests this differential is less, a factor similar to 4.5. From relative Vs contours, depth of Socorro magma body, and conduction time constants, the minimum time required to increase heat flow resulting from midcrustal intrusions is similar to 1-3 m.y. Recent models indicate that observed historic uplift at the Socorro magma body is explained by viscoelastic response of crustal material surrounding the Socorro magma body. Our estimates suggest that a long time scale (similar to 10(6) yr) for emplacement of basaltic magma sill(s) and surface uplift need not be directly related. Based on heat flow, we estimate >600 m of basaltic intrusion during Pliocene-Pleistocene time. Compared with adjacent rift basins, the Socorro magma body area shows anomalous landscape instability but no significant uplift of stream terraces across the magma body. Contiguous areas in the Rio Grande Rift have high heat flow but no present magma layer, no historic uplift, and little seismicity. Elliptical relative Vs crustal contours for the area suggest conductive heat transfer. The relative Vs model implies that the Socorro magma body is fed by narrow conduits (dikes) from the upper mantle and that the depth of the sill-like Socorro magma body is primarily controlled by rheology.