Final Report: Intermediate-Depth Hole No. 1-78-U1

During the period May 28, 1978 to June 30, 1978, an intermediate depth heat flow borehole (1-78-Ul) was completed on the Socorro Prospect, New Mexico. Rock types encountered in the hole ranged from unconsolidated Quaternary alluvium to clays and dense volcanic rocks. Depth of the hole was 1360 feet with the major drilling problems being sticky clays and hard rock. The geothermal gradient measured in this borehole was 2.46 F/100 ft with an average thermal conductivity of 5.9 mcal/cm-sec- C. The calculated heat flow value is 2.7 HFU (1 HFU = 1 {micro}cal/cm{sup 2}-sec). The linearity of the gradient for this hole suggests that heat transport in the shallow subsurface penetrated by the borehole is predominantly by conduction. Based on published data as well as the results of the present survey, a value of about 2.5 HFU is probably representative of the background heat flow in the area of the Socorro Prospect. A surface heat flow of 2.5 HFU implies partial melting in the lower crust and upper mantle beneath the Prospect but does not necessitate the presence of an economic geothermal deposit