Preliminary petrographic and geophysical interpretations of the exploratory geothermal drill hole and core, Redstone, New Hampshire

Abstract

A 3000 foot diamond drill hole was drilled in the Conway Granite in Redstone, New Hampshire. A comprehensive detailed petrographic and physical study of this core was made. The purpose of this study is to supply a sound data base for future geothermal and uranium-thorium studies of the drill core. An estimate of the heat flow potential of the Redstone drill hole gives a heat flow of 1.9 HFU. If only the red phase of the Conway Granite had been intersected the heat flow may have been as much as 2.7 HFU, reaching a temperature of 260/sup 0/C at 6 km. The drill hole intersected four lithologies; the green and red phase of the Conway Granite, the Albany quartz syenite and a medium-grained, hastingsite-biotite granite. The red phase has the highest and most irregular radioactivity. The irregularity is mainly due to minor variations in lithology. The drill core intersected several alteration zones up to a thickness of 150 feet. These alteration zones represent passage of low to medium temperature fluids which might have been mineralized. The Conway Granite has the physical and chemical characteristics necessary for the formation of vein type uranium deposits. The presence of unexplained radiometric anomalies lends support to the existence of such deposits.