Heat-Flow and Heat-Production Studies in North Dakota: ABSTRACT

Abstract

End_Page 780------------------------------Thirty-one new heat-flow determinations made in both oil and water wells in North Dakota range from 0.6 to 1.9 HFU. Heat-production data from basement rocks used with nearby heat-flow values indicate that only two of six sites may be considered to be similar to Basin and Range values for heat flow. One site occurs in southwestern North Dakota in a region west of 103°W where no heat-flow value is less than 1.5 HFU. The other site in north-central North Dakota is problematic, but an eastern United States interpretation is favored. The remaining four sites are interpreted as eastern U.S. values. A transition in heat-flow character from eastern United States values to Basin and Range values occurs west of 103°W long. in southwestern North Dakota. The narrow width (28 km) of the transition zone between heat-flow provinces implies a shallow depth to partly molten lower crust or upper mantle. The heat-flow results coincide with a zone of anomalous electrical conductivity. When used with experimental petrologic data for peridotite in the presence of excess water, temperature calculations suggest that a partial melt zone begins approximately at 45 to 55 km, which coincides with crustal thicknesses from seismic refraction data for southwestern North Dakota. For southwestern North Dakota, uplift of the badlands appears to be a result of partial melting. If the high heat-flow region extends northward into northwestern North Dakota, the generation of petroleum was controlled by the zone of high heat flow. This interpretation implies that source rocks are depleted in their mobile petroleum components within the region of high heat flow. End_of_Article - Last_Page 781------------