Thermal structure of the Cornwall Batholith

Abstract

The Cornubian Batholith is the geological backbone of the Cornwall peninsula, composed of six major granitic plutons (Dartmoor, Bodmin, St. Austell, Carnmenellis, Land’s End, and the Isles of Scilly) and extends SW to the offshore. It is of Permian age and was emplaced into Devonian and Carboniferous sedimentary and igneous rocks that were deformed and regionally metamorphosed during the Variscan orogeny.
Cornwall has long been recognized as having a strong geothermal potential. The first geothermal project began here in 1977 as a research HDR (Hot Dry Rock) project at Rosemanowes Quarry. In the present day, a number of projects are based here with the aim of retrieving geothermal energy for power and heat generation, with perhaps the best-known example being the Eden Project. In all cases, however, the project development relies on the radiogenic heat production as a source of heat. This thermal origin is supported by surface heat flow measurements that show very high values (> 120 mW.m-2).
To support the development of geothermal energy, this work aims to understand the temperature evolution in depth based on an integrated study. The 3D model is the core of this model and will consider the thermal conductivity and heat production in both the granite bodies and covering sediments. The airborne geophysics measurements (including airborne radiometric) is a very good source of information on the heat production in the granites and the heat flow measurements acquired through the last few decades will give a good calibration to the system.