North Pennine Batholith

In 1934, Kingsley Dunham published a paper proposing that ore deposits in the Alston Block were formed due to a granite intrusion beneath Weardale. This was later tested by a gravity survey, which found a large negative gravity anomaly, supporting the hypothesis. In the early 1960s, a borehole was drilled at Rookhope by Durham University, and proved the existence of the intrusion at a depth of 390 m. The intrusion was found to have a weathered top, so couldn't account for the mineralisation that was the basis of the hypothesis that first suggested its existence. In 2004, a second borehole was drilled in Eastgate, and the granite was reached at 270 m below the surface