Geophysical investigations in the Closehouse-Lunedale area

The Lunedale Fault is a growth fault forming the northern edge of a deep Carboniferous sedimentary basin, the Stainmore Trough, which is a potential source of brines and in which thick limestones provide suitable host rocks for mineralisation in favourable structural traps. The geology of the area therefore resembles that of areas containing some of the large Pb-Zn sulphide deposits in Ireland, and the presence of baryte in commercial quantities at Closehouse encourages the search for sulphides. The Lundale Fault,.. including the area around Closehouse Mine, .was investigated by an airborne geophysical survey consisting of magnetic, electromagnetic and radiometric recordings. The magnetic data are of unusual interest for exploration in this area because the Whin dolerite, occurring as sills and dykes, gives rise to pronounced magnetic features, of which some indicate previously unknown intrusions. The baryte deposit in the Closehouse Mine is closely related to the distribution and alteration of the Whin dykes, suggesting that a ground investigation of the aeromagnetic anomalies could be of value in further exploration. The electromagnetic maps do not indicate mineralisation of immediate interest and the amount of ground follow-up work was limited by access problems.