The mineralising fluids can also come from adjacent sedimentary basins, where compaction of sediments can lead to the expulsion of pore-waters (often saline brines), which then migrate into adjacent carbonates.
see http://earthwise.bgs.ac.uk/index.php/Northern_Pennine_Orefield - an extract is given below.
By analogy with the zonation of minerals around the granites of south-west England, and with support from early geophysical studies, a concealed Late Carboniferous (?Variscan?) granite beneath the northern Pennines was postulated to account for the mineralisation. However, the proving of an Early Devonian age for the Weardale Granite in the Rookhope Borehole, drilled in 1960?61, clearly demonstrated that the mineralisation could not be the direct result of granite intrusion. Instead, as a ?high-heat-production? granite, the Weardale Granite is now considered to have driven a convective circulation of mineralising fluids long after its intrusion. From fluid inclusion and isotopic evidence, mineralising brines were derived by dewatering of adjoining sedimentary basins before scavenging metals from the rock through which they passed. Sources of the required chemical elements probably included Lower Palaeozoic basement rocks, the Weardale Granite itself, Carboniferous sedimentary rocks and the Whin Sills. Minerals were deposited in fissure veins by crystallisation from solutions which cooled as they flowed outwards from emanative centres.