Dartmoor granite

Mean and standard deviation recalculated from 5 samples, Appendix A1. Mean δ124/120Sn of -0.04 ‰ (Puratronic). Replicates of a sample averaged. Breakdown (δ124Sn): West Vitifer Mine -0.47; Hemerdon Mine 0.81, 1.03; South Birch Tor Mine 0.01; North Dartmoor -0.56.

Mean and standard deviation recalculated from 5 samples, "Tin isotopes - tin ores" sheet of OSM2; replicates averaged. Detail (δ124Sn): Fox Tor Gurt (0.41), Holmin Beam (0.56), Golden Dagger (-0.38), River Dart (0.38), Dean Moor (-0.01). Devon ores are generally lighter than Cornish ones, according to the authors.

Range of 11 ores, "Lead isotopes - tin ores" sheet of OSM2 (buried placer, surface placer, surface vein). Dean Moor (206Pb/204Pb = 205.5) and the south Dartmoor panned sample (208Pb/204Pb = 135.9, thorium-derived lead) are the most extreme. Cassiterite lead is partly radiogenic and spreads along an isochron: no representative central value. Sites: A44 River Dart alluvial, Black Tor, Brimpts mines North, Dean Moor, Fox Tor Gurt, Golden Dagger, Holmin Beam, Mid-South Dartmoor, North Dartmoor Consols, Ringleshutes shallow open works, River Erme.

Mean and standard deviation recalculated from 3 samples, Table 2: three subsamples of the same placer concentrate from the Dartmoor granite, reduced with graphite (20 to 25 ppm Pb in the metal). Despite a homogenised concentrate, the three measurements differ by 0.7 to 0.9 %: the ore is heterogeneous at this scale (U and Th phases). The reduction residues become enriched in thorogenic lead (up to 1.2 % offset from the metal).

Range of 11 ores, "Lead isotopes - tin ores" sheet of OSM2 (buried placer, surface placer, surface vein). Dean Moor (206Pb/204Pb = 205.5) and the south Dartmoor panned sample (208Pb/204Pb = 135.9, thorium-derived lead) are the most extreme. Cassiterite lead is partly radiogenic and spreads along an isochron: no representative central value. Sites: A44 River Dart alluvial, Black Tor, Brimpts mines North, Dean Moor, Fox Tor Gurt, Golden Dagger, Holmin Beam, Mid-South Dartmoor, North Dartmoor Consols, Ringleshutes shallow open works, River Erme.

Mean and standard deviation recalculated from 3 samples, Table 2: three subsamples of the same placer concentrate from the Dartmoor granite, reduced with graphite (20 to 25 ppm Pb in the metal). Despite a homogenised concentrate, the three measurements differ by 0.7 to 0.9 %: the ore is heterogeneous at this scale (U and Th phases). The reduction residues become enriched in thorogenic lead (up to 1.2 % offset from the metal).

Range of 11 ores, "Lead isotopes - tin ores" sheet of OSM2 (buried placer, surface placer, surface vein). Dean Moor (206Pb/204Pb = 205.5) and the south Dartmoor panned sample (208Pb/204Pb = 135.9, thorium-derived lead) are the most extreme. Cassiterite lead is partly radiogenic and spreads along an isochron: no representative central value. Sites: A44 River Dart alluvial, Black Tor, Brimpts mines North, Dean Moor, Fox Tor Gurt, Golden Dagger, Holmin Beam, Mid-South Dartmoor, North Dartmoor Consols, Ringleshutes shallow open works, River Erme.

Mean and standard deviation recalculated from 3 samples, Table 2: three subsamples of the same placer concentrate from the Dartmoor granite, reduced with graphite (20 to 25 ppm Pb in the metal). Despite a homogenised concentrate, the three measurements differ by 0.7 to 0.9 %: the ore is heterogeneous at this scale (U and Th phases). The reduction residues become enriched in thorogenic lead (up to 1.2 % offset from the metal).