Thorium, eh?
I know of a small intrusion that ran pretty high thorium. An outcrop I was glad I didn't sit and have lunch on. But I didn't know that until weeks later when the samples came back and that one showed a big Th annomaly. Like nothing I'd seen before. Weird looking rock, brown, 1/2 meter thick sill intrusive hosted in metamorphics, fine-grained, considerable carbonate content, probable Cambrian age. Weathered like a dolomite. Just outside a known Th district. Un-claimed....
There's Thorium in them thar hills!