‘Spectacle’ array of 210Po halo radiocentres in biotite: a nuclear geophysical enigma

POLONIUM radiohaloes occur widely and not infrequently (total about 10 15 –10 20 ) in Precambrian rocks but their existence has so far defied satisfactory explanation based on accepted nucleocosmogeochemical theories 1 . Do Po haloes imply that unknown processes were operative during the formative period of the Earth? Is it possible that Po halos in Precambrian rocks represent extinct natural radioactivity 2 and are therefore of cosmological significance? A detailed comparison between an unusual array of Po halo radiocentres and U–Th halo radiocentres is presented here as bearing on the above questions.