THE TINGUAITE BOULDER FAN IN NORTHERN DALARNA, SWEDEN, AND THE PERMO-CARBONIFEROUS RIFTING OF SCANDINAVIA

Boulders of the tinguaites connected with the alkaline Siksjoberget-Ek orrasen massif near Sarna, northern Dalarna, have been distributed sou thward by the inland ice as an erratic fan. The fan and the different tinguaite types indicate that spreading has taken place from two or po ssibly three different centres. Theoretically, these may correspond to protuberances from a plume of alkaline mantle materia in the extensio n of the Permo-Carboniferous rift in the Oslo region, Norway, a model that must be checked using geophysical measurements. A plume may also account for the updoming of porphyry which emerges through the overlyi ng Jotnian sandstone. Two of the tinguaite centres are situated within this dome.