The Geology of Isis Point, North-East Land (Spitsbergen)

Abstract

Summary Isis Point, a rocky island-promontory among the ice-cliffs forming the east coast of North-East Land, consists entirely of igneous and metamorphic rocks. On the north coast, as already known, metamorphosed sediments are intimately invaded by a grey granite; at Isis Point amphibolites are prominent among the metamorphic rocks and the stressed grey granite occurs. Quartz-diorites, scarcely known elsewhere in North-East Land, occur as dykes and veins in the complex and are younger than it. Granodiorites, the now wellknown red and pink “granites” of North-East Land, have field relations similar to those of the diorites; aplite and pegmatite associated with the granodiorites cut the diorites. The granodiorites are younger than, or in part coeval with, the diorites; both are usually unstressed. Evidence based on morainic material from Isis Point suggests that Upper Carboniferous rocks rest directly on the igneous and metamorphic complex nearby, overstepping the sediments of the Hecla Hoek Formation from west to east. Some of the rocks of Isis Point outcrop on the coast farther north and in Great Island and White Island to the north-east; it is logical to associate them with the “Archaean” basement of Barents Shelf. Eastward, the Upper Carboniferous sediments occur in Victoria Island. The paper is a sequel to that by the author published in 1950. I. Introduction Two earlier papers describe rocks collected at Isis Point (Sandford 1926, 1950). The first mentions (p. 620) an isolated diorite, of which a specimen was brought back by a member of the 1924 Oxford expedition (Binney