Title

A. N. Sirotkin, S. G. Skublov

U-­PB ZIRCON AGE OF CRYSTALLINE BASEMENT METAMAFIC ROCKS FROM SPITSBERGEN ARCHIPELAGO AND THE HISTORY OF ITS FORMATION

The geological structure features of two large blocks of an old crystalline basement of Spitsbergen were described according the modern conceptions, the conditions of manifestation of regional metamorphism and aspects of dating of an old thermal metamorphic processes were considered. The later (baikal and caledonian) stages of thermal activation processes of an old craton were studied based on examples of data about metabasic and metaultrabasic rocks which had been intruded by an old migmatites. The age of these events were dated by zircons (U-­Pb method). The genesis of these grains (and it’s separated zones) was determined according the way of the REE distribution in zircon that had been studied, this led to decode the nature of the thermal events (igneous crystallization or metamorphism).
Keywords: Spitsbergen, crystalline basement, basic rocks, ultrabasic rocks, metamorphism, zircon, U-­Pb method, rare earth elements, age of crystallization.