THE LOWER CRUSTAL EARLY PROTEROZOIC METABASITE-ENDERBITE ASSOCIATION OF THE DZHUGDZHUR BLOCK (ALDAN SHIELD): ITS NATURE AND ORIGIN OF PROTOLITHS

Abstract

The origin and growth of the continental crust is one of the main problems in the study of the Earth’s history. At present, the composition of the continental crust is sufficiently well known for the Archean shields, where the crust is exposed. Study of the Early Proterozoic sialic crust encounters serious difficulties because its fields are usually less eroded as compared with Archean shields and are overlain by Upper Proterozoic–Phanerozoic formations. Researchers of Lower Proterozoic rocks on Archean cratons usually deal with either Early Proterozoic volcanosedimentary formations of greenstone belts related to intracratonic rifting or sedimentary fold–thrust complexes. The Early Proterozoic crust developed between Archean cratons is observable only in some tectonic windows. Of greatest interest among them are deep-rooted blocks of metamorphic rocks with exposed lower layers of the Early Proterozoic crust, the igneous protoliths of which provide information on the early stages of its formation. Deep metamorphism settings of rocks in these blocks are confirmed by geothermobarometric data.