ИОРОХАНСКИЙ КОМПЛЕКС МАЛЫХ ИНТРУЗИЙ ВОСТОЧНОЙ ЧАСТИ БУРЕИНСКОГО МАССИВА: ГЕОЛОГИЯ, ВОЗРАСТ, ЗОЛОТОНОСНОСТЬ

Abstract

In this paper we analyze and summarize some recently acquired data coupled with the findings of previous geological, geochronological and metallogenic studies on igneous rocks of the Iorokhan gold-bearing complex in the eastern part of the Bureya massif. Four phases, whose rocks are of hypabyssal and subvolcanic intrusive facies, are shown to define the structure of the Iorokhan complex of minor intrusions; characteristic features of their composition and structural and tectonic settings of localization are given; geological and geochronological data are reported on their age (103 ± 1.0–97.4 ± 6.5 Ma), i.e. late Albian–early Cenomanian. By the ratio of alumina, calcium and alkalis, most of their compositions correspond to I-type high-alumina magnesia and magnesia-ferruginous varieties (A/CNK < 1.1) with low concentrations of HFSE, including HREE. Melting of an amphibolitic source rock produced a melt that could be a deep source of the Iorokhan diorites. A brief description of the Noni deposit is given and the main factors contributing to the localization of gold mineralization are considered. The ranges of the Iorokhan magmatites in the East Bureya volcano-plutonic zone can be considered as one of the fragments of the boundary structure between the continental margin of the eastern part of the Bureya massif and the accretionary wedges of the Sikhote-Alin orogenic belt. The Iorokhan complex of minor intrusions is assumed to be a small fragment of the wide belt of Late Albian–Early Cenomanian magmatite occurrence in the southern Far East of Russia, which formed in a setting of transform continental margin and zones of compression associated with extension resulting in the development of pull-apart basins typical of such margins.