МОНЦОНИТОИДНАЯ АССОЦИАЦИЯ КАВАЛЕРОВСКОГО РУДНОГО РАЙОНА (ПРИМОРЬЕ): ГЕОХРОНОЛОГИЯ И НЕКОТОРЫЕ ВОПРОСЫ ГЕНЕЗИСА

Abstract

Isotope-geochronological study of rocks, forming two large intrusive bodies and an isolated group of small bodies in the western part of the Kavalerovo ore district, has been carried out. They were described in the majority of publications as monzonitic or trachyandesite - monzonitic associations. The time of formation of the study intrusive associations is defined in the range 113-98 Ma by the biotite and amphibole K-Ar method and Rb-Sr method involving the rocks and minerals segregated from them. The interval can be wider (115-95 Ma) with regard to other isotope data, including those on rocks of the effusive facies. It does not contradict the conception of belonging of the investigated association to one magmatic complex. Significant and logical differences in the age of compositionally similar rocks of different massifs have not been established. According to the pattern of geodynamic evolution of the region, the latitic melts chamber, effusive and most intrusive rocks of the complex were formed prior to the initial stage of the Sikhote-Alin subduction volcanic belt. The initial stage of the belt formation is probably registered by the datings of biotite from monzodiorites of the Uglovaya VТS, located in the central part of the district (90 Ma), and of late amphibole from monzonitoids of its western part (91-92 Ma). The geochemical distinctions of the rocks composing different intrusive bodies could be caused by the features of melt evolution in the intermediate hearths or crystallization chambers.