Results of K-Ar and Rb-Sr Datings of the Malyshevo Leucogranite Massif, Eastern Slope of the Middle Urals

摘要

The Ural Mobile Belt is a region of widespread Paleozoic magmatism. In addition, the Mesozoic igneous rocks and endogenic ore mineralization are currently mentioned more and more frequently in connection with either postcollisional extension of the Urals or tectonomagmatic reactivation (see review in). The Malyshevo leucogranite massif and related molybdenum mineralization are often regarded as an example of Mesozoic leucogranites on the eastern slope of the Urals. The leucogranites are exposed as three lenticular bodies, (5-7) x 2 km in size, that extend as a chain along the eastern margin of the largest Murzinka-Adui area of granitic magmatism in the Urals (Fig. 1). The southern Malyshevo Massif and related commercial-scale molybdenum ore mineralization are best studied. The massif is composed of two-feldspar medium-grained leucocratic granites pertaining to several intrusive phases. The preore granite (the main intrusive phase) represented by biotite and biotite-mus-covite varieties differs from biotite-muscovite and muscovite granites of the ore-bearing and postore phases. Granites are crosscut by rare and thin aplite veins, but they are devoid of the pegmatites that are abundant in all other granitic associations of the Murzinka-Adui area. The ore stockwork of the Shameika molybdenum deposit is localized at the eastern contact of the Malyshevo Massif. The mineralization is superimposed both on the granitic rocks and on the enclosing amphibole schists.