PETROGENESIS OF LATE-ARCHEAN GRANITOIDS FROM THE STANOVOI EARLY-PRECAMBRIAN REGION (EASTERN SIBERIA, RUSSIA)

Granitoids of Southern part of Stanovoi early-Precambrian region are m etamorphosed. Theirs zircon U/Pb age is 2.780 +/- 0.005 Ga. They have been intruded along the tectonic contact between Gilyuisky greenstone belt and basement rocks composed of the granulite facies of Zverevskay a series. These granitoids together with surrounding rocks have been m etamorphosed (2.67 +/- 0.03 Ga Rb/Sr method) under amphibolite facies conditions. The granitoids are subdivided onto two groups: granodiorit e and tonalite-trond-hjemite ones differing by a number of geochemical features. It is supposed that the granitoids were produced by partial melting of metamorphically altered oceanic sediments within zone of t he plate subduction under Archean continent. High- and low-alumina ser ies of the granitoids were formed depending on the melting depth and d egree of partial melting. Producing of potassium-bearing calc-alkali r ocks (having mantle I(Sr)) was accompanied by inflow of mantle materia l metled in the presence of potassium-bearing fluid.