Рубидий-стронциевые изотопные данные о палеозойском магматизме в Трынском районе

I. Zagorčev, S. Moorbath. Rubidium-strontium isotopic data on the Paleozoic magmatism in the Trân District. Five whole-rock samples from biotite porphyroid granodiorites at the former mine “Zlata” define an isochron corresponding to an age of 414 ± 61 Ma, initial ⁸⁷Sr/⁸⁶Sr ratio of 0.7058 ± 0.0013 and MSWD of 1.7. Therefore, the probable age of the latest intrusive phases of Ljuckan magmatic complex is Silurian. In view also of the predominantly gabbroic composition of the early magmatic phases it can be assumed that the whole complex was formed by consecutive intrusion and cooling of magmas produced through differentiation, fractionation and contamination of a primary magma of mantle origin. This igneous activity was of Caledonian age.