The role of mafic magmatism in age specification of Devonian continental trough deposits: evidence from the Minusa Basin, western Siberia, Russia

The role of mafic magmatism in age specification of Devonian continental trough deposits: evidence from the Minusa Basin, western Siberia, Russia GELIY S. FEDOSEEVIn the Devonian the Minusa Intermountain Trough (Basin) of Siberia represented a rift structure that was filled with rocks which now occur as strata-like bodies interpreted to be of volcanic origin.The character of the mafic rocks including their upper contacts and geochronological dating, using Rb/Sr, 40 Ar/ 39 Ar, and U/Pb methods, suggests their sill or subvolcanic nature.Porphyry and dolerite sills and basalt formed later (385-405 Mya) than felsic and andesitic volcanic rocks (402-448 Mya).Because these bodies were earlier considered as volcanic flows, it is important to revise the geological succession of the Devonian formations dominated by mafic igneous rocks.•