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

Abstract

In 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, 40Ar/39Ar, 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.