Abstract

The Early Devonian magmatism is a continuation of Late Ludlovian magmatism. In the Sakmara zone (the western slope) a volcano-plutonic complex of effusive suites and subvolcanic intrusions of dacitic and liparite composition together with intrusives of basic composition belong to the Early Devonian magmatism. In the Tagil synclinorium the magmatic suites of the Early Devonian are represented by a trachytic complex and intrusions of syenites and other alkaline rocks.

In the Early Devonian the most active volcanism appeared in the south Urals where andesite-basalt volcanic belts of island-arc type were developed. Near fractures, extrusion of the basalt-liparite suite, which plays the role of host rocks of copper pyrite deposits, took place. In the beginning of the Early Devonian, in connection with the tectonic reconstruction in intrageosyncline, the emplacement of ultrabasics followed by the intrusion of gabbro-diorite plagiogranite complex took place. The volcanic belts of Early Givetian time are displaced to the east from the Early Devonian - Early Eifelian. The central eruptions accompanied by rhythmic ejection of pyroclastic material of andesite-dacite suite are typical for the Givetian and, in the north, for the Eifelian. The subvolcanic intrusions are represented by diorites and quartz diorites.

At the Givetian-Frasnian boundary a reconstruction of structural plan took place, and intrusions of diabase appear, which also developed in the outer zones of geosynclines, in the Russian platform and inactivated structures of Bailkalids of Timan.

The sub-aerial andesite-basaltic and submarine andesite-dacite volcanism is typical for Late Frasnian time in the south Urals. In Famennian time volcanism appears locally in the form of outpouring of basalts.

The last magmatic manifestation connected with the development of the Devonian geosyncline is a post-orogenic complex of gabbro-diabases, diorites syenite-porphyries probably of Early Tournaisian age.

In the Urals deposits of copper, gold, polymetals, iron and chromite are associated with the Devonian magmatism.