Early Paleozoic mafic magmatic events on the eastern margin of the Siberian Craton

Neoproterozoic and Devonian mafic flows, sills and dykes associated with synchronous rifting events are widely distributed along the long-lived Mesoproterozoic to Mesozoic passive eastern margin of the Siberian Craton. Early Paleozoic magmatic events are also present, but are poorly studied, including Early Cambrian volcanic rocks in the Kharaulakh Range and ca. 450 Ma age mafic intrusions of the Suordakh event in the Sette-Daban Range. Both suites of early Paleozoic magmatic rocks are characterized by high Ti concentrations (>3 wt.% TiO2), ocean island basalt (OIB)-type trace element and rare earth element (REE) patterns, and high epsilon(Nd)(t) values that generally vary between 6 and 9. The Kharaulakh magmas were formed during low degree partial melting of an enriched region of mantle at depths >90 km, generating a suite of alkaline basalts. In comparison, the Suordakh magmas were formed during higher degree partial melting of less enriched mantle at depths <90 km, forming alkaline to subalkaline basalts. Both suites are characterized by epsilon(Nd)(t) values suggestive of interaction between enriched and depleted magmas and both were emplaced in within-plate tectonic settings. Although Kharaulakh and Suordakh magmatic rocks have relatively small areal extents, significant parts of them are likely hidden below clastic rocks of the Lower Carboniferous-Jurassic Verkhoyansk Complex. The Kharaulakh magmatic rocks may have counterparts in the Canadian Cordillera, that together could be of sufficient scale to define a Large Igneous Province (LIP). Early Cambrian mafic volcanic rocks in the study area are associated with locally distributed terrigenous units in both the Kharaulakh and Sette-Daban ranges, suggesting that this magmatism was related to a rifting event. Modeling of sedimentary basin subsidence in the Sette-Daban area is also supportive of an Early Cambrian rifting event. However, the intrusive rocks associated with the ca. 450 Ma Suordakh mafic magmatic event are not related to any rift-related sediments or structures. Contemporaneous granites may be interpreted as silicic magmatism associated with a LIP event. (C) 2012 Elsevier B.V. All rights reserved.