The importance and difficulties of identifying mantle plumes in orogenic belts: An example based on the fragmented large igneous province (LIP) record in the Ural fold belt

Abstract

Mantle plumes can be recognized by their magmatic expression as large igneous provinces (LIPs). However, identification of plumes in old, structurally complicated fold belts is particularly difficult due to deformation, which obscures the LIP record. On the other hand, fold belt regions are particularly important in the search for LIPs for at least three reasons: 1) they can represent prior plate margins associated with plume-generated continental breakup and LIP magmatism; 2) the deformation may expose basement rocks (containing LIP units) covered by younger sedimentary rocks elsewhere in the continental block; and 3) they preserve deformed remnants of oceanic LIPs and hot spot chains accreted during ocean closure.Herein we provide an initial survey of the plume /LIP record of one of the world’s great orogenic belts, the Ural fold belt. The following events are identified: The 1750 Ma Navysh event is coeval with units in Sarmatia and Karelia (other parts of Baltica) and on other crustal blocks. The 1385 Ma Mashak event is associated with a range of ore deposit types, is part of Nuna supercontinent breakup, and is postulated to have had a global environmental impact linked to the Calymmian-Ectasian boundary. The ca. 720 Ma Igonino event can be approximately matched with 720 Ma LIPs in northern Laurentia, and elsewhere, which can be linked to the onset of the Sturtian glaciation (Tonian-Cryogenian boundary). The ca. 480 Ma Kidryasovo and 450 Ma Ushat events have age matches in Siberia and other crustal blocks; the ages approximately match the end-Cambrian and end-Ordovician periods, respectively. The 370 Ma Timaiz event belongs to the c. 370 Ma Kola-Dniepr LIP which is widespread in Baltica, has an age match in Siberia and collectively can be linked with the end Devonian period. An Early Carboniferous (350–320 Ma) event follows island-arc/continent collision and slab break-up in the Magnitogorsk zone. Three orogenic/postorogenic plume intraplate episodes are also described, the ca. 285 Ma Stepninsky monzogabbro-granosyenite-granite complex, the 308–304 Ma Kalymbaevsky lamproite complex and units that are coeval with the 251 Ma Siberian Traps LIP, linked to the Ural-Siberian superplume and with the end Permian mass extinction.