African Large Low Shear Velocity Province Research Articles

Long term stability in deep mantle structure: Evidence from the ~ 300 Ma Skagerrak-Centered Large Igneous Province (the SCLIP)

On the basis of large areal extent (~ 0.5 × 10 6 km 2), volume, brevity of eruption interval (± 4 My) and convergent dyke swarms, the flare-up of igneous activity at 297 Ma in NW Europe marks a typical Large Igneous Province (LIP): The Skagerrak-Centered LIP (SCLIP). LIPs are widely but not universally considered products of deep-seated mantle plumes: We test the idea that a Skagerrak plume rose from the core–mantle-boundary (CMB) by restoring the center of SCLIP eruption, using a new reference frame, to its ~ 300 Ma position in a Pangea A type reconstruction. That position (~ 11°N, 16°E, south of Lake Chad in Central Africa) lies vertically above the edge of the African Large Low Shear Velocity Province (LLSVP). It has previously been shown that eruption locations vertically above the edge of one or other of the Earth's two LLSVPs at the CMB characterize nearly all the LIPs erupted since 200 Ma. A deep-sourced SCLIP plume source implies that the edge of the African LLSVP at the CMB has not moved significantly with respect to the spin axis of the Earth during the past 300 My. This is a 30% longer duration for the stability of a deep mantle structure than has been previously demonstrated and suggests that the African LLSVP was at least established by early Permian (Pangea) times.

List of authors

We review intraplate magmatism in Siberia and its folded surroundings from 480 Ma to the present. We describe several large igneous provinces (LIPs) and the intervals in which they were continuously formed within the limits of the Siberian continent: the Altay–Sayan Early Paleozoic magmatic area (598–446 Ma), the Altay–Sayan LIP (408–393 Ma), the Viluy LIP (380–350 Ma), the Barguzin–Vitim LIP (310–275 Ma), the Late Paleozoic rift system of Central Asia (318–242 Ma), the Siberian traps and West Siberian rift system (250–249 Ma), the East-Mongolian and West-Trans-Baikalian LIP (228–195 Ma), and a number of various aged Late Mesozoic and Cenozoic rift zones and magmatic areas (from 160 Ma to the present day).Following Lawver and Muller (1994), Kharin (2000), Lawver et al. (2002) and Chernysheva et al. (2005), we accept the position of the Icelandic hot spot under the Siberian trap area at the Permo-Triassic boundary. That enables us to estimate the geographic coordinates of the Siberian trap location at 250 Ma (they are the same as Iceland today). Presently the Icelandic hot spot is situated above the African large low shear velocity province (LLSVP) that indicates a hot mantle plume. We suggest a set of paleogeographic reconstructions of the Siberian continent for which we evaluate the paleolatitude based on the paleomagnetic data and estimate the paleolongitude position by placing Siberia above the African LLSVP. Furthermore, we estimate the geographic coordinates for other ancient hot spots in the framework of the African LLSVP that we consider to be responsible for the intraplate magmatism during different time periods in the Phanerozoic eon.Available rare element and isotopic characteristics of the intraplate magmatic rocks of Siberia enable us to determine three primary sources – moderately depleted mantle (PREMA), enriched mantle (EM-I and EM-II) – of the mantle origin magma. We propose that the model explains the interaction of the hot mantle plume including hot spots (plume tails) with the Siberian intraplate magmatism areas throughout the Phanerozoic eon.