Low-Ti melts from the southeastern Siberian Traps Large Igneous Province: Evidence for a water-rich mantle source?

Low-Ti melts from the southeastern Siberian Traps Large Igneous Province: Evidence fora water-rich mantle source?

Alexei V Ivanov, Elena I Demonterova, Sergei V Rasskazov and Tatyana A Yasnygina

Institute of the Earths Crust, Siberian Branch of Russian Academy of Sciences, Lermontov St. 128, Irkutsk 664 033, Russia.

e-mail: [email protected] Traps Large Igneous Province (STLIP) is one of the most voluminous volcanic provinces on Earth. The dominant erupted rocks are low-Ti basalts, which make up 80% by volume of the classical Norilsk lava sequence. In the west Siberian basin and Maymecha-Kotuy area, the low-Ti basalts make up about 99% and 50% by volume, respectively. Dolerite sills in the Angara Taseevskaya Syncline at the southeastern STLIP exhibit trace element patterns and Sr isotope ratios typical of the low-Ti basalts of the Norilsk sequence. The most Mg-rich (MgO 9.511 wt%) and hence least dierentiated dolerites are characterized by trace element patterns with Ta-Nb depletion, low Ce/Pb and high Sr/Pr. These trace element features are similar to water-saturated, mantle wedge-derived island arc basalts. These imply an important role of subduction uid-derived trace elements in the source of melting beneath the AngaraTaseevskaya Syncline and other regions of the STLIP. Less magnesium rocks (MgO 3.86.1 wt%) with less prominent Ta-Nb depletion, higher Ce/Pb and lower Sr/Pr could be produced via olivine-plagioclase fractionation of primary high-magnesium melts.

Zolotukhin 1997; Lightfoot and Keays 2005). Interest in STLIP magmatism is reected in a growing number of publications and continuing debate on the causes of its origin (Zorin and Vladimirov 1989; Renne and Basu 1991; Sharma et al 1991;Campbell et al 1992; Lightfoot et al 1993; Wooden et al 1993; Arndt et al 1995; Basu et al 1995;Fedorenko et al 1996; Fedorenko and Czamanske 1997; Walker et al 1997; Basu et al 1998; King and Anderson 1998; Tanton and Hager 2000;Fedorenko et al 2000; Puer 2001; Ryabchikov et al 2001; Jones et al 2002; Reichow et al 2002; Kamo et al 2003; Medvedev et al 2003;Almukhamedov et al 2004; Elkins-Tanton 2005;Ivanov and Balyshev 2005; Ivanov et al 2005;Reichow et al 2005; Saunders et al 2005). Volcanic and intrusive rocks from many localities of

Keywords. Large igneous provinces; basalts; trace elements; Geochemistry; Geodynamics; Mineralogy and Petrology.

J. Earth Syst. Sci. 117, No. 1, February 2008, pp....