Petrogenesis and timing of mafic magmatism, South Taimyr, Arctic Siberia: a northerly continuation of the Siberian Traps?

Reichow, M.K., Saunders, A.D., Scott, R.A., Millar, I.L., Barfod, D. , Pringle, M.S., Rogers, N.W. and Hammond, S. (2016) Petrogenesis and timing of mafic magmatism, South Taimyr, Arctic Siberia: a northerly continuation of the Siberian Traps? Lithos, 248, pp. 382-401. (doi: 10.1016/j.lithos.2016.01.018)

Abstract

The Siberian large igneous province (LIP) forms the world's most extensive continental exposure of basalt and has several sub-provinces surrounding it,whichmay be genetically related. The Taimyr peninsula of north Siberia is one of these sub-provinces and is frequently assumed to be the northerly continuation of the basalts exposed at Noril'sk, the best-studied area of the Siberian LIP. However, the correlation is uncertain. We present new major and trace element data from 35 samples of extrusive and intrusive rocks from Taimyr, with Sr and Nd isotope data from a subset of ten. The Taimyr rocks fall into two groups with low (~7 wt.%) and elevated (~9 wt.%) MgO concentrations. The high-MgO rocks display a restricted range of initial 87Sr/86Sr (0.705 to 0.706) and 143Nd/144Nd (0.5122 to 0.5124) ratios, and share bulk silicate earth normalised rare earth element patterns strikingly similar to data observed in the ore-related Noril'sk intrusions. The remaining low-MgO group samples have a broader range with higher Sr and lower Nd isotope values and higher incompatible trace element ratios (e.g., Th/Ta N 5.3 and La/Smn N 1.7) similar to the crustally-contaminated Nadezhdinsky and Morongovsky suite basalts of the Noril'sk region. The major and trace element data for both groups are consistent with a process of fractional crystallisation coupled with small degrees of assimilation of incompatible-element-enriched lower crust involving different contaminants. Trace element model calculations indicate a process of magma formation at large degrees of partial melting and at pressures of less than 3 GPa, probably within the garnet–spinel transition zone or the spinel stability field of the asthenospheric mantle. We obtained an argon plateau age of ~252 (252.7 ± 1.5) Ma and a ~239 Ma total fusion age from a Taimyr lava and intrusive sample, respectively, confirming that volcanism is only partly contemporaneous with the activity of the Siberian LIP. Although this is in agreement with previous interpretations, we argue that the age difference between both events is only ~13Ma and probably less (~5Ma) although further investigation of the relationship is required. Our data allow correlation with distinct Noril'sk members and most importantly to the ore-bearing (Ni–Cu) intrusions implying that whole rock chemistry could have value as a prospecting tool in Taimyr.

• Item Type: Articles
• Additional Information: We would like to thank V. Pease and G. Fitton for their very thorough and constructive reviews. The authors are grateful for discussions and suggestions by E. Eide, C. Herzberg, I. Parsons, R.Walker, J. Smellie and H. Walderhaug. Reviews of an earlier version by P. Lightfoot and an anonymous reviewer are greatly acknowledged. The 40Ar/39Ar analysis at the Massachusetts Institute of Technology (MIT), Cambridge, USA and the Scottish Universities Environmental Research Centre, East Kilbride, UK, and M.K. Reichow was supported under the Natural Environment Research Council (NERC) grant NE/C003276/1. Radiogenic isotope analyses were supported by NERC Isotope Geosciences Facilities Steering Committee grants IP/933/1106 and IP/1003/1107. The samples M.K. Reichow et al. / Lithos 248–251 (2016) 382–401 399 used for this study were collected during fieldwork organised and largely funded by the Swedish Polar Research Secretariat, for which we are very grateful. This paper is dedicated to the late R.A. Scott who is greatly missed.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Barfod, Dr Dan
• Authors: Reichow, M.K., Saunders, A.D., Scott, R.A., Millar, I.L., Barfod, D., Pringle, M.S., Rogers, N.W., and Hammond, S.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Lithos
• Publisher: Elsevier
• ISSN: 0024-4937
• ISSN (Online): 1872-6143
• Published Online: 08 February 2016