Variability of primordial and recycled noble gases across Iceland’s Western Volcanic Zone.

Cogliati, S.; Hartley, M. E.; Holland, G.; Burgess, R.; Haldórsson, S.; Shorttle, O. and Álvarez Valero, A. (2023). Variability of primordial and recycled noble gases across Iceland’s Western Volcanic Zone. In: Abstract Booklet: DINGUE 2023, p. 11.

URL: https://sites.google.com/ethz.ch/dingueviii/progra...

Abstract

Noble gases (He, Ne, Ar, Kr, Xe) have been widely used to investigate chemical heterogeneities of the Earth’s mantle and their variations through time and space [1]. Different mantle domains having distinctive elemental and isotopic noble gas signatures have been discovered by studying the noble gas compositions of ocean island basalts (OIBs) and mid-ocean ridge basalts (MORBs) [1]. Some OIBs show primordial noble gas signatures that have remained mostly unmodified since the Earth’s formation; instead, MORBs display noble gas systematics of a mantle that has undergone extensive modification following chemical fractionation during melt extraction and magma degassing, mantle convection, and subduction recycling [1]. On Iceland, melts with an OIB-like origin interact and coexist with melts that exhibit MORB-like chemical characteristics. In this hybrid setting, mantle geochemical heterogeneities exist on both long and short lengthscales, and primordial and recycled noble gas signatures can both be present even in a single sample set from the same eruption [2,3]. Spatial variability of primordial noble gases across Iceland within individual neovolcanic zones has been explored in great detail for He isotopes [3]; Ne and Ar isotopes have received more limited attention [4], while Xe isotopes have been investigated only in one single sample (DICE-10) from Miðfell in the Western Volcanic Zone (WVZ) [5,6]. Here, we present new high-precision Ne, Ar, and Xe analyses of basaltic glass from the WVZ and Reykjanes Peninsula extending the available noble gas dataset for this neovolcanic zone. By combining new and existing measurements, we demonstrate that a consistent lateral variability exists in the noble gas signatures of WVZ basalts, with primordial and recycled mantle components being presents in different proportions as well as different proportional contributions of mantle, crust and atmosphere. We discuss possible explanations for the observed noble gas variations and ways to improve our understanding of Iceland’s mantle volatile variability.

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