Basalts from Askja, Iceland have high MgO (5-18 wt %) and high Fe2O3 (5-18 wt %: Baratoux et al., 2011; Mangold et al., 2013, this study) similar to Martian basalts, which have Fe2O3 from 10-33 wt % McSween et al, 2006; Ming et al., 2008]) and MgO around 11 wt. % (McSween et al., 2009). Askja’s cold desert climate provides a good weathering analogueanalog (Mountney and Russell, 2004). Askja is located in the Northern Volcanic Zone of Iceland and basalts have been weathered to form mafic volcaniclastic deposits in a 40-km long sand sheet to the E-SE of the Askja caldera complex (Fig. 1; (Kuritani et al., 2011). The 2014-2015 Holuhraun eruption was emplaced onto the southeastern part of the sand sheet (Fig. 1) and altered the regional geomorphology and may have impacted the geochemistry of the sand sheet itself by addition of wind-blown ash and crystals, plus weathering of the lava flow (MgO content of ~7.1 wt % Geiger et al., 2016). Mangold et al. (2011) found that Icelandic sands show little chemical variations but that study was limited in the number of samples (12 sand samples and 12 rock seven rock, seven sand; Mangold et al., 2011). Here we expand on that study and we have created a morphological and geochemical database with the goal of identifying relevant trends to past and present Martian environments.
The Askja sand sheet, between ~10 cm and ~10 m thick, covers 240 km2 (Mountney and Russell). Mountney and Russell described three distinct sections of the sand sheet. The southwest section is deflationary and defined by very fine to medium grained basaltic sand with cobbles and boulders of lithologies sourced from adjacent to and distal from the sand sheet. The central part is inflating and is dominated by very fine-grained sand, relict lava fields, and small to large sand ripples. The northeast portion is also inflating but that accumulation is limited to topographic depressions. The northeast, characterized by sand mostly composed of pumice from the 1875 Askja eruption and basalt clasts from local lava fields, was not studied in detail here due to the difference in chemistry. Martian basaltic eolian sediments may record a long history of local and global climate change and they may have been potential habitats where water, nutrients and organic carbon mixed below the surface (Blake et al., 2013; Fisk et al., 2013). Basaltic sand fields on Earth have not been characterized as well as felsic sands, but represent a unique analog to deposits such as the Stimson Fm. on Mars (Mangold et al., 2011; Banham et al., 2016; Gupta et al., 2016; Ming et al., 2016; Newsom et al., 2016; Yen et al., 2016) . Eolian dominated weathering prevalent at Askja volcano, Iceland, likely also occurred on Mars and Askja mafic volcaniclastic dunes could be the best morphological and compositional analogueanalog for Martian eolian dunes (Edgett and Lancaster, 1993).