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Arctic Mars Analog Svalbard Expedition
Bockfjord Volcanic Complex
The Quaternary Bockfjord Volcanic Complex (BVC) consists of breccias, diatremes and rare lava flows which formed during violent and volatile-rich volcanic eruptions ca 1 Ma ago, along the western boundary of a Carboniferous to Devonian graben system. Pillow lava deposits on the Sverrefjell volcano (Fig. 1) indicate eruption during an average sealevel ca 300 m higher than present.
Figure 1. Sverrefjell volcano. Summit hight = 500 m.
Hydrothermal alteration of BVC volcanics occurs within pillow lava and palagonite terraces flanking the Sverrefjell volcano (Fig. 1), primarily related to interaction between lava and seawater during eruption. Post eruptive hydrothermal alteration is evident throughout several of the BVC centers, in particular in the exposed central parts of th Sverrefjell volcano. In addition to clay minerals and palagonite, dolomite cemented breccias and abundant microscopic carbonate spherules (Fig. 2) are common alteration products. Coexisting carbonates and zeolites indicate relatively low temperatures below ca 100 °C. Carbonate spherules are typically concentrically zoned with Fe-rich (siderite, ankerite) cores and Mg-rich (dolomite, magnesite) rims, sometimes embedded in a calcite matrix. The texture and composition of the BVC carbonate spherules are identical to carbonates occurring in the martian meteorite ALH84001 (Treiman et al., 2002), and hydrothermal alteration of BVC volcanics represent the only known Terrestrial analog to fluid rock interaction on early Mars.
Figure 2. Left: Fe-Mg-Ca carbonate spherules in hydrothermally altered volcanic rocks (w.o.f. = 0.2 mm). Right: Fe-Mg-Ca carbonate spherules in the Martian meteorite ALH84001, identical to those at Sverrefjell (w.o.f. = 0.2 mm, photo courtesy of Treiman/LPI).
The world’s northernmost hot springs occur along the Breibogen Fault in the vicinity of Sverrefjell. The Troll Springs (Fig. 3) are characterized by spectacular travertine terraces but relatively low output of "warm" 18 °C sulphurous water. Troll Springs travertine deposits are characterized by pool and terrace geometries on scales ranging from 10 m to 1 cm similar to travertine terraces worldwide.
Figure 3. Top left: Extinct and active (JS) hot springs along the Breibogen Fault fault south of Sverrefjell. Top right: Travertine (CaCO3) deposits surrounding the Troll Springs (w.o.f. = 100 m). Bottom: Troll Springs.
Trollosen is a giant thermocarstic spring discharging up to 18m3/sec of cold (6 °C) sulphurous water. Emanating from a ca 4 m wide cave opening, Trollosen allows testing of large robotic- or probe equipment. Chemical and mineralogical data from Trollosen suggest the presence of sulphate-reducing bacteria within the sub-permafrost aquifer (Lauritzen & Bottrell, 1994).
Figure 4: Trollosen giant spring on southern Spitsbergen, discharging from ca 4 m wide cave opening.