The upper right orientation is ~180 o rotated from the main and lower panels. Upper right inset places location of lower right view within Antarctica. Volcano mounts include Bird (BR), Terror (TR), Terra Nova (TN), Erebus (ER), Hut Point (HP) Morning (MR), and Discovery (DS). ![]() Yellow dashed lines represent other antithetic shear zones separating Dry Valleys block (DVB), Royal Society block (RSB), and Skelton block (SB). Other symbols include Southern Victoria Land basin (SVL) and Discovery accommodation zone (D-A-Z). The lower right inset shows regional structural setting 15, 16, 17, including the Ross Fault (green) in the accommodation zone of the terminus of the Terror Rift (TR) and Discovery graben (DG). ![]() Hypothesized Erebus fault zone contains principal low-resistivity structure resolved through the crust. ![]() Note the warm-colored ellipse region southwest of Mount Erebus indicating conductive volumes in the 0–7 km depth range approximately (Supplementary Information). Coordinate ticks denote both UTM Zone 58S (singles) and latitude–longitude (doubles). Site map showing impedance phase-tensor ellipses at the MT sounding locations over Mount Erebus and Ross Island during three field seasons see text for color and shape designations. Erebus offers a unique opportunity to investigate magmatic system processes from the mantle source to the surface and the enigmatic tectonic-structural controls of extensional magmatism and volatile release. However, they also provide important resources such as rare earth elements and precious metals and thus are important to understand 6, 7. Phonolite magmas in other settings have been explosively destructive 5. Compositionally uniform phonolitic lavas have dominated Erebus volcano eruptions for the last 17 ka 4 (Fig. Mount Erebus is the only phonolitic volcano with a persistent summit lava lake 3. Phonolitic-series magma is alkali-rich and highly evolved from its parental basanite. Rift settings and alkalic magmas contribute enormous amounts of CO 2 to the global exosphere budget, with climate-forcing level increases of atmospheric concentrations documented several times during Earth’s history 2. Basaltic alkalic magmas are CO 2-rich because they result from low degrees of partial melting of a mantle source often showing signs of being complexly metasomatized 1. Arc magmas typically have volatiles dominated by H 2O from dehydration of subducted oceanic crust. ![]() Similar content being viewed by othersĪlkalic volcanoes in rift settings stand in stark contrast to calc-alkaline volcanoes in arcs, such as the ring of fire around the Pacific Ocean. Unlike H 2O-rich subduction arc volcanoes, CO 2-dominated Erebus geophysically shows continuous magmatic structure to shallow crustal depths of < 1 km, as the melt does not experience decompression-related volatile supersaturation and viscous stalling. This magmatic valve lies within an inferred, east-west structural trend forming part of an accommodation zone across the southern termination of the Terror Rift, providing a dilatant magma pathway. The lateral turn represents a structural fault-valve controlling episodic flow of magma and CO 2 vapour, which replenish and heat the high level phonolite differentiation zone. Here we show using magnetotelluric data that a steep, melt-related conduit of low electrical resistivity originating in the upper mantle undergoes pronounced lateral re-orientation in the deep crust before reaching shallower magmatic storage and the summit lava lake. Seismic studies provide limited images of the magmatic system. Erebus volcano, Antarctica, with its persistent phonolite lava lake, is a classic example of an evolved, CO 2-rich rift volcano.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |