Experiments to reconstruct the liquidus curve and establish the phase relationships of a basanite (Mg# = 72) from the McMurdo Volcanic Group, (thought to represent a nearly primary magma) used 1.0-3.0 GPa and 1175-1550 degrees C. The results suggest that this basanite could be generated by partial melting either of a spinel Iherzolite (at P = 1.5-2.0 GPa and T = 1390-1490 degrees C) or of a garnet pyroxenite (at P > 3.0 GPa and T > 1550 degrees C) source. Several lines of petrological and geochemical evidence support the latter hypothesis. Moreover, experimental results indicate the presence of mica in the source if it is assumed that the magma lost some water during its ascent to the surface. This is supported by the presence of mica and amphibole-bearing mantle xenoliths hosted in the most primitive volcanic rocks of the McMurdo Volcanic Group. These results and observations suggest that the source of magmas underwent metasomatism prior to partial melting.
Experimental study on a primary basanite from McMurdo Volcanic Group, Antarctica: Inference on its mantle source
ARMIENTI, PIETRO
2000-01-01
Abstract
Experiments to reconstruct the liquidus curve and establish the phase relationships of a basanite (Mg# = 72) from the McMurdo Volcanic Group, (thought to represent a nearly primary magma) used 1.0-3.0 GPa and 1175-1550 degrees C. The results suggest that this basanite could be generated by partial melting either of a spinel Iherzolite (at P = 1.5-2.0 GPa and T = 1390-1490 degrees C) or of a garnet pyroxenite (at P > 3.0 GPa and T > 1550 degrees C) source. Several lines of petrological and geochemical evidence support the latter hypothesis. Moreover, experimental results indicate the presence of mica in the source if it is assumed that the magma lost some water during its ascent to the surface. This is supported by the presence of mica and amphibole-bearing mantle xenoliths hosted in the most primitive volcanic rocks of the McMurdo Volcanic Group. These results and observations suggest that the source of magmas underwent metasomatism prior to partial melting.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
