Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

Help viewing high resolution images Return to article

FIGURE 2 Chondrite-normalized PGE abundances in residual mantle rocks (dashed lines) and mantle-derived magmas (colored lines). Due to extraction of the low-melting-temperature Cu-Ni-sulfide melt, which concentrates Pt and Pd, the PGE patterns of residual mantle rocks are depleted in Pt and Pd. The depletion factor increases with the degree of melting (10 to 40%), and therefore with the amount of magma extracted from the mantle column, due to the concentration of the PGE in monosulfide solid solution (mss) and to the fact that an increase in the degree of melting decreases the amount of mss remaining in the residual mantle. DATA SOURCES: HANDLER AND BENNETT 1999;PEARSON ET AL. 2004; LUGUET ET AL. 2007). Mantle-derived magmas show the opposite behavior: mid-ocean ridge basalts are IPGE-depleted (IPGE = Ir, Os, Ru) relative to the mantle composition because their mantle source still contains base-metal sulfides. In contrast, the very high (30-50%) degree of partial melting needed to generate Archean komatiitic magma, a now-extinct type of highly magnesian magma, consumed all the base-metal sulfides in the mantle, generating PGE abundances (absolute and relative) close to those of the mantle. DATA SOURCES FOR ARCHEAN KOMATIITES: REHKÄMPER ET AL. (1999b); PUCHTEL ET AL. (2004); AND FOR MORB: REHKÄMPER ET AL. (1999b); BEZOS ET AL. (2005)

Return to article