Off-craton mantle composition

Figure 9 Normative spinel Iherzolite mineral abundances (wt.%) versus rock Mg for a subset of 292 off-craton mantle compositions (shaded circles). Data from a given locality were included if compositions had a correlation between Mg and normative olivine with a correlation coefficient (i ) of 0.6 or better. Data sources for xenoliths are Beccaluva et al. (2001a,h), Reid and Woods (1978), Rivalenti et al. (2000), Stem et al. (1999), Vaselli et al. (1995), Wiechert et al. (1997), Xu et al. (1988), and Zangana et al. (1999). Data sources for orogenic Iherzolites are Bodinier et al. (1988), Frey et al. (1985, 1991), Hartmann and Wedepohl (1993), and Lugovic et al. (1991). Open circles are the reconstmcted abyssal peridotite compositions from Figure 7. Also shown are estimates of primitive mantle from Table 2 white square = 1, circle = 2, triangle = 3, diamond = 5, inverted triangle = 6, ex = 7, and shaded star = 8.

The off-craton mantle subset is shown relative to isobaric batch melt extraction curves on plots of normative olivine and major-element oxides versus Mg in Figure 17. Generally speaking, off-craton mantle compositions are consistent with effectively 0-30% melt extraction from fertile upper mantle in the range of 1-5 GPa. The chemical signature recorded in off-craton mantle mimics closely the maximum degree of melt extraction recorded in oceanic mantle, but in contrast there are many samples that show little or... 

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