Mixing mantle components

In the 143Nd/l44Nd vs 87Sr/86Sr plot, draw the mixing triangle at the 20 percent mesh size for a mixture of three mantle components, the depleted mantle (DM), the enriched mantle I (EM I) and the enriched mantle II (EM II). The isotopic ratios and relative concentrations of each component are listed in Table 1.10. 

Figure 1.9 A hypothetical hyperbolic triangle for the mixing of three mantle components in the sense of Zindler and Hart (1986). Data from Table 1.10.

Farley K. A., Natland J. H., and Craig H. (1992) Binary mixing of enriched and undegassed (primitive ) mantle components (He, Sr, Nd, Pb) in Samoan lavas. Earth Planet. Set Lett. Ill, 183-199. 

Figure 2 The Ne-isotopic composition of the atmosphere, compared to different extraterrestrial compositions (compiled by Busemann et al., 2000). MORE data fall on a correlation line extending from air values (Sarda et al., 1988), and reflect mixing between air contamination of the samples with a trapped mantle component with high Ne-isotope ratios. This component is composed of radiogenic Ne and solar Ne (Honda et al., 1993) or Ne-B (Trieloff et al., 2000). OIB such as Loihi with high He/" He ratios reflect mixing of air contamination with a mantle composition that has a lower Ne/ Ne ratio, reflecting a higher time-integrated Ne/(U -h Th) ratio (Honda et al., 1991).

Neon. Ne in MORE has °Ne/ Ne and Ne/ Ne ratios that are significantly higher than those of the atmosphere (9.8 and 0.029, respectively) and fall on a correlation line that is widely interpreted as due to mixing between atmospheric contamination and an upper mantle component. This component in turn is a mixture of solar Ne with a high e/ Ne ratio and radiogenic Ne. Samples from high He/ He OIE have similar... 

Kaneoka (1998) showed that published mantle sample °Ne/ Ne ratios do not correlate with Xe/ °Xe and argued that many data could not be explained by mixing between a mantle component with a single Ne/Xe ratio and air contamination. However, large uncertainties in Xe isotope ratios, uncertainty in the mantle Xe/ °Xe isotope ratio, and uncertainty in the range of Ne/Xe ratios of contaminants, makes this argument weak. 

He/ Ne)crust and (" He/ Ne)mnti are the " He/ Ne ratio of the crust and mantle components before mixing respectively. Further examples of isotope mixing relationships and three-dimensional approaches when resolving three components from the isotope systematics are detailed in the section Description and analysis of multi-component noble gas mixtures in ore fluids. 

Figure 36. Br/Cl vs. I/Cl quartz and barite vein data for replacement Pb-Zn deposits of the Colorado mineral belt (Thrower 1999). The data are compatible with mixing between a mantle component similar in composition to fluids in diamond, and a crastal component with higher Br/Cl and I/Cl values. Note that Black Cloud deposit quartz and barite are co-genetic with sulfide samples shown in Figure 5. Shaded area labeled mantle defined by the range determined for fluids in diamonds (Burgess et al. 2002).

LU Hf but differ markedly from Rb-Sr, U-Pb and Th-Pb. Sm-Nd are immobile under hydrothermal condidons and so their isotopic composition reflects the actual proportions of rock or magma involved in specific petrological processes. The Sm- Nd system, however, has the disadvantage that small amounts of recycled crust mixed with a large proportion of a mantle component become isotopicaliy in Hisibte. 

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