Eclogite rutile

Assuming a Rayleigh distillation process and bulk eclogite/fluid D s for 3 GPa without rutile from Table 2... 

Rudnick R. L., Barth M., Horn I., and McDonough W. F. (2000) Rutile-bearing refractory eclogites missing link between continents and depleted mantle. Science 287, 278-281. 

Clinopyroxenes in eclogite xenoliths have convex-upwards REE patterns that are LREE-enriched relative to HREE. (La) varies from slightly below 1 to —15, while (Yb) varies between 0.1 and 1.5 (Figure 50). As with garnet, Nb-Ta depletions and, to some extent, other HFSE abundances depend on the coexistence of rutile (Jacob and Foley, 1999 Rudnick et al., 2000 Barth et al., 2001). The relatively homogenous REE patterns of eclogitic clinopyroxene contrast markedly with the wide variety of REE patterns observed in peridotitic clinopyroxene. 

Figure 50 Garnet and clinopyroxene trace-element compositions (normalized to primitive mantle), together with their calculated whole-rock compositions (from modal data). Data sources 77 and 29 are rutile-free eclogites from Udachnaya, Siberia (Jacob and Foley, 1999) KEC80-A-2 is a high-Nb-mtile eclogite from Koidu, Sierra Leone...

Calculated bulk rock trace-element systematics of eclogites have wider implications for mantle recycling models and bulk silicate earth mass balance. The subchondritic Nb/Ta, Nb/La, and Ti/Zr of both continental cmst and depleted mantle require the existence of an additional reservoir with superchondritic ratios to complete the terrestrial mass balance. Rudnick et al. (2000) have shown that rutile-bearing eclogites from cratonic mantle have suitably superchondritic Nb/Ta, Nb/La, and Ti/Zr such that if this component formed 1 -6% by weight of the bulk silicate earth, this would resolve the mass imbalance. This mass fraction far exceeds the likely mass of eclogite in the continental lithosphere and so the material is proposed to reside in the lower mantle, possibly at the core-mantle boundary. 

Based on the analysis of quartz, rutile pairs in metamorphic rocks, primarily eclogites. Temperatures based on the Bottinga and Javoy (1975) calibrations of the quartz-muscovite and quartz-garnet thermometers. 

Quartz-rutile pairs have been measured most commonly from eclogites (Vogel and Garlick 1970, Desmons and O Neil 1978, Matthews et al. 1979, Agrinier et al. 1985, Agrinier 1991, Sharp 1995, Rumble and Yui 1998, Zheng et al. 1998, 1999). A few analyses are reported for blueschists and pelites (Matthews and Schliestedt 1984, Sharp... 

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