Spinel trace elements

Spinels. There are limited experimental data on uranium and thorium partitioning between magnetite and melt (Nielsen et al. 1994 Blundy and Brooker 2003). Both studies find U and Th to be moderately incompatible. Blundy and Brooker s results for a hydrous dacitic melt at 1 GPa and 1025°C give Du and D h. of approximately 0.004. The accuracy of these values is compromised by the very low concentrations in the crystals and the lack of suitable SIMS secondary standards for these elements in oxide minerals. Nonetheless, these values are within the range of Djh of magnetites at atmospheric pressure 0.003-0.025 (Nielsen et al. 1994). It is difficult to place these values within the context of the lattice strain model, firstly because there are so few systematic experimental studies of trace element partitioning into oxides and secondly because of the compositional diversity of the spinels and their complex intersite cation ordering. 

CAIs are composed of a variety of minerals, primarily hibonite, perovskite, melilite, spinel, aluminum- and titanium-rich diopside, anorthite, forsterite, and occasionally corundum or grossite. They also show significant enrichments in refractory trace elements. CAIs exhibit a host of isotopic anomalies inherited from incorporated presolar grains or from the early nebula itself. 

Figure 9 A type B1 inclusion from the Allende CVS chondrite. This centimeter-sized marhle consists mainly of melilite (bluish-white), titanium-aluminum-rich calcic pyroxene (bright colors), and anorthite and spinel (not readily visible in photo). Type B1 inclusions figure prominently in the early petrologic, trace element, and isotopic studies of CAIs, in part because of the richness of information about physicochemical histories available from petrologic, chemical and isotopic properties. Ironically, because type B inclusions occur only in CVS chondrites, they are nonrepresentative of CAIs in general. Photograph taken in cross-polarized transmitted fight. The colors are not the true colors of the crystals they are artifacts of the polarized fight.

Jochum K. P., McDonough W. F., Pahne H., and Spettel B. (1989) Compositional constraints on the continental lithospheric mantle from trace elements in spinel peridotite xenoliths. Nature 340, 548-550. 

Figure 21 Abundances of lithophile trace elements normalized to PM values in clinopyroxene, orthopyroxene, olivine, and spinel separated from a peridotite from the Ronda massif (Garrido et al., 2000). Normalizing values after...

Bedini R.-M. and Bodinier J.-L. (1999) Distribution of incompatible trace elements between the constiments of spinel peridotite xenohths ICP—MS data from the East African Rift. Geochim. Cosmochim. Acta 63, 3883—3900. 

Bodinier J.-L., Merlet C., Bedini R. M., Simien E., Remai di M., and Garrido C. J. (1996) Distribution of Nb, Ta, and other highly incompatible trace elements in the lithospheric mantle the spinel paradox. Geochim. Cosmochim. Acta 60, 545-550. 

Garrido C. J., Bodinier J.-L., and Alard O. (2000) Distribution of LILE, REE and HFSE in anhydrous spinel peridotite and websterite minerals from the Ronda massif insights into the nature of trace element reservoirs in the subcontinental lithospheric mantle. Earth Planet. Sci. Lett. 181, 341-358. 

Rampone E., Piccardo G. B., Vannucci R., Bottazzi P., and Ottolini L. (1993) Subsolidus reactions monitored by trace element partitioning the spinel- to plagioclase-facies transition in mantle peridotites. Contrib. Mineral. Petrol. 115, 1-17. 

Figure 16 Trace-element mass-balance for deformed and granular lherzolites and harzburgites from E. Africa illustrating the contribution of a pervasive grain boundary component (PGBC), apatite and spinel reaction rims in wt.% of the total elemental whole-rock budget (after Bedini and Bodinier, 1999).

Because spinel is a very minor phase in peridotites, it makes up only a very small proportion of the trace-element budget (Eggins et al, 1998 Norman, 2001). Spinel has a limited... 

Glaser S. M., Foley S. F., and Gunther D. (1999) Trace element compositions of minerals in garnet and spinel peridotite xenoliths from the Vitim volcanic field, Transbaikalia, eastern Siberia. Lithos 48, 263 —285. 

Ionov D. A. (1996) Distribution and residence of hthophile trace element in minerals of garnet and spinel peridotites an ICP-MS study. J. Conf Abstr. 1, 278. 

O Reilly S. Y., Griffin W. L., and Ryan C. G. (1991) Residence of trace elements in metasomatized spinel Iherzolite xenohths a proton-microprobe study. Contrib. Mineral. Petrol. 109, 98-113. 

Ionov et al. (1993a, 1996) found carbonate in spinel Iherzolite xenoliths as interstitial crystals and as aggregates with calcium-rich olivine and aluminum- and titanium-rich clinopyroxene. They interpreted the former to be primary and the latter as evidence for metasomatism by a carbonate-rich melt. Subsequently, Ionov (1998) measured trace-element abundances in the carbonates and coexisting phases, and proposed the aggregate carbonates were formed by crystal fractionation from a carbonate melt. That these carbonates represent crystallized cumulates,... 

Wilkinson J. F. G. and Taylor S. R. (1980) Trace element fractionation trends of thoeiitic magma at moderate pressure evidence from an Al-spinel ultramafic-mafic inclusion suite. Contrib. Mineral. Petrol. 75, 225-233. 

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