Partitioning of Ca and Al between forsterite and silicate melt in dynamic systems with implications for the origin of Ca, Al‐rich forsterites in primitive meteorites

Abstract

Abstract-We report the results of dynamic crystallization experiments that were specifically designed to study the dependence of Ca and Al partitioning between forsterite and melt in rapidly cooling Caand Al-rich melts. The partitioning of Ca between olivine and silicate melt is found to be independent of the cooling rate within the range of 1.5 to 1000°C/hr and at CaO contents of up to 25 wt%. Within analytical uncertainty, our data plot on the equilibrium partitioning curve obtained by Libourel (1999). The partitioning behavior of Al at high cooling rates is more complex. Aluminum is much more heterogenously distributed in the olivine and the co-existing melt than Ca. But, no systematic trend of Al partition coefficient with cooling rate is observed. We apply the results of the experiments to the formation of meteoritic forsterites with relatively high

Origin of chondritic forsterite grains

“…2C, E and I). Similar to the observations by Pack and Palme (2003) and Pack et al (2004), concentrations of Ca and Al either decrease from core to rim ( Fig. 1A and B) or are constant throughout the grains (Fig.…”

“…10C and E). Pack and Palme (2003) and Pack et al (2004) have shown that high CL intensity is caused by low Fe and high concentrations of Al and especially Ti. Olivine with low concentra- tions of Fe and low concentrations of Al and Ti does not show CL emission.…”

“…Recently, Varela et al (2002); Pack and Palme (2003) and Pack et al (2004) suggested that RF formed in association with refractory melt condensates. This model was briefly discussed in earlier works by Fuchs et al (1973) and Weinbruch et al (2000) to explain the occurrence of melt inclusions in RF grains.…”

The effect of melt composition on mineral-melt partition coefficients: The case of beryllium

“…Both Al and Ti can be sector-zoned in experimental samples, in contrast to Ca, though the effect is minor (Pack and Palme, 2003); the volume-averaging nature of LA-ICP-MS means no such effect was evident in the present study. It is notable that Ca is found only on the Msites of olivine, whereas Al and Ti both partition partially onto the Si site (Hermann et al, 2005;Wan et al, 2008), but the petrological significance of sector zoning remains to be established.…”

Final Report for "Experimental Petrology and Chemistry of Volatile-Bearing Silicate Melts"

“…Although without the classic hourglass shape (e.g., Strong 1969), this feature may be a kind of sector zoning. As shown experimentally by Pack and Palme (2003), olivine can develop classic hourglass sector zoning. Another P-poor region that may relate to sector zoning is observed in a Hawaiian microphenocryst ( Fig.…”