Trapped melts

Wasson, J.T. (1999) Trapped melt in IIIAB irons solid/liquid elemental partitioning during the fractionation of the IIIAB magma. Geochimica et Cosmochimica Acta, 63(18), 2875-89. 

Goodrich C. A., Fioretti A. M., Tribaudino M., and Molin G. (2001) Primary trapped melt inclusions in olivine in the ohvine-augite-orthopyroxene ureihte Hughes 009. Geochim. Cosmochim. Acta 65, 621 —652. 

CIl chondrites also contain a small fraction of isolated olivine and pyroxene grains up to 400 p,m in size with chemical, oxygen isotopic compositions, and rounded inclusions of metallic Fe,Ni and trapped melt indicating that they were derived from chondrules (Leshin et al, 1997). Brearley and Jones (1998) estimate the abundance of olivine and pyroxene at <1 vol.%, but X-ray diffraction studies by Bland et al. (2002) indicate 7 wt.% olivine. The dilference probably reflects a high abundance of olivine crystallites embedded in phyllosilicates (P. A. Bland, private communication). CIl chondrites also contain rare refractory grains with oxygen isotopic compositions comparable to those in CAIs (see Scott and Krot, 2001). 

Figure 23 Chondrite-normalized abundances of REEs in representative harzburgites from the Oman ophiolite (symbols—whole-rock analyses), compared with numerical experiments of partial melting performed with the Plate Model of Vemieres et al. (1997), after Godard et al. (2000) (reproduced by permission of Elsevier from Earth Planet. Set Lett. 2000, 180, 133-148). Top melting without (a) and with (b) melt infiltration. Model (a) simulates continuous melting (Langmuir et al., 1977 Johnson and Dick, 1992), whereas in model (b) the molten peridotites are percolated by a melt of fixed, N-MORB composition. Model (b) is, therefore, comparable to the open-system melting model of Ozawa and Shimizu (1995). The numbers indicate olivine proportions (in percent) in residual peridotites. Bolder lines indicate the REE patterns of the less refractory peridotites. In model (a), the most refractory peridotite (76% olivine) is produced after 21.1% melt extraction. In model (b), the ratio of infiltrated melt to peridotite increases with melting degree, from 0.02 to 0.19. Bottom modification of the calculated REE patterns residual peridotites due to the presence of equilibrium, trapped melt. Models (c) and (d) show the effect of trapped melt on the most refractory peridotites of models (a) and (b), respectively. Bolder lines indicate the composition of residual peridotites without trapped melt. Numbers indicate the proportion of trapped melt (in percent). Model parameters...

Rampone E., Piccardo G. B., Vannucci R., and Bottazzi P. (1997) Chemistry and origin of trapped melts in ophiolitic peridotites. Geochim. Cosmochim. Acta 61, 4557-4569. 

Low-pressure trapped melts crystallize plagioclase, and it has been documented that the relatively much less abundant plagioclase-bearing abyssal peridotites are products of refertihzation by trapped melt (e.g., Dick, 1989). For this reason,... 

H. Jordon, J. A. Gieseke, and P. Baybutt, TRAP-MELT User s Manual, NUREG/CR-0632, BMI-2107, February 1979. 

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