We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
Ca/Al of plagioclase-hosted melt inclusions as an indicator for post-entrapment processes at mid-ocean ridges?
- Authors
Zhang, H. T.; Yang, Y. M.; Yan, Q.-s.; Shi, X.-f.; Zhu, Z.-w.; Su, W.-c.; Qin, C.-j.; Ye, J.
- Abstract
The composition of melt inclusions in basalts erupted at mid-ocean ridges may be modified by post-entrapment processes, so the present composition of melt inclusions may not represent their original composition at the time of entrapment. By combining the melt inclusion composition in samples from the South Mid-Atlantic Ridge at 19°S analyzed in this study, and from the Petrological Database, we found that post-entrapment crystallization processes resulted in higher Ca/Al, Mg#[100 atomic Mg2+/(Mg2++Fe2+)], MgO and FeO contents, and lower CaO and Al2O3 contents of plagioclase-hosted melt inclusions relative to those hosted in olivine. In addition, melt inclusions hosted in plagioclase with anorthite content larger than 80mol.% had been modified more readily than others. By discussing the relationships between Ca/Al and fractional crystallization, post-entrapment crystallization, and the original melt composition, we propose that Ca/Al can be regarded as an indicator of the effect of post-entrapment processes on melt inclusion composition. Specifically, i) when Ca/Al<0.78, melt inclusion compositions corrected for fractional crystallization to Mg#=72 can represent the primary magma at mid-ocean ridges; ii) when 0.78<Ca/ Al<1.0, melt inclusions are mainly modified by post-entrapment crystallization effects, and can reveal the original melt composition after correcting for these effects; iii) when Ca/Al>1.0, the compositions of melt inclusions do not reflect the original melt composition nor preserve information about the mantle source. According to these criteria, plagioclase-hosted melt inclusions with Ca/Al>1.0 in basalts from the South Mid-Atlantic Ridge at19±S cannot represent the composition of the melt at the moment of their entrapment.
- Subjects
MID-Atlantic Ridge; MELT crystallization; PLAGIOCLASE; INCLUSION compounds; CRYSTALLIZATION; THERMODYNAMIC molecular model
- Publication
Geologica Acta, 2016, Vol 14, Issue 1, p1
- ISSN
1695-6133
- Publication type
Article
- DOI
10.1344/GeologicaActa2016.14.1.1