Coexisting amphiboles from blueschist facies metamorphic rocks
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Abstract
Four pairs of associated calcic and sodic amphiboles from blueschist facies metamorphic rocks were analyzed with the electron microprobe and studied by single-crystal X-ray diffraction techniques. Except for ranges in the ratios Mg/(Mg+Fe) and Fe3+/(Fe3++Al+Ti), the sodic amphiboles are similar in chemical composition. The amount of calcium in the M(4)-site ranges only from 0·18 to 0·21 ion per formula unit. The calcic amphiboles, in addition to a range in Mg/(Mg+Fe), vary in Na/(Na+Ca) ratio (0·29–0·48). Three of the calcic amphiboles contain less than 1·5 calcium ions per formula unit, indicating a significant solid solution of sodic amphibole components in the calcic amphibole phase. The a and b unit-cell parameters of the calcic amphiboles decrease with increased content of the sodic component.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Coexisting amphiboles from blueschist facies metamorphic rocks |
| Series title | Journal of Petrology |
| DOI | 10.1093/petrology/10.1.102 |
| Volume | 10 |
| Issue | 1 |
| Year Published | 1969 |
| Language | English |
| Publisher | Oxford University Press |
| Description | 13 p. |
| First page | 102 |
| Last page | 114 |