RE-EQUILIBRATION OF MELT INCLUSIONS TRAPPED BY MAGNESIAN OLIVINE PHENOCRYSTS FROM SUBDUCTION-RELATED MAGMAS: PETROLOGICAL IMPLICATIONS
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dc.contributor.author | Danyushevsky L.V. | |
dc.contributor.author | Della-Pasqua F.N. | |
dc.contributor.author | Sokolov S. | |
dc.date.accessioned | 2021-01-29T07:11:10Z | |
dc.date.available | 2021-01-29T07:11:10Z | |
dc.date.issued | 2000 | |
dc.identifier | https://elibrary.ru/item.asp?id=13779032 | |
dc.identifier.citation | Contributions to Mineralogy and Petrology, 2000, 138, 1, 0068-0083 | |
dc.identifier.issn | 0010-7999 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/24007 | |
dc.description.abstract | We describe and model a potential re-equilibration process that can affect compositions of melt inclusions in magnesian olivine phenocrysts. This process, referred to as “Fe-loss”, can operate during natural pre-eruptive cooling of host magma and results in lower FeOt and higher MgO contents within the initially trapped volume of inclusion. The extent of Fe-loss is enhanced by large temperature intervals of magma cooling before eruption. The compositions of homogenised melt inclusions in olivine phenocrysts from several subduction-related suites demonstrate that (1) Fe-loss is a common process, (2) the maximum observed degree of re-equilibration varies between suites, and (3) within a single sample, variable degrees of re-equilibration can be recorded by melt inclusions trapped in olivine phenocrysts of identical composition. Our modelling also demonstrates that the re-equilibration process is fast going to completion, in the largest inclusions in the most magnesian phenocrysts it is completed within 2 years. The results we obtained indicate that the possibility of Fe-loss must be considered when estimating compositions of parental subduction-related magmas from naturally quenched glassy melt inclusions in magnesian olivine phenocrysts. Compositions calculated from glassy inclusions affected by Fe-loss will inherit not only erroneously low FeOt contents, but also low MgO due to the inherited higher Mg##of the residual melt in re-equilibrated inclusions. We also demonstrate that due to the higher MgO contents of homogenised melt inclusions affected by Fe-loss, homogenisation temperatures achieved in heating experiments will be higher than original trapping temperatures. The extent of overheating will increase depending on the degree of re-equilibration, and can reach up to 50°C in cases where complete re-equilibration occurs over a cooling interval of 200°C. | |
dc.title | RE-EQUILIBRATION OF MELT INCLUSIONS TRAPPED BY MAGNESIAN OLIVINE PHENOCRYSTS FROM SUBDUCTION-RELATED MAGMAS: PETROLOGICAL IMPLICATIONS | |
dc.type | Статья |
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