Response of xenotime to prograde metamorphism
Xenotime is a widespread accessory mineral in lower greenschist to upper amphibolite facies metasedimentary rocks from the Palaeoproterozoic Mount Barren Group, southwestern Australia. Xenotime is closely associated with detrital zircon, commonly forming syntaxial outgrowths, in samples of sandstone...
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| Format: | Journal Article |
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Springer
2011
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| Online Access: | http://hdl.handle.net/20.500.11937/11874 |
| _version_ | 1848747921364746240 |
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| author | Rasmussen, Birger Fletcher, Ian Muhling, J. |
| author_facet | Rasmussen, Birger Fletcher, Ian Muhling, J. |
| author_sort | Rasmussen, Birger |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | Xenotime is a widespread accessory mineral in lower greenschist to upper amphibolite facies metasedimentary rocks from the Palaeoproterozoic Mount Barren Group, southwestern Australia. Xenotime is closely associated with detrital zircon, commonly forming syntaxial outgrowths, in samples of sandstone, micaceous quartzite, slate, phyllite, garnet-bearing semi-pelites, and in kyanite-, garnet-, and staurolite-bearing mica schists. In situ geochronology of xenotime from lower greenschist sandstones has previously yielded multiple U–Pb ages with peaks at ~2.0, ~1.7, and ~1.65 Ga, interpreted to represent the age of detritus, early diagenesis, and a later thermal event, respectively. New U–Pb dating of xenotime in slate yields a major population at ~1.7 Ga with a minor population at ~1.2 Ga, reflecting diagenetic and metamorphic growth, respectively, whereas xenotime in phyllite forms a minor age population at ~1.7 Ga and a main peak at ~1.2 Ga. Mid-greenschist facies semi-pelitic schists (quartz-muscovite-garnet) contain xenotime that formed before 1.8 Ga and at 1.2 Ga, representing detrital and peak metamorphic ages, respectively. Xenotime in samples of amphibolite facies schist (650°C and ~8 kbars) yields U–Pb ages of ~1.2 Ga, coinciding with the time of peak metamorphism. A single analysis of a xenotime core from an amphibolite facies schist gave an age of ~1.8 Ga, consistent with the presence of detrital xenotime.Our results suggest that detrital xenotime may be preserved under greenschist facies conditions, but is largely replaced during upper amphibolite facies conditions. Detrital xenotime is replaced through dissolution–reprecipitation reactions forming compositionally distinct rims during greenschist and amphibolite facies metamorphism at 1.2 Ga. Diagenetic xenotime is present in lower greenschist facies samples, but was not observed in metasedimentary rocks that had experienced temperatures above mid-greenschist facies metamorphism (450°C). The apparent disappearance of detrital and diagenetic xenotime and appearance of metamorphic xenotime during prograde metamorphism indicates that some of the yttrium, heavy rare earth elements, and phosphorus needed for metamorphic xenotime growth are probably derived from the replacement of detrital and diagenetic xenotime. |
| first_indexed | 2025-11-14T06:56:50Z |
| format | Journal Article |
| id | curtin-20.500.11937-11874 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T06:56:50Z |
| publishDate | 2011 |
| publisher | Springer |
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| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-118742017-09-13T16:08:34Z Response of xenotime to prograde metamorphism Rasmussen, Birger Fletcher, Ian Muhling, J. Xenotime Pelitic schists Accessory minerals Metamorphism U–Pb geochronology Xenotime is a widespread accessory mineral in lower greenschist to upper amphibolite facies metasedimentary rocks from the Palaeoproterozoic Mount Barren Group, southwestern Australia. Xenotime is closely associated with detrital zircon, commonly forming syntaxial outgrowths, in samples of sandstone, micaceous quartzite, slate, phyllite, garnet-bearing semi-pelites, and in kyanite-, garnet-, and staurolite-bearing mica schists. In situ geochronology of xenotime from lower greenschist sandstones has previously yielded multiple U–Pb ages with peaks at ~2.0, ~1.7, and ~1.65 Ga, interpreted to represent the age of detritus, early diagenesis, and a later thermal event, respectively. New U–Pb dating of xenotime in slate yields a major population at ~1.7 Ga with a minor population at ~1.2 Ga, reflecting diagenetic and metamorphic growth, respectively, whereas xenotime in phyllite forms a minor age population at ~1.7 Ga and a main peak at ~1.2 Ga. Mid-greenschist facies semi-pelitic schists (quartz-muscovite-garnet) contain xenotime that formed before 1.8 Ga and at 1.2 Ga, representing detrital and peak metamorphic ages, respectively. Xenotime in samples of amphibolite facies schist (650°C and ~8 kbars) yields U–Pb ages of ~1.2 Ga, coinciding with the time of peak metamorphism. A single analysis of a xenotime core from an amphibolite facies schist gave an age of ~1.8 Ga, consistent with the presence of detrital xenotime.Our results suggest that detrital xenotime may be preserved under greenschist facies conditions, but is largely replaced during upper amphibolite facies conditions. Detrital xenotime is replaced through dissolution–reprecipitation reactions forming compositionally distinct rims during greenschist and amphibolite facies metamorphism at 1.2 Ga. Diagenetic xenotime is present in lower greenschist facies samples, but was not observed in metasedimentary rocks that had experienced temperatures above mid-greenschist facies metamorphism (450°C). The apparent disappearance of detrital and diagenetic xenotime and appearance of metamorphic xenotime during prograde metamorphism indicates that some of the yttrium, heavy rare earth elements, and phosphorus needed for metamorphic xenotime growth are probably derived from the replacement of detrital and diagenetic xenotime. 2011 Journal Article http://hdl.handle.net/20.500.11937/11874 10.1007/s00410-011-0650-3 Springer restricted |
| spellingShingle | Xenotime Pelitic schists Accessory minerals Metamorphism U–Pb geochronology Rasmussen, Birger Fletcher, Ian Muhling, J. Response of xenotime to prograde metamorphism |
| title | Response of xenotime to prograde metamorphism |
| title_full | Response of xenotime to prograde metamorphism |
| title_fullStr | Response of xenotime to prograde metamorphism |
| title_full_unstemmed | Response of xenotime to prograde metamorphism |
| title_short | Response of xenotime to prograde metamorphism |
| title_sort | response of xenotime to prograde metamorphism |
| topic | Xenotime Pelitic schists Accessory minerals Metamorphism U–Pb geochronology |
| url | http://hdl.handle.net/20.500.11937/11874 |