The complex hydrothermal history of granitic rocks: Multiple feldspar replacement reactions under subsolidus conditions
Recurring subsolidus re-equilibration of granitic feldspars induced by fluid infiltration events provides a record of fluid-rock interactions that affect large volumes of the Earth's continental crust. This has a direct bearing on the interpretation of the present-day granitic rock mineralogy a...
| Main Authors: | , |
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| Format: | Journal Article |
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Oxford University Press
2009
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| Online Access: | http://hdl.handle.net/20.500.11937/31418 |
| _version_ | 1848753375626133504 |
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| author | Plümper, O. Putnis, Andrew |
| author_facet | Plümper, O. Putnis, Andrew |
| author_sort | Plümper, O. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | Recurring subsolidus re-equilibration of granitic feldspars induced by fluid infiltration events provides a record of fluid-rock interactions that affect large volumes of the Earth's continental crust. This has a direct bearing on the interpretation of the present-day granitic rock mineralogy and geochemistry. We examine Palaeoproterozoic grey and red-stained granitoids from the Simpevarp and Laxemar areas in SE Sweden, particularly focusing on consecutive feldspar replacement reactions, to provide an in-depth understanding of subsolidus re-equilibration of granitic rocks with hydrothermal fluids. The apparently most unaltered grey granitoids contain highly porous oligoclase grains that enclose crystallographically continuous microcline relicts. This texture suggests that the oligoclase is already secondary and may be a replacement product of original microcline. Oligoclase is progressively replaced by albite (~An9) along polysynthetic twinning and intragranular fractures. The features of this replacement are characteristic of a dissolution-reprecipitation mechanism. Fine-grained mica (sericite) is closely associated with the albite porosity within micron-sized pores observable with scanning electron microscopy as well as in nanopores imaged with transmission electron microscopy. The reddening phenomenon in the vicinity of fractures is contemporaneously related to the K-feldspathization of sericite, which is restricted to the altered oligoclase. Submicron size hematite precipitation within orthoclase pores at the replacement front results in the red coloration. The complex associations between the fluid-feldspar reactions indicate that the replacement reactions may be due to sequential fluid infiltration events and that the granitoids have undergone extensive subsolidus re-equilibration, changing the original magmatic mineralogy. Therefore, the effects of large-scale re-equilibrations of granitic rocks through hydrothermal convection systems should be more closely considered. © The Author 2009. Published by Oxford University Press. All rights reserved. |
| first_indexed | 2025-11-14T08:23:31Z |
| format | Journal Article |
| id | curtin-20.500.11937-31418 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T08:23:31Z |
| publishDate | 2009 |
| publisher | Oxford University Press |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-314182017-09-13T15:19:34Z The complex hydrothermal history of granitic rocks: Multiple feldspar replacement reactions under subsolidus conditions Plümper, O. Putnis, Andrew Recurring subsolidus re-equilibration of granitic feldspars induced by fluid infiltration events provides a record of fluid-rock interactions that affect large volumes of the Earth's continental crust. This has a direct bearing on the interpretation of the present-day granitic rock mineralogy and geochemistry. We examine Palaeoproterozoic grey and red-stained granitoids from the Simpevarp and Laxemar areas in SE Sweden, particularly focusing on consecutive feldspar replacement reactions, to provide an in-depth understanding of subsolidus re-equilibration of granitic rocks with hydrothermal fluids. The apparently most unaltered grey granitoids contain highly porous oligoclase grains that enclose crystallographically continuous microcline relicts. This texture suggests that the oligoclase is already secondary and may be a replacement product of original microcline. Oligoclase is progressively replaced by albite (~An9) along polysynthetic twinning and intragranular fractures. The features of this replacement are characteristic of a dissolution-reprecipitation mechanism. Fine-grained mica (sericite) is closely associated with the albite porosity within micron-sized pores observable with scanning electron microscopy as well as in nanopores imaged with transmission electron microscopy. The reddening phenomenon in the vicinity of fractures is contemporaneously related to the K-feldspathization of sericite, which is restricted to the altered oligoclase. Submicron size hematite precipitation within orthoclase pores at the replacement front results in the red coloration. The complex associations between the fluid-feldspar reactions indicate that the replacement reactions may be due to sequential fluid infiltration events and that the granitoids have undergone extensive subsolidus re-equilibration, changing the original magmatic mineralogy. Therefore, the effects of large-scale re-equilibrations of granitic rocks through hydrothermal convection systems should be more closely considered. © The Author 2009. Published by Oxford University Press. All rights reserved. 2009 Journal Article http://hdl.handle.net/20.500.11937/31418 10.1093/petrology/egp028 Oxford University Press unknown |
| spellingShingle | Plümper, O. Putnis, Andrew The complex hydrothermal history of granitic rocks: Multiple feldspar replacement reactions under subsolidus conditions |
| title | The complex hydrothermal history of granitic rocks: Multiple feldspar replacement reactions under subsolidus conditions |
| title_full | The complex hydrothermal history of granitic rocks: Multiple feldspar replacement reactions under subsolidus conditions |
| title_fullStr | The complex hydrothermal history of granitic rocks: Multiple feldspar replacement reactions under subsolidus conditions |
| title_full_unstemmed | The complex hydrothermal history of granitic rocks: Multiple feldspar replacement reactions under subsolidus conditions |
| title_short | The complex hydrothermal history of granitic rocks: Multiple feldspar replacement reactions under subsolidus conditions |
| title_sort | complex hydrothermal history of granitic rocks: multiple feldspar replacement reactions under subsolidus conditions |
| url | http://hdl.handle.net/20.500.11937/31418 |