Sarah Incel, Marie Baïsset, Loïc Labrousse, Alexandre Schubnel
{"title":"斜长石部分熔融及沿变形反应特征","authors":"Sarah Incel, Marie Baïsset, Loïc Labrousse, Alexandre Schubnel","doi":"10.1111/jmg.12702","DOIUrl":null,"url":null,"abstract":"<p>Geological processes involving deformation and/or reactions are highly influenced by the rock grain size, especially if diffusion-controlled processes take place such as metamorphic reactions and diffusion creep. Although many processes, inducing grain-size reduction, are documented and understood at relatively high stresses and low temperatures (e.g., cataclasis) as well as at lower stress and higher temperature conditions (e.g., bulging and subgrain rotation), deformation twinning, a plastic deformation mechanism active in various minerals at lower temperatures, has been neglected as nucleation site for melting and reaction and thus as a cause for grain-size reduction so far. We conducted experiments on natural plagioclase-bearing aggregates at 2.5 to 3 GPa confining pressure and temperatures of 700°C to 950°C using two different deformation apparatus, a deformation multianvil apparatus (DDIA) and a Griggs press, as well as a piston-cylinder apparatus. Regardless of the apparatus type, we observe the breakdown of plagioclase into an eclogite-facies paragenesis, which is associated with partial melting in the high temperature domain of the eclogite facies. Partial melting mostly takes place along the grain and interphase boundaries. However, several melt patches or plagioclase decomposition products coincide with the occurrence of deformation twins and grain-scale microcracking in plagioclase indicating intracrystalline melting and reaction in addition to melting and reaction along grain and interphase boundaries. In the present study, we demonstrate how the interplay between brittle microcracking and plastic deformation twinning can cause intracrystalline melting and/or reaction, which has the potential to lower the effective grain size of plagioclase-rich rocks and thus impacts their reactivity and deformation behaviour.</p>","PeriodicalId":16472,"journal":{"name":"Journal of Metamorphic Geology","volume":"41 3","pages":"449-464"},"PeriodicalIF":3.5000,"publicationDate":"2022-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jmg.12702","citationCount":"2","resultStr":"{\"title\":\"Partial melting and reaction along deformation features in plagioclase\",\"authors\":\"Sarah Incel, Marie Baïsset, Loïc Labrousse, Alexandre Schubnel\",\"doi\":\"10.1111/jmg.12702\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>Geological processes involving deformation and/or reactions are highly influenced by the rock grain size, especially if diffusion-controlled processes take place such as metamorphic reactions and diffusion creep. Although many processes, inducing grain-size reduction, are documented and understood at relatively high stresses and low temperatures (e.g., cataclasis) as well as at lower stress and higher temperature conditions (e.g., bulging and subgrain rotation), deformation twinning, a plastic deformation mechanism active in various minerals at lower temperatures, has been neglected as nucleation site for melting and reaction and thus as a cause for grain-size reduction so far. We conducted experiments on natural plagioclase-bearing aggregates at 2.5 to 3 GPa confining pressure and temperatures of 700°C to 950°C using two different deformation apparatus, a deformation multianvil apparatus (DDIA) and a Griggs press, as well as a piston-cylinder apparatus. Regardless of the apparatus type, we observe the breakdown of plagioclase into an eclogite-facies paragenesis, which is associated with partial melting in the high temperature domain of the eclogite facies. Partial melting mostly takes place along the grain and interphase boundaries. However, several melt patches or plagioclase decomposition products coincide with the occurrence of deformation twins and grain-scale microcracking in plagioclase indicating intracrystalline melting and reaction in addition to melting and reaction along grain and interphase boundaries. In the present study, we demonstrate how the interplay between brittle microcracking and plastic deformation twinning can cause intracrystalline melting and/or reaction, which has the potential to lower the effective grain size of plagioclase-rich rocks and thus impacts their reactivity and deformation behaviour.</p>\",\"PeriodicalId\":16472,\"journal\":{\"name\":\"Journal of Metamorphic Geology\",\"volume\":\"41 3\",\"pages\":\"449-464\"},\"PeriodicalIF\":3.5000,\"publicationDate\":\"2022-11-22\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jmg.12702\",\"citationCount\":\"2\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Metamorphic Geology\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://onlinelibrary.wiley.com/doi/10.1111/jmg.12702\",\"RegionNum\":2,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"GEOLOGY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Metamorphic Geology","FirstCategoryId":"89","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1111/jmg.12702","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOLOGY","Score":null,"Total":0}
Partial melting and reaction along deformation features in plagioclase
Geological processes involving deformation and/or reactions are highly influenced by the rock grain size, especially if diffusion-controlled processes take place such as metamorphic reactions and diffusion creep. Although many processes, inducing grain-size reduction, are documented and understood at relatively high stresses and low temperatures (e.g., cataclasis) as well as at lower stress and higher temperature conditions (e.g., bulging and subgrain rotation), deformation twinning, a plastic deformation mechanism active in various minerals at lower temperatures, has been neglected as nucleation site for melting and reaction and thus as a cause for grain-size reduction so far. We conducted experiments on natural plagioclase-bearing aggregates at 2.5 to 3 GPa confining pressure and temperatures of 700°C to 950°C using two different deformation apparatus, a deformation multianvil apparatus (DDIA) and a Griggs press, as well as a piston-cylinder apparatus. Regardless of the apparatus type, we observe the breakdown of plagioclase into an eclogite-facies paragenesis, which is associated with partial melting in the high temperature domain of the eclogite facies. Partial melting mostly takes place along the grain and interphase boundaries. However, several melt patches or plagioclase decomposition products coincide with the occurrence of deformation twins and grain-scale microcracking in plagioclase indicating intracrystalline melting and reaction in addition to melting and reaction along grain and interphase boundaries. In the present study, we demonstrate how the interplay between brittle microcracking and plastic deformation twinning can cause intracrystalline melting and/or reaction, which has the potential to lower the effective grain size of plagioclase-rich rocks and thus impacts their reactivity and deformation behaviour.
期刊介绍:
The journal, which is published nine times a year, encompasses the entire range of metamorphic studies, from the scale of the individual crystal to that of lithospheric plates, including regional studies of metamorphic terranes, modelling of metamorphic processes, microstructural and deformation studies in relation to metamorphism, geochronology and geochemistry in metamorphic systems, the experimental study of metamorphic reactions, properties of metamorphic minerals and rocks and the economic aspects of metamorphic terranes.