Romain Lafay, Lukas P. Baumgartner, Adélie Delacour
{"title":"反Gorite脱水过程中地幔非均质性和蛇纹石化特征的保存:以Bergell接触Aurele为例","authors":"Romain Lafay, Lukas P. Baumgartner, Adélie Delacour","doi":"10.1111/jmg.12699","DOIUrl":null,"url":null,"abstract":"<p>Major, minor, and trace element geochemistry as well as iron oxidation state and isotopes were investigated in serpentinites and olivine-talc fels present along a metamorphic gradient in the Bergell contact aureole (Central European Alps) to evaluate element mobility during serpentine. This aureole is an ideal target to study dehydration of mantle rocks due to the increase in temperature from greenschist facies conditions (350°C) to amphibolite facies conditions (750°C) at low pressures of 0.4 GPa. Petrography and geochemistry document several events of fluid–rock interaction and metamorphism. Serpentinization of the mantle rocks started on the ocean floor. Subsequent Alpine regional metamorphism led to the formation of antigorite-serpentinites containing olivine and diopside. These antigorite-serpentinites were transformed into olivine-talc fels in a large part of the contact-aureole. Bulk-rock major and trace element compositions maintain the geochemical signature of the precursor antigorite-serpentinites. No apparent changes are indeed observed despite the fact that major dehydration reactions occurred. In addition, changes neither in Fe<sup>3+</sup>/Fe<sub>tot</sub> ratio nor in δ<sup>56</sup>Fe values were observed. Local composition variations of antigorite-serpentinites and olivine-talc fels reflect chemical heterogeneities related to protolith composition and serpentinization processes on the ocean floor prior to contact metamorphism. Hence, prograde dehydration reactions occurring during contact metamorphism did not induce substantial element mobility, change in redox state, or isotopic fractionation in these contact metamorphic rocks.</p>","PeriodicalId":16472,"journal":{"name":"Journal of Metamorphic Geology","volume":null,"pages":null},"PeriodicalIF":3.5000,"publicationDate":"2022-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jmg.12699","citationCount":"1","resultStr":"{\"title\":\"Preservation of mantle heterogeneities and serpentinization signature during antigorite dehydration: The example of the Bergell contact aureole\",\"authors\":\"Romain Lafay, Lukas P. Baumgartner, Adélie Delacour\",\"doi\":\"10.1111/jmg.12699\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>Major, minor, and trace element geochemistry as well as iron oxidation state and isotopes were investigated in serpentinites and olivine-talc fels present along a metamorphic gradient in the Bergell contact aureole (Central European Alps) to evaluate element mobility during serpentine. This aureole is an ideal target to study dehydration of mantle rocks due to the increase in temperature from greenschist facies conditions (350°C) to amphibolite facies conditions (750°C) at low pressures of 0.4 GPa. Petrography and geochemistry document several events of fluid–rock interaction and metamorphism. Serpentinization of the mantle rocks started on the ocean floor. Subsequent Alpine regional metamorphism led to the formation of antigorite-serpentinites containing olivine and diopside. These antigorite-serpentinites were transformed into olivine-talc fels in a large part of the contact-aureole. Bulk-rock major and trace element compositions maintain the geochemical signature of the precursor antigorite-serpentinites. No apparent changes are indeed observed despite the fact that major dehydration reactions occurred. In addition, changes neither in Fe<sup>3+</sup>/Fe<sub>tot</sub> ratio nor in δ<sup>56</sup>Fe values were observed. Local composition variations of antigorite-serpentinites and olivine-talc fels reflect chemical heterogeneities related to protolith composition and serpentinization processes on the ocean floor prior to contact metamorphism. Hence, prograde dehydration reactions occurring during contact metamorphism did not induce substantial element mobility, change in redox state, or isotopic fractionation in these contact metamorphic rocks.</p>\",\"PeriodicalId\":16472,\"journal\":{\"name\":\"Journal of Metamorphic Geology\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":3.5000,\"publicationDate\":\"2022-11-14\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jmg.12699\",\"citationCount\":\"1\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Metamorphic Geology\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://onlinelibrary.wiley.com/doi/10.1111/jmg.12699\",\"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.12699","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOLOGY","Score":null,"Total":0}
Preservation of mantle heterogeneities and serpentinization signature during antigorite dehydration: The example of the Bergell contact aureole
Major, minor, and trace element geochemistry as well as iron oxidation state and isotopes were investigated in serpentinites and olivine-talc fels present along a metamorphic gradient in the Bergell contact aureole (Central European Alps) to evaluate element mobility during serpentine. This aureole is an ideal target to study dehydration of mantle rocks due to the increase in temperature from greenschist facies conditions (350°C) to amphibolite facies conditions (750°C) at low pressures of 0.4 GPa. Petrography and geochemistry document several events of fluid–rock interaction and metamorphism. Serpentinization of the mantle rocks started on the ocean floor. Subsequent Alpine regional metamorphism led to the formation of antigorite-serpentinites containing olivine and diopside. These antigorite-serpentinites were transformed into olivine-talc fels in a large part of the contact-aureole. Bulk-rock major and trace element compositions maintain the geochemical signature of the precursor antigorite-serpentinites. No apparent changes are indeed observed despite the fact that major dehydration reactions occurred. In addition, changes neither in Fe3+/Fetot ratio nor in δ56Fe values were observed. Local composition variations of antigorite-serpentinites and olivine-talc fels reflect chemical heterogeneities related to protolith composition and serpentinization processes on the ocean floor prior to contact metamorphism. Hence, prograde dehydration reactions occurring during contact metamorphism did not induce substantial element mobility, change in redox state, or isotopic fractionation in these contact metamorphic rocks.
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.