Haihao Guo , Johann Tuduri , Zineb Nabyl , Saskia Erdmann , Xiaochun Li , Fabrice Gaillard
{"title":"磷灰石中的稀土元素:揭示碳酸盐岩熔体成分的替代物","authors":"Haihao Guo , Johann Tuduri , Zineb Nabyl , Saskia Erdmann , Xiaochun Li , Fabrice Gaillard","doi":"10.1016/j.epsl.2024.118863","DOIUrl":null,"url":null,"abstract":"<div><p>Carbonatites are fascinating magmatic rocks because of their anomalous compositions, including the fact that some of these rocks host major rare earth element (REE) deposits. Despite much recent work, our understanding of their genesis and the composition of initial carbonatite melts is hindered by two major obstacles: most carbonatites we see are intrusive rocks, and they are commonly affected by metasomatic overprint. Here, we report experimental data in which we use apatite as a geochemical proxy to see back through crystallization and metasomatic events, thus making it possible to decipher the composition of carbonatite melts. We determined partition coefficients between apatite and carbonatite melts for a broad range of elements. The Na-rich nature of carbonatite melts plays an important role in apatite-melt partition coefficients, which are in the range of 1–7 for Sr, Y and REE in carbonatite systems. Using our new experimental data combined with >700 apatite composition data from carbonatites in various geodynamic settings, we show that carbonatite melt REE contents vary by more than two orders of magnitude. This variation cannot be solely produced by crystal-melt fractionation, implying that some carbonatite melts must be REE-rich or REE-poor initially, and that they mostly remain so during differentiation. We conclude that the degree of REE enrichment reflects carbonatite melts produced by immiscibility from variably differentiated alkaline magmas.</p></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":null,"pages":null},"PeriodicalIF":4.8000,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Rare earth elements in apatite: A proxy for unravelling carbonatite melt compositions\",\"authors\":\"Haihao Guo , Johann Tuduri , Zineb Nabyl , Saskia Erdmann , Xiaochun Li , Fabrice Gaillard\",\"doi\":\"10.1016/j.epsl.2024.118863\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>Carbonatites are fascinating magmatic rocks because of their anomalous compositions, including the fact that some of these rocks host major rare earth element (REE) deposits. Despite much recent work, our understanding of their genesis and the composition of initial carbonatite melts is hindered by two major obstacles: most carbonatites we see are intrusive rocks, and they are commonly affected by metasomatic overprint. Here, we report experimental data in which we use apatite as a geochemical proxy to see back through crystallization and metasomatic events, thus making it possible to decipher the composition of carbonatite melts. We determined partition coefficients between apatite and carbonatite melts for a broad range of elements. The Na-rich nature of carbonatite melts plays an important role in apatite-melt partition coefficients, which are in the range of 1–7 for Sr, Y and REE in carbonatite systems. Using our new experimental data combined with >700 apatite composition data from carbonatites in various geodynamic settings, we show that carbonatite melt REE contents vary by more than two orders of magnitude. This variation cannot be solely produced by crystal-melt fractionation, implying that some carbonatite melts must be REE-rich or REE-poor initially, and that they mostly remain so during differentiation. We conclude that the degree of REE enrichment reflects carbonatite melts produced by immiscibility from variably differentiated alkaline magmas.</p></div>\",\"PeriodicalId\":11481,\"journal\":{\"name\":\"Earth and Planetary Science Letters\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":4.8000,\"publicationDate\":\"2024-07-04\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Earth and Planetary Science Letters\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0012821X24002966\",\"RegionNum\":1,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"GEOCHEMISTRY & GEOPHYSICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Earth and Planetary Science Letters","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0012821X24002966","RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
Rare earth elements in apatite: A proxy for unravelling carbonatite melt compositions
Carbonatites are fascinating magmatic rocks because of their anomalous compositions, including the fact that some of these rocks host major rare earth element (REE) deposits. Despite much recent work, our understanding of their genesis and the composition of initial carbonatite melts is hindered by two major obstacles: most carbonatites we see are intrusive rocks, and they are commonly affected by metasomatic overprint. Here, we report experimental data in which we use apatite as a geochemical proxy to see back through crystallization and metasomatic events, thus making it possible to decipher the composition of carbonatite melts. We determined partition coefficients between apatite and carbonatite melts for a broad range of elements. The Na-rich nature of carbonatite melts plays an important role in apatite-melt partition coefficients, which are in the range of 1–7 for Sr, Y and REE in carbonatite systems. Using our new experimental data combined with >700 apatite composition data from carbonatites in various geodynamic settings, we show that carbonatite melt REE contents vary by more than two orders of magnitude. This variation cannot be solely produced by crystal-melt fractionation, implying that some carbonatite melts must be REE-rich or REE-poor initially, and that they mostly remain so during differentiation. We conclude that the degree of REE enrichment reflects carbonatite melts produced by immiscibility from variably differentiated alkaline magmas.
期刊介绍:
Earth and Planetary Science Letters (EPSL) is a leading journal for researchers across the entire Earth and planetary sciences community. It publishes concise, exciting, high-impact articles ("Letters") of broad interest. Its focus is on physical and chemical processes, the evolution and general properties of the Earth and planets - from their deep interiors to their atmospheres. EPSL also includes a Frontiers section, featuring invited high-profile synthesis articles by leading experts on timely topics to bring cutting-edge research to the wider community.