Julie A.-S. Michaud , François Holtz , Daniel J. Kontak , Simon Goldmann , Martin Oeser , Mohamed A. Abu El-Rus , Ali A. Khudeir
{"title":"埃及东部沙漠Mueilha花岗岩含氟长英质稀有金属体系流体介质叠印原生岩浆特征","authors":"Julie A.-S. Michaud , François Holtz , Daniel J. Kontak , Simon Goldmann , Martin Oeser , Mohamed A. Abu El-Rus , Ali A. Khudeir","doi":"10.1016/j.oregeorev.2025.106804","DOIUrl":null,"url":null,"abstract":"<div><div>Fluids are major fractionation agents in granitic systems because they partly control the behaviour and partitioning of elements, including rare metals, during the magmatic-hydrothermal transition and their subsequent redistribution during the later subsolidus stage. The exsolution of magmatic fluids from a volatile-saturated magma and their subsequent circulation commonly result in important textural and geochemical changes with primary magmatic features being entirely overprinted and earlier minerals chemically re-equilibrated. The changes documented herein serve as a basis for tracking the equilibration of a rare-metal granite with interacting fluids. The Mueilha F-Nb-Ta-REE-Y granitic system (Eastern Desert of Egypt) is composed of different facies such as the “red granite”, representing the main volume of the intrusion, and the “border facies”, occurring along the red granite south-western margin. Detailed mineralogical and textural studies of the latter facies document the pervasive and intense transformation of the original highly-evolved granite primarily <em>via</em> coupled dissolution-precipitation. Based on these observations, and complementary whole rock, and mineral major and trace element chemistry, a complex five-stage model of evolution from magmatic to metasomatic is proposed and discussed. As part of this evolution, the border facies represents residual melts extracted at a very late stage of crystallization of the red granite. This process led to a selective enrichment in Nb and Ta, and a corresponding depletion in Li, F, REEs, and Y within the border facies, highlighting the critical role of the timing of extraction in shaping the composition of residual melts. It is suggested that the weak peraluminous character of the intrusion combined with its F content, albeit low (<0.2 wt%), facilitated the observed autometasomatism and associated redistribution of rare metals and REE-Y within the intrusion to form magmatic and hydrothermal disseminated style mineralization typically encountered in rare-metal granites and pegmatites worldwide. We suggest that this study may serve as a useful reference point for investigating comparable settings elsewhere.</div></div>","PeriodicalId":19644,"journal":{"name":"Ore Geology Reviews","volume":"185 ","pages":"Article 106804"},"PeriodicalIF":3.6000,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Overprinting of primary magmatic features by fluid-mediated processes in a F-bearing felsic rare-metal system: the Mueilha granite (Eastern Desert, Egypt)\",\"authors\":\"Julie A.-S. Michaud , François Holtz , Daniel J. Kontak , Simon Goldmann , Martin Oeser , Mohamed A. Abu El-Rus , Ali A. Khudeir\",\"doi\":\"10.1016/j.oregeorev.2025.106804\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><div>Fluids are major fractionation agents in granitic systems because they partly control the behaviour and partitioning of elements, including rare metals, during the magmatic-hydrothermal transition and their subsequent redistribution during the later subsolidus stage. The exsolution of magmatic fluids from a volatile-saturated magma and their subsequent circulation commonly result in important textural and geochemical changes with primary magmatic features being entirely overprinted and earlier minerals chemically re-equilibrated. The changes documented herein serve as a basis for tracking the equilibration of a rare-metal granite with interacting fluids. The Mueilha F-Nb-Ta-REE-Y granitic system (Eastern Desert of Egypt) is composed of different facies such as the “red granite”, representing the main volume of the intrusion, and the “border facies”, occurring along the red granite south-western margin. Detailed mineralogical and textural studies of the latter facies document the pervasive and intense transformation of the original highly-evolved granite primarily <em>via</em> coupled dissolution-precipitation. Based on these observations, and complementary whole rock, and mineral major and trace element chemistry, a complex five-stage model of evolution from magmatic to metasomatic is proposed and discussed. As part of this evolution, the border facies represents residual melts extracted at a very late stage of crystallization of the red granite. This process led to a selective enrichment in Nb and Ta, and a corresponding depletion in Li, F, REEs, and Y within the border facies, highlighting the critical role of the timing of extraction in shaping the composition of residual melts. It is suggested that the weak peraluminous character of the intrusion combined with its F content, albeit low (<0.2 wt%), facilitated the observed autometasomatism and associated redistribution of rare metals and REE-Y within the intrusion to form magmatic and hydrothermal disseminated style mineralization typically encountered in rare-metal granites and pegmatites worldwide. We suggest that this study may serve as a useful reference point for investigating comparable settings elsewhere.</div></div>\",\"PeriodicalId\":19644,\"journal\":{\"name\":\"Ore Geology Reviews\",\"volume\":\"185 \",\"pages\":\"Article 106804\"},\"PeriodicalIF\":3.6000,\"publicationDate\":\"2025-07-26\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Ore Geology Reviews\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0169136825003646\",\"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":"Ore Geology Reviews","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0169136825003646","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOLOGY","Score":null,"Total":0}
Overprinting of primary magmatic features by fluid-mediated processes in a F-bearing felsic rare-metal system: the Mueilha granite (Eastern Desert, Egypt)
Fluids are major fractionation agents in granitic systems because they partly control the behaviour and partitioning of elements, including rare metals, during the magmatic-hydrothermal transition and their subsequent redistribution during the later subsolidus stage. The exsolution of magmatic fluids from a volatile-saturated magma and their subsequent circulation commonly result in important textural and geochemical changes with primary magmatic features being entirely overprinted and earlier minerals chemically re-equilibrated. The changes documented herein serve as a basis for tracking the equilibration of a rare-metal granite with interacting fluids. The Mueilha F-Nb-Ta-REE-Y granitic system (Eastern Desert of Egypt) is composed of different facies such as the “red granite”, representing the main volume of the intrusion, and the “border facies”, occurring along the red granite south-western margin. Detailed mineralogical and textural studies of the latter facies document the pervasive and intense transformation of the original highly-evolved granite primarily via coupled dissolution-precipitation. Based on these observations, and complementary whole rock, and mineral major and trace element chemistry, a complex five-stage model of evolution from magmatic to metasomatic is proposed and discussed. As part of this evolution, the border facies represents residual melts extracted at a very late stage of crystallization of the red granite. This process led to a selective enrichment in Nb and Ta, and a corresponding depletion in Li, F, REEs, and Y within the border facies, highlighting the critical role of the timing of extraction in shaping the composition of residual melts. It is suggested that the weak peraluminous character of the intrusion combined with its F content, albeit low (<0.2 wt%), facilitated the observed autometasomatism and associated redistribution of rare metals and REE-Y within the intrusion to form magmatic and hydrothermal disseminated style mineralization typically encountered in rare-metal granites and pegmatites worldwide. We suggest that this study may serve as a useful reference point for investigating comparable settings elsewhere.
期刊介绍:
Ore Geology Reviews aims to familiarize all earth scientists with recent advances in a number of interconnected disciplines related to the study of, and search for, ore deposits. The reviews range from brief to longer contributions, but the journal preferentially publishes manuscripts that fill the niche between the commonly shorter journal articles and the comprehensive book coverages, and thus has a special appeal to many authors and readers.