{"title":"Archean age and radiogenic source for the world’s oldest emeralds","authors":"R. Nicklas, J. Day, R. Alonso-Pérez","doi":"10.7185/geochemlet.2232","DOIUrl":null,"url":null,"abstract":"New 87 Rb- 87 Sr data are reported for emeralds from Gravelotte, South Africa and Muzo, Colombia, the first such data in 30 years. The Gravelotte deposit is inferred to be the world ’ s oldest emerald deposit from the ∼ 2.97 Ga U-Pb age of the associated pegmatite. The majority of Gravelotte emeralds plot on an 87 Rb- 87 Sr errorchron with an age of 2883 ± 131 Ma, close to the pegmatite age, demonstrating that the emeralds are Mesoarchean in age. The Muzo emerald data, when combined with data from nearby Colombian emerald deposits, define an age of ∼ 48 Ma, younger than muscovite Ar-Ar ages (65 – 62 Ma), likely reflecting the resetting of 87 Rb- 87 Sr in some emeralds. The initial Sr isotopic composition for Gravelotte emeralds is radiogenic ( 87 Sr/ 86 Sr i = 0.841), and their trace element signatures support their formation from a mature, high Rb/Sr, felsic continental crustal protolith in the Mesoarchean. Direct 87 Rb- 87 Sr dating of emeralds holds promise for offering constraints on both mineralisation ages and source compositions.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":" ","pages":""},"PeriodicalIF":3.4000,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Geochemical Perspectives Letters","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.7185/geochemlet.2232","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}
引用次数: 0
Abstract
New 87 Rb- 87 Sr data are reported for emeralds from Gravelotte, South Africa and Muzo, Colombia, the first such data in 30 years. The Gravelotte deposit is inferred to be the world ’ s oldest emerald deposit from the ∼ 2.97 Ga U-Pb age of the associated pegmatite. The majority of Gravelotte emeralds plot on an 87 Rb- 87 Sr errorchron with an age of 2883 ± 131 Ma, close to the pegmatite age, demonstrating that the emeralds are Mesoarchean in age. The Muzo emerald data, when combined with data from nearby Colombian emerald deposits, define an age of ∼ 48 Ma, younger than muscovite Ar-Ar ages (65 – 62 Ma), likely reflecting the resetting of 87 Rb- 87 Sr in some emeralds. The initial Sr isotopic composition for Gravelotte emeralds is radiogenic ( 87 Sr/ 86 Sr i = 0.841), and their trace element signatures support their formation from a mature, high Rb/Sr, felsic continental crustal protolith in the Mesoarchean. Direct 87 Rb- 87 Sr dating of emeralds holds promise for offering constraints on both mineralisation ages and source compositions.
期刊介绍：
Geochemical Perspectives Letters is an open access, internationally peer-reviewed journal of the European Association of Geochemistry (EAG) that publishes short, highest-quality articles spanning geochemical sciences. The journal aims at rapid publication of the most novel research in geochemistry with a focus on outstanding quality, international importance, originality, and stimulating new developments across the vast array of geochemical disciplines.
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