世界上最古老祖母绿的太古代和放射成因来源

IF 3.4 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Geochemical Perspectives Letters Pub Date : 2022-09-01 DOI:10.7185/geochemlet.2232

R. Nicklas, J. Day, R. Alonso-Pérez

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引用次数: 0

摘要

报道了南非Gravelotte和哥伦比亚Muzo祖母绿的87 Rb- 87 Sr数据，这是30年来首次获得此类数据。根据其伴生伟晶岩的~ 2.97 Ga U-Pb年龄推断，该砾石矿床是世界上最古老的祖母绿矿床。砾石型祖母绿的锆石年龄为2883±131 Ma，与伟晶岩的锆石年龄接近，属于中太古代。Muzo祖母绿数据与附近哥伦比亚祖母绿矿床的数据相结合，确定了~ 48 Ma的年龄，比白云母Ar-Ar年龄(65 - 62 Ma)年轻，可能反映了一些祖母绿中87 Rb- 87 Sr的重置。砾石祖母绿的初始Sr同位素组成为放射性成因(87 Sr/ 86 Sr i = 0.841)，其微量元素特征支持其形成于中太古代成熟的高Rb/Sr长英质大陆地壳原岩。祖母绿的直接87 Rb- 87 Sr定年有望提供矿化年龄和来源成分的限制。

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Archean age and radiogenic source for the world’s oldest emeralds

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Archean age and radiogenic source for the world’s oldest emeralds

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.

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来源期刊

Geochemical Perspectives Letters Earth and Planetary Sciences-Geochemistry and Petrology

CiteScore

7.00

自引率

2.00%

发文量

审稿时长

15 weeks

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.