U–Pb (SHRIMP-II) Age of Zircon from Granites of Bolshoi Tyuters Island (Gulf of Finland, Russia) and the Problem of the Ediacaran Thermal Event in the Region

IF 0.7 4区地球科学 Q4 GEOSCIENCES, MULTIDISCIPLINARY Doklady Earth Sciences Pub Date : 2024-05-02 DOI:10.1134/s1028334x24601573

S. G. Skublov, E. N. Terekhov, N. B. Kuznetsov, A. B. Makeyev, L. I. Salimgaraeva

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Abstract

New data on the U–Pb age (SHRIMP-II) and trace element composition (SIMS) of zircons from granites of Bolshoi Tyuters Island (Outer Islands of the Gulf of Finland) are presented. The upper intersection of the discordia (1825 ± 11 Ma) is taken as the age of crystallization of granites cutting through secondary quartzites and thereby determines their youngest age. Subconcordant zircons located in the upper part of the discordia have growth oscillatory zoning and geochemical characteristics of zircons of magmatic origin. The age of the lower intersection of discordia and concordia is about 570 Ma. It is supported by the independent zircon generation represented by black CL domains and rims in magmatic zircons characterized by increased contents of non-formula elements (light REEs, Ca, P, Ti, Nb, etc.), up to anomalous values. The age of the lower intersection of discordia and concordia can be considered as related to the Timan (Ediacaran) or Finnmark (Early Caledonian) thermal activation of the Fennoscandian Shield discovered earlier based on zircons from Kola Group gneisses.

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俄罗斯芬兰湾）Bolshoi Tyuters 岛花岗岩锆石的 U-Pb (SHRIMP-II) 年龄和该地区埃迪卡拉热事件问题

摘要介绍了来自 Bolshoi Tyuters 岛（芬兰湾外岛）花岗岩的锆石的 U-Pb 年龄（SHRIMP-II）和微量元素组成（SIMS）的新数据。将不协合带的上交点（1825 ± 11 Ma）作为切割次生石英岩的花岗岩的结晶年龄，从而确定了其最年轻的年龄。位于不和谐带上部的亚和谐锆石具有岩浆源锆石的生长振荡分带和地球化学特征。不和谐带与和谐带下部交汇处的年龄约为 570 Ma。岩浆锆石中以黑色 CL 域和边缘为代表的独立锆石生成证实了这一点，其特征是非公式元素（轻型 REEs、Ca、P、Ti、Nb 等）含量增加，甚至达到异常值。根据科拉群片麻岩中的锆石，可以认为不和谐区和和谐区的下部交汇处的年龄与早先发现的芬诺斯坎地盾的蒂曼（埃迪卡拉纪）或芬马克（早加里东纪）热激活有关。

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来源期刊

Doklady Earth Sciences 地学-地球科学综合

CiteScore

1.40

自引率

22.20%

发文量

138

审稿时长

3-6 weeks

期刊介绍： Doklady Earth Sciences is a journal that publishes new research in Earth science of great significance. Initially the journal was a forum of the Russian Academy of Science and published only best contributions from Russia. Now the journal welcomes submissions from any country in the English or Russian language. Every manuscript must be recommended by Russian or foreign members of the Russian Academy of Sciences.