T. A. Myskova, A. S. Nikonova, K. A. Nikonov, I. A. Zhitnikova, P. A. Lvov
{"title":"Kichany Structure of the Archean Tiksheozero Greenstone Belt of the Fennoscandian: Evidence from New Geochemical and Geochronological Data","authors":"T. A. Myskova, A. S. Nikonova, K. A. Nikonov, I. A. Zhitnikova, P. A. Lvov","doi":"10.1134/S0016702924700496","DOIUrl":null,"url":null,"abstract":"<p>New geological, geochemical, and geochronological (U-Pb zircon) data obtained on the greenstone rocks of the Kichany structure from the Archean Tiksheozero greenstone belt made it possible to clarify and supplement the previously proposed stratification schemes. The composition of the identified sequences, the order and duration of their formation have been specified. The Archean supracrustal rocks are divided into three sequences. The lower sequence (previously not identified) is represented by a bimodal series: tholeiitic metabasalts and felsic metavolcanics, with subordinate metagraywackes. It has been formed for over 20 million years (from 2788 ± 5 to 2766 ± 9 Ma). Sm–Nd data obtained on basaltic metaandesites (Sm–Nd model age 2.86 Ga and ε<sub>Nd</sub> = 2.92) indicate their mantle nature. Metarhyolites from the lower sequence with a Sm–Nd model age of 2.89 Ga and ε<sub>Nd</sub> = 2.59 were generated from a source with a short residence time. The differentiated volcanic series of the upper sequence (from basalts to dacites) has been also formed for about 20 million years (2738 ± 7–2716 ± 7 Ma). The parental melts for the intermediate–felsic metavolcanics of the upper sequence are variably enriched in ancient crustal matter. The oldest rocks with a Sm–Nd model age of 2.84 Ga and ε<sub>Nd</sub> = 2.67 were formed during the Early Neoarchean crust-forming event. The younger rocks have a different contribution of ancient crustal material: significant contribution for dacites (Sm–Nd model age of 3 Ga and ε<sub>Nd</sub> = 0.4) and less significant contribution for dacitic andesites (Sm–Nd model age of 2.89 Ga and ε<sub>Nd</sub> = 1.73). In the Paleoproterozoic (from 1786 ± 11 to 1796 ± 6 Ma), the supracrustal rocks of the Kichany structure underwent metamorphic transformations.</p>","PeriodicalId":12781,"journal":{"name":"Geochemistry International","volume":"62 9","pages":"979 - 1003"},"PeriodicalIF":0.7000,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Geochemistry International","FirstCategoryId":"89","ListUrlMain":"https://link.springer.com/article/10.1134/S0016702924700496","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
引用次数: 0
Abstract
New geological, geochemical, and geochronological (U-Pb zircon) data obtained on the greenstone rocks of the Kichany structure from the Archean Tiksheozero greenstone belt made it possible to clarify and supplement the previously proposed stratification schemes. The composition of the identified sequences, the order and duration of their formation have been specified. The Archean supracrustal rocks are divided into three sequences. The lower sequence (previously not identified) is represented by a bimodal series: tholeiitic metabasalts and felsic metavolcanics, with subordinate metagraywackes. It has been formed for over 20 million years (from 2788 ± 5 to 2766 ± 9 Ma). Sm–Nd data obtained on basaltic metaandesites (Sm–Nd model age 2.86 Ga and εNd = 2.92) indicate their mantle nature. Metarhyolites from the lower sequence with a Sm–Nd model age of 2.89 Ga and εNd = 2.59 were generated from a source with a short residence time. The differentiated volcanic series of the upper sequence (from basalts to dacites) has been also formed for about 20 million years (2738 ± 7–2716 ± 7 Ma). The parental melts for the intermediate–felsic metavolcanics of the upper sequence are variably enriched in ancient crustal matter. The oldest rocks with a Sm–Nd model age of 2.84 Ga and εNd = 2.67 were formed during the Early Neoarchean crust-forming event. The younger rocks have a different contribution of ancient crustal material: significant contribution for dacites (Sm–Nd model age of 3 Ga and εNd = 0.4) and less significant contribution for dacitic andesites (Sm–Nd model age of 2.89 Ga and εNd = 1.73). In the Paleoproterozoic (from 1786 ± 11 to 1796 ± 6 Ma), the supracrustal rocks of the Kichany structure underwent metamorphic transformations.
期刊介绍:
Geochemistry International is a peer reviewed journal that publishes articles on cosmochemistry; geochemistry of magmatic, metamorphic, hydrothermal, and sedimentary processes; isotope geochemistry; organic geochemistry; applied geochemistry; and chemistry of the environment. Geochemistry International provides readers with a unique opportunity to refine their understanding of the geology of the vast territory of the Eurasian continent. The journal welcomes manuscripts from all countries in the English or Russian language.