Agates from Mesoproterozoic Volcanics (Pasha–Ladoga Basin, NW Russia): Characteristics and Proposed Origin
Agate gemstones occurring in the Mesoproterozoic volcanic rocks of the Priozersk Formation (PrF) within the Pasha–Ladoga Basin (Fennoscandian Shield, NW Russia) were investigated to characterize the mineral and geochemical composition of the agates and provide new information concerning their origin...
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ftdoajarticles:oai:doaj.org/article:301e5e7bb1224d619fe58a3cd614bf62 2023-05-15T16:12:04+02:00 Agates from Mesoproterozoic Volcanics (Pasha–Ladoga Basin, NW Russia): Characteristics and Proposed Origin Evgeniya N. Svetova Sergei A. Svetov 2022-12-01T00:00:00Z https://doi.org/10.3390/min13010062 https://doaj.org/article/301e5e7bb1224d619fe58a3cd614bf62 EN eng MDPI AG https://www.mdpi.com/2075-163X/13/1/62 https://doaj.org/toc/2075-163X doi:10.3390/min13010062 2075-163X https://doaj.org/article/301e5e7bb1224d619fe58a3cd614bf62 Minerals, Vol 13, Iss 62, p 62 (2022) agates Mesoproterozoic volcanics Fennoscandia Shield Raman spectroscopy X-ray diffraction SEM-EDS Mineralogy QE351-399.2 article 2022 ftdoajarticles https://doi.org/10.3390/min13010062 2023-01-22T01:26:47Z Agate gemstones occurring in the Mesoproterozoic volcanic rocks of the Priozersk Formation (PrF) within the Pasha–Ladoga Basin (Fennoscandian Shield, NW Russia) were investigated to characterize the mineral and geochemical composition of the agates and provide new information concerning their origin. Optical and scanning electron microscopy, EDS microanalysis, X-ray powder diffraction, X-ray fluorescence spectrometry, Raman spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), and C-O isotope analysis were used for the study. Agate mineralization appears mostly as an infill of fissures, cavities, gas vesicles in massive and vesicular basalts, lava-breccias. The mineral composition of agates is dominated by alpha-quartz (fibrous chalcedony, microcrystalline and macrocrystalline quartz), but it also displays abundances of calcite. The characteristic red-brownish agate’s coloration is caused by multiple hematite inclusions distributed in an agate matrix. The study revealed the two phases of agate formation in the PrF volcanics, which are most likely controlled by two distinctly different fluids and/or their mixture. At first, agates appeared due to post-magmatic iron-rich fluids. The late hydrothermal activity was probably triggered by intrusion of gabbro-dolerite sill and resulted in the second phase of agate formation. We suggest that the late hydrothermal fluids remobilized the iron compounds from the crust of weathering underlying the PrF volcanics, which led to additional formation of vein agates and filling of gas vesicles with hematite-rich calcite/silica matter. Article in Journal/Newspaper Fennoscandia Fennoscandian Directory of Open Access Journals: DOAJ Articles Minerals 13 1 62 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
agates Mesoproterozoic volcanics Fennoscandia Shield Raman spectroscopy X-ray diffraction SEM-EDS Mineralogy QE351-399.2 |
spellingShingle |
agates Mesoproterozoic volcanics Fennoscandia Shield Raman spectroscopy X-ray diffraction SEM-EDS Mineralogy QE351-399.2 Evgeniya N. Svetova Sergei A. Svetov Agates from Mesoproterozoic Volcanics (Pasha–Ladoga Basin, NW Russia): Characteristics and Proposed Origin |
topic_facet |
agates Mesoproterozoic volcanics Fennoscandia Shield Raman spectroscopy X-ray diffraction SEM-EDS Mineralogy QE351-399.2 |
description |
Agate gemstones occurring in the Mesoproterozoic volcanic rocks of the Priozersk Formation (PrF) within the Pasha–Ladoga Basin (Fennoscandian Shield, NW Russia) were investigated to characterize the mineral and geochemical composition of the agates and provide new information concerning their origin. Optical and scanning electron microscopy, EDS microanalysis, X-ray powder diffraction, X-ray fluorescence spectrometry, Raman spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), and C-O isotope analysis were used for the study. Agate mineralization appears mostly as an infill of fissures, cavities, gas vesicles in massive and vesicular basalts, lava-breccias. The mineral composition of agates is dominated by alpha-quartz (fibrous chalcedony, microcrystalline and macrocrystalline quartz), but it also displays abundances of calcite. The characteristic red-brownish agate’s coloration is caused by multiple hematite inclusions distributed in an agate matrix. The study revealed the two phases of agate formation in the PrF volcanics, which are most likely controlled by two distinctly different fluids and/or their mixture. At first, agates appeared due to post-magmatic iron-rich fluids. The late hydrothermal activity was probably triggered by intrusion of gabbro-dolerite sill and resulted in the second phase of agate formation. We suggest that the late hydrothermal fluids remobilized the iron compounds from the crust of weathering underlying the PrF volcanics, which led to additional formation of vein agates and filling of gas vesicles with hematite-rich calcite/silica matter. |
format |
Article in Journal/Newspaper |
author |
Evgeniya N. Svetova Sergei A. Svetov |
author_facet |
Evgeniya N. Svetova Sergei A. Svetov |
author_sort |
Evgeniya N. Svetova |
title |
Agates from Mesoproterozoic Volcanics (Pasha–Ladoga Basin, NW Russia): Characteristics and Proposed Origin |
title_short |
Agates from Mesoproterozoic Volcanics (Pasha–Ladoga Basin, NW Russia): Characteristics and Proposed Origin |
title_full |
Agates from Mesoproterozoic Volcanics (Pasha–Ladoga Basin, NW Russia): Characteristics and Proposed Origin |
title_fullStr |
Agates from Mesoproterozoic Volcanics (Pasha–Ladoga Basin, NW Russia): Characteristics and Proposed Origin |
title_full_unstemmed |
Agates from Mesoproterozoic Volcanics (Pasha–Ladoga Basin, NW Russia): Characteristics and Proposed Origin |
title_sort |
agates from mesoproterozoic volcanics (pasha–ladoga basin, nw russia): characteristics and proposed origin |
publisher |
MDPI AG |
publishDate |
2022 |
url |
https://doi.org/10.3390/min13010062 https://doaj.org/article/301e5e7bb1224d619fe58a3cd614bf62 |
genre |
Fennoscandia Fennoscandian |
genre_facet |
Fennoscandia Fennoscandian |
op_source |
Minerals, Vol 13, Iss 62, p 62 (2022) |
op_relation |
https://www.mdpi.com/2075-163X/13/1/62 https://doaj.org/toc/2075-163X doi:10.3390/min13010062 2075-163X https://doaj.org/article/301e5e7bb1224d619fe58a3cd614bf62 |
op_doi |
https://doi.org/10.3390/min13010062 |
container_title |
Minerals |
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13 |
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1 |
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62 |
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1765997298363400192 |