Geochemistry, mineral chemistry and pressure–temperature conditions of the Jõhvi magnetite quartzites and magnetite-rich gneisses, NE Estonia
The Jõhvi magnetite quartzites (MagQ) occur as subvertical beds with a complicated structural outline in biotite-garnet-cordierite and pyroxene gneisses which in places also contain high concentrations of iron. Drill core study shows that the complex of MagQ and magnetite-rich gneisses may be up to...
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| Format: | Article |
| Language: | English |
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Estonian Academy Publishers
2021-03-01
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| Series: | Estonian Journal of Earth Sciences |
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| Online Access: | https://kirj.ee/wp-content/plugins/kirj/pub/earth-2-2021-71-93_20210812095521.pdf |
| _version_ | 1817998441160114176 |
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| author | Alvar Soesoo Siim Nirgi Kristjan Urtson Margus Voolma |
| author_facet | Alvar Soesoo Siim Nirgi Kristjan Urtson Margus Voolma |
| author_sort | Alvar Soesoo |
| collection | DOAJ |
| description | The Jõhvi magnetite quartzites (MagQ) occur as subvertical beds with a complicated structural outline in biotite-garnet-cordierite and pyroxene gneisses which in places also contain high concentrations of iron. Drill core study shows that the complex of MagQ and magnetite-rich gneisses may be up to 100 m thick. The MagQ provide a wide range of chemical composition: SiO2 ranges between 40.3 and 60.1 wt%, Al2O3 between 1.7 and 19.7 wt% and total iron between 15 and 45.2 wt%. This study also revealed unusually high manganese contents of 1â6 wt%. The rare earth element (REE) patterns of MagQ and the surrounding gneisses partly overlap. Cutting granitoids form two different REE patterns. Magnetite occurs as anhedral grains elongated along rock fabric, as rounded inclusions in other minerals or as tiny platelets along grain edges and along cleavage planes of amphibole and biotite. Sulphides are present as pyrite, pyrrhotite and other minor sulphide minerals (chalcopyrite, galena and sphalerite). Analysis of the magnetite grains from drill core J-1 shows that classifying Jõhvi magnetites into a certain deposit type is not unambiguous.
The garnetâbiotite geothermometer revealed metamorphic temperatures between 650 and 750 ºC. The garnetâbiotiteâplagioclaseâquartz geobarometer yielded the pressure range of 2.9 to 4.9 kbar. However, having in mind that the entire Jõhvi ore complex may be a result of repeated metasomatic events, which have influenced the primary volcanic-sedimentary sequences, the estimate of primary pressureâtemperature conditions might not be a straightforward task. The current understanding of the geological-geochemical correlation hints at geological similarities between the Bergslagen area in Sweden and the Jõhvi Zone in Estonia. |
| first_indexed | 2024-04-14T02:52:40Z |
| format | Article |
| id | doaj.art-9cb7fb2c68704252b75d090ddca34271 |
| institution | Directory Open Access Journal |
| issn | 1736-4728 1736-7557 |
| language | English |
| last_indexed | 2024-04-14T02:52:40Z |
| publishDate | 2021-03-01 |
| publisher | Estonian Academy Publishers |
| record_format | Article |
| series | Estonian Journal of Earth Sciences |
| spelling | doaj.art-9cb7fb2c68704252b75d090ddca342712022-12-22T02:16:13ZengEstonian Academy PublishersEstonian Journal of Earth Sciences1736-47281736-75572021-03-01702719310.3176/earth.2021.0510.3176/earth.2021.05Geochemistry, mineral chemistry and pressure–temperature conditions of the Jõhvi magnetite quartzites and magnetite-rich gneisses, NE EstoniaAlvar Soesoo0Siim Nirgi1Kristjan Urtson2Margus Voolma3Department of Geology, University of Tartu, Ravila 14A, 50411 Tartu, EstoniaDepartment of Geology, University of Tartu, Ravila 14A, 50411 Tartu, Estonia; Geological Survey of Estonia, Kreutzwaldi 5, 44314 Rakvere, EstoniaDepartment of Geology, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia; kristjan.urtson@taltech.ee; urtson@gi.eeInstitute of Geology at Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia; margus.voolma@ttu.eeThe Jõhvi magnetite quartzites (MagQ) occur as subvertical beds with a complicated structural outline in biotite-garnet-cordierite and pyroxene gneisses which in places also contain high concentrations of iron. Drill core study shows that the complex of MagQ and magnetite-rich gneisses may be up to 100 m thick. The MagQ provide a wide range of chemical composition: SiO2 ranges between 40.3 and 60.1 wt%, Al2O3 between 1.7 and 19.7 wt% and total iron between 15 and 45.2 wt%. This study also revealed unusually high manganese contents of 1â6 wt%. The rare earth element (REE) patterns of MagQ and the surrounding gneisses partly overlap. Cutting granitoids form two different REE patterns. Magnetite occurs as anhedral grains elongated along rock fabric, as rounded inclusions in other minerals or as tiny platelets along grain edges and along cleavage planes of amphibole and biotite. Sulphides are present as pyrite, pyrrhotite and other minor sulphide minerals (chalcopyrite, galena and sphalerite). Analysis of the magnetite grains from drill core J-1 shows that classifying Jõhvi magnetites into a certain deposit type is not unambiguous. The garnetâbiotite geothermometer revealed metamorphic temperatures between 650 and 750 ºC. The garnetâbiotiteâplagioclaseâquartz geobarometer yielded the pressure range of 2.9 to 4.9 kbar. However, having in mind that the entire Jõhvi ore complex may be a result of repeated metasomatic events, which have influenced the primary volcanic-sedimentary sequences, the estimate of primary pressureâtemperature conditions might not be a straightforward task. The current understanding of the geological-geochemical correlation hints at geological similarities between the Bergslagen area in Sweden and the Jõhvi Zone in Estonia.https://kirj.ee/wp-content/plugins/kirj/pub/earth-2-2021-71-93_20210812095521.pdfiron oremagnetite quartzitesgeochemistryore mineralspressure–temperature conditionsjõhvi zoneestonia. |
| spellingShingle | Alvar Soesoo Siim Nirgi Kristjan Urtson Margus Voolma Geochemistry, mineral chemistry and pressure–temperature conditions of the Jõhvi magnetite quartzites and magnetite-rich gneisses, NE Estonia Estonian Journal of Earth Sciences iron ore magnetite quartzites geochemistry ore minerals pressure–temperature conditions jõhvi zone estonia. |
| title | Geochemistry, mineral chemistry and pressure–temperature conditions of the Jõhvi magnetite quartzites and magnetite-rich gneisses, NE Estonia |
| title_full | Geochemistry, mineral chemistry and pressure–temperature conditions of the Jõhvi magnetite quartzites and magnetite-rich gneisses, NE Estonia |
| title_fullStr | Geochemistry, mineral chemistry and pressure–temperature conditions of the Jõhvi magnetite quartzites and magnetite-rich gneisses, NE Estonia |
| title_full_unstemmed | Geochemistry, mineral chemistry and pressure–temperature conditions of the Jõhvi magnetite quartzites and magnetite-rich gneisses, NE Estonia |
| title_short | Geochemistry, mineral chemistry and pressure–temperature conditions of the Jõhvi magnetite quartzites and magnetite-rich gneisses, NE Estonia |
| title_sort | geochemistry mineral chemistry and pressure temperature conditions of the johvi magnetite quartzites and magnetite rich gneisses ne estonia |
| topic | iron ore magnetite quartzites geochemistry ore minerals pressure–temperature conditions jõhvi zone estonia. |
| url | https://kirj.ee/wp-content/plugins/kirj/pub/earth-2-2021-71-93_20210812095521.pdf |
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