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Volume 53 (2022): Edition 1 (January 2022)

Volume 52 (2021): Edition 1 (January 2021)

Volume 51 (2020): Edition 1 (January 2020)

Volume 50 (2019): Edition 1-4 (December 2019)

Volume 49 (2018): Edition 1-4 (December 2018)

Volume 48 (2017): Edition 1-4 (December 2017)

Volume 47 (2016): Edition 1-4 (December 2016)

Volume 46 (2015): Edition 1-2 (June 2015)

Volume 45 (2014): Edition 3-4 (December 2014)

Volume 45 (2014): Edition 1-2 (June 2014)

Volume 44 (2013): Edition 3-4 (July 2013)

Volume 44 (2013): Edition 1-2 (June 2013)

Volume 43 (2012): Edition 3-4 (December 2012)

Volume 43 (2012): Edition 1-2 (March 2012)

Volume 42 (2011): Edition 4 (October 2011)

Volume 42 (2011): Edition 2-3 (September 2011)

Volume 42 (2011): Edition 1 (March 2011)

Volume 41 (2010): Edition 3-4 (December 2010)

Volume 41 (2010): Edition 1-2 (June 2010)

Volume 40 (2009): Edition 1-4 (December 2009)

Volume 39 (2008): Edition 3-4 (December 2008)

Volume 39 (2008): Edition 1-2 (June 2008)

Volume 38 (2007): Edition 2 (December 2007)

Volume 38 (2007): Edition 1 (June 2007)

Volume 37 (2006): Edition 2 (December 2006)

Volume 37 (2006): Edition 1 (June 2006)

Détails du magazine
Format
Magazine
eISSN
1899-8526
Première publication
05 Feb 2007
Période de publication
1 fois par an
Langues
Anglais

Chercher

Volume 53 (2022): Edition 1 (January 2022)

Détails du magazine
Format
Magazine
eISSN
1899-8526
Première publication
05 Feb 2007
Période de publication
1 fois par an
Langues
Anglais

Chercher

3 Articles
Accès libre

Mesoarchean melt and fluid inclusions in garnet from the Kangerlussuaq basement, Southeast Greenland

Publié en ligne: 14 Feb 2022
Pages: 1 - 9

Résumé

Abstract

The present work reports the first anatectic melt inclusions found so far in the Mesoarchean basement in East Greenland. Using optical microscope observations and MicroRaman spectroscopy, we show that garnets in metasedimentary migmatite contain primary polycrystalline aggregates which can be confidently interpreted as former droplets of anatectic melt, i.e. nanogranitoids. In some cases, they coexist with coeval fluid inclusions under conditions of primary fluid-melt immiscibility. The re-evaluation of the metamorphic pressure and temperature conditions with up-to-date phase equilibria modelling, combined with the identification of nanogranitoids and fluid inclusions, suggests metamorphic peak equilibration and partial melting in presence of a COH-fluid at T ~1000°C and P > 7 kbar. To date, this is the oldest verified occurrence of nanogranitoids and fluid-melt immiscibility during garnet growth in a partially molten environment.

Mots clés

  • Melt inclusion
  • Precambrian
  • Greeland
Accès libre

High temperature transformation of iron-bearing minerals in basalt: Mössbauer spectroscopy studies

Publié en ligne: 28 May 2022
Pages: 10 - 19

Résumé

Abstract

The high temperature decomposition of basalt from Lower Silesia (Poland) was followed by Mössbauer spectroscopy investigation. The Fe content of the sample was ~9.0 at.%. The X-ray diffraction analysis shows that augite (37%) and olivine (12%) are major Fe-bearing mineral components. The sample also contains significant amount of anorthite (22%) and nepheline (17%). The sample was heated at various temperatures between 200°C and 1100°C for three hours. Up to a temperature of 500°C changes in contribution of Fe-bearing minerals are insignificant. Heating in the temperature range from 500°C to 1100°C leads to a systematic increase in contribution of iron oxides at the cost of contribution of silicate minerals, like augite and olivine. Mössbauer spectrum obtained after heating at 1100°C showed hematite as the main iron oxide phase. The ratio of Fe3+/Fetot in the non-heated sample was equal to 0.51 and after heating at 1100°C this ratio amounted to 0.89.

Mots clés

  • basalts
  • high temperature affects
  • Mössbauer spectroscopy
  • Fe-bearing minerals
Accès libre

Mineralogical and geochemical evidence for two-stage silicification of serpentinized peridotites from the Szklary Massif (NE Bohemian Massif)

Publié en ligne: 15 Jun 2022
Pages: 20 - 35

Résumé

Abstract

Previously unknown exposures of silicified serpentinites have been documented within the Szklary Massif, which is a fragment of the tectonically dismembered Central Sudetic Ophiolite (NE Bohemian Massif). On the basis of textural, mineralogical and chemical differences, two types of silicified serpentinites have been distinguished in this study (Type I and Type II). Type I is characterized by well-preserved primary minerals cut by numerous veinlets filled with microscale euhedral quartz crystals. Studied samples of Type I are enriched in silica (from 62 to 69 wt.% SiO2) and depleted in magnesium (from 10 to 19 wt.% MgO) in comparison to serpentinized peridotites from the Szklary Massif. Type II is almost exclusively composed of amorphous or poorly crystalline silica, with microquartz aggregates being the most abundant form. Silicified serpentinites of Type II show extremely high values of silica (from 83 to 90 wt.% SiO2) and low magnesium concentrations (from 4 to 8 wt.% MgO). Both types of silicified serpentinites have elevated content of REE and many other trace elements generally regarded as incompatible. We infer that the earlier silicification event was caused by the percolation of Si-rich hydrothermal fluids derived from igneous rocks, which intruded this area from ca. 380 to 330 Ma. A subsequent silicification event is the result of silica remobilization during intense chemical weathering under tropical conditions, which could have occurred between Late Cretaceous and Miocene.

Mots clés

  • silicified serpentinites
  • silicification
  • serpentinized peridotites
  • cathodoluminescence imaging
  • Szklary Massif
3 Articles
Accès libre

Mesoarchean melt and fluid inclusions in garnet from the Kangerlussuaq basement, Southeast Greenland

Publié en ligne: 14 Feb 2022
Pages: 1 - 9

Résumé

Abstract

The present work reports the first anatectic melt inclusions found so far in the Mesoarchean basement in East Greenland. Using optical microscope observations and MicroRaman spectroscopy, we show that garnets in metasedimentary migmatite contain primary polycrystalline aggregates which can be confidently interpreted as former droplets of anatectic melt, i.e. nanogranitoids. In some cases, they coexist with coeval fluid inclusions under conditions of primary fluid-melt immiscibility. The re-evaluation of the metamorphic pressure and temperature conditions with up-to-date phase equilibria modelling, combined with the identification of nanogranitoids and fluid inclusions, suggests metamorphic peak equilibration and partial melting in presence of a COH-fluid at T ~1000°C and P > 7 kbar. To date, this is the oldest verified occurrence of nanogranitoids and fluid-melt immiscibility during garnet growth in a partially molten environment.

Mots clés

  • Melt inclusion
  • Precambrian
  • Greeland
Accès libre

High temperature transformation of iron-bearing minerals in basalt: Mössbauer spectroscopy studies

Publié en ligne: 28 May 2022
Pages: 10 - 19

Résumé

Abstract

The high temperature decomposition of basalt from Lower Silesia (Poland) was followed by Mössbauer spectroscopy investigation. The Fe content of the sample was ~9.0 at.%. The X-ray diffraction analysis shows that augite (37%) and olivine (12%) are major Fe-bearing mineral components. The sample also contains significant amount of anorthite (22%) and nepheline (17%). The sample was heated at various temperatures between 200°C and 1100°C for three hours. Up to a temperature of 500°C changes in contribution of Fe-bearing minerals are insignificant. Heating in the temperature range from 500°C to 1100°C leads to a systematic increase in contribution of iron oxides at the cost of contribution of silicate minerals, like augite and olivine. Mössbauer spectrum obtained after heating at 1100°C showed hematite as the main iron oxide phase. The ratio of Fe3+/Fetot in the non-heated sample was equal to 0.51 and after heating at 1100°C this ratio amounted to 0.89.

Mots clés

  • basalts
  • high temperature affects
  • Mössbauer spectroscopy
  • Fe-bearing minerals
Accès libre

Mineralogical and geochemical evidence for two-stage silicification of serpentinized peridotites from the Szklary Massif (NE Bohemian Massif)

Publié en ligne: 15 Jun 2022
Pages: 20 - 35

Résumé

Abstract

Previously unknown exposures of silicified serpentinites have been documented within the Szklary Massif, which is a fragment of the tectonically dismembered Central Sudetic Ophiolite (NE Bohemian Massif). On the basis of textural, mineralogical and chemical differences, two types of silicified serpentinites have been distinguished in this study (Type I and Type II). Type I is characterized by well-preserved primary minerals cut by numerous veinlets filled with microscale euhedral quartz crystals. Studied samples of Type I are enriched in silica (from 62 to 69 wt.% SiO2) and depleted in magnesium (from 10 to 19 wt.% MgO) in comparison to serpentinized peridotites from the Szklary Massif. Type II is almost exclusively composed of amorphous or poorly crystalline silica, with microquartz aggregates being the most abundant form. Silicified serpentinites of Type II show extremely high values of silica (from 83 to 90 wt.% SiO2) and low magnesium concentrations (from 4 to 8 wt.% MgO). Both types of silicified serpentinites have elevated content of REE and many other trace elements generally regarded as incompatible. We infer that the earlier silicification event was caused by the percolation of Si-rich hydrothermal fluids derived from igneous rocks, which intruded this area from ca. 380 to 330 Ma. A subsequent silicification event is the result of silica remobilization during intense chemical weathering under tropical conditions, which could have occurred between Late Cretaceous and Miocene.

Mots clés

  • silicified serpentinites
  • silicification
  • serpentinized peridotites
  • cathodoluminescence imaging
  • Szklary Massif

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