Geochemical behavior of chromium in minerals of high-Mg rocks, associated with granitoid massifs of the Urals
Research subject. High-magnesium rocks associated with the granitoid massifs of the Urals are represented by gabbro-diorites and their melanocratic varieties (hornblendites), as well as by diorites and quartz diorites. These rocks are composed of amphibole porphyrocrists frequently combined with cli...
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A.N. Zavaritsky Institute of Geology and Geochemistry
2019-07-01
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| Series: | Литосфера |
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| Online Access: | https://www.lithosphere.ru/jour/article/view/1177 |
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| author | S. V. Pribavkin G. A. Кallistov Т. A. Оsipova I. A. Gottman E. A. Zin’kova |
| author_facet | S. V. Pribavkin G. A. Кallistov Т. A. Оsipova I. A. Gottman E. A. Zin’kova |
| author_sort | S. V. Pribavkin |
| collection | DOAJ |
| description | Research subject. High-magnesium rocks associated with the granitoid massifs of the Urals are represented by gabbro-diorites and their melanocratic varieties (hornblendites), as well as by diorites and quartz diorites. These rocks are composed of amphibole porphyrocrists frequently combined with clinopyroxene and phlogopite immersed in a basis of acid plagioclase with interstitial quartz and potassium feldspar. In addition to a high magnesium content of 0.5–0.8 units, these rocks are characterized by extremely high chromium contents of up to 1200 ppm.Methods. The study of the composition of high-magnesium rocks was performed using an ELAN 9000 inductively coupled plasma mass spectrometer, an SX-100 Cameca electron probe microanalyzer and an energy dispersive device INCAEnergy 450 X-Max 80. The detection limit for Cr2O3 was equal to 0.05 wt. % and 0.2 wt. % for the microanalyzer and the energy dispersive device, respectively. Results. The two main mineral associations related to magmatic and post-magmatic processes are found to be different in terms of chromium behaviour. The average concentrations of chromium oxide in the minerals from the magmatic association varied within the range (wt. %) of 0.10–0.50, 0.29–0.68, 0.08-0.36 and 0.0–1.6 for different samples of clinopyroxene, amphibole, phlogopite and their variations, respectively. The post-magnetic association included minerals representing the products of postmagmatic (hydrothermal) transformation of pyroxenes and alumina amphibole into low-alumina magnesia hornblende, actinolite, titanite, epidote and muscovite. The transformation of chromospinelide at this stage had been accompanied by exchange processes with silicates, as a result of which the silicates were enriched with chromium. The average concentrations of chromium oxide in the minerals of this association were (wt. %) 0.24–0.80, 1.38–3.08, 1.03 and 3.5 in the samples of amphibole, epidote, titanite and muscovite, respectively.Conclusion. It is assumed that the crystallization of the early association of iron-magnesium silicates proceeded from aqueous high-magnesium melts. The subsequent post-magmatic change of such silicates led to the development of phases with a similar and occasionally higher chromium content. This fact can be explained by the interaction of silicates with chromite under the conditions of low fluid oxidation, which was insufficient for the formation of magnetite. |
| first_indexed | 2024-12-19T05:02:16Z |
| format | Article |
| id | doaj.art-edcf2d877e8e4de398bab50ac2688d80 |
| institution | Directory Open Access Journal |
| issn | 1681-9004 2500-302X |
| language | English |
| last_indexed | 2024-12-19T05:02:16Z |
| publishDate | 2019-07-01 |
| publisher | A.N. Zavaritsky Institute of Geology and Geochemistry |
| record_format | Article |
| series | Литосфера |
| spelling | doaj.art-edcf2d877e8e4de398bab50ac2688d802022-12-21T20:35:03ZengA.N. Zavaritsky Institute of Geology and GeochemistryЛитосфера1681-90042500-302X2019-07-0119341643510.24930/1681-9004-2019-19-3-416-4351166Geochemical behavior of chromium in minerals of high-Mg rocks, associated with granitoid massifs of the UralsS. V. Pribavkin0G. A. Кallistov1Т. A. Оsipova2I. A. Gottman3E. A. Zin’kova4A.N. Zavaritsky institute of Geology and Geochemistry, Urals Branch of RASA.N. Zavaritsky institute of Geology and Geochemistry, Urals Branch of RASA.N. Zavaritsky institute of Geology and Geochemistry, Urals Branch of RASA.N. Zavaritsky institute of Geology and Geochemistry, Urals Branch of RASA.N. Zavaritsky institute of Geology and Geochemistry, Urals Branch of RASResearch subject. High-magnesium rocks associated with the granitoid massifs of the Urals are represented by gabbro-diorites and their melanocratic varieties (hornblendites), as well as by diorites and quartz diorites. These rocks are composed of amphibole porphyrocrists frequently combined with clinopyroxene and phlogopite immersed in a basis of acid plagioclase with interstitial quartz and potassium feldspar. In addition to a high magnesium content of 0.5–0.8 units, these rocks are characterized by extremely high chromium contents of up to 1200 ppm.Methods. The study of the composition of high-magnesium rocks was performed using an ELAN 9000 inductively coupled plasma mass spectrometer, an SX-100 Cameca electron probe microanalyzer and an energy dispersive device INCAEnergy 450 X-Max 80. The detection limit for Cr2O3 was equal to 0.05 wt. % and 0.2 wt. % for the microanalyzer and the energy dispersive device, respectively. Results. The two main mineral associations related to magmatic and post-magmatic processes are found to be different in terms of chromium behaviour. The average concentrations of chromium oxide in the minerals from the magmatic association varied within the range (wt. %) of 0.10–0.50, 0.29–0.68, 0.08-0.36 and 0.0–1.6 for different samples of clinopyroxene, amphibole, phlogopite and their variations, respectively. The post-magnetic association included minerals representing the products of postmagmatic (hydrothermal) transformation of pyroxenes and alumina amphibole into low-alumina magnesia hornblende, actinolite, titanite, epidote and muscovite. The transformation of chromospinelide at this stage had been accompanied by exchange processes with silicates, as a result of which the silicates were enriched with chromium. The average concentrations of chromium oxide in the minerals of this association were (wt. %) 0.24–0.80, 1.38–3.08, 1.03 and 3.5 in the samples of amphibole, epidote, titanite and muscovite, respectively.Conclusion. It is assumed that the crystallization of the early association of iron-magnesium silicates proceeded from aqueous high-magnesium melts. The subsequent post-magmatic change of such silicates led to the development of phases with a similar and occasionally higher chromium content. This fact can be explained by the interaction of silicates with chromite under the conditions of low fluid oxidation, which was insufficient for the formation of magnetite.https://www.lithosphere.ru/jour/article/view/1177high-mg dioritesgranitoid massifsmineral associationschromiteamphibolepyroxenemicastitaniteepidotechromium distribution |
| spellingShingle | S. V. Pribavkin G. A. Кallistov Т. A. Оsipova I. A. Gottman E. A. Zin’kova Geochemical behavior of chromium in minerals of high-Mg rocks, associated with granitoid massifs of the Urals Литосфера high-mg diorites granitoid massifs mineral associations chromite amphibole pyroxene micas titanite epidote chromium distribution |
| title | Geochemical behavior of chromium in minerals of high-Mg rocks, associated with granitoid massifs of the Urals |
| title_full | Geochemical behavior of chromium in minerals of high-Mg rocks, associated with granitoid massifs of the Urals |
| title_fullStr | Geochemical behavior of chromium in minerals of high-Mg rocks, associated with granitoid massifs of the Urals |
| title_full_unstemmed | Geochemical behavior of chromium in minerals of high-Mg rocks, associated with granitoid massifs of the Urals |
| title_short | Geochemical behavior of chromium in minerals of high-Mg rocks, associated with granitoid massifs of the Urals |
| title_sort | geochemical behavior of chromium in minerals of high mg rocks associated with granitoid massifs of the urals |
| topic | high-mg diorites granitoid massifs mineral associations chromite amphibole pyroxene micas titanite epidote chromium distribution |
| url | https://www.lithosphere.ru/jour/article/view/1177 |
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