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4 Acta Geologica Polonica

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Hydrothermal alteration of chevkinite: insights from natural rocks and experiments

100%

Macdonald R. , Bagiński B.

Acta Geologica Polonica

2022

tom Vol. 72, no. 4

413--421

The contributions of the members of the Department of Geochemistry, Mineralogy and Petrology, University of Warsaw, to the study of the chevkinite-group of minerals (CGM) are described. The range of research topics includes: (i) geochemical and mineralogical studies of natural occurrences of the group, and attempts to relate their chemical composition to host lithology; (ii) detailed analysis of the hydrothermal alteration of CGM in various settings, with the aim of understanding element redistribution and the potential implications for ore formation. An ongoing series of high P-T experiments is providing quantitative information on the pressures, temperatures and melt water conditions under which the alteration assemblages have formed. Various spectroscopic techniques are being used to determine the structure of the CGM and to identify cation distribution in the structures.

Ba-Fe titanates in Peralkaline granite of the Ilímaussaq Complex, South Greenland

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Cegiełka M. , Bagiński B. , Macdonald R. , Marciniak-Maliszewska B. , Stachowicz M.

Acta Geologica Polonica

2022

tom Vol. 72, no. 1

1--8

A peralkaline granite of the Ilímaussaq Complex, South Greenland, contains the rare mineral henrymeyerite [(Ba0.92Na 0.05Ca0.03) 1.0(Ti6.87Fe2+1.04Nb 0.03)7.9O 16], a low-Fe Ba titanate [(Ba0.74 Ca0.02Na 0.05) 0.8 (Ti4.9o Fe2+0.15Nb 0.04)5.1O 11], and an unidentified Ba titanosilicate. Both titanates show the coupled substitution 2Na+ + Si4+→ Ba2+ + Ti4+. The minerals are present as tiny crystals fringing ilmenite inclusions in an amphibole crystal and are thought to have formed during the hydrothermal stage of the granite’s evolution.

Zirconium silicates in a peralkaline granite: a record of the interplay of magmatic and hydrothermal processes (Ilímaussaq complex, Greenland)

61%

Cegiełka M. , Bagiński B. , Macdonald R. , Belkin H. E. , Kotowski J. , Upton B. G. J.

Acta Geologica Polonica

2022

tom Vol. 72, no. 2

235--245

Compositional and textural data are presented for zircon, secondary Zr-silicates, catapleiite and elpidite in a peralkaline granite from the Ilímaussaq complex, south Greenland. The zircon is essentially stoichiometric, with (Zr + Hf + Si) = 1.96–1.98 a.p.f.u. The secondary Zr-silicates show a wide range of Zr/Si atomic ratios (0.13–0.79). The catapleiite varies from close to stoichiometric to a Na-depleted type showing cation deficiency (5.2–5.8 a.p.f.u.). Elpidite shows similar variations (7.2–9.0 a.p.f.u.). Textural relationships between the Zr phases are interpreted to show that magmatic zircon interacted with hydrous fluids exsolved from the magma to form the secondary Zr-silicates. Formation of catapleiite was late-magmatic, in equilibrium with a Na-Si-bearing fluid. This was followed by the crystallization of elpidite, the fluid having a different Na/Si ratio. Both catapleiite and elpidite experienced Na-loss during late-stage hydrothermal alteration.

Chevkinite-group minerals in Poland

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Nejbert K. , Bagiński B. , Kotowski J. , Jokubauskas P. , Jurewicz E. , Macdonald R.

Acta Geologica Polonica

2020

tom Vol. 70, no. 1

97--106

The chevkinite group of minerals are REE,Ti-silicates increasingly recognized as widespread accessory phases in a wide range of igneous and metamorphic parageneses. Members of the group are here recorded from five localities in Poland: a two-pyroxene andesite from the Kłodzko-Złoty Stok intrusion, a trachyandesite intrusion north of the Pieniny Mountains, a rapakivi-type granite from the Krasnopol intrusion, an anorthosite from the Suwałki Anorthosite Massif, and nepheline syenite from the Ełk syenite massif. Specific members found are chevkinite-(Ce), perrierite-(Ce) and, potentially, the Al-dominant analogue of perrierite-(Ce). The case is made that chevkinite-group minerals will, through systematic investigation, be found in a wide range of Polish igneous and metamorphic rocks.