Cookeite occurs in pseudomorphs after sekaninaite associated with muscovite, quartz, tourmaline, albite, nontronite, and chlorite in pegmatite No. 1 (proximal cookeite type), and in pockets lined with albite and quartz in the Oldřich pegmatite (distal cookeite type), Dolní Bory-Hatě, Bory pegmatite district, Moldanubian Zone, Czech Republic. The mineral assemblages of the Bory pegmatites with common Al,Fe-rich minerals (annite, schorl, sekaninaite, andalusite, diaspore, ilmenite, and almandine) suggest their primitive, peraluminous, LCT geochemical signature. Proximal cookeite forms aggregates of sheets, up to ~500 μm in diameter, intergrown with prevailing muscovite and quartz. Beige to grayish, porous aggregates of distal cookeite, up to 15 cm in size, consist of thin sheets, up to ~70 μm in diameter, locally associated with small grains of pyrite and pale brown siderite as a matrix. Electron microprobe data of cookeite from the No. 1 and Oldřich pegmatites yielded very similar results: Si (3.23–3.27, 3.21–3.32 apfu) and Al (4.59–4.65, 4.48–4.65 apfu), respectively, and low concentrations of Fe (Fetot ⩽ 0.08 apfu), Mg (⩽ 0.07 apfu), and K (⩽ 0.15 apfu). Concentrations of Li, B, and Be obtained by LA-ICP-MS (and wet chemical analysis—Li, Oldřich) of cookeite from both pegmatite dikes yielded an average of 2.22 wt.% Li2O (0.78 apfu) and 2.38 wt.% Li2O (0.84 apfu), low contents of B = 370–780 ppm and 250–430 ppm, and very low Be ⩽16 ppm and ⩽1.2 ppm for pegmatite No. 1 and the Oldřich pegmatite, respectively. Strong hydrothermal alteration of common Li-bearing sekaninaite (0.11–0.55 wt.% Li2O) is evident and a potential source of Li for both the proximal and distal cookeites. Cookeite precipitated from hydrothermal fluids at T ~350–270 °C and P < ~2 kbar. These data are consistent with the cookeite formation in granitic pegmatites and the distal cookeite demonstrates the high mobility of Li in hydrothermal conditions. The crystallization of cookeite at the No. 1 and Oldřich pegmatites was followed by crystallization of an Fe-rich mineral—nontronite and siderite, respectively.
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Research Article|
November 01, 2015
Two Paragenetic Types of Cookeite from the DolnÍ Bory-hatĚ Pegmatites, Moldanubian Zone, Czech Republic: Proximal and Distal Alteration Products of Li-bearing Sekaninaite
Milan NovÁk;
Milan NovÁk
§
Department of Geological Sciences, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic
§Corresponding author e-mail address: mnovak@sci.muni.cz
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Renata ČopjakovÁ;
Renata ČopjakovÁ
Department of Geological Sciences, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic
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Marek Dosbaba;
Marek Dosbaba
Department of Geological Sciences, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic
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Michaela VAŠINOVÁ GaliovÁ;
Michaela VAŠINOVÁ GaliovÁ
Department of Chemistry, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic Central European Institute of Technology (CEITEC), Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
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Dalibor VŠianskÝ;
Dalibor VŠianskÝ
Department of Geological Sciences, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic
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Josef StanĚk
Josef StanĚk
Department of Geological Sciences, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic
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The Canadian Mineralogist (2015) 53 (6): 1035–1048.
Article history
received:
10 Nov 2014
accepted:
09 Sep 2015
first online:
17 Nov 2017
Citation
Milan NovÁk, Renata ČopjakovÁ, Marek Dosbaba, Michaela VAŠINOVÁ GaliovÁ, Dalibor VŠianskÝ, Josef StanĚk; Two Paragenetic Types of Cookeite from the DolnÍ Bory-hatĚ Pegmatites, Moldanubian Zone, Czech Republic: Proximal and Distal Alteration Products of Li-bearing Sekaninaite. The Canadian Mineralogist ; 53 (6): 1035–1048. doi: https://doi.org/10.3749/canmin.1400090
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Index Terms/Descriptors
- alkali metals
- almandine
- alteration
- andalusite
- annite
- carbonates
- Central Europe
- chlorite group
- clay minerals
- coexisting minerals
- cookeite
- Czech Republic
- diaspore
- electron probe data
- Europe
- formula
- garnet group
- granites
- ICP mass spectra
- igneous rocks
- ilmenite
- lithium
- mass spectra
- metals
- mica group
- Moldanubian
- nesosilicates
- nontronite
- orthosilicates
- oxides
- paragenesis
- pegmatite
- plutonic rocks
- pseudomorphism
- ring silicates
- schorl
- sheet silicates
- siderite
- silicates
- spectra
- tourmaline group
- sekaninaite
- Dolni Bory-Hate Pegmatite
Latitude & Longitude