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1

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

Nicoli Gautier, Gresky Kerstin, Ferrero Silvio

Mineralogia

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2022

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Vol. 53, iss. 1

1--9

EN

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.

2

Magmatic and post-magmatic phenomena in the Karkonosze granite and its metamorphic envelope (West Sudetes, SW Poland)

Kozłowski A., Ilnicki S., Matyszczak W., Marcinowska A.

Acta Geologica Polonica

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2016

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Vol. 66, no. 3

451--471

EN

Mineralogical studies of the Karkonosze granite (ca. 322–312 Ma) and its surroundings in West Sudetes (SW Poland) have provided data on Nb-Ta-REE minerals from pegmatites in the NE part of the pluton and several new finds of Ag minerals and 15 oxygenic Bi phases, hitherto not reported from the massif. The Karkonosze pegmatites are enriched in HREE as fergusonite-(Y) or xenotime-(Y) appear in almost every studied pegmatite, together with a subordinate assemblage of the aeschynite, euxenite or columbite group. The abundance of LREE minerals such as allanite-(Ce) and the monazite group, correlates inversely with the Nb-Ta-Ti minerals, whilst an early generation of monazite-(Ce) revealed an exceptionally high amount of Nd (up to 22 wt.% of Nd2O3). The physical and chemical conditions during the magmatic and post-magmatic processes were reconstructed and the effects of contact metamorphism in amphibolites from hornfelsed zones examined. Changes in solution composition and concentration at the early magmatic stage (825–920ºC), pegmatitic stage overlapping with hydrothermal (560°C which ended at 160–90°C) and clearly hydrothermal stage (400 to 110°C) were studied in detail by means of melt and fluid inclusions in quartz. Furthermore, post-magmatic fluids, including some enriched in Li and B, were identified in rock-forming quartz from the whole pluton. In turn, study of the amphibolites indicates that the pair cummingtonite + anorthite or the presence of Ca-rich plagioclase with actinolite seem to be reliable mineral proxies of the thermal impact of the granitoid body on amphibolites in its envelope. The inferred conditions of the contact processes (450–550°C, 2.5–4.8 kbar) point to an elevated geothermal gradient (ca. 32–45°C/km) probably reflecting the heat flow induced by the Karkonosze intrusion. Moreover, despite the textural and mineral changes imposed by regional and contact metamorphism, the amphibolites have their pre-metamorphic (magmatic) geochemical features undisturbed.

3

Phosphate and silicate inclusions in apatite and pyroxene from the Precambrian nelsonite and jotunite of NE Poland

Kozłowska A., Wiszniewska J.

Archiwum Mineralogiczne

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2001

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T. 54

5-21

EN

Melt inclusions were investigated in apatite from nelsonite from the Suwałki anor-thosite massif and in pyroxene from the Fe–Ti–P-rich monzodiorite (jotunite) from the Sejny massif, both of Proterozoic age and occurring within the ranges of the Mazury crystalline complex in NE Poland. The melt inclusions in apatite were filled by an agg-regate of pyroxene, apatite, calcite, plagioclase, biotite, halite, sylvite, ore mineral plus aqueous solution and gas bubble. At 880oC in the inclusions two melts: silicate and phosphate one, were observed which neither homogenized nor changed their propor-tions up to 1080oC. This indicated the formation of nelsonite from the melt composed of two immiscible phases. Inclusions in pyroxene from jotunite were filled by pyroxene, feldspar, apatite, carbonate and ore mineral with gas bubble. Their homogenization tem-peratures were from 1090 to 1180oC; at 1000 to 1030oC in silicate melt small droplets of carbonate and phosphate melt were visible, homogenizing subsequently in one melt phase. The behaviour of the two melts in the studied inclusions may indicate a genetic affinity of nelsonite with monzodioritic rocks.

4

Perovskite from the Międzyrzecze sill near Bielsko-Biała in the Polish Carpathians (the type area of the teschenite association)

Włodyka R., Karwowski Ł.

Archiwum Mineralogiczne

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2000

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T. 53, z. 1-2

109-131

EN

For the first time perovskite has been observed in the western part of the Polish Flysch Carpathians, in the olivine glimmerite sill of the Bielsko-Biala vicinity. Perovskite and titaniferous magnetite belong to the latest minerals, filling the interstices between diopside and phlogopite. Detailed investigations: chemical and thermal analysis, X-ray diffraction as well as infrared and gamma spectroscopy, indicated that the studied perovskite is almost pure CaTiO3 (perovskite sensu stricto) containing only 2.60 to 4.20 wt. % REE2O3, 2.40 to 3.60 wt. % Nb2O5, 0.40 to 1.20 wt. % Fe2O3 and 0.80 to 1.10 wt. % Na2O. The unit cell parameters and tilt angle of the (Ti,Nb,Fe)O6 octahedra are very similar to those typical of the perovskite specimens from other alkaline ultrabasic complexes. Total homogenization of several melt inclusions was achieved at about 1000°C; trapped phases (probably pyrrhotite or chalcopyrite) did not dissolve in the melt inclusion filling. The observed formation of titanite or titaniferous garnets replacing perovskite was controlled by a low leach rate of calcium from perovskite structure and a high activity of SiO2 in hydrothermal fluids. The leaching of Nb and LREE elements, stimulated by perovskite fracturing, was caused by CO2-bearing fluids.

PL

W sillu glimmerytu oliwinowego w Międzyrzeczu Górnym koło Bielska-Białej stwierdzono występowanie perowskitu, wypełniającego interstycja pomiędzy diopsydem i flogopitem. Minerał ten, wspólnie z magnetytem należy do ostatnich faz krystalizujących z niedosyconego krzemionką stopu magmowego. Badany perowskit poddano analizie chemicznej, badaniom metodami rentgenostrukturalnymi, spektroskopii absorbcyjnej w podczerwieni oraz badaniom termicznym. Zarejestrowano ponadto widmo jego promieniowania oraz oznaczono temperatury homogenizacji inkluzji. Stwierdzono tylko niewielkie wahania w składzie chemicznym badanego perowskitu; skład ten pozwala zaliczyć rozważany minerał do grupy perowskitów sensu stricto (CaTiO3). Do głównych jego domieszek należą lekkie ziemie rzadkie grupy cerowej, niob, żelazo oraz sód. Oznaczony skład chemiczny perowskitu z Międzyrzecza, parametry jego komórki elementarnej, jak również kąty dystorsji oktaedru nie odbiegają swymi wartościami od analogicznych oznaczeń dla perowskitów z innych alkalicznych kompleksów ultrazasadowych. Oznaczone temperatury homogenizacji inkluzji stopu wynoszą około 1000 C. Badany perowskit jest minerałem nietrwałym w środowisku działania roztworów hydrotermalnych. Fluidy wzbogacone w CO2 powodowały ługowanie lekkich ziem rzadkich grupy cerowej z jego struktury, zaś roztwory wzbogacone w SiO2 oraz pozbawione dwutlenku węgla powodowały transformację perowskitu w tytanit lub aranaty z szeregu andradyt-melanit-schorlomit.