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Pregled bibliografske jedinice broj: 631942

Inclusions and intergrowths in monazite-(Ce) and xenotime-(Y): Thermal behavior and relation to crystal-chemical properties


Tomašić, Nenad; Bermanec, Vladimir; Škoda, Radek; Šoufek, Marin; Čobić, Andrea
Inclusions and intergrowths in monazite-(Ce) and xenotime-(Y): Thermal behavior and relation to crystal-chemical properties // Contributions to the 6th International Symposium on Granitic Pegmatites / Simmons, William B. ; Webber, Karen L. ; Falster, Alexander U. ; Roda-Robles, Encarnacion ; Marquez-Zavalia, Maria-Florencia ; Galliski, Miguel Angel (ur.).
New Orleans: Rubellite Press, 2013. str. 142-143 (predavanje, međunarodna recenzija, sažetak, znanstveni)


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Naslov
Inclusions and intergrowths in monazite-(Ce) and xenotime-(Y): Thermal behavior and relation to crystal-chemical properties

Autori
Tomašić, Nenad ; Bermanec, Vladimir ; Škoda, Radek ; Šoufek, Marin ; Čobić, Andrea

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Contributions to the 6th International Symposium on Granitic Pegmatites / Simmons, William B. ; Webber, Karen L. ; Falster, Alexander U. ; Roda-Robles, Encarnacion ; Marquez-Zavalia, Maria-Florencia ; Galliski, Miguel Angel - New Orleans : Rubellite Press, 2013, 142-143

Skup
6th International Symposium on Granitic Pegmatites

Mjesto i datum
Bartlett NH, Sjedinjene Američke Države, 26.05.2013. - 31.05.2013

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
monazite; xenotime; inclusions; crystal-chemical properties

Sažetak
Inclusions and intergrowths in monazite and xenotime have proven to be of a great importance when mineral formation, metamictization induced by actinide content, and different metasomatic and metamorphic events are considered. Three monazite and a single xenotime sample were investigated for inclusions and intergrowths therein. Two of the monazite samples come from the Garta and Eptevann granite pegmatites in Aust-Agder province and the xenotime sample from the Eikeråsen (Eretveit) pegmatite (Norway). The third monazite sample was collected from the carbonatite dykes of Eureka Farm, Namibia, Chemical analyses (EMPA), X-ray powder diffraction (XRD), scanning electron microscope (SEM) employing backscatter electron (BSE) and energy dispersion (EDS) detector for crystal-chemical characterization of the host and inclusion/intergrowth minerals. To estimate thermal behavior of the host minerals and their inclusions at 1 atm, the minerals were heated (annealed) at 200, 500, 800 and 1000°C for 24 hours and examined by XRD afterwards. The EMPA gave monazite-(Ce) composition for all monazite samples, with Ce2O3 ranging from 22.69 to 34.53%, ThO2 ranging from 9.18 to 9.92% and UO2 ranging from 0.47 to 0.53%. An exception is monazite-(Ce) from Eureka Farm, being considerably depleted in ThO2 and UO2 (0.6 and 0.03%, respectively). The xenotime-(Y) sample contains 0.75% ThO2 and 1.15% UO2. BSE images of the pegmatite monazite samples revealed several types of inclusions such as altered monazite areas, an anhedral ThSiO4 phase and apatite inclusions. In many cases, ThSiO4 inclusions are surrounded by altered monazite with increased Y2O3 and UO2 content and slightly decreased SiO2 relative to unaltered monazite. Xenotime-(Y) also contains ThSiO4 inclusions, which are sometimes intergrown with uraninite. Zircon, mica and quartz are intergrown with xenotime. These obviously indicate a complex evolution of inclusion formation that would fit well into the proposed dissolution-reprecipitation model described for the inclusions in monazite and xenotime of the granite pegmatites in the Hidra anorthosite massif (Hetherington & Harlov, 2008). In monazite-(Ce) from the carbonatite dykes mainly cheralite inclusions occur. Sparse ThO2 euhedral inclusions also occur. Annealing experiments for all monazite and xenotime samples induced a slight decrease of unit cell volume ranging 0.66-0.76%. Measurements of crystallite size and strain for monazite from Eptevann and from Eureka Farm showed an increase of crystallite size and decrease of the strain with temperature increments. The crystallite size of unheated carbonatite monazite is by an order of magnitude larger compared to the pegmatite monazite. This can be attributed to very low actinide content in the sample from carbonatite, causing less intensive structure disturbances. The diffraction peak 200 was also used as a diagnostic feature of crystal structure adjustments during the annealing process. Full with at half (FWHM) and intensity of the maxima were determined by using pseudo-Voight function to fit the peak. Generally, for all the minerals the values decrease with increasing temperatures (Figure 2), while the intensity increases. An exception is xenotime-(Y) in which a phase with monazite-structure type crystallizes above 800°C, most probably huttonite. Inclusions of ThSiO4 in the unheated monazite and xenotime are most likely thorite, which is frequently metamictized (Seydoux-Guillaume et al., 2007). During annealing they recrystallize and occur as a discrete phase in xenotime. However, in the case of monazite, two scenarios are possible: either crystallization of huttonite and co-existence (overgrowth?)(Harlov et al., 2005) with monazite, that is disguised in powder diffraction patterns by peak overlapping of the two phases with the same structure type, or thermally induced incorporation of ThSiO4 into monazite. Previous experimental data showed preferable incorporation of ThSiO4 component into monazite relative to xenotime at the same temperature range but significantly higher pressures (Seydoux-Guillaume et al., 2002). Since the fate of the observed inclusions upon thermal treatment cannot be unambiguously concluded solely using diffraction techniques, the annealed samples must be examined using electron microscopy.

Izvorni jezik
Engleski

Znanstvena područja
Geologija



POVEZANOST RADA


Projekti:
119-0000000-1158 - Međudjelovanje minerala i okoliša (Bermanec, Vladimir, MZOS ) ( CroRIS)

Ustanove:
Prirodoslovno-matematički fakultet, Zagreb

Profili:

Avatar Url Marin Šoufek (autor)

Avatar Url Vladimir Bermanec (autor)

Avatar Url Andrea Čobić (autor)

Avatar Url Nenad Tomašić (autor)


Citiraj ovu publikaciju:

Tomašić, Nenad; Bermanec, Vladimir; Škoda, Radek; Šoufek, Marin; Čobić, Andrea
Inclusions and intergrowths in monazite-(Ce) and xenotime-(Y): Thermal behavior and relation to crystal-chemical properties // Contributions to the 6th International Symposium on Granitic Pegmatites / Simmons, William B. ; Webber, Karen L. ; Falster, Alexander U. ; Roda-Robles, Encarnacion ; Marquez-Zavalia, Maria-Florencia ; Galliski, Miguel Angel (ur.).
New Orleans: Rubellite Press, 2013. str. 142-143 (predavanje, međunarodna recenzija, sažetak, znanstveni)
Tomašić, N., Bermanec, V., Škoda, R., Šoufek, M. & Čobić, A. (2013) Inclusions and intergrowths in monazite-(Ce) and xenotime-(Y): Thermal behavior and relation to crystal-chemical properties. U: Simmons, W., Webber, K., Falster, A., Roda-Robles, E., Marquez-Zavalia, M. & Galliski, M. (ur.)Contributions to the 6th International Symposium on Granitic Pegmatites.
@article{article, author = {Toma\v{s}i\'{c}, Nenad and Bermanec, Vladimir and \v{S}koda, Radek and \v{S}oufek, Marin and \v{C}obi\'{c}, Andrea}, year = {2013}, pages = {142-143}, keywords = {monazite, xenotime, inclusions, crystal-chemical properties}, title = {Inclusions and intergrowths in monazite-(Ce) and xenotime-(Y): Thermal behavior and relation to crystal-chemical properties}, keyword = {monazite, xenotime, inclusions, crystal-chemical properties}, publisher = {Rubellite Press}, publisherplace = {Bartlett NH, Sjedinjene Ameri\v{c}ke Dr\v{z}ave} }
@article{article, author = {Toma\v{s}i\'{c}, Nenad and Bermanec, Vladimir and \v{S}koda, Radek and \v{S}oufek, Marin and \v{C}obi\'{c}, Andrea}, year = {2013}, pages = {142-143}, keywords = {monazite, xenotime, inclusions, crystal-chemical properties}, title = {Inclusions and intergrowths in monazite-(Ce) and xenotime-(Y): Thermal behavior and relation to crystal-chemical properties}, keyword = {monazite, xenotime, inclusions, crystal-chemical properties}, publisher = {Rubellite Press}, publisherplace = {Bartlett NH, Sjedinjene Ameri\v{c}ke Dr\v{z}ave} }




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