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Britholite-(Ce) from the metaluminous granite of SW Egypt

Kamaleldin M. Hassan
Kamaleldin M. Hassan
   | 06 abr 2023
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Article Category: Letter
Publicado en línea: 06 abr 2023
Páginas: 11 - 17
Recibido: 12 dic 2022
Aceptado: 20 feb 2023
DOI: https://doi.org/10.2478/mipo-2023-0002
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© 2023 Kamaleldin M. Hassan, published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.

Figure 1

Geological map of southwestern Egypt (modified from EGSMA 1981). The region is a hyperarid desert with maximum daily temperatures ranging from 16°C during December to 48°C in June and rains occurring rarely.
Geological map of southwestern Egypt (modified from EGSMA 1981). The region is a hyperarid desert with maximum daily temperatures ranging from 16°C during December to 48°C in June and rains occurring rarely.

Figure 2

Photomicrographs of samples GR1 and GR2. (A) Image of a britholite prism, taken under XPL. (B) Image of a platy tabular crystal of britholite, taken under XPL. (C-D) Images of a euhedral tabular britholite, taken under PPL and XPL, showing center zonation and a resobed border. (E-F) Images of another euheral britholite, taken under PPL and XPL, showing rims around a core. Mineral abbreviations are: Bt—biotite; Bri—britholite; Mgt—magnetite; Mc—microcline; Pl—plagioclase; Qtz—quartz; Ser—sericite; Zrn—zircon; Ttn—titanite.
Photomicrographs of samples GR1 and GR2. (A) Image of a britholite prism, taken under XPL. (B) Image of a platy tabular crystal of britholite, taken under XPL. (C-D) Images of a euhedral tabular britholite, taken under PPL and XPL, showing center zonation and a resobed border. (E-F) Images of another euheral britholite, taken under PPL and XPL, showing rims around a core. Mineral abbreviations are: Bt—biotite; Bri—britholite; Mgt—magnetite; Mc—microcline; Pl—plagioclase; Qtz—quartz; Ser—sericite; Zrn—zircon; Ttn—titanite.

Figure 3

BSE images of REE grains from samples GR1 and GR2. (A) BSE image of the britholite depicted in Fig. 2E, displaying compositional zoning. (B) BSE image of another britholite crystal. In (A) and (B) the dotted red lines partially mark the original crystal outline. (C-D) BSE images of britholite grains with different levels of brightness and, hence, different chemical composition. (E-F) BSE images of britholite partially changed to REE-rich silicate.
BSE images of REE grains from samples GR1 and GR2. (A) BSE image of the britholite depicted in Fig. 2E, displaying compositional zoning. (B) BSE image of another britholite crystal. In (A) and (B) the dotted red lines partially mark the original crystal outline. (C-D) BSE images of britholite grains with different levels of brightness and, hence, different chemical composition. (E-F) BSE images of britholite partially changed to REE-rich silicate.

Figure 4

Compositions of the analyzed britholite samples in the cationic diagrams (A) P + M2+ versus Si + REE and (B) M2+ + Th + U versus 2REE (n = number of samples; R2, coefficient of determination). The ideal apatite and britholite-(Ce) endmembers are plotted as stars. Symbols: filled rectangular, Vilalva et al. 2013; open triangular, Nash 1972; open rectangular, Orlandi et al. 1989; open circular, Mulluso et al. 2012; filled circulars, Kudrina et al. 1961; filled triangular, this work.
Compositions of the analyzed britholite samples in the cationic diagrams (A) P + M2+ versus Si + REE and (B) M2+ + Th + U versus 2REE (n = number of samples; R2, coefficient of determination). The ideal apatite and britholite-(Ce) endmembers are plotted as stars. Symbols: filled rectangular, Vilalva et al. 2013; open triangular, Nash 1972; open rectangular, Orlandi et al. 1989; open circular, Mulluso et al. 2012; filled circulars, Kudrina et al. 1961; filled triangular, this work.

Figure 5

Modal data of the samples GR1 and GR2 plotted on the IUGS quartz-alkaline feldspar-plagioclase diagram of the plutonic rocks.
Modal data of the samples GR1 and GR2 plotted on the IUGS quartz-alkaline feldspar-plagioclase diagram of the plutonic rocks.

SEM-EDS analyses (wt%) of duplicate mineral spots (A and B) from GR1 and GR2; BDL—below detecton limit.

A B ± 1σ % Errors
Britholite
SiO2 17.10 15.90 0.60 3.64
ThO 7.00 8.34 0.54 8.73
UO2 BDL BDL
ZrO BDL BDL
Al2O3 7.90 6.82 0.54 7.34
La2O3 13.30 15.10 0.90 6.34
Ce2O3 24.70 26.70 1.00 3.89
Pr2O3 2.20 1.94 0.13 6.28
Nd2O3 5.00 5.15 0.07 1.48
Sm2O3 BDL BDL
Gd2O3 BDL BDL
FeO 8.00 7.58 0.21 2.69
Cr2O3 BDL BDL
MgO 4.30 3.12 0.59 16.0
CaO 5.90 6.50 0.30 4.80
Na2O 1.24 0.65 0.30 31.22
K2O 0.53 0.80 0.13 20.30
P2O5 BDL BDL
SO3 0.27 0.20 0.03 14.89
F 2.51 1.07 0.72 40.28
Total 99.95 99.87
Magnetite
SiO2 2.40 2.40 0.00 0.00
Al2O3 0.60 0.80 0.10 14.28
FeO 93.80 94.70 0.45 0.48
Cr2O3 1.14 0.74 0.20 21.28
MgO 0.30 0.40 0.05 14.29
Na2O 0.70 1.00 0.15 17.65
Total 98.94 100.04
Zircon
SiO2 29.80 28.30 0.75 2.58
ZrO 68.10 67.80 0.15 0.22
Al2O3 0.30 0.30 0.00 0.00
FeO 0.70 1.30 0.30 30.00
CaO 0.60 0.30 0.30 33.33
Na2O 0.50 0.90 0.20 28.57
Total 100.0 98.90
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