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Thorite inclusions in zircon of the monzogranite, Lower Nubia, SW Egypt

Kamaleldin M. Hassan
Kamaleldin M. Hassan
 und 
Irena Brunarska
Irena Brunarska
   | 19. Dez. 2023
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Article Category: Original Paper
Online veröffentlicht: 19. Dez. 2023
Seitenbereich: 69 - 77
Eingereicht: 15. Sept. 2023
Akzeptiert: 22. Nov. 2023
DOI: https://doi.org/10.2478/mipo-2023-0007
Schlüsselwörter
© 2023 Kamaleldin M. Hassan et al., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.

Figure 1.

Geological map of south-western Egypt (Revised from GSMA 1981).
Geological map of south-western Egypt (Revised from GSMA 1981).

Figure 2.

Optical microscope images of the Lower Nubian monzogranite. (A) Image in cross-polarized light showing a gneissose texture—the segregation of felsic (feldspars and quartz) and mafic minerals (biotite and its alteration product clinochlore). (B) Image in plane-polarized light showing numerous grains of zircon widely distributed throughout the thin section. (C) Image in cross-polarized light for radioactive halos or pleochroic halos (burnt mark) around zircon enclosed in biotite and having a cloudy altered appearance. Mineral abbreviations in alphabetical order: Bt—biotite, Br-(Ce)—britholite-cerium, Ccl—clinochlore, Mc—microcline, Pl— plagioclase, Qtz—quartz, Ser—sercite, Ttn—titanite, Zrc—zircon.
Optical microscope images of the Lower Nubian monzogranite. (A) Image in cross-polarized light showing a gneissose texture—the segregation of felsic (feldspars and quartz) and mafic minerals (biotite and its alteration product clinochlore). (B) Image in plane-polarized light showing numerous grains of zircon widely distributed throughout the thin section. (C) Image in cross-polarized light for radioactive halos or pleochroic halos (burnt mark) around zircon enclosed in biotite and having a cloudy altered appearance. Mineral abbreviations in alphabetical order: Bt—biotite, Br-(Ce)—britholite-cerium, Ccl—clinochlore, Mc—microcline, Pl— plagioclase, Qtz—quartz, Ser—sercite, Ttn—titanite, Zrc—zircon.

Figure 3.

BSE images of zircon grains in the studied samples: (A) Elbow-shaped zircon twin showing corrosion embayment on the right side of the grain. (B) Stubby zircon prism with one pyramidal termination and having vertical fractures and broken parts. (C) Corroded zircon prism, with weakly-rounded edges.
BSE images of zircon grains in the studied samples: (A) Elbow-shaped zircon twin showing corrosion embayment on the right side of the grain. (B) Stubby zircon prism with one pyramidal termination and having vertical fractures and broken parts. (C) Corroded zircon prism, with weakly-rounded edges.

Figure 4.

BSE images of zircon grains in the studied samples showing small micro-inclusions of thorite (white areas). (A) Pentagonal cone-shaped grain showing corrosion embayment on the upper left side of the grain. (B) Grain with slightly rounded edges. (C) Euhedral grain with unequally developed bipyramids, showing grooves and eroded surfaces.
BSE images of zircon grains in the studied samples showing small micro-inclusions of thorite (white areas). (A) Pentagonal cone-shaped grain showing corrosion embayment on the upper left side of the grain. (B) Grain with slightly rounded edges. (C) Euhedral grain with unequally developed bipyramids, showing grooves and eroded surfaces.

Figure 5.

BSE images of zircon grains in the studied samples containing larger micro-inclusions of thorite (white areas). (A) Heptagonal shape grain. (B) Another heptagonal grain slightly rounded edges, and corrosion embayment on the upper side of the grain.
BSE images of zircon grains in the studied samples containing larger micro-inclusions of thorite (white areas). (A) Heptagonal shape grain. (B) Another heptagonal grain slightly rounded edges, and corrosion embayment on the upper side of the grain.

Representative SEM-EDS analyses (wt %, above) and corresponding structural formulae [4 (O) apfu, below] for zircon and its thorite inclusions from the Nubian monzogranite.

Primary magmatic zircon Smaller thorite inclusions Larger thorite inclusions
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
SiO2 29.06 29.47 29.53 29.81 30.42 29.85 31.59 29.77 28.52 31.17 30.24 24.71 26.08 19.12 25.32 22.81
ThO2 BDL BDL BDL BDL BDL BDL BDL 3.12 6.61 3.71 11.56 47.97 65.98 53.18 67.02 48.69
UO2 BDL 0.45 0.29 BDL BDL BDL 0.89 BDL BDL BDL BDL 14.08 BDL 15.15 BDL 11.85
AI2O3 0.46 BDL BDL BDL BDL 0.64 BDL 0.21 BDL 1.55 1.89 1.82 1.30 0.72 1.33 1.29
Ce2O3 BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL 1.70 BDL BDL BDL 1.91
Nd2O3 BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL 1.57 BDL BDL BDL 1.61
Fe2O3 0.75 BDL 0.27 BDL 0.28 0.33 0.64 BDL 0.63 0.89 1.07 BDL BDL BDL BDL BDL
ZrO2 67.31 69.48 69.19 68.12 69.92 66.35 65.66 65.15 63.29 59.58 50.13 5.66 5.70 9.66 1.94 10.04
HfO2 1.57 BDL BDL 1.15 BDL 1.17 BDL BDL BDL BDL 1.44 BDL BDL BDL BDL BDL
MgO 0.15 BDL BDL BDL BDL BDL 0.21 BDL BDL 0.16 BDL BDL BDL BDL BDL BDL
CaO BDL BDL BDL 0.40 BDL 0.73 0.27 0.92 0.57 1.19 1.38 1.59 BDL 1.38 3.05 1.19
Na2O 0.41 0.29 0.46 BDL 0.39 0.59 0.50 0.83 0.38 0.72 1.21 0.90 0.94 0.80 1.33 0.61
K20 0.26 0.30 0.25 0.52 BDL 0.34 0.24 BDL BDL 1.02 1.08 BDL BDL BDL BDL BDL
Total 99.97 99.99 99.99 100.00 101.1 100.00 100.00 100.00 100.00 99.99 100.00 100.00 100.00 100.01 99.99 100.00
Si 0.93 0.92 0.90 0.94 0.94 0.93 0.97 0.94 0.92 0.97 0.99 1.10 1.15 0.94 1.13 1.07
Th - - - - - - - 0.02 0.05 0.02 0.08 0.48 0.66 0.59 0.68 0.52
U - 0.00 0.00 - - - 0.01 - - - - 0.13 - 0.16 - 0.13
Al 0.04 - - - - 0.05 - 0.02 - 0.13 0.16 0.09 0.15 0.09 0.07 0.16
Ce - - - - - - - - - - - 0.03 - - - 0.07
Nd - - - - - - - - - - - 0.02 - - - 0.06
Fe 0.01 - 0.01 - 0.01 0.02 0.03 - 0.06 0.07 0.06 - - - - -
Zr 1.04 1.06 1.06 1.04 1.05 1.01 0.99 1.01 1.00 0.90 0.79 0.12 0.12 0.23 0.04 0.22
Hf 0.01 - - 0.01 - 0.01 - - - - 0.01 - - - - -
Mg 0.01 - - - - - 0.01 - - 0.00 - - - - - -
Ca - - - 0.01 - 0.02 0.01 0.03 0.02 0.02 0.04 0.08 - 0.07 0.13 0.06
Na 0.03 0.02 0.03 - 0.02 0.04 0.03 0.04 0.02 0.04 0.08 0.05 0.08 0.05 0.11 0.05
K 0.01 0.01 0.01 0.02 - 0.01 0.01 - - 0.01 0.04 - - - - -
Sum 2.08 2.01 2.01 2.02 2.02 2.09 2.06 2.06 2.07 2.16 2.25 2.10 2.16 2.13 2.16 2.34
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