干旱区生态环境知识资源中心(Arid): Mineralogy and geochemistry of Nb-, Ta-, Sn-, U-, Th-, and Zr-bearing granitic rocks from Abu Rusheid shear zones, South Eastern Desert, Egypt

Arid

DOI	10.1007/s11631-011-0505-7
	Mineralogy and geochemistry of Nb-, Ta-, Sn-, U-, Th-, and Zr-bearing granitic rocks from Abu Rusheid shear zones, South Eastern Desert, Egypt
	Ali, M. A.; Lentz, D. R.; Hall, D. C.
通讯作者	Ali, MA
来源期刊	ACTA GEOCHIMICA
ISSN	2096-0956
EISSN	2365-7499
出版年	2011
卷号	30 期号:2 页码:226-247
英文摘要	Granite-hosted, Nb- ,Ta-, Sn-, U-, Th-, and Zr (Hf)-bearing mineralization from the Abu Rusheid shear zones occurs about 97 km southwest of the town of Marsa Alam, South Eastern Desert, Egypt. The SSE-trending brittle-ductile Abu Rusheid shear zones crosscut the peralkalic granitic gneisses and cataclastic to mylonitic rocks (mylonite, protomlyonite, and ultramylonite). The northern shear zone varies in width from 1 to 3 m with a strike length of >500 m, and the southern shear zone is 0.5 to 8 m wide and >1 km long. These shear zones locally host less altered lamprophyre and locally sheared granitic aplite-pegmatite dykes. The rare-metal minerals, identified from the peralkalic granitic gneisses and cataclastic to mylonitic rocks are associated with muscovite, chlorite, quartz, fluorite, pyrite, magnetite, and rare biotite that are restricted to the Abu Rusheid shear zones; these are columbite-tantalite and pyrochlore (var. betafite) in the northern shear zone and ferrocolumbite in the southern shear zone. Cassiterite occurs as inclusions in the columbite-tantalite minerals. U- and Th- minerals (uraninite, thorite, uranothorite, ishikawaite, and cheralite) and Hf-rich zircon coexist. Magmatic (?) zircon contains numerous inclusions of rutile, fluorite, U-Th and REE minerals, such as uranothorite, cheralite, monazite, and xenotime. Compositional variations in Ta/(Ta+Nb) and Mn/(Mn+Fe) in columbite range from 0.07-0.42 and 0.04-0.33, respectively, and Hf contents in zircon from 1.92-6.46 of the two mineralized shear zones reflect the extreme degree of magmatic fractionation. Four samples of peralkalic granitic gneisses and cataclastic to mylonitic rocks from the southern shear zone have very low TiO2(0.02 wt%-0.04 wt%), Sr [(15-20)x10(-6)], and Ba [(47-78)x10(-6)], with high Fe2O3T (0.94 wt%-1.99 wt%), CaO (0.14 wt%-1.16 wt%), alkalis (9.2 wt%-10.1 wt%), Rb [(369-805)x10(-6)], Zr [(1033-2261)x10(-6)], Nb [(371-913)x10(-6)], U [(51-108)x10(-6)], Th [(36-110)x10(-6)], Ta [(38-108)x10(-6)], Pb [(39-364) x10(-6)], Zn [(21-424)x10(-6)], Y [(8-304)x10(-6)], Hf [(29-157)x10(-6)], and SREE [(64-304)x10(-6)], especially HREE [(46-167)x10(-6)]. Three samples from the northern shear zone also have very low TiO2 (0.03 wt%), Sr [(11-16)x10(-6)], and Ba [(38-47)x10(-6)], with high Fe2O3T (1.97 wt%-2.91 wt%), CaO (0.49 wt%-1.01 wt%), alkalis (7.2 wt%-8.3 wt%), Rb [(932-978)x10(-6)], Zr [(1707-1953)x10(-6)], Nb [(853-981)x10(-6)], Ta [(100-112)x10(-6)], U [(120-752)x10(-6)], Th [(121-164) x10(-6)], Pb [(260-2198)x10(-6)], Zn [(483-1140)x10(-6)], Y [(8-304)x10(-6)], Hf [(67-106)x10(-6)], and SREE [(110-231) x10(-6)], especially HREE [(91-177) x10 (-6)]. The very high Rb/Sr (57.5-88.9), and low Zr/Hf (16.9-25.6), Nb/Ta (7.7-9.8), and Th/U (0.21-1.01) are consistent with very fractionated fluorine-bearing granitic rocks that were altered and sheared. The field evidence, textural relations, and compositions of the ore minerals suggest that the main mineralizing event was magmatic (629+/-5 Ma, CHIME monazite), with later hydrothermal alteration and local remobilization of the high-field-strength elements.
英文关键词	uranium thorium zircon columbite-tantalite fluorite monazite xenotime age dating granitic gneisses South Eastern Desert Egypt
类型	Article
语种	英语
收录类别	ESCI
WOS记录号	WOS:000218326800010
WOS关键词	ELECTRON-MICROPROBE ; SAMARSKITE-GROUP ; URANIUM ; COMPLEX ; RICH ; MINERALIZATION ; ISHIKAWAITE ; MONAZITES ; ELEMENTS ; THORIUM
WOS类目	Geochemistry & Geophysics
WOS研究方向	Geochemistry & Geophysics
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/329740
作者单位	[Ali, M. A.] Nucl Mat Author, PO 530, Cairo, Egypt; [Lentz, D. R.] New Brunswick Univ, Dept Geol, UNB, St John, NB, Canada; [Hall, D. C.] New Brunswick Univ, Microscopy & Microanal Facil, UNB, St John, NB, Canada
推荐引用方式 GB/T 7714	Ali, M. A.,Lentz, D. R.,Hall, D. C.. Mineralogy and geochemistry of Nb-, Ta-, Sn-, U-, Th-, and Zr-bearing granitic rocks from Abu Rusheid shear zones, South Eastern Desert, Egypt[J],2011,30(2):226-247.
APA	Ali, M. A.,Lentz, D. R.,&Hall, D. C..(2011).Mineralogy and geochemistry of Nb-, Ta-, Sn-, U-, Th-, and Zr-bearing granitic rocks from Abu Rusheid shear zones, South Eastern Desert, Egypt.ACTA GEOCHIMICA,30(2),226-247.
MLA	Ali, M. A.,et al."Mineralogy and geochemistry of Nb-, Ta-, Sn-, U-, Th-, and Zr-bearing granitic rocks from Abu Rusheid shear zones, South Eastern Desert, Egypt".ACTA GEOCHIMICA 30.2(2011):226-247.