Geochemistry, Nd isotopes and U-Pb SHRIMP zircon dating of Neoproterozoic volcanic rocks from the Central Eastern Desert of Egypt: New insights into the ∼750 Ma crust-forming event

被引:162
作者
Ali, Kamal A. [1 ]
Stern, Robert J. [1 ]
Manton, William I. [1 ]
Kimura, Jun-Ichi [2 ]
Khamees, Hossam A. [3 ]
机构
[1] Univ Texas Dallas, Dept Geosci, Richardson, TX 75080 USA
[2] Shimane Univ, Dept Geosci, Matsue, Shimane 6908504, Japan
[3] Nucl Mat Author, El Maadi, Kattamyia, Egypt
基金
美国国家科学基金会;
关键词
Arabian-Nubian Shield; Neoproterozoic; SHRIMP dating; Nd isotopes; Metavolcanics; ARABIAN-NUBIAN SHIELD; AFRICAN OROGEN; SHEAR SYSTEM; EVOLUTION; OPHIOLITES; COMPLEX; PETROGENESIS; CLASSIFICATION; GRANITOIDS; BASEMENT;
D O I
10.1016/j.precamres.2009.03.002
中图分类号
P [天文学、地球科学];
学科分类号
07 ;
摘要
Submarine tholeiitic and calc-alkaline basalt and andesite with subordinate dacite, metamorphosed to greenschist facies, are exposed at Wadi Kareim and Wadi El Dabbah, Central Eastern Desert of Egypt. These metavolcanic sequences are representative of early stages of Neoproterozoic crust formation in the northern part of the Arabian-Nubian Shield. The magmas were primitive to moderately fractionated, as indicated by average Mg# (54), Cr (191 ppm) and Ni (69 ppm). Their REE patterns are slightly fractionated [(La/Yb)(N) = 1.3-3.9], and multi-element diagrams show Ba, Sr, K and Rb enrichments and Nb and Ta depletions, typical of modern convergent margin igneous rocks. Tectonic discrimination diagrams also show affinities with modern convergent margin magmas, suggesting that Wadi El Dabbah lavas formed in a volcanic arc that experienced cryptic crustal contamination, whereas Wadi Kareim lavas formed in a back-arc basin. Positive initial epsilon Nd (+5.1 to +8.9) and Nd model ages (0.64-0.79 Ga) indicate that the crust is juvenile and was extracted from a depleted mantle source. Wadis Kareim and El Dabbah metavolcanic rocks are dated at similar to 750 Ma (U-Pb SHRIMP) but contain abundant pre-Neoproterozoic zircons which might be derived from underlying sediments or perhaps older continental crust. These results indicate that a major similar to 750 Ma crust-forming event involving ophiolite generation and eruption of juvenile melts was important for the formation of the crust. (c) 2009 Elsevier B.V. All rights reserved.
引用
收藏
页码:1 / 22
页数:22
相关论文
共 65 条
  • [1] Origin of the Wadi Haimur-Abu Swayel gneiss belt, south Eastern Desert, Egypt: petrological and geochronological constraints
    Abd El-Naby, HH
    Frisch, W
    [J]. PRECAMBRIAN RESEARCH, 2002, 113 (3-4) : 307 - 322
  • [2] Abdel-Monem A.A., 1979, B I APPL GEOLOGY KIN, V3, P165
  • [3] Agar R. A., 1992, Open File Report DGMR-OF-10-15
  • [4] ALI KA, INT J EARTH SCI, DOI DOI 10.1007/S0051-009-0427-3
  • [5] Andresen A, 2009, INT J EARTH SCI, V98, P481, DOI [10.1007/s00531-007-0276-x, 10.1007/s00531-007-027]
  • [6] TEMORA 1: a new zircon standard for Phanerozoic U-Pb geochronology
    Black, LP
    Kamo, SL
    Allen, CM
    Aleinikoff, JN
    Davis, DW
    Korsch, RJ
    Foudoulis, C
    [J]. CHEMICAL GEOLOGY, 2003, 200 (1-2) : 155 - 170
  • [7] A late Neoproterozoic magmatic core complex in the Eastern Desert of Egypt: emplacement of granitoids in a wrench-tectonic setting
    Breger, M
    Bauernhofer, A
    Pelz, K
    Kloetzli, U
    Fritz, H
    Neumayr, P
    [J]. PRECAMBRIAN RESEARCH, 2002, 118 (1-2) : 59 - 82
  • [8] Compston W., 1984, Journal of Geophysical Research, V89, P525, DOI 10.1029/JB089iS02p0B525
  • [9] Atlas of zircon textures
    Corfu, F
    Hanchar, JM
    Hoskin, PWO
    Kinny, P
    [J]. ZIRCON, 2003, 53 : 469 - 500
  • [10] NEODYMIUM ISOTOPES IN THE COLORADO FRONT RANGE AND CRUST-MANTLE EVOLUTION IN THE PROTEROZOIC
    DEPAOLO, DJ
    [J]. NATURE, 1981, 291 (5812) : 193 - 196