Structural controls on Neoproterozoic mineralization in the South Eastern Desert, Egypt: an integrated field, Landsat TM, and SIR-C/X SAR approach

The Arabian–Nubian Shield represents a complex amalgam of arcs and microcontinents assembled during Neoproterozoic closure of the Mozambique Ocean. The 750–720 Ma Allaqi suture is an arc/arc collision zone, formed when the Gerf terrane in the north overrode the circa 830–720 Ma Gabgaba terrane in the south, prior to closure of the Mozambique Ocean. Neoproterozoic rocks include ophiolitic ultramafic–mafic rocks, metasediments, intermediate metavolcanic rocks, intrusive gabbro-diorite rocks, granodiorites, biotite granites, and leucocratic granites. High-pressure/low-temperature metamorphism has been documented in rocks of the suture zone. Mineral deposits include nickel–copper–platinum and podiform chromite in ultramafic rocks, marble, gold-bearing quartz-veins in D2 and D3 shear zones, and radioactive mineralization associated with late leucocratic granitic rocks. Integrated field mapping and remote sensing techniques are used to distinguish and map the relationships between rock units, structures, and alteration zones associated with mineral deposits along the Allaqi suture of Egypt’s SE Desert. Landsat TM images processed using a band ratioing technique show different rock types remarkably well, and are able to distinguish between alteration zones associated with ultramafic rocks (listwaenites) and those associated with leucocratic granitic rocks (greisenization, silicification and albitization). Black and white L-band SIR-C/X SAR images outline foliations, faults and folds that control mineralization at several deposits in the area, whereas color composite multiband Chh-Lhh-Lhv SIR-C/X SAR images reveal some elliptical granitic bodies that host radioactive mineralization. E-trending, tight to isoclinal, gently dipping folds, thrust faults and subvertical shear zones related to the Allaqi suture are overprinted by N-oriented structures related to the Wadi Ungate shear zone, formed during collision of east and west Gondwana during closure of the Mozambique Ocean. The location of the Wadi Ungate shear zone in the Wadi Shellman area was previously unknown due to burial of basement rocks beneath thin dry sands. A new structural map was prepared using Landsat TM ratio images and SIR-C/X SAR imagery. SIR-C/X SAR data conveys considerably more information about rocks and structures beneath the thin sand cover than discernible from aerial photographs or Landsat TM images. 2002 Published by Elsevier Science Ltd.

[1]  R. Shackleton.  Review of Late Proterozoic sutures, ophiolitic mélanges and tectonics of eastern Egypt and north-east Sudan , 1994 .

[2]  H. B.,et al.  Mineral Deposits , 2018, Nature.

[3]  Robert J. Stern,et al.  Sutures and shear zones in the Arabian-Nubian Shield , 1996 .

[4]  M. J. Roobol,et al.  A late Proterozoic ophiolite complex at Jabal Ess in northern Saudi Arabia , 1979, Nature.

[5]  J. Stacey,et al.  U-Pb Isotopic evidence for the accretion of a continental microplate in the Zalm region of the Saudi Arabian Shield , 1985, Journal of the Geological Society.

[6]  G. Schubert,et al.  Phanerozoic addition rates to the continental crust and crustal growth , 1984 .

[7]  B. Storey.  Geodynamic Map of Gondwana Supercontinent Assembly Edited by Raphael Unrug Council for Geoscience, Pretoria, South Africa and Bureau de Recherches Géologiques et Minières, Orléans, France, (1996). 4 sheets. $50. , 1998, Antarctic Science.

[8]  K. C. Nielsen,et al.  Orientation of late Precambrian sutures in the Arabian-Nubian shield , 1990 .

[9]  Peter Copeland,et al.  The Neoproterozoic Keraf Suture in Ne Sudan: Sinistral Transpression Along the Eastern Margin of West Gondwana , 1998, The Journal of Geology.

[10]  W. Manton,et al.  Geochronology of the late Precambrian Hamisana shear zone, Red Sea Hills, Sudan and Egypt , 1989, Journal of the Geological Society.

[11]  C. G. Andre.  Evidence for Phanerozoic reactivation of the Najd fault system in AVHRR, TM, and SPOT images of central Arabia , 1989 .

[12]  T. Harrison,et al.  The tectonic evolution of Asia , 1996 .

[13]  Rushdi Said.  The Geology Of Egypt , 1962 .

[14]  I. Dalziel.  On the organization of American plates in the Neoproterozoic and the breakout of Laurentia , 1992 .

[15]  J. R. Vail.  Pan-African (late Precambrian) tectonic terrains and the reconstruction of the Arabian-Nubian Shield , 1985 .

[16]  M. Timothy,et al.  Neoproterozoic dextral faulting on the Najd fault system, Saudi Arabia, preceded sinistral faulting and escape tectonics related to closure of the Mozambique ocean , 1999 .

[17]  T. Ramadan,et al.  Mapping Gold-Bearing Massive Sulfide Deposits in the Neoproterozoic Allaqi Suture, Southeast Egypt with Landsat TM and SIR-C/X SAR Images , 2001 .

[18]  A. Ries,et al.  The Late Proterozoic ophiolite of Sol Hamed, NE Sudan , 1983 .

[19]  Alexander F. H. Goetz,et al.  Discrimination of rock types and detection of hydrothermally altered areas in south-central Nevada by the use of computer-enhanced ERTS images , 1974 .

[20]  Michael Abrams,et al.  Remote sensing for porphyry copper deposits in southern Arizona , 1983 .

[21]  Raymond E. Arvidson,et al.  Mapping of serpentinites in the Eastern Desert of Egypt by using Landsat thematic mapper data , 1986 .

[22]  S. Berhe.  Ophiolites in Northeast and East Africa: implications for Proterozoic crustal growth , 1990, Journal of the Geological Society.

[23]  H. Blodget,et al.  Geological mapping by use of computer-enhanced imagery in western Saudi Arabia , 1982 .

[24]  R. Greiling,et al.  A structural synthesis of the Proterozoic Arabian-Nubian Shield in Egypt , 1994 .

[25]  R. Stern.  ARC Assembly and Continental Collision in the Neoproterozoic East African Orogen: Implications for the Consolidation of Gondwanaland , 1994 .

[26]  J. R. Vail.  Pan-African crustal accretion in north-east Africa , 1983 .

[27]  M. Abdelsalam.  The Oko Shear Zone, Sudan: post-accretionary deformation in the Arabian-Nubian Shield , 1994, Journal of the Geological Society.

[28]  Raymond E. Arvidson,et al.  Extension of the Najd Shear System from Saudi Arabia to the central eastern desert of Egypt based on integrated field and LANDSAT observations , 1988 .

[29]  I. M. Hussein,et al.  Wadi Onib: A dismembered Pan-African ophiolite in the Red Sea Hills of the Sudan , 1982 .

[30]  Said A. El-Nisr.  Late precambrian volcanism at Wadi Allaqi, south Eastern Desert, Egypt: evidence for transitional continental arc/margin environment , 1997 .

[31]  A. Sengor.  Paleotectonics of Asia : fragments of a synthesis. , 1996 .

[32]  I. G. Gass,et al.  Jabal al Wask, northwest Saudi Arabia: An Eocambrian back-arc ophiolite , 1976 .

[33]  D. Stoeser,et al.  Pan-African microplate accretion of the Arabian Shield , 1985 .

[34]  M. Sultan,et al.  Atmur-Delgo suture: A Neoproterozoic oceanic basin extending into the interior of northeast Africa , 1994 .

[35]  T. Kusky,et al.  Evolution of the East African and related orogens, and the assembly of Gondwana , 2003 .

[36]  P. Townsend.  Principles and Applications of Imaging Radar: Manual of Remote Sensing , 2000 .