Multiscale geological mapping using multispectral data. The Jabali (Yemen) case study
Jean Paul DEROIN(1), Ismail AL GANAD(2), Paul BENOIT(3), Florian TEREYGEOL(4) and Jürgen HECKES(5)
(1) Université Paris-Est, 5 boulevard Descartes, 77454 Marne la Vallée, France
(2) Geological Survey and Mineral Resources Board, AL Tharir, Sana'a, Yemen
(3) Université Paris 1, Centre Malher, 75004 Paris, France
(4) CEA - UMR IRAMAT, CEA, 91 Saclay, France
(5) Deutsches Bergbau-Museum, Deutsches Bergbau-Museum, Bochum, Germany
The test site is located between Sana’a and Ma’rib in the North-Western part of Yemen, a desert country at the southern edge of the Arabian Peninsula. Close to the contact with the basement, the carbonate platform contains Zn-Pb-Ag mineralizations at Jabali. During the pre-Islamic period and until the 14th century AD, the Jabali area was mined for silver. From 2004 onwards, new archaeological and geological investigations have been carried out. Landscapes are characterised by karstic plateaus, magmatic bodies and the large endoreic Wadi Al Jawf Basin. Only large-scale geological mapping is available for that area. Maps at 1:250,000 have been established using Landsat remote-sensing data in the 1970’s.
A multiscale analysis of the geological setting of Jabali has been hired including ALOS data (right now AVNIR-2 and PALSAR data are available). ALOS-AVNIR-2 allows to recognize the regional extent of the geological units and tectonic features. At a larger scale, Landsat ETM+, Landsat TM and Spot panchromatic data have been explored. The geological interpretation of QuickBird data for the mine area results in a map representing 14 image-facies. These latter could be correlated with the lithologies as observed in the field. The detailed analysis of the Jabal Amrah laccolith is also in progress.
Teleanalytical geological mapping is a very powerful method to analyse and interpret the geological setting of a poorly-known region. During this study, new geological topics have been pointed out such as the setting of the Jabal Amrah magmatic body, the extent of Zn-Pb-Ag mineralizations, the mapping of Quaternary terraces or the detailed cartography of (de)dolomitization phenomena. Among the set of available sensors, ALOS-AVNIR-2 sensor with its 10m-ground resolution and its visible-near infrared range appears as a good compromise for classical geological mapping at 1:50,000, complementary to the widespread large-scale Landsat imagery and to the higher resolution data (for example QuickBird or Spot 5).