Abstract
The current work investigates the Cambrian Manganese ore deposits from Wadi Dana at central Wadi Araba region. This investigation aims to unravel the chemistry and micro-textures of the mineral paragenetic sequence for these manganese ore deposits. Particularly the Fe–Mn intimate intergrowth micro texture and the epigenetic Mn mineralization associated with Cu minerals. The combination of the synchrotron-based X-ray fluorescence (syn-XRF) micro-mapping and X-ray absorption fine structure (XAFS) techniques were used. They provide a clear picture of the elemental distribution of Mn, Fe, Cu, and Pb and other elements presented within the ore micro textures. Besides, it determines the exact elemental speciation. The results obtained gave a better understanding of the elemental atomic structures and eventually the depositional environment. Particularly, the syn-XRF micro-mapping reveals the existing of many successive evolution stages in the Mn ores. Besides, the X-ray Absorption Near Edge Structure (XANES) results showed that the micro-rhythmic texture is changing from Mn+4 (Pyrolusite) into Fe+3 (Hematite). This is evidence for the role of Eh as the main controlling factor during the ore formation. Eventually, indicating tentatively the paleoceanography setting of the Mn deposits. This is related to the continuous transgression-regression on the sea level in a semi-closed sea.
Highlights
The main manganese deposit outcrops at Wadi Dana area, at the central Wadi Araba region 9 (Fig. 1)
The rhythmic nature of this wave-like texture that ranges from continues cycles from pure Mn to pure Fe ends. This structure and mineral changes need to be clarified by identifying the metal valences by executing the X-ray Absorption Near Edge Structure (XANES) measurements for several points taken in cross-section from Mn-end into Fe-end
After allocating the best cross-section, Syn-XRF elemental mapping, which helped in allocating the Mn and Fe XANES results reveals the changing from Mn (IV) (e.g. Pyrolusite MnO2) to Fe(III) (e.g. Hematite Fe2O3), as shown in Figure (3)
Summary
The main manganese deposit outcrops at Wadi Dana area, at the central Wadi Araba region 9 (Fig. 1). Manganese is hosted in the middle Cambrian Dolomite Limestone Shale Unit (DLSU). This formation consists of the lower calcareous part and upper siliceous part. Since the manganese of Wadi Dana area is the larger manganese deposit in Jordan, it was studied by many authors (Khoury, 1986; Shaltoni, 1988; El-Hasan, 1999; El-Hasan and Lataifeh, 2001; El-Hasan et al, 2000, 2001b & 2008). It is a common mineral in supergene Mn deposits, (Ghosh, and Dean, 1980). Hematite was identified by ore microscopy and XRD, to be associated with Pyrolusite
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