Recarbonation of metamorphosed marls,Jordan |
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| Institution: | 1. Centre for Energy (M473), The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia;2. Beijing Key Laboratory of Emission Surveillance and Control for Thermal Power Generation, North China Electric Power University, Beijing 102206, China;1. Laboratory for Ground Stone Tools Research, Zinman Institute of Archaeology, University of Haifa, 199 Abba Khoushy Ave. Mount Carmel, Haifa 3498898, Israel;2. Zinman Institute of Archaeology, University of Haifa, Haifa, Israel;3. Use-Wear Laboratory, Zinman Institute of Archaeology, University of Haifa, Israel;4. Lower Saxony State Museum, Department of Research/Collections, Archaeology Division, Willy-Brandt-Allee 5, 30169 Hanover, Germany;1. Dep. of Geography and Environmental Management, University of Waterloo, 200 University Ave West, Waterloo, ON, N2L 3G1, Canada;2. Institute for Soil Science and Land Evaluation, Biogeophysics, University of Hohenheim, Emil-Wolff-Straße 27, DE-70599 Stuttgart, Germany |
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| Abstract: | The Maqarin area, northern Jordan, hosts some unusual, hyperalkaline (pH= 12.5) groundwaters discharging from thermally metamorphosed bituminous marls which formed through spontaneous, in situ combustion of the bitumen. The groundwaters have evolved geochemically through hydration, recarbonation and sulphatization of high temperature minerals. Mineralogical relations of the carbonate phases were examined by XRD and cathodoluminescence in conjunction with a detailed investigation of stable isotope ratios by Nd-YAG laser microsampling. Carbon-13 contents trace the sequence of alteration reactions, involving high temperature decarbonation of host biomic marl, followed by in situ recarbonation of secondary calcium hydroxide and calcium-silicate-hydrates (CSH).Carbonation took place shortly after thermal metamorphism, when non-saturated conditions allowed an atmosphere rich in CO2 from adjacent combustion zones to access reaction sites. Low δ18OCaCO3 values suggest that the earliest phase of recarbonation took place by reaction with hydroxide at elevated temperatures while later phases formed at cooler temperatures. Variable14 activities show that soil CO2 was a component of the later recarbonating atmosphere. Once saturated conditions prevailed in the alteration zone, recarbonation ended and alteration evolved to hydroxide and sulphate dissolution reactions. The recarbonation reactions are a field-scale analogue of recarbonation and14C attenuation in cementitious barriers for radioactive waste repositories. |
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