Clay Mineral Assemblages Derived from Experimental Acid-sulfate Basaltic

  • WEATHERING. N. J. Tosca
  • Published 2009

Abstract

Introduction: Clay-bearing assemblages identified on the ancient martian surface have the potential to yield detailed paleo-environmental constraints on the Noachian climate. The formation of clay minerals in low-temperature aqueous environments is dependent on a number of parameters including initial pH, chemistry, temperature, host lithology, drainage and hydrology [1,2]. As a result, the formation of clay minerals from chemical weathering has been studied for decades by a number of techniques [2]. However, the formation of clay minerals at low-temperature is notoriously slow and difficult to achieve in the laboratory. Closed-system basaltic weathering experiments were conducted on pristine analog olivine-basalt and basaltic glass at a variety of water-to-rock ratios and initial pH. The experiments were run at controlled conditions for 295 days and almost all of the experiments have yielded enough clay to be separated and analyzed in detail and linked to the parent aqueous solution. These experiments capture a limited range in environmental variables but offer a unique opportunity to connect the formation of specific clay minerals to aqueous chemistry in a controlled experimental setting. Methods: The starting materials used in the study, a crystalline olivine-basalt and a glassy scoriaceous ba-salt, were obtained from Ward's Natural Science. The crystalline basalt is dominated by augite and plagioclase and contains olivine with accessory Fe-Ti oxides and residual glass. The scoria is fine-grained and glassy, highly vesicular and dominated by plagioclase and py-roxene. Bulk samples of starting materials were cut on all sides to attempt to remove surface features, and then crushed to 74-420 μm and <74 μm size fractions. Ul-trafine particles were removed by periodic rinsing and sonication in acetone. Experiments were run in 50 mL centrifuge tubes capped under ambient oxidizing atmosphere with Tef-lon tape and were placed in a 25(±1)

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Cite this paper

@inproceedings{Tosca2009ClayMA, title={Clay Mineral Assemblages Derived from Experimental Acid-sulfate Basaltic}, author={WEATHERING. N. J. Tosca}, year={2009} }