Eolian dust and the coupled origin of terra rossa and karst: Unified geodynamics
We present conclusive new field and petrographic evidence that terra rossa clays form by replacement of limestone by authigenic clay at a moving metasomatic front several centimeters wide, with the clays major chemical elements, Fe, Al and Si, coming from dissolved eolian dust, as suggested by 87/86 Sr isotope ratios. The replacement of calcite by clay exhibits (under the microscope) a serrated texture that proves that the replacement happens not by dissolution-precipitation as conventional wisdom has it, but by pressure-solution driven by the crystallization stress. Strikingly, the acid produced by the isovolumetric replacement of clay for limestone quickly dissolves out additional porosity/permeability, triggering a reactive-infiltration instability which is theoretically predicted to convert the moving front into a set of wormholes and funnels and sinks-the very karst morphology that in nature does contain the terra rossa itself. This is why terra rossa and karst are associated.
E.Merino A.Banerjee S.Dworkin
Department of Geological Sciences, Indiana University, Bloomington, IN, USA Geology Department, Baylor University, Waco, TX, USA
国际会议
第十二届水-岩相互作用国际研讨会(P0roceedings of the 12th International Symposium on Water-Rock Interaction)
昆明
英文
17-22
2007-07-31（万方平台首次上网日期，不代表论文的发表时间）