Terra rossa genesis, implications for karst, and eolian dust: A geodynamic thread
Terra rossa genesis, implications for karst, and eolian dust: A geodynamic thread
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DOI：
10.1086/524675
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发表时间：
2008-01-01
影响因子：
1.8
通讯作者：
Banerjee, Amlan
中科院分区：
文献类型：
--
作者：
Merino, Enrique;Banerjee, Amlan
虽然红地一直被认为是由石灰岩的残余溶解和/或由碎屑泥、灰或灰尘在先前存在的喀斯特石灰岩上的堆积而形成的，但我们提出了新的确凿的野外和岩石学证据，表明红地是由石灰岩在几厘米宽的移动交代锋中被自生粘土取代而形成的。红粘土的主要化学元素，Al， Fe和Si，可能来自溶解的风沙。粘土对方解石的替代呈现出锯齿状的微柱状结构，这有助于证明替代不是通过溶解沉淀发生的，正如传统观点所认为的那样，而是由粘土晶体生长产生的结晶应力驱动方解石的压力溶解。用粘土等体积代替石灰石所产生的酸迅速溶解了前缘内相邻石灰岩中额外的孔隙/渗透率，引发了反应渗透的不稳定性，从理论上讲，这种不稳定性应该将移动的反应前沿转化为一组虫洞，然后是漏斗，然后是下沉——这是自然界中确实包含红土本身的喀斯特形态。这很好地解释了为什么红土和喀斯特是联系在一起的。
Although terra rossa has long been thought to form by residual dissolution of limestone and/or by accumulation of detrital mud, ash, or dust on preexisting karst limestones, we present conclusive new field and petrographic evidence that terra rossa forms by replacement of limestone by authigenic clay at a moving metasomatic front several centimeters wide. The red clay's major chemical elements, Al, Fe, and Si, probably come from dissolved eolian dust. The replacement of calcite by clay exhibits a serrated, microstylolitic texture that helps prove that replacement happens not by dissolution-precipitation, as conventional wisdom has it, but by pressure solution of calcite driven by the crystallization stress generated by the growth of clay crystals. The acid produced by the isovolumetric replacement of limestone by clay quickly dissolves out additional porosity/permeability in an adjacent slice of limestone within the front, triggering a reactive-infiltration instability that should, theoretically, convert the moving reaction front into a set of wormholes, then funnels, then sinks-the very karst morphology that in nature does contain the terra rossa itself. This beautifully explains why terra rossa and karst are associated.