Self-Organization in Agate: Textures, Composition, and Dynamic Crystallization Modelling

该项目将研究火山玛瑙中结构和成分的重复、自组织模式的成因。这些模式被认为是相互关联的。非平衡系统的自组织包括在没有预先存在的结构或周期性外部原因的情况下自发地产生重复模式。要探索的主要模式是(A)由扭曲的玉髓纤维组成的条带与由非扭曲的纤维组成的条带的系统互层，(B)由我们的模型预测并由阴极发光揭示的相关的振荡微量元素剖面，以及(C)玛瑙石英的系统纤维状、快速长度的习性。该研究包括玛瑙结晶自催化机理的定量动力学模拟、结晶前沿的形态不稳定性分析、微观观察以及离子探针的痕量和微量元素分析。这些分析将使用麻省理工学院由美国国家科学基金会资助的离子探测器进行。该项目将阐明具有地球化学、晶体化学和岩石学意义的自组织系统的动力学，以及控制晶体形态和晶体结构的地球化学因素。

This project will investigate the genesis of repetitive, self- organization patterns of texture and composition in volcanic agates. These patterns are believed to be interlinked. Self- organization of a non-equilibrium system involves the spontaneous generation of a repetitive pattern without preexisting structures or periodic outside causes. The main patterns to be explored are (a) the systematic interlayering of bands made up of twisted chalcedony fibers with bands consisting of non-twisted fibers, (b) the associated oscillatory minor-element profile predicted by our present model and revealed by cathodoluminescence, and (c) the systematically fibrous, length-fast habit of agate quartz. The proposed research consists of quantitative dynamical modeling of agate crystallization by an autocatalytic mechanism, morphological instability analysis of the crystallization front, microscopic observations, and trace- and minor-element analyses by ion probe. These analyses will be carried out with the NSF-funded ion probe at MIT. This project will clarify the dynamics of a self- organizing system with geochemical, crystallochemical, and petrological significance, and geochemical factors controlling crystal morphology and crystalline textures.