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Evolution of deformation bands, insights from structural diagenesis
Journal of Structural Geology ( IF 2.6 ) Pub Date : 2021-02-01 , DOI: 10.1016/j.jsg.2020.104257
Ricardo de Souza Rodrigues , Fernando César Alves da Silva , Valéria Centurion Córdoba

Abstract The vast majority of deformation bands (Dbs) studies focus on structural analysis only and neglect chemical/diagenetic effects. Here we report the structural diagenesis of Dbs occurring in the Tucano Basin (NE-Brazil). Although the occurrence of these structures in this basin has been well registered in literature, none of the researches related to them addressed the linking between structural and diagenetic processes. To fill this gap, we performed a multiscale (macro, meso and microscopic) analysis. Some key outcrops were selected and sampled for microscopic studies in order to investigate the deformational mechanisms active during Dbs formation and the coeval diagenetic processes. The diagenetic analysis reveals that the sandstones attained a minimum burial depth around 3 km and a temperature ≥100oC, which means they reached the deep mesodiagenesis field. The nucleation of Dbs in these rocks started in the transition between the late eodiagenesis and initial (shallow) mesodiagenesis. In such conditions, the active deformational regime was the hydroductile flow, expressed by the dragging (bending) of rocks’ bedding (S0) by the Dbs. In the syn-lithification stage, transitional bands (hydroductile-cataclastic) developed exhibiting SC-type patterns and sigmoidal fractures. During deep mesodiagenesis, the cataclastic bands were formed by the cataclastic flow. These types of Dbs developed after mesodiagenetic quartz overgrowth and before (or synchronically) to chemical dissolution processes. The formation of tectonic matrix at this stage, along with the siliceous/ferruginous cementations, enhanced the strength of these structures.

中文翻译:

变形带的演化,来自构造成岩作用的见解

摘要 绝大多数变形带 (Dbs) 研究仅关注结构分析,而忽略了化学/成岩作用。在这里,我们报告了在 Tucano 盆地(巴西东北部)发生的 Dbs 的结构成岩作用。尽管该盆地中这些构造的出现已在文献中得到很好的记录,但与它们相关的研究都没有涉及构造和成岩过程之间的联系。为了填补这一空白,我们进行了多尺度(宏观、中观和微观)分析。为了研究 Dbs 形成过程中活跃的变形机制和同时期的成岩过程,我们选择并取样了一些关键的露头进行微观研究。成岩分析显示,砂岩最小埋深约3km,温度≥100oC,这意味着他们到达了深层中成岩领域。这些岩石中 Dbs 的成核开始于晚成岩作用和初始(浅层)中成岩作用之间的过渡。在这种情况下,活跃的变形状态是水延流动,由 Dbs 对岩石层理 (S0) 的拖动(弯曲)表示。在同岩化阶段,过渡带(水延性-碎裂岩)发育,表现出 SC 型模式和 S 形裂缝。在深部中成岩作用过程中,碎裂带是由碎裂流形成的。这些类型的 Db 在中成岩石英过度生长之后和化学溶解过程之前(或同步)形成。这一阶段构造基质的形成以及硅质/铁质胶结物增强了这些结构的强度。这些岩石中 Dbs 的成核开始于晚成岩作用和初始(浅层)中成岩作用之间的过渡。在这种情况下,活跃的变形状态是水延流动,由 Dbs 对岩石层理 (S0) 的拖动(弯曲)表示。在同岩化阶段,过渡带(水延性-碎裂岩)发育,表现出 SC 型模式和 S 形裂缝。在深部中成岩作用过程中,碎裂带是由碎裂流形成的。这些类型的 Db 在中成岩石英过度生长之后和化学溶解过程之前(或同步)形成。这一阶段构造基质的形成以及硅质/铁质胶结物增强了这些结构的强度。这些岩石中 Dbs 的成核开始于晚成岩作用和初始(浅层)中成岩作用之间的过渡。在这种情况下,活跃的变形状态是水延流动,由 Dbs 对岩石层理 (S0) 的拖动(弯曲)表示。在同岩化阶段,过渡带(水延性-碎裂岩)发育,表现出 SC 型模式和 S 形裂缝。在深部中成岩作用过程中,碎裂带是由碎裂流形成的。这些类型的 Db 在中成岩石英过度生长之后和化学溶解过程之前(或同步)形成。这一阶段构造基质的形成以及硅质/铁质胶结物增强了这些结构的强度。
更新日期:2021-02-01
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