Deformation mechanisms of deeply buried and surface-piercing Late Pre-Cambrian to Early Cambrian Ara Salt from interior Oman
Deformation mechanisms of deeply buried and surface-piercing Late Pre-Cambrian to Early Cambrian Ara Salt from interior Oman
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阿曼内陆深埋和地表穿透的晚前寒武世至早寒武世阿拉盐的变形机制
DOI：
10.1007/s00531-009-0443-3
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发表时间：
2010
影响因子：
2.3
通讯作者：
P. Kukla
中科院分区：
文献类型：
--
作者：
J. Schoenherr;Z. Schleder;J. Urai;R. Littke;P. Kukla
我们比较了南阿曼盐盆深部(3.5-5千米)晚前寒武纪至早寒武世Ara盐底辟的微构造，以及Ghaba盐盆穿透地表的盐丘。横向上，这些盆地相距约500公里，但属于同一构造-沉积体系。来自钻井和露头的良好数据情况允许对从沉积到深埋，以及通过重新激活底辟上升到地表穿透的地层和变形机制进行独特的量化。伽马辐照和刻蚀薄片的微观结构表明，位错蠕变和流体辅助的晶界迁移是深亚表层的主要变形机制。表面的微结构特征是大的、老的、富含亚晶的晶体。这些“老”的晶体部分被“新的”无亚晶和亚晶贫乏的晶体所取代，这些晶体显示出伽马辐射装饰的生长带和纤维状微结构，这表明压力溶液蠕变和静态再结晶，很可能是由于表面穿透和暴露。用亚颗粒测压法测得地下盐类的最大差应力为1.7 Mpa，表层盐类的最大差应力为3.4 Mpa，后者反映了盐类在上升到地表的过程中底辟‘茎’的高应力状态。
We compared microstructures of Late Pre-Cambrian to Early Cambrian Ara Salt diapirs from the deep subsurface (3.5–5 km) of the South Oman Salt Basin and from surface-piercing salt domes of the Ghaba Salt Basin. Laterally, these basins are approximately 500 km apart but belong to the same tectono-sedimentary system. The excellent data situation from both wells and outcrops allows a unique quantification of formation and deformation mechanisms, spanning from sedimentation to deep burial, and via re-activated diapir rise to surface piercement. Microstructures of gamma-irradiated and etched thin sections indicate dislocation creep and fluid-assisted grain boundary migration as the main deformation mechanisms operating in the deep subsurface. Microstructures from the surface are characterised by large ‘old’ subgrain-rich crystals. These ‘old’ grains are partly replaced by ‘new’ subgrain-free and subgrain-poor crystals, which show gamma irradiation-decorated growth bands and fibrous microstructures, indicative of pressure solution creep and static recrystallisation, most likely due to surface piercement and exposure. Using subgrain size piezometry, the maximum differential stresses for the subsurface salt is 1.7 MPa and those for the surface-piercing salt is 3.4 MPa, the latter value displaying the high stress conditions in the diapir ‘stem’ as the salt rises on its way to the surface.