Karst and Early Fracture Networks in Carbonates, Turks and Caicos Islands, British West Indies
Karst and Early Fracture Networks in Carbonates, Turks and Caicos Islands, British West Indies
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英属西印度群岛特克斯和凯科斯群岛碳酸盐岩的岩溶和早期断裂网络
DOI：
10.2110/jsr.2007.052
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发表时间：
2007
影响因子：
2
通讯作者：
D. Viggiano
中科院分区：
文献类型：
--
作者：
S. Guidry;M. Grasmueck;D. Carpenter;A. Gombos;S. Bachtel;D. Viggiano
摘要在第四纪碳酸盐岩的研究中，早期裂隙网络对成岩作用的影响一直没有得到充分的重视。由于缺乏这种细节，理解和预测古碳酸盐岩序列中与碳酸盐岩相关的成岩非均质性和优先流体流动路径特别具有挑战性。更新世鲕粒砂岩的凯科斯平台提供了一个很好的机会，以评估早期成岩蚀变风格的相对重要性的裂缝，是一个合适的模拟地下碳酸盐岩储层。详细的断裂分析（例如，利用高分辨率三维探地雷达（三维探地雷达），协助探索断裂的因果关系和分布以及与岩溶的关系。对四种模型进行了评价，以解释所观察到的漏斗分布：（1）重力，边缘控制，（2）构造断裂控制，（3）先行地形控制，（4）混合模型。根据对西凯科斯台地上大量裂缝（n = 306）的观察，早期裂缝丰富，且主要为边缘平行。这些裂缝网络在石灰岩矿物学稳定之前就已建立，从而表明在碳酸盐岩成岩作用中，成岩非均质性很早就已形成。普罗维登夏莱斯漏斗的空间分布可能是先前地形、边缘平行断裂系统和大气流体之间复杂相互作用的结果。由此产生的成岩蚀变远比与地形高点相关的简单的、无限制的流星透镜体复杂得多。任何试图模拟碳酸盐岩早期成岩作用的尝试都不应忽视裂缝作为成岩促进剂和成岩各向异性模板的作用。
Abstract Historically, studies of Quaternary carbonates have not adequately addressed the influence of early fracture networks on diagenesis. Because of this lack of detail, understanding and predicting fracture-related diagenetic heterogeneities and preferential fluid flow pathways in ancient carbonate successions is particularly challenging. The Pleistocene oolitic grainstones of the Caicos platform provide an excellent opportunity to evaluate the relative importance of fractures on early diagenetic alteration styles, and are a suitable analog for subsurface carbonate reservoirs. Detailed analyses of fractures (e.g., orientation, aperture, spacing, fill material) from Caicos outcrops combined with high-resolution, three-dimensional ground-penetrating radar (3D GPR), assisted in exploring the causality and distribution of fractures and relationship to karst. Four models were evaluated to explain the observed distribution of dolines: (1) gravitational, fractured-margin controlled, (2) tectonic-fracture controlled, (3) antecedent-topography controlled, and (4) a hybrid model. Based on observations of numerous fractures (n = 306) on the western Caicos platform, early fractures are abundant and dominantly margin-parallel. These fracture networks are well established in limestones prior to mineralogical stabilization, thereby indicating that diagenetic heterogeneities evolve very early in carbonate diagenesis. The spatial distribution of dolines on Providenciales is likely the result of a complex interplay between the antecedent topography, margin-parallel fracture systems, and meteoric fluids. Resultant diagenetic alteration is far more complicated than simple, unconfined, meteoric lenses associated with topographic highs. Any attempts to model early diagenesis in carbonates should not dismiss the role of fractures as diagenetic facilitators and diagenetic anisotropy templates.