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首页> 外文期刊>Sedimentology: Journal of the International Association of Sedimentologists >Origin, characteristics and distribution of fault-related and fracture-related dolomitization: Insights from Mississippian carbonates, Isle of Man
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Origin, characteristics and distribution of fault-related and fracture-related dolomitization: Insights from Mississippian carbonates, Isle of Man

机译：与断层有关和与断裂有关的白云石化的成因，特征和分布：来自曼岛的密西西比碳酸盐的见解

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Visean limestones on the Isle of Man host numerous examples of fault-controlled and fracture-controlled dolomitization, which have been investigated to determine their macro-scale to micro-scale characteristics, geofluid origin, timing and relation to basin evolution. Geobodies composed of fabric destructive, ferroan, non-planar dolomite range from several centimetres to >300 m wide and tens to hundreds of metres long parallel to faults and/or fractures; they have sharply defined margins, cross-cut stratigraphy and locally finger out along beds or bed boundaries for tens of metres. Larger geobodies accompany NNE-SSW extensional faults with substantial breccia zones. One of these bodies hosts a sphalerite-rich breccia deposit cemented by dolomite. Saddle dolomite lines or fills vugs and fractures within dolomite geobodies, and is a minor late diagenetic phase in undolomitized limestones. Replacive dolomite has low matrix porosity owing to non-planar texture and associated cementation, and there is no evidence for subsequent leaching. Three dolomite stages are discriminated by texture, cathodoluminescence petrography and electron microscopy. Disseminated 'Dolomite 1' is substantially replaced and may be residual early diagenetic dolomite. Pervasive 'Dolomite 2' and 'Dolomite 3' have overlapping carbon-oxygen-strontium isotopic and fluid-inclusion characteristics that indicate precipitation from allochthonous, high-temperature (98 to 223 degrees C) and high-salinity (15 to 24 wt% NaCl eq.) brines. These variably equilibrated with host limestones and mixed with resident pore fluids. Overlying mudrocks formed a seal for ascending fluids. Integration of data from the mineral deposit suggests that fault-fracture systems tapped different deep-seated fluid reservoirs at different temperatures, and implies fluid interactions with both metamorphic basement and sedimentary cover in large-scale circulation systems. This phenomenon probably took place during Mesozoic rifting, although an earlier event at the end of the Early Carboniferous cannot be discounted. In either case, a transient heat flow anomaly, previously unrecognized in the Irish Sea region, may be required to account for the hottest fluids.
机译：马恩岛的Visean石灰岩有许多断层控制和断裂控制的白云石化的例子，这些例子已被研究以确定其宏观到微观尺度的特征，地流体的起源，时间和与盆地演化的关系。由破坏性的织物，铁的，非平面的白云石构成的地体，其范围与断层和/或裂缝平行，范围从几厘米到> 300 m，长到几十到几百米;它们边缘清晰，横切地层，沿床或床边界局部伸出数十米。较大的地质体伴随着具有大量角砾岩带的NNE-SSW伸展断裂。这些矿体之一是由白云石胶结而成的富含闪锌矿的角砾岩矿床。鞍状白云岩在白云岩地质体中排成一线或充满孔洞和裂缝，是非硬质化石灰岩中次要的成岩相。由于非平面质地和相关的胶结作用，可替换的白云石具有较低的基质孔隙度，并且没有随后浸出的证据。通过质地，阴极发光石像学和电子显微镜来区分三个白云岩阶段。散布的“白云岩1”已被基本替代，可能是残留的早期成岩白云岩。普遍的“白云岩2”和“白云岩3”具有重叠的碳-氧-锶同位素和流体包裹体特征，表明来自异源，高温（98至223摄氏度）和高盐度（15至24 wt％NaCl）的沉淀当量）盐水。这些与宿主石灰岩可变地平衡，并与驻留的孔隙流体混合。上覆的泥岩形成了用于上升流体的密封。矿床数据的整合表明，断层-断裂系统在不同的温度下利用了不同的深层流体储层，并暗示了在大规模循环系统中流体与变质基底和沉积物覆盖层之间的相互作用。这种现象很可能是在中生代裂谷期间发生的，尽管早期石炭纪末期的较早事件不能忽略。在这两种情况下，都可能需要在爱尔兰海地区以前无法识别的瞬态热流异常来解释最热的流体。

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