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首页> 外文学位 >Origin and formation of dolostone in the Devonian Brilon Reef Complex, Northeastern Rhenish Schiefergebirge, Germany.
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Origin and formation of dolostone in the Devonian Brilon Reef Complex, Northeastern Rhenish Schiefergebirge, Germany.

机译：白云岩的起源和形成在德国东北Rhenish Schiefergebirge的泥盆纪布里昂礁复合体中。

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摘要

The Middle to Upper Devonian Brilon Reef Complex in the Northeastern Rhenish Schiefergebirge hosts several dolostone intervals of variable thickness that show striking petrographic similarities with pervasively dolomitized hydrocarbon reservoir rocks and host rocks of MVT-deposits in Western Canada. Although not of economic significance, the Brilon Reef Complex serves as a case study to enhance the understanding of the origin and formation of dolostone.; The Middle and Upper Devonian carbonates of the so-called "Massenkalk", which make up the bulk of the complex, can be mapped as facies types characteristic of fore-reef, reef-core, and back-reef (lagoonal) depositional environments. The stratigraphic correlation of drill cores-is complicated by (1) the scarcity of index fossils; (2) lateral changes in lithofacies; (3) displacements, fracturing, and brecciation due to Variscan (thrust) and post-Variscan (normal) faults; and (4) the effects of other post-sedimentary processes (e.g., karst).; The dolostone intervals consist of grey matrix dolomite (dolomite Type 1) and two types of coarse crystalline milky-white dolomite (occurring as a recrystallization product of grey matrix dolomite and as saddle dolomite cement) followed by sulfide minerals and late calcite cements. The distribution of dolostone and associated sulfide mineralization appears to be largely controlled by post-Variscan fracturing in the vicinity of deep-reaching, NNW--SSE bending faults. Carbonate facies types as well as pre-Variscan diagenesis and textures related to the Variscan deformation do not appear to have any significant influence on the distribution of dolostone in the Brilon Reef Complex.; Based on petrographic, geochemical, and microthermometric data, dolomitization, limestone recrystallization, dolomite recrystallization, dolomite cementation, sulfide mineralization, calcitization, and calcite cementation in the Brilon Reef Complex are the result of at least four episodic pulses of highly saline, hydrothermal fluids (salinity between 16 and 26 equiv. wt.% NACl, Th = 70 to 120°C) during a distinct phase of regional uplift and wrench tectonics in the Late Cretaceous/Early Tertiary. Seismic pumping and hydrothermal convection along the NNW--SSE bending faults may have been the driving mechanism for the episodic ascent and circulation of the dolomitizing and ore-forming fluids.; Present-day saline groundwaters in the adjacent Munsterland Cretaceous Basin are saline to highly saline (TDS up to 250000 mg/l), ascend on NNW--SSE trending faults, and have the same range of Sr isotope compositions as the investigated carbonates from the Brilon Reef Complex. However, the hydrochemical and isotope dam show that pans of the regional aquifer in this basin and the underlying Paleozoic strata have been flushed by subrecent meteoric water. Thus, these waters do not bear a direct genetic relationship with the fault-controlled hydrothermal mineralization in the Brilon Reef Complex, and, consequently, the possibility that formation fluids from the MCB were driven into the Brilon Reef Complex to generate dolomites, sulfides, and calcites in the fracture systems remains elusive.; The comparison of the results of this study with one local example from the Northern Rhenish Schiefergebirge and with the regional example of pervasive dolomitization in the Western Canada Sedimentary Basin emphasizes the point that occurrences of ancient dolostone have to be interpreted within their local and regional geologic and paleohydrogeologic context.
机译：Rhenish Schiefergebirge东北部的中上泥盆统Brilon礁群拥有几个厚度可变的白云岩层段，这些岩层层与加拿大西部普遍的白云石化的油气储层岩和MVT沉积岩层具有惊人的岩石学相似性。尽管不具经济意义，但布里隆礁综合体仍是一个案例研究，可增进对白云石起源和形成的了解。所谓“ Massenkalk”的中，上泥盆统碳酸盐，构成了该复合体的大部分，可以映射为前礁，礁芯和后礁（泻湖）沉积环境的特征相类型。钻芯的地层相关性由于（1）缺乏索引化石而变得复杂。 （2）岩相的横向变化； （3）由于瓦里斯卡纳（推力）和瓦里斯卡纳后（正常）断层引起的位移，破裂和开裂； （4）其他沉积后过程（例如岩溶）的影响；白云岩层段由灰色基质白云岩（白云岩类型1）和两种类型的粗晶乳白色白云岩（作为灰色基质白云岩的再结晶产物和鞍状白云石水泥而出现），其后是硫化物矿物和晚方解石水泥。在深层NNW-SSE弯曲断层附近，白垩岩的分布和相关的硫化物矿化似乎在很大程度上受后瓦里斯断裂的控制。碳酸盐岩相类型以及瓦里斯坎前的成岩作用和与瓦里斯坎变形有关的质地似乎对布里隆礁复合体中白云岩的分布没有明显影响。根据岩石学，地球化学和显微热学数据，在Brilon Reef Complex中白云石化，石灰石重结晶，白云石重结晶，白云石胶结，硫化物矿化，钙化和方解石胶结是高盐度，热液性流体的至少四个间歇脉冲的结果（在晚白垩世/早第三纪的区域隆起和扳手构造的不同阶段，盐度在16至26当量重量百分比的氯化氢之间，Th = 70至120°C）。沿NNW-SSE弯曲断层的地震抽运和热液对流可能是白云石化和成矿流体的偶发上升和循环的驱动机制。邻近芒斯特兰白垩纪盆地的当今含盐地下水从含盐到高含盐量（TDS高达250000 mg / l），在NNW-SSE趋势断裂上上升，并且具有与所研究碳酸盐岩中碳酸盐相同的Sr同位素组成范围Brilon礁复合体。然而，水化学和同位素坝显示该盆地和下古生界地层中的含水层被最近的陨石水冲刷了。因此，这些水与Brilon Reef复杂区的断层控制热液矿化没有直接的遗传关系，因此，来自MCB的地层流体被驱入Brilon Reef复杂区以生成白云岩，硫化物和裂缝系统中的方解石仍然难以捉摸。这项研究结果与北部Rhenish Schiefergebirge的一个当地实例以及加拿大西部沉积盆地中普遍的白云石化的区域实例的比较，强调了这一点，即必须在其当地和区域的地质构造中解释古代白云岩的发生。古水文地质背景。

著录项

  • 作者

    Grobe, Matthias.;

  • 作者单位

    University of Alberta (Canada).;

  • 授予单位 University of Alberta (Canada).;
  • 学科 Geology.; Physics Atmospheric Science.
  • 学位 Ph.D.
  • 年度 1999
  • 页码 412 p.
  • 总页数 412
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地质学;大气科学（气象学）;
  • 关键词

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