首页> 中文期刊> 《大地构造与成矿学》 >论热液角砾岩构造系统及研究内容、研究方法和岩相学填图应用

论热液角砾岩构造系统及研究内容、研究方法和岩相学填图应用

         

摘要

Issues including diagenetic and metallogenic mechanism of ore-bearing and barren breccias, mapping units, and tectonic lithofacies mapping are valuable in researching and reconstructing ore-field tectonic patterns, however, they are still conundrums for geologists to break. In the diagenetic- and metallogenic hydrothermal breccia systems, hydrothermal breccias are locies of multistage hydrothermal metasomatism, geochemical coupling and superimposing, and recorded the geological processes in the tectonic lithofacies. Therefore, comprehensive investigations of these issues may shed light on the diagenetic and metallogenic theories. In this paper, conception on tectonic system of hydrothermal breccias was proposed, and its research objective, methodology and techniques of lithofacies-mapping were put forward based on our previous study. On the basis of classification framework of breccias presented in the study, the complexity of hydrothermal breccias is addressed and the methodology and techniques of tectonic lithofacies mapping units are established, and meanwhile, case studies of hydrothermal breccias using new methods and technique associations in reconstruction of the tectonic systems are given. Research objectives of tectonic system of hydrothermal breccia include types of lithofacies and establishment of lithofacies sequences, which cover geometry, kinematics, dynamics, chronology, and materials of the lithofacies-body and lithofacies-domain. On one hand, natures of their materials may be studied by means of petrology, petrography, petrographical geochemistry, and lithogeochemistry. On the other hand, their chronology may be precisely restrained by modern methods such as LA-ICP-MS zircon U-Pb dating subsequent to the analysis of tectonic deformation. Furthermore, methodology included different research scale, pattern of tectonic deformation, and domain of tectonic deformation systematically in order to mapping and analyze the lithofacies-body in four dimension of the space (x-y-z)-time (t) and the space (x-y-z)-capacity of materials (M) and in five dimensions of the space (x-y-z)-time(t)- capacity of materials (M). There may exist several geological settings which are constructive environments for the tectonic system of hydrothermal breccias. First, there are several special geological conditions in the compound magmatic intrusions which are favorable for the tectonic system of hydrothermal breccias, including magma immiscibility and crystallization, coupling between cooling magma and pre-existing tectonics in wallrocks, coupling between syn-magmatic intrusions brittle-ductile shear zone and magmatic intrusive process, and magmatic intrusion superimposed by late fluids. Secondly, the subvolcanic intrusion and late magmatic intrusion in the district of volcanic lithofacies are favorable to produce the tectonic systems of hydrothermal breccias. Thirdly, the tectonic system of hydrothermal superimposed breccias may be generated by later basin fluids, hot-fluid intrusion, and complex magmatic intrusions during the deformation stage of the sedimentary basin, if there are pre-existing lithofacies systems of volcanic breccias, karst breccias, and sedimentary breccias in sedimentary basin. Finally, the tectonic system of hydrothermal breccias may be more easily formed in composite intrusions of tectonics-magmatic-breccia complex. In summary, the main formation mechanism for the tectonic system of hydrothermal breccias covers complex magmatic intrusions, volcanic and subvolcanic intrusions, and basin fluids during the later deformation of sedimentary basin. All of four types for the tectonic system of hydrothermal breccias belong to the ore-field tectonic types, and are accounting for diagenetic-metallogenic mechanism of many mineral commodities associations. The techniques of tectonic lithofacies mapping are very helpful to reconstruct diagenetic- and metallogenic centers for the different system of hydrothermal breccias, and thus are important in expecting of concealed tectonic type and blind ore deposits at the depth.%含矿热液角砾岩类和非含矿角砾岩类的成岩成矿机制、独立填图单元确定和构造岩相学填图等问题,一直是困惑地质学家的难题。有效解决这些难题,对于研究和恢复矿田构造具有重要价值。在热液角砾岩成岩成矿系统中,热液角砾岩类不但是流体–岩石的多期次地球化学耦合与叠加作用、强烈流体交代作用的物理–化学反应库,也是各类叠加地质作用过程和结果的构造岩相学物质记录。因此,对其深入研究有助于提升成岩成矿系统理论认识水平。在综述以往研究基础上,本文提出了热液角砾岩构造系统概念、研究内容、研究方法和技术组合。在对角砾岩相系分类基础上,针对热液角砾岩相系的复杂性,通过岩相学填图实例解剖,总结专项填图中构造岩相学填图单元建立方法和填图技术,探索采用岩相学填图恢复热液角砾岩构造系统的新方法及技术组合。通过专项研究认为热液角砾岩系统主要形成有利的构造地质背景有:(1)复式侵入岩体在多期次岩浆侵入过程中,岩浆结晶分异和不混溶作用、岩浆冷却与围岩–先存构造多重耦合过程、同岩浆侵入期的脆韧性剪切带耦合、侵入岩体在后期构造–流体叠加过程等,对于形成热液角砾岩构造系统有利;(2)在火山岩相系中,早期次火山侵入体、晚期次火山岩侵入体和后期岩浆侵入岩体等,对于形成热液角砾岩体构造系统十分有利;(3)在沉积盆地后期叠加改造过程中,先存火山角砾岩、岩溶角砾岩和沉积角砾岩相系等,在后期盆地流体注入和多期次岩浆侵入过程中,有利于形成叠加热液角砾岩体构造系统;(4)在多期次的构造–岩浆–角砾岩杂岩带中,有利于形成热液角砾岩构造系统。研究认为多期次岩浆侵入体、火山–次火山岩侵入体和盆地中热流体是形成热液角砾岩构造系统的主要机制,包括与多期次复式侵入体有关的岩浆热液角砾岩构造系统、火山–次火山热液角砾岩构造系统、构造热液角砾岩构造系统和复合热液角砾岩系统等,它们均属矿田构造类型,也是多矿种共生矿床的成岩成矿机制。采用构造岩相学专项填图技术,对不同类型热液角砾岩构造系统及成岩成矿中心进行重建,有助于寻找和发现深部隐蔽构造和隐伏铁氧化物铜金型(IOCG)矿床找矿预测。

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