马元铅锌矿角砾岩成因及其成矿作用研究

发布时间：2018-10-05 19:54

【摘要】：陕西省南郑县马元铅锌矿产于扬子北缘震旦系灯影组地层中,具有很大的找矿远景。近十几年来,众多研究者对马元地区铅锌矿床的成岩成矿物质来源及成矿机理进行了大量研究和总结,取得了较大的进展。多数地质学者认为,该地区的铅锌矿床和MVT型铅锌矿比较相似,可与之进行类比。从区域上看,本区铅锌矿床受三方面因素的控制:1.基底构造;2.盖层构造;3.角砾岩带。在大多数矿床中矿体充填在张性断裂和各种破碎带中,矿床赋存于上震旦统灯影组角砾状白云岩中,受层位、岩性和次级断裂构造等因素影响,矿床产状与灯影组地层产状大致相同。构造角砾岩越发育,矿化程度就越强。许多研究学者都注意到了马元矿区特殊的矿石构造,即角砾状矿石。并将角砾岩作为一种找矿标志,但是对本区铅锌矿床中角砾岩及角砾状矿石的具体特征及其成因并未进行过详细研究。本文在对马元地区进行地质调查的基础上,通过岩相学观察和电子探针分析,在结合角砾岩的岩石学特征、力学特征及碑坝地区的构造隆升,划分了本区角砾岩的类型,阐述了角砾岩在空间上的分布特征、各种角砾岩的岩石学特征,以及与矿化的关系,进一步探讨了该区角砾岩的成因及成矿意义。得出了以下主要认识:根据角砾岩的结构、构造和岩石碎裂程度等不同特点,以及表现出来的力学性质差异,将马元矿区角砾岩划分为:①初裂岩;②构造角砾岩;③碎裂岩三种类型。由于构造隆升作用的影响,在震旦系上统灯影组层位发生层间滑脱或滑动,使灯影组上段中上部的厚层状白云岩发生拉张破裂而使岩块坠碎、挤碎或搓碎,发生位移后,又被胶结就形成了角砾岩。同时也形成了马元铅锌矿的容矿构造系统,即角砾岩破碎带和放射状横向小断层。马元铅锌矿的赋矿层位为上震旦统灯影组上段第三岩性层中,矿化程度与构造角砾岩的发育成正相关关系。由于构造隆升而在台坪下方产生了大规模的热水循环成矿系统,它通过不断地萃取并吸收基底杂岩中的Pb、Zn等有用组份及灯影组下部含藻白云岩中的有机质,形成了大量的富有机质含Pb、Zn、Ba等成份的热卤水;同时,由于地壳上升和基底隆升使得震旦系上统灯影组地层发生层间滑动及滑脱形成破碎角砾岩带,使含矿卤水通过基底断裂及裂隙通道运移到层间破碎角砾岩带中充填而成矿。
[Abstract]:Mayuan lead-zinc deposit in Nanzheng County, Shaanxi Province is in the formation of Dengying formation of Sinian system in the northern margin of Yangzi. In recent ten years, many researchers have made a great deal of research and summary on the source and mechanism of diagenetic minerals of lead and zinc deposits in Mayuan area, and made great progress. Most geologists think that the lead-zinc deposits in this area are similar to MVT type lead and zinc deposits and can be compared with them. Regionally, the lead-zinc deposit in this area is controlled by three factors: 1. 1. Basement structure 2. Caprock structure 3. Breccia belt In most of the deposits, the orebodies are filled in tensional faults and various broken zones, and the deposits occur in the breccia dolomite of the Dengying formation of the Upper Sinian, which is affected by such factors as the horizon, lithology and secondary fault structure, etc. The occurrence of the deposit is approximately the same as that of the Dengying formation. The more developed the tectonic breccia, the stronger the mineralization degree. Many researchers have noticed the special ore structure of Mayuan mine, that is, breccia ore. Breccia is regarded as a prospecting marker, but the specific characteristics and genesis of breccia and breccia in lead-zinc deposit in this area have not been studied in detail. On the basis of geological survey in Mayuan area, by means of petrographic observation and electron probe analysis, combined with the petrological and mechanical characteristics of breccia and the uplift of structure in the area of Stele Dam, the types of breccia in this area are classified in this paper. The distribution characteristics of breccia in space, petrological characteristics of various breccia and its relation with mineralization are expounded. The genesis and metallogenic significance of breccia in this area are further discussed. The main conclusions are as follows: according to the different characteristics of breccia, such as structure, structure and degree of rock fragmentation, as well as the difference of mechanical properties, the breccia in Mayuan mining area is divided into two structural breccia, the primary fissure rock and the structural breccia. 3 three types of cataclastic rocks. Due to the influence of tectonic uplift, interlayer slippage or slip occurred in the upper Dengying formation of the Sinian, which caused the thick layered dolomite in the upper part of the Dengying formation to be stretched and ruptured, resulting in the falling, crushing or crashing of the rock block, and the displacement occurred. Breccia is formed by cementation. At the same time, the ore-bearing structure system of Mayuan lead-zinc deposit was formed, that is breccia fracture zone and radial transverse small fault. The ore-bearing horizon of Mayuan lead-zinc deposit is the third lithologic layer of the upper member of Dengying formation of Upper Sinian, and the mineralization degree is positively correlated with the development of tectonic breccia. Because of the tectonic uplift, a large scale hydrothermal circulation metallogenic system is produced under the platform, which continuously extracts and absorbs the useful components such as Pb,Zn from the basement complex and organic matter from the algae-bearing dolomite in the lower part of the Dengying formation. A large number of hot brines with rich organic matter, such as Pb,Zn,Ba and so on, were formed, and at the same time, because of the rise of the crust and the uplift of the basement, the strata of the Upper Sinian Dengying formation occurred interlaminar sliding and slippage to form a broken breccia zone. The ore-bearing brine is transported to the interlayer broken breccia belt through the basement fault and fissure channel to form ore.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.4;P588.212.5

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