【作者】 刘淑文；

【导师】 薛春纪； 裴先治；

【作者基本信息】 长安大学 ， 地质工程， 2006， 博士

【摘要】 南秦岭成矿带的泥盆系及其中贱金属、贵金属及菱铁矿大型-超大型矿床引世人关注，研究主要从岩石学、地层学、矿床学、地球化学、大地构造学等角度对南秦岭成矿带开展了多方位“立体交叉”式的研究，取得了丰硕的成果，但从地质流体角度开展的研究工作较少，而且已有的研究工作也主要集中于泥盆系成矿区的典型矿床上。论文工作主要从盆地动力演化出发，把盆地充填分为水成沉积和热水沉积两个序列，以水成沉积为基础，对古生代流体活动的产物-热水沉积岩石/矿石开展系统的研究，查明古生代带盆地演化过程中幕式流体活动过程，从流体活动角度探讨南秦岭古生代盆地构造-沉积演化与流体成岩成矿关系，反演盆地流体过程与深部构造的关系，揭示盆地流体活动的成矿效应。通过对“南秦岭古生代盆地演化中幕式流体成岩成矿作用研究”，取得了以下几个方面的主要进展： 1、通过全面整理分析南秦岭区域地质成果资料，从基底特点、沉积纪录、构造作用、岩浆事件、热流过程等方面进一步明确了南秦岭古生代流体过程与成矿作用的大陆边缘动力学背景及热水沉积环境。 南秦岭早古生代是扬子陆块北部被动大陆边缘，伸展背景下东西向裂陷海槽发育；晚古生代因勉略洋打开而从扬子北缘分离成为微板块，受古老隆起、基底断裂、同生断层等伸展构造的影响，成为有多个不同性质二级盆地发育的多岛海域，并且主张应力总体上由南北向转化为东西向。新元古代-早古生代为主的双峰式火山岩、基性侵入岩等也很可能进一步指示了该时期南秦岭被动陆缘下的地幔热点活动背景。正是在这种具有地幔热点活动和伸展构造背景的地堑式边缘海盆中出现了明显的热水沉积环境：①海盆正常充填序列中的不同层位发育了不同性质和规模的热水沉积岩和同生热水蚀变岩；②海盆内的正常水成沉积物也表现出有机质成熟度（泥盆系青石垭组饱和烃/芳香烃=3.12）、古海水温度（泥盆纪海盆为53.9℃～88.9℃）、盐度（泥盆纪海盆盐度为14wB％ NaCl）、以及同位素组成(δ¹⁸O值为9.57‰)等方面的异常。 2、在南秦岭旬阳盆地志留系新识别出钠长石岩、硅质岩、铁碳酸盐岩等热水沉积岩，这将南秦岭热水沉积作用推至早古生代，不仅使南秦岭古生代流体活动和热水沉积记录更加全面系统，而且证明了本地区下古生界铅锌矿床属海底热水沉积-改造成因，明确了找矿方向。 产在旬阳盆地志留系铅锌矿集区的钠长石岩、硅质岩、铁碳酸盐岩等热水沉积岩，它们或独立成层产于铅锌硫化物矿层以下层位，或直接作为铅锌硫化物矿层的容矿岩石，与志留系水成沉积岩层整合产出，同步褶皱，但其岩相学、矿物学、地球化学的特殊之处表明它们明显有别于正常水成沉积岩石。 钠长石岩产在含矿层以下层位，具厚层块状、条带状、角砾状构造，均粒微细晶结构、内碎屑结构；其化学组成以富含SiO₂、Al₂O₃及Na₂O为特征，富Fe、Mn，贫Co、Ni、Cu等微量元素；在Fe-Mn-（Cu+Ni+Co）和P-Y关系图上，均反映为热水沉积成因；钠长石岩与围岩具有相似的稀土配分模式，但稀土总量较围岩偏低；反映了钠长石岩与下伏地层以及基底岩石之间的密切物质联系。钠长石岩中锆石透射光、反射光图像以及ShirmpU-Pb测年结果均反映出锆石来源于基底岩石中的继承性锆石，进一步证明了钠长石岩是由海水沿同生断裂向下渗透，被加热并和基底富钠质岩石（基底武当群、耀岭河群为一套富钠质的浅变质沉积火山岩系）及所流经的地层柱发生面型淋滤，经热液通道喷发出海底，形成了具有海底喷-流热水沉积特征的层纹状、层块状、及角砾状钠长石岩。 发育在铅锌含矿层中层状、层纹状硅质岩，主要由微-细晶它形粒状石英镶嵌组成。硅质岩化学组成以SiO₂为主，Al、Ti、Mg相对贫乏；Fe/Ti、Al/（Al+Fe+Mn）、（Fe+Mn）/Ti及FeO/Fe₂O₃比值表明具有热水沉积成因性质。硅质岩中Zn、Pb、As、Sb、Ag等微量元素富集；在更多还原

【Abstract】 The southern Qinling region is one important continental ore-forming belts in China. The survey and study of the Devonian base metal sulfide deposits in this region have made remarkable progress. The research on South Qinling metallogenic belts launching in multi-direction "high" type mainly involves such fields as petrology, stratigraphy, metallogeny, geochemistry, tectonic structural geology, which has produced remarkable achievement, but the research from the perspective of fluid is comparably less. What’s more, it mainly focuses on typical deposit of Devonian ore-forming zone. The starting point of the study is from basin dynamic evolution, dividing basin sediments into one-basic aspect of aqueous sediment and the other hydrothermal one, carrying out systematic research on Paleozoic fluid activities’ product-hydrothermal and sedimentary rock to identify time-space distribution of episodic-fluid activities in the basin evolution’s process and discussing the relationship between the basic tectonic sedimentary evolution and diagenesis-mineralization of fluid by perspective of fluid activities, so as to deduct the connection of fluid process with deep-seated structure in reverse way and to reveal mineralization effect of basin fluid forming of rock and ores ,major progress has been made as follows :1. Through a comprehensive analysis of collection of regional geological data to the South Qinling, the mechanics setting and Paleozoic continental margin hydrothermal sedimentary environment in South Qinling is further clarified from several aspects such as basement features, sedimentary records, structural events and thermal process: In early Paleozoic, South Qinling is of north passive continental margin of Yangtze plate, and the setting of plume （hot spot） is obvious; in late Paleozoic, it converted to some divided rift-sag basin controlled by strenched fault within Qinling plate, Therefore, heating-extension-thining-fault-subsidence of the crustal can be know as an element geologic environment of formation of hydrothermal sedimentary rock by synthesizing three sides feature of tectonics background and sedimentary environment and terrestrial heat background.2. Systematic studies have been launched on lead-zinc deposit of Xunyang Paleozoic Silurian system discovered by recent exploration, which first distinguish hydrothermal sedimentary rocks such as albite rock, siliceous rock, ferruginous carbonate rock, barite rock, which close associated with lead-zinc deposit in ore-bearing series, and furthermore these studies first refer to their sequence, combination, petrology, mineralogy, geochemical characteristic, contributing a lot for geologist to learn structural evolution of South Qinling Silurian basin and hot-water sedimentary genic of lead-zinc deposit.Hydrothermal sedimentary albitite below the ore-bearing rock is conformity and gradational transition with the strata in space, and it has massive, banded, brecciated structure and fine equigranular and intraclastic texture, and inner clastic texture. It is chemically characterized by enrichment in SiO₂、Al₂O₃ and Na₂O. In the Fe-Mn-（Cu+Co+Ni）× 10 diagram, all samples fall in the hydrothermal sediment field. It’s ∑REE、LREE、HREE are lower than the country rocks, but the chondrite REE patterns are similar. So, it’s materials are extracted from Na-rich basement rocks and sedimentary collumn underlying the albitite .Laminated and banded siliceous rocks are widely distributed in the ore-bearing rock, this siliceous rocks are chemically very pure, and their SiO₂ contents exceed 89 percent. The contents of the trace elements vary considerably, and most of them are lower then their Clarke values in the earth’s crust. Neverthless, the siliceous rocks are remarkable enriched in the trace elements as Zn、Pb、As、Sb and Ag. In the Fe-Mn-（Cu+Ni+Co）×10 triangle diagrams, all samples fall in the hydrothermal sediment field. The siliceous rocks are characterized by low total REE contents(the average content being 4.09×10^-6),更多还原