【作者】 刘勇；

【导师】 刘云华；

【作者基本信息】 长安大学 ， 矿物学、岩石学、矿床学， 2013， 硕士

【摘要】 西秦岭地区是我国重要的金矿产区之一，该区矿产时空分布具有分段成群成带展布的特点，枣子沟金矿床即位于西秦岭西段的夏河—合作金矿矿集区中，为近年来在西秦岭地区新探明的一个特大型金矿（截止2012年12月，已探明资源储量累计达150吨）。枣子沟矿区围岩地层为中三叠世古浪堤组细碎屑岩（部分变质为板岩）及灰岩，区内无大的岩体出露，但发育有以NEE向为主的中酸性侵入岩脉，出露面积占矿区总面积的30%以上，外围广泛发育中生代的花岗岩类侵入体，以美武岩体、德乌鲁岩体、阿姨山岩体为主，同时也分布有大量的中酸性脉岩。金矿（化）体主要赋存于闪长玢岩类脉体中，及其与围岩地层的内外接触带内，产状严格受NE、NW和近NS向三组断裂构造控制，成矿晚期阶段的近EW向含金辉锑矿化石英脉切割部分NE、NW向矿体。区内原生金矿化类型为斑岩型和石英脉型：前者矿石矿物组合主要为金+黄铁矿+毒砂，含少量黄铜矿、方铅矿等，矿石构造以星散浸染状和细脉浸染状为主；后者矿石矿物为金+辉锑矿，呈块状赋存于石英脉中。矿体围岩蚀变受构造及多期次热液活动的影响，蚀变矿物组成复杂，分带不明显，以断裂破碎带及脉岩与围岩地层的接触带为中心，向两侧蚀变强度逐渐减弱，矿化强度同时也减弱，即两者存在正相关性。矿床的地质地球化学特征、稀土元素和稳定同位素（H、O、S、Pb）示踪等综合研究表明，枣子沟金矿成矿作用与区内闪长玢岩类脉岩活动密切相关，脉岩与金矿化是同一构造-岩浆活动旋回内区域地壳演化、壳-幔相互作用的系列产物，由此造成两者在时空上的密切关系，但由于脉岩本身所携带的成矿物质不足以形成如此规模的金矿，金矿床的成矿流体、硫、及金属物质应与闪长玢岩类脉岩同源，大部分是从玢岩脉体源区的大岩基上升到浅部闪长玢岩脉部位及断裂破碎带中，两者物质成分上具有相同来源和继承演化的成因联系。与成矿有关的（石英）闪长玢岩形成年龄为~216Ma，稍晚于夏河—合作矿集区内的花岗岩类年龄，为印支晚期。印支运动在秦岭造山带是很明显和强烈的，尤其是印支晚期的后碰撞伸展阶段，岩浆活动和成矿作用更为强烈。伸展阶段应力状态的快速转换，引发地幔上涌和深部物质上升，同位素资料表明地幔流体向地壳浅部运移扩散是秦岭造山带有色金属矿产成矿的重要机制，上地幔物质和能量向地壳运移扩散以及壳幔物质的交换循环，极有利于矿床的形成。前人研究成果显示该区域金及其他金属矿床的成矿时代具有印支期成矿的特征，同时结合斑岩型矿床成矿时代与斑岩体成岩时代基本同时或稍后，认为枣子沟金矿床形成于印支晚期，并且在西秦岭造山带具有寻找印支晚期与后碰撞伸展环境有关的斑岩型金矿床的巨大潜力。综合以上研究，初步建立了枣子沟金矿床的成矿演化模式，目前矿区内所发现的矿床仅位于斑岩岩脉的顶部，表明其深部具有较大的找矿潜力。更多还原

【Abstract】 Western Qinling is one of the important gold deposit areas of China, the time-spacedistribution of mineral resources within the areas has the characteristics ofdistribution into groups and belts. Zaozigou gold mine located in the Xiahe-Hezuo oreconcentration area of gold, with proved gold resources over150tons ending December2012,is a king-size gold deposit in the Western Qinling Belt.The Zaozigou mining area’s primary stratum are the fine-grained clastic rocks (part hasmetamorphosed to slate) intercalated with limestone of the Middle-Triassic Gulangdiformation and intermediate-acid dike rock. The exposed dikes, accounting for30%of the totalmining area, are mainly controlled by the NEE. There are many Mesozoic granitic intrusivemass around the mining area, which are dominated by Meiwu, Dewulu, Ayishan Pluton andlots of intermediate-acid dike rock. The gold ore bodies controlled by the NE, NW, NS andEW are hosted in the slate and porphyrite dikes, The mineralization styles of the Zaozigougold deposit can be classified into porphyry type and quartz-vein type: former’s ore mineralincludes gold+pyrite+arsenopyrite and little chalcopyrite, galena etc., with the pepper-and-saltand veinlet-disseminated structure; the latter’s ore mineral is the gold+stibnite, massivestructure. Under the effect of regional tectonics and multi-periods hydrothermal activity, orewallrock alteration mineral is heterogeneous which has no obvious zoning. From the faultzone or the contact zone between dikes and sedimentary stratum to the sides, the alterationgrows gradually weaker and the gold values also declines, showing the strong correlation.Evidences from the geological and geochemical characteristics of the deposit, rareelements and the stable isotope elements(H, O, S, Pb)etc. indicate that the closerelationships between ore-forming event and diorite-porphyrite. Porphyrite dikes andmineralization are all the serial tectono-magmatic evolutionary products of regional crust andmantle-crust interactions, thus, associating each other in time and space. Since the mineralsubstance of porphyrite dikes is not enough to form so large-scale gold mine, the ore fluid,sulphur and metallic substance are considered to be homologous with the porphyrite dikes. Most of the mineral substance originate from the under batholith which is the source ofporphyrite, and then transport to the shallow porphyrite dikes or the broken-rock zone. Bothof them have the same souce and genetic development.The forming age of (quartz) dioritic porphyrite which have the relation of mineralizationis about216Ma, which is a little later than the granitoids of Xiahe-Hezuo ore concentrationarea and belongs to the later Indosinian. It is obvious that the Indosinian movement of Qinlingorogenic belt, especially the magmatic activity and metallization of the later Indosinian’s post–collisional extensional stage. The quick changes of stress during the extensional stage causethe upwelling of asthenospheric and deep material. Isotopic information indicates that theore-forming process of Qinling is the migration of mantle material. It is advantageous for themineralization in the exchange and recycling of the material and heat from the upper mantle.The achievement which has been made shows that the western Qinling regional mainmetallogenic epoch is the Indosinian, and based on the phenomenon that the age of porphyrytype deposit’s forming age is a little later than porphyry’age or synchronous, indicating thatthe Zaozigou gold deposit was formed during the end of Indosinian and there are hugepotentials within the western Qinling orogenic belt for prospecting porphyry gold deposit ofthe end stage of the Triassic post-collisional extensional environment.Based on the above studies, the metallogenic evolution model of Zaozigou gold deposithas been preliminary established. The minerals dicovered within the exploration areas arelocated in the top position of porphyrite dikes, which indicates the bright prospect of the deepareas.更多还原