甘肃省玛曲县大水金矿稳定同位素地球化学特征

发布时间：2018-03-21 17:35

本文选题：矿床特征　切入点：稳定同位素　出处：《成都理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：甘肃省玛曲县大水金矿床是90年代初在甘肃省南部西倾山地区发现的国内外十分罕见的富赤铁矿硅质岩型金矿类型。该金矿不仅矿床规模大、品位高、埋藏浅、矿石成分简单、易采易选,且矿化特征极为独特。目前,国内外对该类型金矿床的研究程度较低,对此类矿床的深入研究有利于进一步认识西秦岭造山带构造演化历史和成矿规律,也有利于整个秦岭造山带地区矿产勘查评价工作,同时也有利于寻找新的大水式富赤铁矿硅质岩型金矿勘探工作的深入开展,并有利于研究金矿成矿机理和深化成矿理论。大水金矿田位于甘肃省西秦岭晚古生代-中生代多金属成矿带上,前人已对其做了大量的研究,在成矿构造,成矿动力,成矿年龄等方面取得了重要成果,但对本金矿的成矿流体来源以及成矿模式缺乏确切的论证。大量研究资料表明,复杂成因的大水金矿在时域上,地域上都与稳定同位素密切相关,因此,稳定同位素的研究有利于解决大水金矿的成矿流体来源,进一步认识西秦岭构造带的成矿规律,也有利于完善金矿床的成矿机制理论。本文首先调研了大水金矿的区域地质背景,矿区地质特征,矿床地质特征,阐述了大水金矿的稳定同位素地球化学特征,确定了本次研究以方解石,灰岩,硅质岩为研究对象,测定了方解石,灰岩碳氧锶同位素组成,并借以方解石水—岩理论方法进行模拟。得出以下结论:(1)大水金矿方解石的的碳氧同位素地球化学特征,推测出成矿流体可能来源于深源。方解石氧同位素地球化学特征,推测出早期流体与岩浆活动有关,晚期流体与大气降水有关。(2)Sr同位素组成在探讨成矿物质来源方面也能发挥重要作用,大水金矿的锶同位素地球化学特征,推测出硅化灰岩可能来源于壳幔混合区。(3)大水金矿围岩与矿石的CaO和SiO2呈明显的负相关,因此,可进行水岩反应模拟,模拟显示,大水金矿成矿流体的可溶性碳以H2CO3为主,早期流体的碳可能来自于深源,晚期流体有大气降水加入,大水金矿的形成温度与流体包裹体测温一致,为中低温热液矿床。通过分析稳定同位素地球化学特征,可以认为,大水金矿的成矿流体来源很复杂,可能多种成因为成矿流体提供了物源,此外,浅部热液也对成矿具有重要作用。
[Abstract]:The Dashui gold deposit in Maqu County, Gansu Province, is a very rare type of hematite rich siliceous type gold deposit found in Xidushan area of southern Gansu Province in the early 1990s. This gold deposit is not only large in scale, high in grade, shallow in burial, but also simple in ore composition. At present, the degree of research on this type of gold deposit at home and abroad is relatively low, and the further study of this kind of deposit is helpful to further understand the tectonic evolution history and metallogenic law of the West Qinling orogenic belt. It is also conducive to the exploration and evaluation of mineral resources in the entire Qinling orogenic belt and to the further development of the exploration work for new large water hematite rich siliceous rock type gold deposits. The Dashui gold ore field is located in the late Paleozoic and Mesozoic polymetallic metallogenic belt in the West Qinling Mountains of Gansu Province. Important achievements have been made in ore-forming age, but the source of ore-forming fluid and metallogenic model of the gold deposit are not proved exactly. A large number of research data show that the gold deposit with complex genesis is in time domain. Therefore, the study of stable isotopes is helpful to solve the source of ore-forming fluid of Dashui gold deposit and to further understand the metallogenic regularity of the West Qinling tectonic belt. In this paper, the regional geological background, the geological characteristics of the ore area and the geological characteristics of the deposit are investigated, and the stable isotope geochemical characteristics of the Dashui gold deposit are expounded. It has been determined that the calcite, limestone and siliceous rocks are the objects of this study. The isotopic compositions of calcite and limestone are determined. The following conclusions can be drawn from the following conclusions: (1) the carbon and oxygen isotopic geochemical characteristics of calcite in Dashui gold deposit, and it is inferred that the ore-forming fluid may have originated from deep source. The oxygen isotope geochemical characteristics of calcite may be derived from the ore-forming fluid. It is inferred that the early fluid is related to magmatic activity, and the late fluid is related to precipitation. Sr isotopic composition may also play an important role in exploring the source of ore-forming materials, and the geochemical characteristics of strontium isotope of Dashui gold deposit. It is inferred that silicified limestone may originate from the crust-mantle mixed area. 3) the surrounding rock of Dashui gold deposit is negatively correlated with the CaO and SiO2 of the ore. Therefore, the water rock reaction can be simulated, and the simulation shows that the soluble carbon of the ore-forming fluid in the Dashui gold deposit is mainly H2CO3. The carbon of the early fluid may come from the deep source, the late fluid has the addition of atmospheric precipitation, the formation temperature of the Dashui gold deposit is consistent with the temperature of fluid inclusions, and it is a middle-low temperature hydrothermal deposit. By analyzing the geochemical characteristics of stable isotopes, it can be concluded that, The source of ore-forming fluid in Dashui gold deposit is very complex, and there may be many kinds of ore-forming fluids that provide material source. In addition, shallow hydrothermal fluid also plays an important role in mineralization.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.51

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