若尔盖铀矿田含矿岩系中硅质岩成因及其成矿意义

发布时间：2018-03-04 05:17

本文选题：若尔盖铀矿田　切入点：硅质岩　出处：《成都理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：若尔盖铀矿田主要位于四川省若尔盖县境内南秦岭铀成矿带西段,其主体部分为由古生界地层构成的白龙江复背斜,是中国重要的碳硅泥岩型铀矿产地。矿床群主要产于下志留统羊肠沟组、塔尔组和拉垅组一套浅变质硅-灰岩系中,并严格受岩性、构造和地球化学环境控制,是目前中国矿床数量最多、规模最大、工业意义和经济意义显著且发展前景明朗的碳硅泥岩型铀矿田,因而倍受广大矿床地质工作者所关注。硅质岩是若尔盖铀矿田碳硅泥岩型铀矿的重要含矿岩石之一。区内硅质岩依据结构和成因可分为泥晶硅质岩、变晶硅质岩、硅化硅质岩以及钙化硅质岩四种类型。本文主要从硅质岩的常量元素地球化学、微量元素地球化学、稀土元素地球化学以及硅同位素地球化学等特征来查明若尔盖铀矿田含矿岩系中硅质岩的成因。以因子分析方法为基础,系统分析各含矿主岩、热液矿物(石英、方解石)、矿石微量元素之间的相关性,探讨硅质岩与铀成矿的关系等。通过本文的研究,取得了以下成果认识:1.硅质岩常量元素地球化学特征硅质岩中的SiO2含量平均值为95.72%,表明岩石中几乎不含陆源泥质沉积物。其Al/(Al+Fe+Mn)比值均值为0.21,Fe/Ti比值均值为55.69,(Fe+Mn)/Ti比值均值为61.78,这些比值特征均表明其为热水沉积成因。在Al-Fe-Mn三角图和Al2O3-SiO2成因标准模式图上,硅质岩的投点亦均投影在热水成因区内。MnO/TiO2平均值为5.226,反映硅质岩可能形成于深海盆地环境;MgO/Al2O3平均值高达0.940,表明其形成于高盐度的海水沉积环境。2.硅质岩微量元素地球化学特征本区硅质岩中的微量元素具高U元素含量而低Zr元素含量特征,暗示其可能为热水成因且形成环境可能远离陆源沉积。Th/U比值、Sr/Ba比值均远小于1,表现出明显的热水成因,同时Rb/Sr比值偏低,反映了硅质岩沉积时有富铁镁质物源加入,说明当时存在强烈的扩张裂解作用。3.硅质岩稀土元素地球化学特征区内硅质岩的稀土元素北美页岩标准化配分曲线呈左倾型,多数样品中具有负Ce异常和弱的正Eu异常,其δCe平均值为0.80,δEu平均值为1.2,具有热水沉积硅质岩的典型特征。4.硅质岩同位素地球化学本区灰黑色纹层状硅岩的?30Si值为-0.4‰~+0.2‰(平均值为0.017‰),显示为远离大陆的深海沉积。石英脉的?30Si值为-0.1‰~+0.5‰(平均值为0.25‰),为热水来源的石英。硅灰过渡岩石的?30Si值为-0.2‰,表明硅化的过程有地下热水参与。矿化硅岩的?30Si值为-0.1‰~+0.5‰,说明在原始深水有热水参与的化学沉积硅岩基础上,受到了成矿期含矿热液的再次改造。5.含矿岩类与铀成矿关系若尔盖铀矿田含矿岩系中各种岩石的微量元素特征表明,硅质岩、矿化硅质岩、硅灰岩、硅质岩矿石等富集的微量元素种类具有一定的相似性,在微量元素原始地幔标准化蛛网图上可明显分为两类不同的配分曲线,其中英安斑岩与板岩具有相似的配分形态,而硅质岩、矿化硅质岩、硅灰岩、硅质岩矿石、矿化硅灰岩、灰岩、热液方解石脉及石英脉等的配分曲线大体一致,反映铀成矿与硅质岩、硅-灰岩以及热液方解石脉和石英脉等关系密切。本区含矿岩类具有代表意义的主因子有六个。分别为F1主因子:Cr-GaZr-Nb-Hf-Ta-W-Pb-Th,代表深源的英安斑岩和板岩;F2主因子:LiBe-Sc-Ga-Rb-Zr-Nb-Cs-Hf-Th,代表陆源细碎屑岩类的微量元素组合;F3主因子:Co-Ni-Zn-Y-Mo-U,代表成矿期的方解石脉矿石及部分硅灰岩;F4主因子:V-Cu-Mo-U,代表硅岩矿石及部分含矿方解石脉;F5主因子:Bi-Pb-Ba,代表沉积硅岩;F6主因子:Sr,代表沉积灰岩及硅化灰岩。其中,F5主因子与F6主因子关系密切,为海洋化学沉积成因;F2主因子、F3主因子、F4主因子关系较为密切,与矿化作用过程有关;F1主因子相对对立。由此表明成矿与硅岩、硅-灰岩以及热液方解石脉和石英脉等关系密切。6.硅质岩的成矿意义本区硅质岩铀平均含量达10.955×10-6,而钍平均含量仅有0.534×10-6,Th/U只有0.059,属富铀的沉积建造。该地区硅质岩极低的Th/U值可能暗示岩石中的U主要为活性铀。因此,若尔盖含矿岩系中硅质岩的高铀含量和极低的Th/U值对铀的成矿十分有利,由热水沉积作用所形成的硅质岩系为后期铀的成矿奠定了良好的物质基础。本区钙化硅岩(硅灰岩)不仅孔隙度大,而且易于产生脆性变形而形成层间破碎带,利于含矿热液在其中进行运移和沉淀富集。因此硅质岩不仅是成矿的有利矿源层,由硅质岩经碳酸盐化所形成的钙化硅岩(硅灰岩)亦为成矿提供了十分有利的空间。上述认识对于深化若尔盖铀矿田的矿床成因认识,指导该地区的铀矿找矿勘查工作具有重要的指导意义。
[Abstract]:Joel Guy is located in the western part of the territory of Sichuan Province, the main ore field in Ruoergai County in southern Qinling Mountains uranium metallogenic belt, the main part of the grounds of Paleozoic strata composed of white Longjiang anticlinorium, is an important Chinese carbon silicon mudstone type uranium deposit deposit group is mainly produced in the producing area. The Lower Silurian narrow ditch group, Tal Group and pull long epimetamorphic silicon group grey rocks, and strictly controlled by the lithology, tectonic and geochemical environment, is currently the largest number of the largest Chinese deposit, industry, and economic significance is obvious and the development prospects of carbon silicon mudstone type uranium ore field, the ore geologists and thus much attention. The siliceous rocks is one of the important ore bearing rock Joel Guy carbon silicon mudstone type uranium ore field in the region. Based on the structure and origin of siliceous rocks can be divided into argillaceous siliceous rocks, metacryst siliceous rocks, siliceous rocks and siliceous rocks of silicified calcification in four types. This paper mainly from silicon Major elements of rock geochemistry, trace element geochemistry, REE geochemistry and isotopic geochemical characteristics of silicon to genesis of siliceous rocks in Ruoergai uranium ore field, the ore bearing rock series in. Using factor analysis method based on system analysis of the ore hosting rocks, hydrothermal minerals (quartz, calcite), the correlation between to explore the relationship between trace elements of ores, rocks and siliceous uranium mineralization. Through this research, the following results have been achieved: the content of SiO2 1. siliceous rock major element geochemistry of siliceous rocks in the average value of 95.72%, indicating that the rock contains few terrigenous mud sediments. The mean ratio of Al/ (Al+Fe+Mn) 0.21, the ratio of Fe/Ti mean value is 55.69, the ratio of /Ti (Fe+Mn) value was 61.78, the ratio of these features indicate that the hydrothermal sedimentary origin. In the Al-Fe-Mn diagram and Al2O3-SiO2 of standard patterns, siliceous rocks Cast point are also projected in the hydrothermal area.MnO/TiO2 with an average of 5.226, reflecting the siliceous rocks formed in deep sea basin environment; the average MgO/Al2O3 value of up to 0.940, suggesting that the trace elements formed in high salinity seawater sedimentary environment.2. siliceous rock trace element geochemical characteristics of the siliceous rocks in the area with high U content while the low content of Zr element, suggesting that it may be hot water causes and the formation of terrigenous sedimentary environment may be away from the.Th/U ratio, Sr/Ba ratio is far less than 1, showing obvious causes of hot water, while the Rb/Sr ratio is low, reflecting the sedimentary siliceous rocks have rich mafic source added that rare earth elements, there was a strong expansion cracking.3. siliceous rock geochemical characteristics of rare earth elements in the area of the siliceous rocks of North American shale normalized REE curve is left leaning, with negative Ce anomaly and weak positive Eu anomalies in most samples, the The average value of Ce is 0.80 Eu, an average of 1.2, with the typical characteristics of chert siliceous rock.4. isotopic geochemistry of the black lamellar siliceous rocks? 30Si = -0.4% ~+0.2% (average 0.017 per thousand), shown as deep-sea sediments far from the mainland. Quartz veins? The 30Si value is -0.1% ~+0.5% (average 0.25 per thousand), for the hot water source of quartz. Wollastonite transition rock? 30Si value is -0.2%, that the process of the underground water in the silicified rocks. Mineralization of silicon? 30Si value is -0.1% ~+0.5%, the hot water and the chemical sedimentary siliceous rocks based on the original deep water, by the mineralization of ore fluid containing.5. re transformation of various rock ore rock type relationship with uranium mineralization in Ruoergai uranium ore field, the ore bearing rock series in the trace element characteristics indicate that the mineralization of siliceous rocks, siliceous rocks, limestone, kinds of trace element enrichment of siliceous rock ore etc. There are some similarities, in the spider diagram of trace elements in primitive mantle standard can be obviously divided into two different types of distribution curve, which is similar to the dacite porphyry and slate with morphology, and siliceous rocks, mineralization of chert, siliceous limestone, siliceous rock and ore mineralization, limestone, limestone, hydrothermal calcite and quartz vein and the distribution curve is consistent, reflecting the uranium mineralization and siliceous rocks, silicon limestone and hydrothermal calcite and quartz veins are closely related. The main factor in the area of ore rock representative has six main factors: F1 respectively. Cr-GaZr-Nb-Hf-Ta-W-Pb-Th, on behalf of the deep dacite porphyry and slate; F2 main factor: LiBe-Sc-Ga-Rb-Zr-Nb-Cs-Hf-Th, trace elements represent terrigenous microclastic rocks; F3 main factor: Co-Ni-Zn-Y-Mo-U, represent the metallogenic period of calcite ore and limestone; F4 main factor: V-Cu-Mo-U, on behalf of silicon rock Stone and ore bearing calcite veins; F5 main factor: Bi-Pb-Ba, sedimentary cherts; F6 main factor: Sr, sedimentary limestone and silicified limestone. The relationship between the F5 factors and F6 factors closely, for the marine chemical sedimentary origin; F2 factor, F3 factor, F4 factor. The more closely related to the mineralization process; F1 factor contrast. These results indicated that mineralization and Metallogenic Significance of siliceous rocks, the average content of siliceous rocks closely.6. silicon limestone and hydrothermal calcite and quartz vein between the area of 10.955 * 10-6 siliceous rocks, uranium and thorium, the average content is only 0.534 * 10-6, Th/U is only 0.059, is a sedimentary uranium rich siliceous rocks is very low. Th/U built the area value may suggest that the rocks in the major U activity of uranium. Therefore, high content of uranium ore containing siliceous rock series in Ruoergai and low Th/U value of uranium mineralization is very favorable, formed by hot water sedimentation The siliceous rocks lay a good material foundation for later mineralization of uranium. Calcification of silicon rocks in this area (limestone) not only large porosity, and prone to brittle deformation and the formation of interlayer fracture zone, favorable ore bearing hydrothermal in migration and precipitation accumulation. So the siliceous rocks are not only favorable source of ore mineralization the calcification of siliceous rocks siliceous rock formed by carbonate (limestone) provides very favorable space for the mineralization. The understanding of the genesis of the deposit of Ruoergai uranium ore field, deepen understanding, has important guiding significance to guide the region's uranium ore prospecting work.

【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】：P619.14;P588.244

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