甘肃沃尔给花岗岩体中黑云母的成分特征及对成岩成矿的指示意义

发布时间：2018-02-28 06:09

本文关键词： 黑云母成因温压计花岗岩碱度西秦岭　出处：《中国地质大学(北京)》2017年硕士论文　论文类型：学位论文

【摘要】：西秦岭造山带是中国大陆中央造山带的重要组成部分之一,沃尔给楔卡金矿位于西秦岭造山带的西段、力士山-围挡山断裂带北侧,西土房—大槐沟断裂带近东西向横穿矿区而过。本文通过甘肃省沃尔给楔卡金矿1:1万土壤地球化学测量数据,运用R型聚类分析方法对测量数据进行了分析。结果显示:8种元素可分为三类:第一类为Sb、As、Au、Pb、Ag中低温元素组合;第二类为Cu、Zn中高温元素组合;第三类以Hg为代表的挥发性元素。根据单元素异常分布特征及元素组合异常,结合地层、岩性、构造等有利控矿因素综合圈定出3个找矿靶区,分别为Ⅰ、Ⅱ和Ⅲ号异常区。运用系统核理论对该三个异常进行评价结果认为:Ⅰ、Ⅱ和Ⅲ号异常区系统的核分别为{Au,Pb}、{Au}及{Cu},系统稳定性强,其中Ⅰ和Ⅱ号异常区经钻探和槽探等工程验证,矿化位置、规模与元素异常浓集中心位置吻合较好,说明在这两个异常区内,土壤地球化学测量所显示的异常为矿致异常。对于核为{Cu}的Ⅲ号异常区系统,认为其属于以Cu、Au为主要成矿元素的异常系统。土壤次生晕所显示的异常分布区恰恰位于花岗质岩侵入体内部及其与碳酸盐岩的接触带,暗示土壤次生晕所显示的异常与花岗质岩有关。本文选取位于矿区内与成矿空间关系密切的花岗岩之黑云母为研究对象,通过对其细致的岩相学观察和其矿物成分原位分析,探讨了黑云母的形成条件及其对成岩成矿的指示意义。根据黑云母的Fe~(2+)-Fe~(3+)-Mg~(2+)三角图解及logfO_(2-)T图解,估算其结晶时的氧逸度(logfO_2)变化范围是10-11~10-13,结晶温度约在670℃~715℃之间。依据黑云母全铝压力计公式计算所得成岩压力为1.56~2.04kbar,相应的侵位深度在5.91~7.72km之间。依据黑云母的TFeO-MgO-Al_2O_3组份图解,认为该花岗岩体属于造山带钙碱性岩系,岩石成因与板块俯冲作用有关。黑云母Fe~(2+)-Fe~(3+)-Mg~(2+)成分特点还显示岩体具有幔源I型花岗岩特征。通过对研究区及国内52个各类矿床与成矿有关岩体中黑云母的主量元素化学成分进行统计和分析,并进行寄主岩石碱度判别。结果发现:与Cu、Au成矿有关的岩体几乎都位于高碱度区域内,而与Sn矿形成有关的岩体均属于低碱度岩石系列。岩浆熔体早期至岩浆后期热液阶段,氧逸度的变化由高到低、介质的碱度逐渐增强,Cu、Au矿床的形成大致经历这样的成岩成矿过程。岩浆结晶过程早期低氧逸度、高碱度有利于Sn的活化迁移,岩浆期后热液阶段的高氧逸度、低碱度有利于锡石的沉淀,但是由于锡石沉淀过程中不断消耗O_2,而致使其较高的氧逸度显著降低。碱度与氧逸度之间的相互作用、相互影响进而引起矿化的发生。本区的花岗质岩体由于具有幔源混入的I型花岗岩成因类型特征,结合区域地质背景,可能形成于板内叠覆造山环境下,其黑云母成分特点与华南同熔型花岗岩类大体一致。岩体结晶在较高的氧逸度(logf O_2NiNiO+1)环境,因此对于金、铜等亲硫元素的迁移和富集十分有利。本区具有金、铜成矿潜力。
[Abstract]:The western Qinling Mountains orogenic belt is one of the most important part of the Central Orogenic Belt, China, wall to wedge card gold deposit is located in the western Qinling Mountains orogenic belt of the west, Alex Hill - Wai Shan fault zone on the north side block, West Real - Huai ditch fault zone near East-West across the mining area and Gansu province. This paper gave wal card gold wedge 1:1 000 soil geochemical survey data, using the R cluster analysis on the measurement data are analyzed. The results showed that 8 kinds of elements can be divided into three categories: the first category is Sb, As, Au, Pb, Ag in low temperature elements; the second class is Cu, high temperature Zn element in combination; volatile elements third the class represented by Hg. According to the lithologic anomaly distribution and elements of single element composite anomalies, combined with the formation, structure, and other favorable ore controlling factors comprehensive delineated 3 prospecting target area, respectively, for I, II and III anomaly area. Using the system theory of the nuclear abnormal three The evaluation result showed that I, II and III anomaly system for nuclear were {Au, Pb}, {Au} and {Cu}, the stability of the system, in which I and II anomaly area by drilling and trenching engineering verification, mineralization location, size and element anomaly concentration center positions agree well with that in the two anomaly area in the soil geochemical survey shows abnormal ore caused anomaly. As for the nuclear III anomaly area {Cu} system, think it belongs to Cu, Au for the abnormal system of main ore-forming elements. Soil secondary halo shows on the abnormal distribution area is located in the granitic intrusive rocks and carbonate rocks and body contact with hints about anomalies and granitic rock soil secondary halo shows. This selection is located within the mining area and mineralization in close spatial relationship of biotite granite as the research object, through the detailed petrographic observations and the mineral composition of the original An analysis, explore the formation conditions of biotite and its significance for mineralization. The biotite Fe~ (2+) -Fe~ (3+) -Mg~ (2+) and logfO_ (2-) triangular diagram T diagram, estimate the crystallization in the oxygen fugacity (logfO_2) in the range of 10-11~10-13, the crystallization temperature between about 670 DEG ~715 DEG. On the basis of biotite geobarometer calculated diagenetic pressure of 1.56~2.04kbar, depth of emplacement of the corresponding 5.91~7.72km. On the basis of the biotite TFeO-MgO-Al_2O_3 component diagram, that the granites belong to calc alkaline rocks in orogenic belt, petrogenesis associated with subduction of biotite. Fe~ (2+) -Fe~ (3+) -Mg~ (2+) also showed the composition characteristics of rock mass has the characteristics of mantle derived I type granite. Through statistical analysis of the study area and biotite domestic 52 kinds of ore deposits related to mineralization in the rock mass of main elements of chemical composition, and host Rock identification. The results showed that the alkalinity and Cu, Au rock related to mineralization are almost located in the high alkalinity region, and the formation of the rock mass are low alkalinity rock series and Sn ore magma melt. The early to late magmatic hydrothermal stage, the oxygen fugacity changes from high to low, medium alkalinity gradually increased. Cu, the formation of Au deposits experienced diagenesis and mineralization process. Early magmatic crystallization process under the low oxygen fugacity, high alkalinity activation and migration for Sn, post magmatic hydrothermal stage high oxygen fugacity, conducive to cassiterite precipitation and low alkalinity, but due to the consumption of O_2 tin stone precipitation process, and the higher the oxygen fugacity decreased significantly. The interaction between the basicity and oxygen fugacity, mutual influence and cause the occurrence of mineralization in this area. The granitic rocks due to formation of I type granite type mantle mixed characteristics, combined with regional geological background That may be formed in the plate superposition orogeny environment, the biotite composition characteristics of Southern China and the same type of granite typemelting generally consistent. The rock mass crystallization at higher oxygen fugacity (logf O_2NiNiO+1), so for the gold, copper migration and enrichment of sulphophile elements is very favorable. This area has the gold, copper metallogenic potential.

【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P588.121;P612

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