【作者】 刘小滨；

【导师】 李胜荣；

【作者基本信息】 中国地质大学（北京） ， 矿物学、岩石学、矿床学， 2009， 硕士

【摘要】 麻棚岩体位于太行山中段石湖大型金矿西北部2～3千米处,关于该岩体与成矿关系尚未从成因矿物学角度进行系统研究。岩体与太古宇阜平群变质岩呈侵入接触,是由石英闪长岩（边缘相）、花岗闪长岩（过渡相）及花岗岩（中心相）组成的复式岩体。本文选取花岗闪长岩和花岗岩为研究对象,进行了如下研究。造岩矿物成因矿物学研究得出:斜长石环带异常,长石含高Fe₂O₃和TiO₂,反映了岩浆的氧化环境及混合特征。角闪石属钙质角闪石亚族,富Mg,在TiO₂-Al2O3图解位于壳幔混合区,反映壳幔混合特点;碱质变化较大;富含Fe3+是氧化环境的标志。黑云母富镁,AlVI含量较低,MF平均值0.56,符合同熔型特征;黑云母MnO偏高,MgO含量介于壳幔黑云母MgO含量之间,在Fe3+- Fe2+- Mg 2+图中黑云母全部落入壳幔混合区,黑云母与角闪石中具石英包体,说明壳幔混合源特点。角闪石-黑云母矿物温压计与前人研究结果显示,温度主要为740℃～760℃,压力主要为2×108～3×108Pa,氧逸度lgfo2主要为-14.60～-10.77。副矿物成因矿物学研究得出:锆石为典型岩浆锆石;其形态研究表明岩体结晶液相线温度约为900℃,岩浆期岩浆富水、富碱质;锆石微量元素表明岩浆具相对氧化的结晶环境,源区以壳源为主,有幔源物质混入。锆石U-Pb测年表明:麻棚岩体形成年龄为130Ma左右;初步推断岩体与脉岩为同源关系;金成矿略晚于130Ma,可能略晚几个Ma。大量磁铁矿和榍石共生组合,且角闪石富镁,说明岩浆氧逸度较高,指示磁铁矿系列。包体中磷灰石为细长针状,有些为短柱状,含MgO0.07%、FeO0.27%、TiO₂0.20%,为岩浆混合标志。岩石地球化学研究表明:岩体由岩体边缘性→过渡相→中心相, SiO₂及全碱含量逐渐增加,而∑R"O、铝则逐渐减少,总体上贫硅,富含铝、碱及二价元素为钙碱性系列,具高钾特征;成因类型为I型花岗岩;相对富集部分成矿元素,富含碱土金属元素Sr、Ba,而贫岩浆演化晚阶段的碱金属Rb;岩体岩浆源区为下地壳,可能有地幔物质的混入,演化不彻底。综上所述,麻棚岩体与脉岩为同源关系;属I型花岗岩,岩浆源区为下地壳,有幔源物质的混入,形成年代为130Ma左右,具有氧化环境,富含碱质,有利于金的运移富集。更多还原

【Abstract】 Mapeng intrusion lies in the northwest 2～3 kilometers of the large gold deposit in Shihu, which is from Mid-Taihang mountain. The relationship between the intrusion and mineralization hasn’t been studied systematically from the Genetic Mineralogy. Mapeng intrusion has an instrusive contact with metamorphic rocks of Archaeozoic Fuping group, which is composed of quartz diorite （border facies）, granodiorite （transitional facies）, granite （central facies）. This paper studies granodiorite and granite, and the conclusions are as follows.The study on Genetic Mineralogy of rock-forming mineral shows that: plagioclase zonings are abnormal, Fe₂O₃ and TiO₂ are high in feldspar, which reflect the oxidation environment and mixing characteristics of magma. Amphiboles are the calc-amphibole subtribe, and are rich magnesium mineral, located in the area of MC in TiO₂-Al2O3 diagram, all of those characteristics on amphiboles indicate magmatic mixing; On the other hand the characteristics of the changing alkaline largely and the rich Fe3+ are the sign of the oxidation environment. All characteristics of rich Mg, low AlVI and the average of MF （0.56） on biotites indicate marke of syntexis type; MnO in biotites are higher, the quantity of MgO in biotites are the quantities between shell source and mantle source, Biotites are located in the area of MC in Fe3+- Fe2+- Mg 2+ diagram, quartzes are wrapped in biotites and amphiboles, all of those characteristics on biotites indicate magmatic mixing. The indicator of hornblende-biotite and the former reseaches show: the main temperatures of the intrusion are 740℃～760℃, the main pressure of the intrusion are 2×108～3×108Pa, the main oxygen fugacities lgfo2 of the intrusion are -14.60～-10.77.The study on Genetic Mineralogy of accessory mineral shows that: zircons are divided in the typical magmatogene zircons, the study of zircon shape shows crystallizing liquidus temperature of the intrusion is 900℃, and the magma are richer in water and alkaline; Trace elements of zircon indicates a relative oxidation environment of magmatic crystallization, that the source region is main with shell source and mixed by mantle source. U-Pb zircon dating indicates the formation age of Mapeng intrusion is about 130Ma; the relationships between the intrusion and dykes are primarily considered to be homologous. Intergrowth of a large number of magnetite and spineline and rich Mg in amphiboles indicate the higher oxygen fugacities of magma, and also indicate that the intrusion belongs to magnetite series. Aptities are long and thin needle-like and some are short prismatic, the quantity of MgO、FeO、TiO₂ of aptities are respectively 0.07%、0.27%、0.20%, the characteristics of aptities indicate the magmatic mixing.The study of geochemistry shows that: with the contents of the SiO₂ and whole alkali increasing gradually from the border facies, transitional facies to central facies of the Mapeng intrusion, the value of∑R"O and Al presents decreasing inversely. The intrusion is rich in Al, alkali and divalent ion but poor in Si generally, which belongs to calc-alkaline series, and has the characters of high K; The geneses of the intrusion is I-type granite, and the intrusion has the high value of the mineralization elements and Sr, Ba but low value of Rb; The origin source of the magma located at the lower crust and maybe mix partial mantle material, and its evaluation is not thorough.In conclution, Mapeng intrusion has the homoeologous relationship with the dykes, and it is divided into I-type granite which is come from lower crust with mantel material mixing. Its formation age is 130Ma±, and during the process of the intrusion, the magmatic environment is under the oxidation conditions and rich in alkali so that it is advantageous for migration and enrichment of Au.更多还原