钦-杭带南段坡仔营斑岩型钼矿中黄铁矿微组构及其标型意义

发布时间：2018-05-21 20:19

  本文选题：黄铁矿 + 扫描电镜　； 参考：《岩石学报》2017年03期

【摘要】：坡仔营钼矿是钦-杭成矿带南段最重要斑岩型矿床之一。该矿床发育典型"中心式面型蚀变"和A、B和D三种类型矿化脉。为了加深对其成矿过程的认识,本研究选取不同矿脉中黄铁矿,通过扫描电镜(SEM)、X射线粉晶衍射(XRD)和激光拉曼光谱(Raman),研究其微组构标型特征,以期反演成矿过程的热力学及动力学信息。SEM结果显示,A脉内黄铁矿较少,呈100~200μm半自形-他形,籽晶呈扁平乳滴状;B脉黄铁矿强烈发育,呈500~1000μm自形-半自形,籽晶呈近椭圆形层状;D脉内黄铁矿呈立方体产出,粒度10~20mm左右,三组相互垂直晶纹发育,籽晶棱角状线形展布。A脉→B脉→D脉中黄铁矿粒度逐渐变大,籽晶更加规则,指示成矿早期至晚期,黄铁矿结晶速度逐渐变缓,成生环境趋于稳定。XRD结果展示,各样品谱线均发育着多组黄铁矿特征峰,但其强峰发育存在差异。A脉最强峰为28.5°,次强峰37.1°;B脉和D脉相应峰位分别为37.1°、33.1°和33.1°、56.3°。衍射峰型特征表明,A脉样品晶形应以(1 1 1)面组成的正八面体单形为主,其次为(2 1 0)晶面组成的五角十二面体,其成生温度应大于300度;B脉样品应以(2 1 0)组成的五角十二面体单形为主,其次为(1 0 0)晶面组成的立方体单形,形成温度应介于200~300℃之间或略大;D脉样品主要以(1 0 0)晶面组成的立方体为主,其形成温度应小于200℃。Raman光谱揭示,A脉样品的νEg=348.0~350.7cm~(-1)、νAg=385.2~386.5cm~(-1)、νTg=441.9~422.8cm~(-1),与之相比,B脉和D脉的对应值分别向低频偏移2~6cm~(-1)和5~14cm~(-1);A脉样品的散射强度IEg=388.8~745.5、IAg=1532.8~2071.8、ITg=238.9~254.4,而B及D脉样品的散射强度依次明显增强。自A脉→B脉→D脉,拉曼位移向低频偏移,散射强度依次增强,指示三者的成生压力依次降低。本研究认为,坡仔营斑岩型钼矿的成生早期为一个高温、高压岩浆热液活动为主阶段,随着成矿温度、压力的降低,成矿系统氧逸度逐渐降低,硫及金属元素逐步转变为金属硫化物形式而成矿。
[Abstract]:Pozaiying molybdenum deposit is one of the most important porphyry deposits in the southern segment of Qinghang metallogenic belt. There are three types of mineralization veins in this deposit: central surface alteration and AZB and D. In order to better understand the metallogenic process of pyrite in different veins, the microfabric characteristics of pyrite were studied by scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and laser Raman spectroscopy (Ram). The thermodynamic and kinetic information of the ore-forming process can be retrieved. SEM results show that there is less pyrite in the vein, 100 ~ 200 渭 m semiautomorphism, and the seed crystal is strongly developed in the flat emulsion drop B vein, and in the 500 ~ 1000 渭 m self-shape -semi-automorphism. The pyrite in the D vein of the seed crystal is cubic, the grain size is about 10~20mm, and the three groups of vertical grain develop mutually. The grain size of pyrite in the D vein is gradually larger, and the grain size of the seed crystal grain is more regular, and the grain size of the pyrite grain in the D vein is gradually larger, and the grain size of the pyrite in the D vein is more regular, and the grain size is more regular. The results indicate that the crystallization rate of pyrite gradually slows down from the early to late metallogenic period, and the forming environment tends to be stable. XRD results show that there are many groups of pyrite characteristic peaks in the spectrum lines of each sample. However, there were differences in the development of strong peaks. The strongest peak was 28.5 掳, and the corresponding peak positions of 37.1 掳B and D were 37.1 掳/ 33.1 掳and 33.1 掳/ 56.3 掳, respectively. The diffraction peak pattern shows that the crystal shape of the sample is mainly octahedral simplex, followed by pentagonal dodecahedron. The forming temperature should be greater than 300 掳B vein samples should be composed of pentagonal dodecahedron simplex, followed by cubic simplex composed of 100) crystal plane. The formation temperature should be between 200 鈩，

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