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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。
The Kapok campybdenum deposit is one of the most important porphyry deposits in the southern section of Chin-Hang metallogenic belt. The deposit developed typical “center-type alteration” and A, B and D three types of mineralization veins. In order to deepen the understanding of the metallogenic process, pyrite from different veins was selected to study its microstructure index by scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and Raman spectroscopy Type features in order to reverse the thermodynamic and kinetic information of mineralization processes. The results of SEM showed that there were fewer pyrites in vein A, which were semicircular shape with 100 ~ 200μm shape and flat droplet shape in seed vein. B vein pyrite developed strongly and appeared in the shape of 500 ~ 1000μm , And the seeds were almost oval in shape. The pyrite in the D vein was cubic with a grain size of about 10-20 mm. The three groups had perpendicular grain growth and the angular distribution of seeds was linear. In the A vein → B vein → D vein, the grain size of pyrite became larger and the seeds more regular, which indicated that the crystallization rate of pyrite gradually became slow and the growth environment became stable. XRD results show that each sample line are characterized by multiple sets of pyrite characteristic peaks, but the development of strong peaks there are differences. The highest peak of A vein was 28.5 ° and the second peak was 37.1 °. The corresponding peaks of B vein and D vein were 37.1 °, 33.1 ° and 33.1 °, respectively, and 56.3 °. The characteristics of the diffraction peaks indicate that the crystal form of the A-pulse sample should be dominated by the regular octahedron with the (1 1 1) plane and the pentagonal dodecahedron with the (2 1 0) plane as its formation temperature should be greater than 300 The samples of B vein should be mainly composed of pentagonal dodecahedron with (2 1 0), followed by the cubic form with (1 0 0) crystal plane, the formation temperature should be between 200 ~ 300 ℃ or slightly Large; D pulse samples mainly composed of (100) crystal cubic surface, the formation temperature should be less than 200 ℃. Raman spectroscopy revealed that νEg = 348.0 ~ 350.7cm -1, νAg = 385.2 ~ 386.5cm -1, and νTg = 441.9 ~ 422.8cm -1 in the A-vein samples. In contrast, B The corresponding values of pulse and D pulse were shifted to 2 ~ 6cm ~ (-1) and 5 ~ 14cm ~ (-1) to low frequency, respectively. The scattering intensities of sample A were IEg = 388.8 ~ 745.5, IAg = 1532.8 ~ 2071.8, ITg = 238.9 ~ 254.4, while the scattering intensities of samples B and D were significantly enhanced. From A pulse → B pulse → D pulse, Raman shift to low frequency shift, the scattering intensity in turn increased, indicating that the three students in order to reduce the pressure. This study suggests that the Early Paleozoic of the Poziping porphyry type molybdenum deposit is mainly a high temperature and high pressure magmatic hydrothermal activity. With the decrease of metallogenetic temperature and pressure, the oxygen fugacity of the ore-forming system gradually decreases and the sulfur and Metal elements are gradually transformed into metal sulfide forms and mineralization.