Mineralogical Characteristic of Dashan Stone from Shoushan and Its Genesis
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摘要:
矿物学特征对矿床成因的研究具有重要指示意义。为探究寿山大山石的矿物学特征及成因,本研究利用偏光显微观察、X射线粉末衍射、拉曼光谱及电子探针等表征方法,对寿山大山石的矿物学特征进行了深入研究,并依据矿物学特征探讨了流体性质、形成环境及温度。结果显示,寿山大山石的主要矿物组成为高岭石和迪开石,部分为叶腊石,次要矿物为石英、黄铁矿、赤铁矿、锐钛矿和金红石等,部分矿物(如黄铁矿等)表面可见溶蚀现象。拉曼光谱及电子探针结果显示,寿山大山石中锐钛矿、金红石、黄铁矿的存在均与岩浆热液有关,而黄铁矿中As与S和Fe的负相关及表面溶蚀现象,指示成矿流体应先经历了还原环境又经历了氧化环境。依据寿山大山石主要矿物组合及Al2O3-SiO2-H2O体系矿物的相变温压条件,得出大山石矿物组合达到稳定时温度约为250~270 ℃。
Abstract:Mineralogical characteristics have significant indicative importance in the study of the genesis of ore deposits. To investigate the mineralogical characteristics and genesis of Dashan stone from Shoushan, this study utilized polarizing microscopy, X-ray powder diffraction, Raman spectroscopy, and electron microprobe analysis to conduct an in-depth investigation of the mineralogical features. Based on these characteristics, the fluid properties, formation environment, and temperature were discussed. The main minerals of Dashan stone from Shoushan are kaolinite and dickite, with some pyrophyllite; the secondary minerals include quartz, pyrite, hematite, anatase, rutile, and ilmenite, among others. Some minerals, such as pyrite, show signs of surface dissolution. The Raman spectra and electron microprobe results indicate that the presence of anatase, rutile, and pyrite in Dashan stone from Shoushan is related to magmatic hydrothermal fluids. The negative correlation between As and S and Fe in pyrite, along with the dissolution phenomena on its surface, suggest that the ore-forming fluids experienced a reduction environment followed by an oxidation environment. Based on the main mineral assemblage of Dashan stone from Shoushan and the phase change temperature-pressure conditions of the Al2O3-SiO2-H2O system, it is concluded that the stable temperature for the mineral assemblage of Dashan Stone is approximately 250-270 ℃.
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表 1 黄铁矿Fe/(S+As)值与其产出部位的关系Table 1. The relationship between the Fe/(S+As) ratio of pyrite and its occurrence location
产地 产出部位 矿石类型 平均值 Fe/% S/% As/% Fe/(S+As) 前苏联(周学武,2004) 深部 石英脉型 45.615 52.350 1.550 0.846 中部 细脉浸染型 45.720 51.680 1.280 0.863 浅部 石英脉型 46.565 49.775 0.505 0.926 寿山大山石 粒状 44.660 52.180 1.020 0.840 图 1 寿山大山石样品的偏光显微特征: (a) 单偏光下大山石的隐晶质结构;(b) 正交偏光下石英脉穿插于高岭石基质中;(c) 反射光下流纹状构造;(d) 反射光下黄色寿山大山石样品中的黄色脉状矿物沿裂隙分布;(e) 反射光下黄铁矿溶交代锐钛矿;(f) 反射光下晶体的溶蚀空洞及溶蚀凹坑Figure 1. Polarizing microscopic characteristics of Dashan stone samples from Shoushan: (a) plane-polarized light, the cryptocrystalline structure; (b) cross-polarized light, quartz veins interspersed within the kaolinite matrix; (c) reflected light, flow pattern structure; (d) reflected light, yellow vein minerals in the yellow sample distributed along the fractures; (e) reflected light, pyrite replacing anatase; (f) reflected light, dissolution cavities and etch pits in the crystals -
图 1 寿山大山石样品的偏光显微特征: (a) 单偏光下大山石的隐晶质结构;(b) 正交偏光下石英脉穿插于高岭石基质中;(c) 反射光下流纹状构造;(d) 反射光下黄色寿山大山石样品中的黄色脉状矿物沿裂隙分布;(e) 反射光下黄铁矿溶交代锐钛矿;(f) 反射光下晶体的溶蚀空洞及溶蚀凹坑
Figure 1. Polarizing microscopic characteristics of Dashan stone samples from Shoushan: (a) plane-polarized light, the cryptocrystalline structure; (b) cross-polarized light, quartz veins interspersed within the kaolinite matrix; (c) reflected light, flow pattern structure; (d) reflected light, yellow vein minerals in the yellow sample distributed along the fractures; (e) reflected light, pyrite replacing anatase; (f) reflected light, dissolution cavities and etch pits in the crystals
表 1 黄铁矿Fe/(S+As)值与其产出部位的关系
Table 1 The relationship between the Fe/(S+As) ratio of pyrite and its occurrence location
产地 产出部位 矿石类型 平均值 Fe/% S/% As/% Fe/(S+As) 前苏联(周学武,2004) 深部 石英脉型 45.615 52.350 1.550 0.846 中部 细脉浸染型 45.720 51.680 1.280 0.863 浅部 石英脉型 46.565 49.775 0.505 0.926 寿山大山石 粒状 44.660 52.180 1.020 0.840 -
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