大宝山多金属矿床氧化微粒的X射线衍射和近红外光谱分析及其意义

XRD and NIR Analysis of Oxidation Particles in Dabashan Polymetallic Deposit and Its Significance

利用XRD和NIR技术对大宝山东岗岭组下亚组氧化矿中7个氧化物样品微粒进行分析,其中前4个样品为同一标高,后3个样品为不同标高。XRD,NIR研究结果表明随着氧化程度的加深(04-2→04-3→04-4),Al—OH矿物吸收峰位所对应的波长不断加大(2160.72→2163.05→2200.36nm),说明矿物中的阳离子Al被取代,产生贫Al现象;且对应的峰的强度从7.08×10^-4,7.83×10^-3到6.66×10^-2,说明Al—OH矿物的含量不断上升;另外SO2-4矿物所对应的吸收峰位(1938.80→1946.94→1926.47nm)的强度从5.635×10^-2,1.82×10^-2到1.668×10^-2,说明随着氧化的进行,SO2-4矿物的含量不断下降,结合前人研究,我们可以推测出早期形成的铜多金属硫化物矿床在后期发生强烈氧化作用,使得硫化矿体氧化,其中的硫经氧化形成强酸性硫酸溶液,围岩受到硫酸溶液的腐蚀,转变成松散的黏土;在04-2,04-3,13-1号样品中发现钠明矾石和钾明矾石,矾类矿物的大量发现说明该矿区的氧化淋滤作用仍在进行;通过XRD与NIR技术发现了石英、绢云母、方解石、绿帘石、角闪石、透闪石、金云母、绿泥石、高岭土等矿物,很好的反映出蚀变类型,且与此区域的地质特征相吻合,目前近红外已开始用于矿床勘查中的蚀变填图。通过光谱分析发现了矿床深部氧化过程与阳离子取代间的关系,并以光谱学的视角验证了前人对于大宝山矿床成因的解释。研究表明一方面XRD和NIR可以有效的分析土壤和岩石的矿物成分,从而为该地区矿床矿石研究提供服务;另一方面NIR可以波长的迁移情况反映离子交代,峰的尖锐程度反映结晶程度,峰的强度反映矿物含量,这些独具的优势使其可以从微观角度研究矿物的氧化。不过有一点需要指出来,和近红外与X射线衍射在其他领域的研究相比,这两种技术在地质学的应用需要进一步加深,包括地质学应用的理论基础研究和光谱的分析解释手段,以尽量做到不仅可以通过光谱技术分析出所对应的矿物类型还能快速分析出不同矿物的含量及同一矿物的不同构型。

XRD and NIR techniques were used to analyze the seven oxide sample particles in the lower sub-group oxidized ore of the Dabaoshan dong Gangling Formation. The first four samples were of the same elevation and the latter three samples were of different elevations. XRD and NIR results show that as the degree of oxidati on deepens (04-2→04-3→04-4), the wavelength corresponding to the absorptio n peak of Al-OH mineral increases continuously (2 160.72→2 163.05→2 200.36 nm). It is indicated that the cationic Al in the mineral is substituted, resul ting in an Al-poor phenomenon;and the corresponding peak intensity is from 7 .08×10^-4 , 7.83×10^-3 to 6.66×10^-2 , which indicates that the content of Al-OH minerals is increasing;in addition, the intensity of the a bsorption peak corresponding to SO2- 4 mineral (1 938.80→1 946.94→1 9 26.47 nm) is from 5.635×10^-2 , 1.82×10^-2 to 1.668×10^-2 . It is indicated that the content of SO2- 4 minerals decreases with the progress of oxidation. Combined with previous studies, we can speculate that t he early formation of copper polymetallic sulphide deposits will undergo strong oxidation in the later stage, causing the sulfide ore bodies to oxidize. Oxida tion forms a strongly acidic sulfuric acid solution, and the surrounding rock i s corroded by a sulfuric acid solution to convert it into loose clay;Sodiumalum ite and potassium alumite were found in samples 04-2, 04-3, 13-1. A large number of strontium minerals indicate that the oxidative leaching of the ore is still ongoing;Minerals such as quartz, sericite, calcite, epidote, hornblen de, tremolite, phlogopite, chlorite, kaolin, etc. have been discovered by XRD and NIR techniques, which reflect the type of alteration, and the geologic al features of the area are consistent. At present, near-infrared spectrosco py has been used for alteration mapping in mineral deposit exploration. In this paper, the re lationship between the deep oxidation process of the deposit and the cation subs titution was discovered by means of spectroscopy, and the interpretation of the genesis of the Dabaoshan deposit was verified by the spectroscopy. The results of this paper show that on the one hand, XRD and NIR can effectively analyze th e mineral composition of soil and rock, and provide services for the ore deposi t research in this area. On the other hand, NIR can reflect the ion transfer a nd the sharpness of the peak reflects the crystallization. The intensity of the peak reflects the mineral content, and these unique advantages make it possibl e to study the oxidation of minerals from a microscopic point of view. However, there is one point that needs to be pointed out. Compared with the research of NIR and X-ray diffraction in other fields, the application of these two techn ologies in geology needs to be further deepened, including the theoretical basi s for the application to geology research and analysis and interpretation of th e spectrum, in order to not only analyze the corresponding mineral types by spe ctroscopy, but also quickly analyze the content of different minerals and diffe rent configurations of the same mineral.