皖北卧龙湖煤矿岩-煤蚀变带黄铁矿拉曼光谱特征及意义

Micro-Raman Spectral Characteristics and Implication of FeS2from Metamorphic Belt between Coal and Intrusion in Wolonghu Coal Mine of Anhui Province,China

选取皖北卧龙湖煤矿岩浆侵入区,研究其岩-煤蚀变带内不同形态和期次FeS_2的拉曼光谱特征。结果显示,依据峰型组合(M)、拉曼位移(Δν)和散射强度(I)的不同,各样品数据可以划分为Ⅰ型、Ⅱ型和Ⅲ型3类。Ⅰ型样品发育5个较强的散射峰,E_g值(1.16~1.59×10~3)和A_g值(2.33~2.53×10~3)均较高,T_g值(0.20~0.27×10~3)一般较低。与之不同,Ⅱ型样品拉曼谱线上仅可见到前3个散射峰,不发育后2个散射峰;其E_g值、A_g值及T_g值均与Ⅰ型相似。Ⅲ型样品与前两类均不同,仅发育327.6~328.8和389.0~390.1cm^(-1)两个较强的散射峰,样品Eg值(0.94~1.14×10~3)较高,Ag值(0.27~0.33×10~3)较低,Tg值低于检测限。分析表明,Ⅰ型样品的前三个散射峰分别为与黄铁矿的Fe-[S_2]^(2-)变形振动、伸缩振动和S—S伸缩振动相关;后两个散射峰分别与石墨微晶振动和石墨晶面内C—C伸缩振动对应,展现出黄铁矿特征和天然焦的共同特征,推测为遭受天然焦混染的黄铁矿混晶。Ⅱ型样品发育前3个散射峰,指示其为典型的黄铁矿晶体;而Ⅲ型样品的谱峰特征与白铁矿相似,推测其有可能为黄铁矿的低温白铁矿变晶。进一步分析还表明,Ⅰ型和Ⅱ型拉曼散射强度相近,Ⅲ型样品较前二者明显偏低,暗示Ⅰ型和Ⅱ型样品形成压力相近,而Ⅲ型样品形成压力较低;三者Ag峰分别依次较前者向高频偏移4.4~6.7和4.5~8.4cm^(-1),这指示Ⅰ型、Ⅱ型和Ⅲ型样品的形成温度依次显著降低。依据上述光谱证据认为,淮北卧龙湖煤矿内蚀变煤和过渡带内黄铁矿均为中高温产物,应为岩-煤蚀变过程中的产物;而侵入岩内发育黄铁矿的低温白铁矿变体很可能为岩体固结后的次生产物。

Some FeS_2 samples among metamorphic belt between coal and intrusion from Wolonghu mine in the north of Anhui Province were retrieved to characterize the signature of Raman Spectral.The results show that,all Raman data of different samples can be divided into 3types asⅠ,Ⅱ andⅢ according to distinct differences of in Raman mode（M）,Raman shift（Δν）and scattering intensity（Ⅰ）.There are five strong scattering modes including high value E_g（1.16～1.59×10^3）,high value A_g（2.33～2.53×10^3）and low value T_g（0.20～0.27×10^3）in typeⅠand only former three modes in typeⅡ although the value of E_g,A_g and T_g are similar between them.While there are only two modes of high value Egabout 327.6～328.8cm^（-1） and low value A_g389.0～390.1cm^（-1）.Our analyses indicate that typeⅠsamples must be mixed crystal of pyrite and natural coke for the former three peaks are same to deformation and stretching vibration of Fe-[S_2]^（2-）and stretching vibration of S—S in pyrite,while the latter two are similar to the vibration of Tiny graphite crystals and stretching vibration of C—C among graphite crystal from Raman data.And typeⅡsample may be pyrite for typical pyrite Scattering peak and Type Ⅲ sample possibility are lowtemperature crystalloblastic of pyrite for Marcasite spectrum features in Raman.Further analysis also showed that the formation pressure of typeⅠ andⅡ are the same while typeⅢsamples formed in low pressure for Raman scattered intensity of typeⅠandⅡ are similar,and typeⅢ samples is obviously lower than the former two.And the formation temperature of typeⅠ,typeⅡand typeⅢsignificantly decreased in turn for Agpeak of them are turn to high frequency about 4.4～6.7,4.5～8.4cm^（-1） respectively compared with the former.Thus,The authors＇ studies suggest that pyrite samples from Metamorphic coal and metamorphic zone in Wolonghu coal mine are products in high temperature,but samples from Magmatic rocks are Marcasite formed at low temperature.