新疆软玉仔料中黑色树枝状物质的拉曼光谱和显微结构特征

软玉仔料表层微裂隙处常见一种黑色树枝状物质，该物质极大程度地揭示了仔料历经的次生风化过程，然而目前对其岩石矿物学特征研究甚少。选取新疆软玉仔料为研究对象，采用电子探针、激光拉曼光谱仪和扫描电子显微镜就其表层微裂隙处黑色树枝状物质的化学成分、拉曼光谱和显微结构进行测试分析。结果表明：黑色树枝状物质的主要化学成分为MnO和BaO，MnO含量为49.045%~54.012%，BaO含量为9.012%~10.961%。拉曼光谱分析显示软玉仔料主体部分主要由透闪石矿物组成，而黑色树枝状物质则主要由表生锰矿物和有机质组成。表生锰矿物中由MnO₆八面体Mn—O伸缩振动所致拉曼特征谱峰位于475，498，510，575和617 cm-1附近;且树枝各处锰矿物结晶程度不一，表现为拉曼谱峰强度和峰形尖锐程度存在区别。有机质由分子结构中C—C伸缩振动和分子结构单元间缺陷、无序排列所致拉曼特征谱峰分别位于1 590和1 370 cm-1附近。扫描电子显微镜观察显示黑色树枝状物质呈薄膜状覆盖于交织排列的透闪石纤维表面，并与其突变接触。综合化学成分、拉曼光谱和显微结构测试分析，软玉仔料中黑色树枝状物质的形成与河流中锰化合物和有机质的多期次沉降有关。

Raman Spectra and Microstructure Characteristics of Dendrite in Xingjiang Nephrite Gravel

Dendrite shaping as micro fractures is commonly found in surface of nephrite gravel and it reveals its weathering process.Howev er,study on the petrological and mineralogical characteristics of dendrite in n ephrite gravel is so far limited.Therefore,Xingjiang nephrite gravel was selec ted as researching sample,while electron microprobe(EPMA),Raman spectrosco py (Raman)and scanning electron microscope(SEM)were used to study the samp le in terms of the chemical composition,Raman spectra and microstructure charac teristics.The results are shown as follows,EPMA analysis indicates that MnO an d BaO are the major chemical compositions for dendrite.The contents of MnO and BaO are 49.045%~54.012% and 9.012%~10.961% respecti vely.Raman spectra analysis shows that matrix of nephrite gravel mainly consis ts of tremolite,while dendrite mainly consists of supergene manganese minerals and organic matter.Raman peaks relating to Mn-O stretching vibration mode of MnO6 octahedra in supergene manganese minerals appear at nearly 475,498,510,575 and 617 cm-1.In addition,intensity and sharpness of the Raman peaks mentioned above being different indicates that supergene manganese mineral s are with different crystallinity in each test location.Raman peak relating t o C-C stretching vibration mode in organic matter appears at 1 590 cm-1;while Raman peak appearing at 1 370 cm-1 is related to structure defect a nd disordered arrangement.SEM result reveals that the dendrite thin film cover s on and contacts abruptly with the tremolite fibers which are arranged in pilot axitic texture.Chemical composition,Raman spectra and microstructure charact eristics comprehensively indicate that the formation of dendrite in nephrite gra vel is related to multi-stage deposition of manganese compounds and organic mat ter in the river.