广西桂北垒洞煌斑岩中金刚石的发现及其矿物组合特征

The discovery of diamond and mineral association characteristics in Leidong lamprophyre,the northern Guangxi

桂北罗城垒洞煌斑岩(云煌岩)中发现了与安徽栏杆地区相似的金刚石。垒洞云煌岩呈岩筒状产出并有明显分带性,从岩筒中心→边缘可分为3个相带:中心相为具气孔状-杏仁状构造云煌岩和角砾状云煌岩;过渡相为云煌岩;边缘相为强碳酸岩化-褐铁矿化云煌岩。本次发现的金刚石产于中心相气孔状-杏仁状构造云煌岩中,岩石主要由富镁黑云母、透长石、辉石、角闪石(或闪辉矿物假象)组成。发现的金刚石其拉曼光谱具有1331cm^-1处的金刚石特征峰,红外吸收光谱显示既含有1282cm^-1吸收峰,又含有1175cm^-1吸收峰的ⅠaAB型金刚石特征。电子探针分析表明,垒洞煌斑岩中金刚石伴生矿物组合为镁-铁铝榴石、铬尖晶石亚族的含镁铬铁矿和镁铬铁矿,以及贫铬透辉石、碳硅石和橄榄石。与其他地区含矿煌斑岩相比,矿物组合既有相同也有不同之处,为广西金刚石找矿提供依据。

The paper reports the natural diamond discovered in Leidong lamprophyre of Luocheng,Guangxi Province,which shares the similar characteristics with the diamond found in Langan district,Anhui Province.Leidong lamprophyre occurred as the pipe form,could be divided into three phase zoning from its centre to margin,they are vesicular-amygdaloidal structure and brecciated structure mica-lamprophyre,homogeneous structure mica-lamprophyre,intensely carbonated-limonite lithified mica-lamprophyre respectively.The diamond was discovered in the rock of central phase,the rock is mainly made of eastonite,sanidine,pyroxene,hornblende(or pseudomorph).The diamond got from Leidong lamprophyre has the peak at 1331 cm^-1 in Raman spectra-the diamond characteristic peak,and has two peaks at 1282 cm^-1 and 1175 cm^-1 in infrared absorption spectrum-theⅠaAB type diamond characteristic peaks.The results of electronic probe analysis show that the associated minerals of diamond are mainly almandine with certain magnesium content,and chromite with certain magnesium content and magnochromite-both in chromium spinel subfamily,and the poor-chromium diopside,moissanite and olivine.Compared with indicator mineral combination in other area's ore-containing lamprophyre,have the same characteristics,also the different.The result of the study may provide an import reference for diamond exploration in Guangxi.