扬子克拉通西部砂矿型金刚石的CL和FTIR光谱分析及在金刚石生长速率研究中的意义

鉴于当前人们在有效重建天然金刚石的生长过程等中所遇到的困难，如果能在微观层面上详细分析金刚石的生长过程，高度关注金刚石的生长速度，就可以为人们探讨金刚石的生长过程、分析其深部科学意义提供更为精准的科学线索。基于此，以扬子克拉通西部沅水流域砂矿型金刚石为研究对象，从微区研究的角度，采用CL光谱分析金刚石的生长环带，界定其生长微区；再利用FTIR光谱研究不同生长微区的生长时间；最后，利用生长微区的长度除以微区的生长时间，计算出不同微区的生长速度，进而分析其意义。样品的CL和FTIR光谱研究结果表明，该金刚石既发育早期生长环带，也发育后期再生长环带，其中早期生长环带为规则的平直带，环带总体呈阶梯状，大部分边缘呈不规则锯齿状；金刚石样品为IaAB型，氮总量介于47.88~321.89 μg·g-1，其最低结晶温度为1 490 K，不同部位在地幔中的停留时间不尽相同，且停留的时间最大介于0.264~4.6 Ga；金刚石样品不同生长环带之间的生长速率存在较大差异，介于9.26~5 218.18 μm·Ga-1。同时，样品的生长并不是各向均匀生长，而是具有一定优先取向。

Study on the CL and FTIR Spectra of the Alluvial Diamond from Western Yangtze Craton and Its Significance in the Growth Rate Analysis of the Diamond

In order to provide scientific clues for reconstructing effectively the process of natural diamond growth,the diamond sample from the western Yangtze Craton is studied with CL and FTIR spectra.In the paper,the micro-section of growth of the sample was defined with CL spectra,while the growth time of each diamond section was determined with FTIR spectra;besides,the growth rate of the diamond section was calculated.The results of CL and FTIR spectra analysis of the sample show that there are early CL growth zonings which are terrace and jagged straight zonings and late CLre-growth zonings in the diamond.The concentration of nitrogen varies greatly from 47.88～321.89 μg · g-1 in the diamond which is type IaAB.The minimal crystalline temperature of the sample is 1 490 K.The residence time of the diamond section in the mantle depending on the positions varies greatly from 0.264～4.6 Ga.The growth rate of the diamond section depending on the positions is 9.26～5 218.18 μm · Ga-1.Furthermore,the growth of the different diamond section is heterogeneous with preferential direction.