环带钾长石、榍石和锆石的显微结构与微区组成特征分析

南秦岭沙河湾石英二长岩中的钾长石、榍石和锆石具有明显的成分环带。利用电子探针(EPMA)波谱仪(WDS)、扫描电子显微镜(SEM)及其附带的能谱仪(EDS)和激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)对造岩矿物环带钾长石、榍石和锆石的显微结构与微区组成进行表征。结果表明：钾长石中K+被Na+，Ca2+，Ba2+，Fe2+和Ce3+不同程度替代。榍石中Ca2+被V3+，Ce3+和Ba2+等替代，Ti4+被Fe2+和Al3+等替代。锆石含Fe，Th，U，Nb，Ta，Y，Hf，Yb和Pb等稀土和微量元素。钾长石中元素浓度由高到低为Si，Al，K，Ca，Na，Mg和Ba，其中K和Na互补，较亮处Ba含量高，越靠近边缘，Si升高、K升高与Na降低趋势越明显。榍石中元素浓度由高到低为Ca，Si，Ti，Ba，V，Ce，Al和Fe，较亮处Fe含量较高。锆石中元素浓度由高到低为Zr，Si，Nd，Ce，Hf，U，Pb和Th，Hf与Zr呈明显的互补关系，核部Zr含量较边部高，核部Hf、U和Th含量较边部低。

The Characteristics of Microstructure and Chemical Compositions of K-Feldspar, Sphene and Zircon with Zoning Structure

K-feldspar, sphene and zircon in quartz monzonite from Shahewan, south Qinling, showing strong zoning structure. Characteristics of microstructure and chemical compositions of K-feldspar, sphene and zircon with zoning structure were investigated using advanced instruments of electron probe micro analyses equipped with wavelength dispersive spectrometer (EPM-WDS), scanning electron microscopy with energy dispersive spectrometer (SEM-EDS) and laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS). Our study suggests that K+ could be substituted by small amounts of Na+, Ca2+, Ba2+, Fe2+ and Ce3+. Ca2+ in sphene could be replaced by V3+, Ce3+, Ba2+ and Ti4+ could be substituted by both Fe2+ and Al3+. Zircon contains trace elements like Fe, Th, U, Nb, Ta, Y, Hf, Yb and Pb. Concentration of Si, Al, K, Ca, Na, Mg and Ba in K-feldspar ranked from high to low, among which the contents of K and Na are negatively correlated, the lighter part of BSE images featuring K-feldspar is attributed to comparably higher Ba content, additionally, Si and K contents are elevated while Na content decreased rimward. Ca, Si, Ti, Ba, V, Ce, Al and Fe concentration listed downward, among which higher iron content corresponds to brighter portion of BSE images. Element concentration of zircon could be ranked from high to low as Zr, Si, Nd, Ce, Hf, U, Pb and Th, in which Hf and Zr exhibit negatively correlated. Zr concentration increased while Hf, U and Th concentration decreased from core to rim.