谱学分析在造山带硅质岩中的应用及其地质意义

南秦岭造山带旬阳盆地吕河地区发育有泥盆系硅质岩剖面，该剖面中的硅质岩以谱学特征为基础的微区特征清晰的记录了硅质岩的形成及后期演变信息。以南秦岭造山带旬阳盆地吕河硅质岩样品为对象，借助XRF、拉曼光谱、红外光谱和X射线粉晶衍射分析结果表明：该硅质岩内矿物主要为低温石英并包含极少量的碳酸盐矿物。XRD分析结果进一步证实该碳酸盐矿物为白云石。在吕河硅质岩内，SiO₂结构463 cm-1附近拉曼特征峰经高斯拟合后的峰面积和FWHM值证实发生了低温石英的重结晶作用，该过程中伴随了流体作用引发的有序度变化和石英颗粒的自身有序度变化。在重结晶过程中，石英颗粒的自身重结晶伴随了有序度随时间推移而逐渐增高。流体作用对硅质岩的改造表现为硅质岩内碳酸盐脉体的穿插，该过程还导致低温石英有序度提升，其中越靠近矿物边缘处的SiO₂结构有序度越高。造山带演化过程对硅质岩进行的改造主要体现在两个方面：一方面，构造应力破坏了岩石的连续性并为后期热液流体的运移穿插提供了空间；另一方面，后期流体作用的参与促进了石英颗粒重结晶的进程。红外光谱可以系统的识别硅质岩内矿物的结构类型，拉曼光谱分析可以揭示原位（in situ）微组构特征，XRD在硅质岩内微量杂质矿物的识别优势明显，这些谱学手段为研究硅质岩的成岩演化提供了重要示范。

Application of Analytical Techniques of Spectroscopy on Cherts in Orogenic Belt and Its Geological Significances

The Devonian cherts profile was developed in Lvhe area, Xunyang basin of southern Qinling orogenic belt, and the microfabric features based on spectroscopy characteristics clearly recorded information of diagenesis and later stage evolution of the cherts. Cherts in Lvhe area, Xunyang basin of southern Qinling orogenic belt were taken as object, by means of Raman spectroscopy，Fourier transform infrared spectroscopy and X-ray powder diffraction，and the results of this study showed that：low temperature quartz and a small quantity of carbonate minerals were the two main mineral phases of the cherts, and XRD analysis further proved the carbonate minerals were dolomites. Within the cherts in Lvhe area，Gauss fitting FWHM and Area values of the 463 cm-1 Raman shift of SiO₂ texture confirmed that recrystallization had occurred in the SiO₂ minerals. Alone with this process, variations of degree of order were triggered by fluid effects as well as the quartz itself. During the recrystallization process of the quartz, degree of order went up. The cherts were altered by later fluids, apart from the intersected late vein, the alteration reflected in that the closer to the edge of the fluids in the quartz, the higher the crystallinity and degree of order. In this study, alteration of cherts made by orogeny mainly reflected in two aspects：on the one hand，tectonic stress destroyed the continuity of the cherts and provides space for migration and intersection of later stage hydrothermal fluids；On the other hand，participation of the late fluids accelerated the recrystallization of quartz. In this study, infrared spectroscopy is capable of identifying mineral structure type systematically, and Raman spectrum analysis can reveal in situ microfabric characteristics, and XRD shows significant advantage in discriminating trace impurity minerals in cherts. These spectroscopy methods provide important demonstrations in studying the diagenetic evolution of the cherts.