Deformation history reconstruction using single quartz grain Raman microspectroscopy data

Abstract

One of the most common minerals in the Earth's crust, quartz, is stable across a wide range of temperature and pressure conditions. As its microstructure is sensitive to diverse deformation mechanisms, quartz may provide valuable information regarding the structural evolution of many different rock types. Using Raman microspectroscopy, single quartz grains and monomineralic domains characterized by different deformation conditions can be identified and separated. In this study, three microstructurally extreme quartz grain types were discriminated from a subsurface shear zone: grains with undulose extinction (T0), grains with subgrains (T1), and grains with recrystallized grains (T2). Moreover, several microstructurally transitional grains were measured, which represent combinations of the aforementioned extremes. Statistical analysis revealed that the microscopically identified extreme grains possess significantly different spectral attributes and as such can be divided on the basis of certain variables of their respective Raman spectra. The three extreme quartz grain types were formed by different deformation mechanisms and thus represent distinct deformation conditions. The T0‐T1‐T2 spectral space can therefore also be considered a virtual deformational space. Although each complex quartz grain measured also appears elsewhere in the deformation process defined by T0‐T1‐T2 extreme conditions, they together represent a successive deformation path. This combined pathway is assumed to be characteristic for the whole rock volume under study. Finally, the computed Raman spectroscopy‐based virtual deformational space enabled the determination of the structural evolution of the analyzed shear zone. Copyright © 2014 John Wiley & Sons, Ltd.