Textural analysis of a microcrystalline quartz using X-Ray and Electron Backscatter Diffraction (EBSD) techniques

An unusual microcrystalline quartz texture has been recognized in the investigation of pervasively silicified ore-bearing horizons occurring in the uppermost part of carbonate platform sequences of different ages (from Precambrian to Mesozoic) and of different geotectonic settings. This peculiar texture has been labeled “grid-work texture”, and derives only by a rather fast and preferred crystallization of quartz on the pre-existing morphological faces of other developed quartz crystals. The 001 pole figures obtained by X-ray textural analysis describe this grid-work texture as constituted by two components of orientation: one component at about 35° from the normal to the surface of the sample and a second orientation component having the c axes oriented at about 75° from the normal to the surface of the sample. Textural maps and parameters obtained by EBSD found very similar components of orientation highlighting as 30-40° and 70-80° misorientations are very common; moreover they allowed to establish as many of the quartz crystals are characterized by Dauphiné Twin boundaries.