Nature of Infill Material on the Discontinuities of the Muntele Mare Granite (Romania)

The Bozgai open quarry in the Muntele Mare granite massif offers an excellent opportunity to investigate the influence of alteration processes on granitic rock, especially owing to the extensive exposure of granite and specific mineral assemblages of hydrothermal genesis to atmospheric conditions. The alteration processes generated secondary minerals located on the primary minerals of the affected rocks or deposited as infill material along the granite discontinuities. Natural and oriented samples of the Bozgai quarry of the infill material were investigated using polarized light microscopy, X-ray diffraction, and scanning electron microscopy to obtain images and identify their mineralogical composition. The hydrothermal vein material consists of kaolinite, illite, pyrite, marcasite, quartz, iron hydroxides, albite, and microcline. Jarosite and gypsum were also formed by the oxidization of pyrite and marcasite exposed to atmospheric oxygen and meteoric water. The secondary minerals play a particularly important role in the reduced rock slope stability in the Bozgai quarry.