Petrography of marbles from Caçapava do Sul, RS, Southern Brazil
DOI:
https://doi.org/10.5902/2179460X25458Abstract
The Caçapava do Sul region, State of Rio Grande do Sul, is characterized by the occurrence of a granitic batholith (Caçapava Granite), that has an outcrop of about 25 by 10 km, oriented North- South. The Caçapava Granite is surrounded by a belt of metamorphites belonging to the Porongos Group, assigned to Upper Precanbrian by RIBEIRO et alii: (1966). Among the metamorphites occur a carbonatic rock body, lens shaped, with clear contacts, interpenetrated by granitic apophises and with an outcrop of about 17 km2. Samples of this rock body were studied by microscopic, difratometry and spectrometry of X ray, electronic microprobe and chemical analyses aiming at identifying and characterizing the carbonatic and silicatic minerals. Through staining techniques it was possible to distinguish dolomite (Do), calcite (Cc) and ferriferous calcite (Ccf). The modal and chemical analysis showed that the carbonatic minerals were more abundant than the silicatic ones being these last ones restricted to of the rock bands. The detected silicatic minerals were the following: talc, tremolite, diopside, forsterite, chlorite and phlogopite. In smaller amounts titanite, apatite and quartz also occur. Serpentine resulting from alterations in the olivine is also very common. The final conclusion with these studies, about the carbonatic rocks, indicate that they are contact impure dolomitic marbles.
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