TITLE:
Petrographic Characteristics of Manganese Bearing Rocks of Banswara Manganese Ores Belt, District Banswara, Rajasthan (India)
AUTHORS:
Mohd Shaif, F. N. Siddiquie, Subir Mukhopadhyay
KEYWORDS:
Petrographical Characters, Banswara Manganese Ores Belt, Lunavada, Aravalli, Garnet, Modal Analysis
JOURNAL NAME:
Open Journal of Geology,
Vol.7 No.7,
July
27,
2017
ABSTRACT: In this paper, we described the petrographical characters of the Mn-bearing
rock types outcropping in the Kalakhuta, Ghatia, Gararia, Itala, Wagaicha,
Tambesara and Talwara villages of Banswara district. The Mn associated rocks
in the study area are phyllite, schist, quartzite and limestone. The mineral assemblage
in phyllite formed under greenschist facies metamorphism. Petrographic
studies of various phyllite samples also reveal that porphyroblasts of
biotite sat in the fine-grained micaceous matrix (Biotite, muscovite, chlorite)
along with quartz, opaque and ore minerals. Petrographic studies of schist reveal
its formation under prograde metamorphism. Mineral assemblages observed
in schist are typical of greenschist to lower amphibolite facies. The
various schist samples at places show clusters made up of perfect rhombshaped
garnets which suggest the increase in the grade of metamorphism. The
quartzites are disposed conformably with the phyllites, and are at times brecciated
and re-cemented by secondary chert and manganese. These Mn-bearing
quartzites are with sutured/serrated and straight grain boundaries. The
quartzite samples are fully composed of quartz showing undulose extinction
with subordinate feldspar, micas and carbonatic materials. The petrographic
characteristics explain that mostly limestones are the dolomitic composition
but some ferruginous varieties are also noticed at places. The purer variety of
limestone consists of calcite, dolomite and some magnetite but tremolite,
quartz and some minute flakes of biotite also occur in impure variety.