Volume 5, No. 3, September 2019

General Information

  • ISSN: 2395-647X (Online)
  • Abbreviated Title:  Int. J. Geol. Earth Sci.
  • Editor-in-Chief: ​Prof. Marina Fernandez de la Cruz, Department of Petrology and Geochemistry, Faculty of Geological Sciences, Complutense University of Madrid, Spain
  • Associate Editor: Sujitha R. Reddy, Savitha Darsha
  • Executive Editor: Ms. Yoyo Y. Zhou
  • DOI: 10.18178/ijges
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International Journal of Geology and Earth Sciences
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Field and Petrography of the Rocks from the Gobbagurthi Area in the Khammam Schist Belt, Khammam District, Telangana State, India

B. Shankar1, and M. Narsimha Reddy2
1.Department of Geology, University College of Science, Saifabad, Osmania University, Hyderabad 500004.
2.Department of Geology, Osmania University, Hyderabad 500007

Abstract—Petrographic characterization of Amphibolites and associated rocks from the Gobbagurthi area in the Khammam Schist Belt covers an area about of 240 sq.km, scale 2cm =1km (1: 50000), the Survey of India Toposheet no 65 C/7 and 65 C/8 the latitude and longitudes are 170 10’ - 170 21’ N and 800 15’ - 800 27’ E. The area has been covered with 200 representative lithological samples and made 100 thin sections among the amphibolites, metabasalts, metadolerites, anorthosites, granulites, gneisses and schists. The modal analyses, geological settings of the area, field descriptions and petrographic characters of the rocks are investigated. The mineralogical and textural characteristic of the rocks from the Gobbagurthi area are describes in vary textural features from magmatic to metamorphic deformation. The original cumulate characters of mafic to ultramafic intrusives (layered complex), ophitic to sub-ophitic textures from meta-basalts and meta-dolerites. These are modified by the later metamorphic imprint and recrystellization under amphibolite and granulite facies of metamorphism. Due to recrystellization and basaltic processes the micro structures were formed as Coronal and sieved garnets.The KSB forms retrograde metamorphism from granulte to amphibolies, amphibolite to greenschist facies condition. The original mineral grains in each rock-units are modified by late dynamic deformations in which coarse-grained minerals (plagioclase, hornblende, clinopyroxene and Fe-Ti oxides) are broken-down to form undeformed smaller recrystallized grains by grain boundary migration and recrystallization (mortar texture) at low temperature conditions. Textural equilibrium between polygonal mineral grains with smooth planar boundaries and triple junctions in the rock-units of KSB suggest solid-state recrystallization due to grain boundary migration during plastic deformation at higher temperatures. This type of textural features is overprinted on early folded gneissose and schistose rocks, streaky amphibolites and metamorphosed mafic & ultramafic lavas. Hornblende coronas around clinopyroxene and Fe-Ti oxides, epitaxial overgrowth of hornblende over clinopyroxene, scapolite over plagioclase and zoisite / clinozoisite mineral growth over plagioclase and hornblende indicate replacement textures in the rocks of Gobbagurthi area in KSB.

Index Terms—Amphibolites, Gneisses and schists, Modal analysis, Khammam Schist Belt

Cite:B. Shankar and M. Narsimha Reddy, "Field and Petrography of the Rocks from the Gobbagurthi Area in the Khammam Schist Belt, Khammam District, Telangana State, India," International Journal of Geology and Earth Science, Vol. 5, No. 3, pp. 1-18, September 2019.