Please use this identifier to cite or link to this item: http://hdl.handle.net/10603/68240
Title: Geology of the precambrian rocks of the Tyrssad Weiloi area Khasi hills Meghalaya
Researcher: Borah, Arun Kumar
Guide(s): Rahman, S
Keywords: Argillaceous
Mesoscopic
Microcline
Porphyritic
Precambrian
Ptygmatic
Tyrssad-Weiloi
Xenoliths
University: Gauhati University
Completed Date: 31/12/1983
Abstract: The Precambrian rocks of the Tyrssad-Weiloi area comprises of the quartzo-feldspathic gneiss, the arenaceous and argillaceous metasedi-ments of the Shillong Group, the Khasi greenstones (meta-dolerites) and the porphyritic granites of the South Khasi pluton. The gneiss forms the basement rocks of the area, overlain unconformably by the Shillong Group of rocks. The early intrusives, the Khasi greenstones show intrusive rela-tions only with the Shillong Group, but the later intrusive, the porphy-ritic granites have affected all the older rocks including the greenstones. The granite has a thermal aureole around it. The quartzo-feldspathic gneiss is a para-gneiss, whose composi-tion stands between arkose and pelite. The gneiss has become migmatitic near the contact of the granite. The Shillong Group of rocks and the greenstones suffered low grade regional metamorphism prior to the intru-sion of the granite. The pelitic members of the Shillong Group developed andalusite hornfels within the thermal aureole of the granite. Likewise, the low grade assemblage, actinolite-chlorite-epidote-elbite (greenschist) of the meta-dolerites have recrystallized into hornblende-hornfels at the proximity of the granite. The petro-chemistry of the greenstones resemble the composition of the tholeiitic basalts and dolerites. The South Khasi granite is a normal biotite granite. The presence of complex twins in plagioclase, zonally arranged inclusions in microcline, sharply euhedral zircons etc., support a magmatic origin of the granite. Tectonically, the rocks of the area have suffered at least seven different phases of deformation (D). The first five (D1 - D5) were respon-sible for the development of various types of folds and associated struc-tures observed in the gneiss and in the rocks of the Shillong Group. Deformation D6 was associated with the emplacement of the granite while D7 produced some shear or crush zones and associated pseudotachylites.
Pagination: 
URI: http://hdl.handle.net/10603/68240
Appears in Departments:Department of Anthropology

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01_title page.pdfAttached File22.64 kBAdobe PDFView/Open
02_certificate.pdf187.67 kBAdobe PDFView/Open
03_acknowledgement.pdf36.83 kBAdobe PDFView/Open
04_content.pdf170.4 kBAdobe PDFView/Open
05_list of plates.pdf194.04 kBAdobe PDFView/Open
06_list of tables.pdf44.91 kBAdobe PDFView/Open
07_terms and terminology used.pdf32.96 kBAdobe PDFView/Open
08_abstract.pdf344.08 kBAdobe PDFView/Open
09_chapter 1.pdf1.14 MBAdobe PDFView/Open
10_chapter 2.pdf1.74 MBAdobe PDFView/Open
11_chapter 3.pdf7.85 MBAdobe PDFView/Open
12_chapter 4.pdf1.61 MBAdobe PDFView/Open
13_chapter 5.pdf4.31 MBAdobe PDFView/Open
14_chapter 6.pdf1.97 MBAdobe PDFView/Open
15_chapter 7.pdf2.97 MBAdobe PDFView/Open
16_chapter 8.pdf638.8 kBAdobe PDFView/Open
17_chapter 9.pdf1.35 MBAdobe PDFView/Open
18_chapter 10.pdf717.03 kBAdobe PDFView/Open
19_chapter 11.pdf139 kBAdobe PDFView/Open
20_summary and conclusions.pdf156.52 kBAdobe PDFView/Open
21_bibliography.pdf634.76 kBAdobe PDFView/Open
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