Please use this identifier to cite or link to this item: http://hdl.handle.net/10603/66555
Title: Petrology and geochemistry of the precambrian rocks around Ajagarh hills Agia Goalpara district Assam
Researcher: Sarmah, Bhaskar Bikash
Guide(s): Chowdhary, P K
Keywords: Amphibolite
Geochemistry
Geology
Granulite
Mineral
Petrology
Precambrian
Rocks
University: Gauhati University
Completed Date: 31/10/2001
Abstract: The Ajagarh hills area in Goalpara District, Assam predominantly consists of basic granulites, generally hornblendepyroxene and pyroxene-bearing variety. Quartzofeldspathic (occasionally migmatitic and garnetiferous variety), garnetiferous metapelites, scapolite- bearing calc-silicate gneisses and amphibolites (restricted to the northern part) and retrograded granulites (in the proximity of shear zones) are present in minor amounts. This thesis deals with petrology of the area, studied by means of petrographic, mineral-chemical and whole rock-chemical methods supplemented by geothermobarometric and fluid barometric data. The rocks are believed to represent a volcano-sedimentary sequence affected by high grade metamorphic event during earliest compressional deformational episode (F1 folding) as a consequence of emplacement of basic magma synchronous of F1 folding. Trace and REE elements study indicates that the earliest magmatic rocks which were completely amphibolites) possess a continental character and represent the basaltic melt derived from low melting of upper mantle. The petrographic data and the structural characteristics of the rocks show that the amphibolite facies assemblages in the north and granulites in the south, metamorphosed under one single deformational episode although, a gradual change in terms of metamorphic grade is evident from mineral paragenesis as well as from TiO2-content in biotite, Ca-content in plagioclase and edenite component of amphiboles. Electron probe analyses of coexisting minerals indicate an attainment of metamorphic equilibrium. P-T-PH20 conditions of metamorphic equilibration are estimated by means of different types of mineral geothermometers, geobarometers and fluid barometers in combination with a comparison of relevant experimental data. Resulting estimates for the peak metamorphic event are T-6500C, P-6 kbar (average) for amphibolite zone and T-7500C, P-7 kbar (average) for granulite zone with a variable PH2O. The retrogressed metamorphic event which preceded...
Pagination: 
URI: http://hdl.handle.net/10603/66555
Appears in Departments:Department of Geological Science

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05_acknowledgement.pdf250.91 kBAdobe PDFView/Open
06_abstract.pdf505.33 kBAdobe PDFView/Open
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09_chapter 2.pdf993.85 kBAdobe PDFView/Open
10_chapter 3.pdf1.32 MBAdobe PDFView/Open
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12_chapter 5.pdf963.07 kBAdobe PDFView/Open
13_chapter 6.pdf802.82 kBAdobe PDFView/Open
14_chapter 7.pdf454.23 kBAdobe PDFView/Open
15_bibliography.pdf476.57 kBAdobe PDFView/Open
16_appendix.pdf20.55 kBAdobe PDFView/Open


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