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Metamorphic history of sapphirine- and relict-kyanite-bearing Mg-Al rich rocks at Hatimunda Hill near Junagarh, Kalahandi District, Orissa

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Title Metamorphic history of sapphirine- and relict-kyanite-bearing Mg-Al rich rocks at Hatimunda Hill near Junagarh, Kalahandi District, Orissa
 
Creator PATEL, SC
BEHERA, S
MOHANTY, A
SINGH, AK
PATEL, SK
 
Subject t-x relationships
eastern-ghats
mobile-belt
high-temperature
southern india
granulites
petrology
minerals
garnet
thermobarometry
sapphirine
cordierite
phlogopite
relict kyanite
decompression
eastern ghats
 
Description Cordierite-phlogopite dominated Mg-AL rich rocks occur as small enclaves at the Hatimunda hill near Junagarh in the Orissa sector of the Eastern Chats belt. Peak mineral assemblages in these rocks included phlogopite, bronzite, kyanite (now relict) and quartz/corundum. Sapphirine typically occurs as corona around corundum or in clusters along with corundum. The sapphirine is slightly more aluminous than the MgO:AL(2)O(3):SiO2 ratio of 7:9:3. Textural criteria and phase analysis in the model system MAS indicate the following reactions: Opx + Sil + Qtz = Crd; Opx + Sil = Crd + Crn; and Opx + Cm = Spr + Crd. A qualitative petrogenetic grid shows that these reactions may be crossed in sequence along a decompressional P-T trajectory. The rocks preserve textural evidence of formation of sapphirine, at least in part, from phlogopite and sillimanite. P-T conditions for peak metamorphism were 700-800 degreesC and >8 kbar based on the stability field of mineral assemblages. Texturally, early kyanite and late sillimanite indicate that the decompression is possibly part of a clockwise P-T path. This interpretation is supported by the occurrence of Mg-rich garnet (X-Prp = 0.47) in the amphibole-dominated Mp-Al rich schist of the neighbouring Jilindara area.
 
Publisher GEOLOGICAL SOC INDIA
 
Date 2011-07-30T05:25:03Z
2011-12-26T12:52:40Z
2011-12-27T05:39:24Z
2011-07-30T05:25:03Z
2011-12-26T12:52:40Z
2011-12-27T05:39:24Z
2001
 
Type Article
 
Identifier JOURNAL OF THE GEOLOGICAL SOCIETY OF INDIA, 57(5), 417-427
0016-7622
http://dspace.library.iitb.ac.in/xmlui/handle/10054/7860
http://hdl.handle.net/10054/7860
 
Language en