Formation history and protolith characteristics of granulite facies metamorphic rock in Central Cathaysia deduced from U-Pb and Lu-Hf isotopic studies of single zircon grains

2005 ◽  
Vol 50 (18) ◽  
pp. 2080 ◽  
Author(s):  
Jinhai YU
Keyword(s):  
Metamorphic Rock ◽  
Granulite Facies ◽  
Formation History ◽  
Isotopic Studies ◽  
Single Zircon

Metamorphic evolution and zircon geochronology of early Proterozoic granulites in the Aravalli Mountains of northwestern India

2005 ◽  
Vol 142 (3) ◽  
pp. 287-302 ◽  
Author(s):  
A. B. ROY ◽  
ALFRED KRÖNER ◽  
P. K. BHATTACHAYA ◽  
SANJEEV RATHORE
Keyword(s):  
Granite Gneiss ◽  
Granulite Facies ◽  
Granulite Facies Metamorphism ◽  
Granulite Metamorphism ◽  
History Of ◽  
Single Zircon ◽  
Northwest India ◽  
Orogenic Cycle ◽  
Age Range ◽  
Rock Association

Granulites including a charnockite suite, mafic granulites, pelitic granulites, metanorite dykes and their retrograde varieties occur as discontinuous shear zone-bounded bodies within the Archaean basement comprising a granite gneiss–amphibolite–metasedimentary rock association in the central part of the Aravalli Mountains, northwest India. The entire suite, named the Sandmata Complex, preserves a complex history of tectonothermal evolution. Except for their strongly foliated margins, the granulite bodies are largely massive. Partial melting in the ‘country rocks’ led to the development of migmatite gneisses close to the contact of the granulite, a feature not as common in the rocks further away from the granulite contact. Geothermobarometry of massive granulites indicates Tmax>900°C and Pmax∼7.5 kbar. The retrograde granulites, which formed at lower amphibolite/upper greenschist-facies conditions, experienced channelized hydration reactions concomitant with shearing. These rocks locally appear as hornblende–biotite-bearing foliated granulite with or without Cpx or Opx. The rocks seem to have followed an inverse PTt path and have undergone an earlier phase of near-isobaric cooling. Our single zircon Pb–Pb ages indicate that the exhumation of granulites to the shallower amphibolite-facies levels with concomitant melting in the country rocks took place between 1690 Ma and 1621 Ma. Assuming that the granulite-facies metamorphism took place at around 1725 Ma, we relate the entire process of granulite metamorphism and exhumation covering an age range between 1725 and 1621 Ma to the rift basin opening stages of the Delhi Orogenic cycle that culminated at c. 1450 Ma.

Single Zircon Evaporation and SHRIMP Ages for Granulite‐Facies Rocks in the Mozambique Belt of Tanzania

2001 ◽  
Vol 109 (2) ◽  
pp. 171-189 ◽  
Author(s):  
Sospeter Muhongo ◽  
Alfred Kröner ◽  
A. A. Nemchin
Keyword(s):  
Granulite Facies ◽  
Mozambique Belt ◽  
Single Zircon ◽  
Zircon Evaporation

Application Of Electron Probe Analyses Of Minerals In Discussing The Relationship Between Ductile Deformation And Metamorphism

1990 ◽  
Vol 48 (2) ◽  
pp. 250-251
Author(s):  
Fan Guochuan ◽  
Sun Zhongshi
Keyword(s):  
Chemical Composition ◽  
Shear Deformation ◽  
Electron Probe ◽  
General Rule ◽  
Granulite Facies ◽  
Ductile Deformation ◽  
Higher Temperature ◽  
Ductile Shear ◽  
The Relationship ◽  
Ductile Shear Deformation

Under influence of ductile shear deformation, granulite facies mineral paragenesis underwent metamorphism and changes in chemical composition. The present paper discusses some changes in chemical composition of garnet in hypers thene_absent felsic gnesiss and of hypersthene in rock in early and late granulite facies undergone increasing ductile shear deformation .In garnet fetsic geniss, band structures were formed because of partial melting and resulted in zoning from massive⟶transitional⟶melanocrate zones in increasing deformed sequence. The electron-probe analyses for garnet in these zones are listed in table 1 . The Table shows that Mno, Cao contents in garnet decrease swiftly from slightly to intensely deformed zones.In slightly and moderately deformed zones, Mgo contents keep unchanged and Feo is slightly lower. In intensely deformed zone, Mgo contents increase, indicating a higher temperature. This is in accord with the general rule that Mgo contents in garnet increase with rising temperature.

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