Formation of garnet clusters during polyphase metamorphism

Terra Nova ◽  
2012 ◽  
Vol 25 (2) ◽  
pp. 144-150 ◽  
Author(s):  
David Floess ◽  
Lukas Baumgartner
Keyword(s):  
Polyphase Metamorphism

Polyphase metamorphism in the eastern Carnic Alps (N Italy–S Austria): clay minerals and conodont Colour Alteration Index evidence

2007 ◽  
Vol 97 (6) ◽  
pp. 1213-1229 ◽  
Author(s):  
Covadonga Brime ◽  
Maria Cristina Perri ◽  
Monica Pondrelli ◽  
Claudia Spalletta ◽  
Corrado Venturini
Keyword(s):  
Clay Minerals ◽  
Carnic Alps ◽  
Conodont Colour Alteration Index ◽  
Polyphase Metamorphism ◽  
Colour Alteration

scholarly journals The crystalline units of the High Himalayas in the Lahul–Zanskar region (northwest India): metamorphic–tectonic history and geochronology of the collided and imbricated Indian plate

1990 ◽  
Vol 127 (2) ◽  
pp. 101-116 ◽  
Author(s):  
U. Pognante ◽  
D. Castelli ◽  
P. Benna ◽  
G. Genovese ◽  
F. Oberli ◽  
...  
Keyword(s):  
Shear Zones ◽  
Sensu Stricto ◽  
Crustal Thickening ◽  
Indian Plate ◽  
Low Grade ◽  
Lesser Himalaya ◽  
Medium Temperature ◽  
Polyphase Metamorphism ◽  
Early Palaeozoic ◽  
Northwest India

AbstractIn the High Himalayan belt of northwest India, crustal thickening linked to Palaeogene collision between India and Eurasia has led to the formation of two main crystalline tectonic units separated by the syn-metamorphic Miyar Thrust: the High Himalayan Crystallines sensu stricto (HHC) at the bottom, and the Kade Unit at the top. These units are structurally interposed between the underlying Lesser Himalaya and the very low-grade sediments of the Tibetan nappes. They consist of paragneisses, orthogneisses, minor metabasics and, chiefly in the HHC, leucogranites. The HHC registers: a polyphase metamorphism with two main stages designated as M1 and M2; a metamorphic zonation with high-temperature recrystallization and migmatization at middle structural levels and medium-temperature assemblages at upper and lower levels. In contrast, the Kade Unit underwent a low-temperature metamorphism. Rb–Sr and U–Th–Pb isotope data point to derivation of the orthogneisses from early Palaeozoic granitoids, while the leucogranites formed by anatexis of the HHC rocks and were probably emplaced during Miocene time.Most of the complicated metamorphic setting is related to polyphase tectonic stacking of the HHC with the ‘cooler’ Kade Unit and Lesser Himalaya during the Himalayan history. However, a few inconsistencies exist for a purely Himalayan age of some Ml assemblages of the HHC. As regards the crustal-derived leucogranites, the formation of a first generation mixed with quartzo-feldspathic leucosomes was possibly linked to melt-lubricated shear zones which favoured rapid crustal displacements; at upper levels they intruded during stage M2 and the latest movements along the syn-metamorphic Miyar Thrust, but before juxtaposition of the Tibetan nappes along the late- metamorphic Zanskar Fault.

Two contrasting accretion v. collision orogenies: insights from Early Paleozoic polyphase metamorphism in the Altun–Qilian–North Qaidam orogenic system, NW China

2018 ◽  
Vol 474 (1) ◽  
pp. 153-181 ◽  
Author(s):  
Jianxin Zhang ◽  
Chris Mattinson ◽  
Shengyao Yu ◽  
Yunshuai Li ◽  
Xingxing Yu ◽  
...  
Keyword(s):  
Early Paleozoic ◽  
Nw China ◽  
North Qaidam ◽  
Polyphase Metamorphism

scholarly journals The early Archaean to Proterozoic history of the Isukasia area, southern West Greenland

1986 ◽  
Vol 154 ◽  
pp. 1-80
Author(s):  
A.P Nutman
Keyword(s):  
Volcanic Rocks ◽  
Amphibolite Facies ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Stratigraphic Sequence ◽  
Supracrustal Belt ◽  
History Of ◽  
High Grade Metamorphism ◽  
Polyphase Metamorphism ◽  
Chemical Sediments

The c. 3800 Ma Isua supracrustal belt and associated smaller bodies of supracrustal rocks are intruded by >3600 Ma orthogneisses. A coherent stratigraphic sequence is recognised consisting of interlayered metabasic rocks, metasediments derived from volcanic rocks, chemical sediments, and metabasic and ultramafic intrusions. Despite repeated deformation and high-grade metamorphism sedimentary structures are locally preserved. The depositional environment was probably an immersed volcanic region remote from areas of significantly older crust. Conglomeratic structures in a metachert and banded iron formation unit suggest shoaling and shallow water conditions. Felsic sediments locally preserve evidence of deposition from turbidite flows. The Isua supracrustal rocks are regarded as thin fragments of a thicker, more extensive sequence. The orthogneisses that intrude the supracrustal rocks consist of 3750-3700 Ma multiphase tonalites (the grey gneisses) which were first intruded by the basic Inaluk dykes, then by abundant shallow-dipping swarms of c. 3600 Ma granite sheets (the white gneisses) and finally by c. 3400 Ma pegmatitic gneiss sheets. These early Archaean rocks were metamorphosed under amphibolite facies conditions and repeatedly deformed prior to intrusion of the Tarssartôq basic dykes in the mid Archaean. In the late Archaean (3100-2500 Ma) there was polyphase metamorphism up to amphibolite facies grade and two or more stages of deformation and local intrusion of granitic gneiss sheets and pegmatites. However, despite general strong deformation there is a large augen of low deformation preserved within the arc of the Isua supracrustal belt. During the Proterozoic there was intrusion of basic dykes, major faulting with associated recrystallisation under uppermost greenschist to lowermost amphibolite facies conditions, followed by heating and intrusion of acid dykes at c. 1600 Ma. No profitable mineralisations have been located.

Proterozoic polyphase metamorphism in the Chhotanagpur Gneissic Complex (India), and implication for trans-continental Gondwanaland correlation

2008 ◽  
Vol 162 (3-4) ◽  
pp. 385-402 ◽  
Author(s):  
A.K. Maji ◽  
S. Goon ◽  
A. Bhattacharya ◽  
B. Mishra ◽  
S. Mahato ◽  
...  
Keyword(s):  
Polyphase Metamorphism

scholarly journals Early Paleozoic polyphase metamorphism in northern Tibet, China

2017 ◽  
Vol 41 ◽  
pp. 267-289 ◽  
Author(s):  
Jianxin Zhang ◽  
Shengyao Yu ◽  
C.G. Mattinson
Keyword(s):  
Early Paleozoic ◽  
Northern Tibet ◽  
Polyphase Metamorphism
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