GEOSCAN, résultats de la recherche


TitreMonazite geochronology and petrology of kyanite- and sillimanite-grade migmatites from the northwestern flank of the eastern Himalayan syntaxis
AuteurPalin, R M; Searle, M P; St-Onge, M R; Waters, D J; Roberts, N M W; Horstwood, M S A; Parrish, R R; Weller, O M; Chen, S; Yang, J
SourceGondwana Research 2013 p. 1-25,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20120124
Documentpublication en série
Mediaen ligne; numérique
Lat/Long OENS 93.5000 95.0000 30.2500 28.7500
Sujetsmonazite; migmatites; roches métamorphiques; faciès métamorphiques; pétrologie des roches métamorphiques; conditions de pression-température; interprétations tectoniques; cadre tectonique; milieux tectoniques; pétrographie; géochronologie; tectonique; géochimie
Illustrationslocation maps; plots; tables; photomicrographs; cross-sections
ProgrammeBases de données couvrant les trois territoires (Géologie du substratum rocheux), GEM : La géocartographie de l'énergie et des minéraux
Résumé(disponible en anglais seulement)
A combined geochronological and petrological study of pelitic migmatites from the northwestern flank of the eastern Himalayan syntaxis has constrained the timing and P - T conditions of two high-grade metamorphic events that affected the south Lhasa block (Asian margin) and provides newinsight into the tectonothermal evolution of the India - Asia collision. U(-Th) - Pb dating of in situ monazite shows that upper amphibolite-facies sillimanite-grademetamorphismand consequent partial melting occurred between c. 71 and 50 Ma at P - T conditions above 6.3 ± 1.2 kbar and 750 ± 30 °C. Further partialmelting at upper amphibolite-facies kyanite-grade conditions occurred between c. 44 and 33 Ma at minimum P - T conditions of 10.4 ± 1.0 kbar and 698 ± 20 °C. These data are interpreted to record a south Lhasa blockmid-crustal sillimanite-grade melting event in the Late Cretaceous to Early Eocene related to regional heat advection caused by coeval and prolonged emplacement of Gangdese batholith units. This was followed by a higher pressure and lower temperature kyanite-grade melting event during the Middle Eocene to Early Oligocene associated with deformation and crustal thickening in the
south Lhasa block, coeval with kyanite-grade metamorphism along the Himalaya, as a result of the on-going India - Asia collision. These partially-melted crustal lithologies offer potential sources (or otherwise analogs for sources) for the Miocene emplacement of adakitic intrusions previously documented in the eastern Himalayan syntaxis region.