Article (Scientific journals)
Shoshonitic liquid line of descent from diorite to granite: the Late Precambrian post-collisional Tismana pluton (South Carpathians, Romania)
Duchesne, Jean-Clair; Berza, Tudor; Liégeois, Jean-Paul et al.
1998In Lithos, 45, p. 281-303
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Keywords :
hybridization; fractional crystallization; Pan-African; trace element modelling; mingling; Nd-Sr isotopes
Abstract :
[en] The post-collision late-kinematic Tismana pluton belongs to the shoshonitic series. It is part of a Late Precambrian basement within the Alpine Danubian nappes of the South Carpathians (Romania). This pluton displays an exceptionally complete range of compositions from ultramafic to felsic rocks (granites). Widespread mingling/mixing relationships at all scales give rise to a variety of facies. A liquid line of descent from the diorites to the granites is reconstructed by considering the variation in major and trace elements (REE, Sr, Rb, Ba, Nb, Zr, Hf, Zn, V, Co, Cr, U, Th, Ga, Pb) from 33 selected samples as well as mineral/melt equilibrium relationships. The first step of fractional crystallization is the separation from a monzodioritic parent magma of a peridotitic cumulate similar to the ultramafic rock found in the massif. A possible contamination by lower crustal mafic component takes place at this stage. The second step marks the appearance of apatite and Fe-Ti oxide minerals as liquidus phases, and the third step, saturation of zircon. Mixing by hybridisation of magmas produced at different stages of the evolution along the liquid line of descent is also operating (endo-hybridisation). As depicted by Nd and Sr isotopes, fractional crystallization was combined to an important early contamination by a mafic lower crust in a deep-seated magma chamber and to a later and mild contamination by a felsic medium crust in an intermediate chamber. The mingling essentially occurred during the final emplacement in the high-level magma chamber. The monzodioritic parent magma, identified by major and trace element modelling, is shown by Sr and Nd isotopes to have its source in the lithospheric mantle or in a juvenile mafic lower crust derived from it. The necessarily recent enrichment in K2O and associated elements of the lithospheric mantle is likely to be related to the preceding Pan-African subduction period. The partial melting of this newly formed deep source has to be linked to a major change in the thermal state of the plate.
Disciplines :
Earth sciences & physical geography
Author, co-author :
Duchesne, Jean-Clair ;  Université de Liège - ULiège > Département de géologie > Pétrologie et géochimie endogènes
Berza, Tudor;  Geological Institute of Romania, Bucharest
Liégeois, Jean-Paul ;  Africa Museum, Tervuren > Département de géologie
Vander Auwera, Jacqueline ;  Université de Liège - ULiège > Département de géologie > Pétrologie et géochimie endogènes
Language :
English
Title :
Shoshonitic liquid line of descent from diorite to granite: the Late Precambrian post-collisional Tismana pluton (South Carpathians, Romania)
Publication date :
1998
Journal title :
Lithos
ISSN :
0024-4937
Publisher :
Elsevier Science, Amsterdam, Netherlands
Volume :
45
Pages :
281-303
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 03 July 2008

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