TY  - JOUR
A1  - Rehman, Hafiz Ur
A1  - Lee, Hao-Yang
A1  - Chung, Sun-Lin
A1  - Khan, Tahseenullah
A1  - Yamamoto, Hiroshi O´Brien
T1  - Source and mode of the Permian Panjal Trap magmatism: Evidence from zircon U-Pb and Hf isotopes and trace element data from the Himalayan ultrahigh-pressure rocks
JF  - Lithos : an international journal of mineralogy, petrology, and geochemistry
N2  - We present an integrated study of LA-ICP-MS U-Pb age, Hf isotopes, and trace element geochemistry of zircons from the Himalayan eclogites (mafic rocks) and their host gneisses (felsic rocks) from the Kaghan Valley in Pakistan in order to understand the source and mode of their magmatic protoliths and the effect of metamorphism. Zircons from the so-called Group I (high-pressure) eclogites yielded U-Pb mean ages of 259 +/- 10 Ma (MSWD = 0.74), whereas those of Group II (ultrahigh-pressure) eclogites yielded 48 3 Ma (MSWD = 0.71). In felsic gneisses the central or core domains of zircons yielded ages similar to those from Group I edogites but zircon overgrowth domains yielded 47 +/- 1 Ma (MSWD = 1.9). Trace element data suggest a magmatic origin for Group I-derived (having Th/U ratios: >0.5) and metamorphic origin for Group II -derived (Th/U < 0.07) zircons, respectively. Zircon Hf isotope data, obtained from the same dated spots, show positive initial Hf-176/Hf-177 isotopic ratios referred to as "epsilon(Hf)(t)" of around +10 in Group I eclogites; +7 in Group II eclogites; and +8 in felsic gneisses zircons, respectively, thus indicate a juvenile mantle source for the protolith rocks (Panjal Traps) with almost no contribution from the ancient crustal material. The similar epsilon(Hf)(t) values, identical protolith ages and trace element compositions of zircons in felsic (granites or rhyolites) and mafic (basalt and dolerite) rocks attest to a bimodal magmatism accounting for the Panjal Traps during the Permian. Later, during India-Asia collision in Eocene times, both the felsic and mafic lithologies were subducted to mantle-depths (>90 km; coesite-stable) and experienced ultrahigh-pressure metamorphism before their final exhumation. (C) 2016 Elsevier B.V. All rights reserved.
KW  - Himalaya
KW  - Panjal Traps
KW  - UHP edogites and felsic gneisses
KW  - Zircon U-Pb age
KW  - Hf isotopes
KW  - Trace element geochemistry
Y1  - 2016
U6  - https://doi.org/10.1016/j.lithos.2016.06.001
SN  - 0024-4937
SN  - 1872-6143
VL  - 260
SP  - 286
EP  - 299
PB  - Elsevier
CY  - Amsterdam
ER  -