TY  - JOUR
A1  - Rehman, Hafiz Ur
A1  - Tanaka, Ryoji
A1  - Kobayashi, Katsura
A1  - Tsujimori, Tatsuki
A1  - Nakamura, Eizo
A1  - Yamamoto, Hiroshi
A1  - Khan, Tahseenullah
A1  - Kaneko, Yoshiyuki
T1  - Oxygen isotopes in Indian Plate eclogites (Kaghan Valley, Pakistan): Negative delta O-18 values from a high latitude protolith reset by Himalayan metamorphism
JF  - Lithos : an international journal of mineralogy, petrology, and geochemistry
N2  - Oxygen isotope compositions are reported for the first time for the Himalayan metabasites of the Kaghan Valley, Pakistan in this study. The highest metamorphic grades are recorded in the north of the valley, near the India-Asia collision boundary, in the form of high-pressure (HP: Group I) and ultrahigh-pressure (UHP: Group II) eclogites. The rocks show a step-wise decrease in grade from the UHP to HP eclogites and amphibolites. The protoliths of these metabasites were the Permian Panjal Trap basalts (ca. 267 +/- 2.4 Ma), which were emplaced along the northern margin of India when it was part of Gondwana. After the break-up of Gondwana, India drifted northward, subducted beneath Asia and underwent UHP metamorphism during the Eocene (ca. 45 +/- 1.2 Ma). At the regional scale, amphibolites, Group I and II eclogites yielded delta O-18 values of +5.84 and +5.91 parts per thousand, +1.66 to +424 parts per thousand, and -2.25 to +0.76 parts per thousand, respectively, relative to VSMOW. On a more local scale, within a single eclogite body, the delta O-18 values were the lowest (-2.25 to-1.44%.) in the central, the best preserved (least retrograded) parts, and show a systematic increase outward into more retrograded rocks, reaching up to +0.12 parts per thousand. These values are significantly lower than the typical mantle values for basalts of + 5.7 +/- 0.3 parts per thousand. The unusually low or negative delta O-18 values in Group II eclogites potentially resulted from hydrothermal alteration of the protoliths by interactions with meteoric water when the Indian plate was at southern high latitudes (similar to 60 degrees S). The stepwise increase in delta O-18 values, among different eclogite bodies in general and at single outcrop-scales in particular, reflects differing degrees of resetting of the oxygen isotope compositions during exhumation-related retrogression. (C) 2014 Elsevier B.V. All rights reserved.
KW  - Himalaya
KW  - Kaghan
KW  - UHP eclogites
KW  - Oxygen isotope compositions
KW  - Laser fluorination
Y1  - 2014
U6  - https://doi.org/10.1016/j.lithos.2014.09.007
SN  - 0024-4937
SN  - 1872-6143
VL  - 208
SP  - 471
EP  - 483
PB  - Elsevier
CY  - Amsterdam
ER  -