Metamorphic history and tectonic evolution of the Himalayan UHP eclogites in Kaghan valley, Pakistan

Hafis Ur Rehman, Hiroshi Yamamoto, M. Ayub Khan Khalil, Eizou Nakamura, Muhammad Zafar, Tahseenullah Khan

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Eclogites of the Kaghan valley, Pakistan Himalaya were investigated petrographically and geochemically. Based on petrography, geochemistry and mineral compositions, metamorphic history and a reasonable tectonic model are proposed. Eclogites exposed in the Kaghan valley are classified into two groups. Group I eclogites appear as massive and Group II are lens-type. Group I eclogites have a mineral assemblage of garnet, omphacitic clinopyroxene, quartz, Symplectite with rare epidote and phengite. Accessory minerals include abundant zircon, rutile, ilmenite, and rare apatite. Group II eclogites have a mineral assemblage of garnet, omphacitic clinopyroxene, phengite, quartz/coesite, epidote, and symplectite. In accessory minerals rutile and ilmenite are common while zircon and apatite are rare. Different types of protolith are proposed for these eclogites. Group I eclogites have higher Fe0 and Ti02, contents and trace element contents, and seem to be derived from gabbroic protolith. Group II eclogites have lower Fe0 and Ti02 and trace element contents and were derived from basalts. Pressure-temperature-time path was constructed for the Kaghan valley eclogites using various mineral assemblages along with textural relationship and inclusions study. At least three distinct metamorphic stages were identified. The first stage is the prograde garnet growth stage deduced from the inclusion paragenesis in garnet core. The second stage records the ultrahigh pressure metamorphic stage deduced from the presence of coesite inclusions in omphacitic clinopyroxene. The third stage is the decompression stage and is deduced from the quartz-albite-amphibole symplectite portions. These petrological and geochemical results combined with isotopic ages reported elsewhere indicate that basalts and associated gabbroic dikes were emplaced at about 267 Ma when the Indian plate was moving northward and passing above an unknown hot spot. The closure of the Tethys and initiation of collision of the Indian plate with the Kohistan-Ladakh Island Arc is reported from 65-50 Ma. After that the leading-edge of the Indian plate underwent eclogite facies metamorphism at 49 Ma and when it reached to depths of about 100 km, the ultrahigh-pressure metamorphic event took place at 46 Ma.

Original languageEnglish
Pages (from-to)242-254
Number of pages13
JournalJournal of Mineralogical and Petrological Sciences
Volume103
Issue number4
DOIs
Publication statusPublished - 2008

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Pakistan
symplectite
tectonic evolution
valleys
Indian plate
tectonics
garnet
histories
clinopyroxene
valley
minerals
coesite
phengite
accessory mineral
garnets
mineral
epidote
quartz
rutile
history

Keywords

  • Kaghan valley
  • Pakistan Himalaya
  • Tectonic model
  • Ultrahigh-pressure eclogites

ASJC Scopus subject areas

  • Geophysics
  • Geology

Cite this

Metamorphic history and tectonic evolution of the Himalayan UHP eclogites in Kaghan valley, Pakistan. / Rehman, Hafis Ur; Yamamoto, Hiroshi; Khalil, M. Ayub Khan; Nakamura, Eizou; Zafar, Muhammad; Khan, Tahseenullah.

In: Journal of Mineralogical and Petrological Sciences, Vol. 103, No. 4, 2008, p. 242-254.

Research output: Contribution to journalArticle

Rehman, Hafis Ur ; Yamamoto, Hiroshi ; Khalil, M. Ayub Khan ; Nakamura, Eizou ; Zafar, Muhammad ; Khan, Tahseenullah. / Metamorphic history and tectonic evolution of the Himalayan UHP eclogites in Kaghan valley, Pakistan. In: Journal of Mineralogical and Petrological Sciences. 2008 ; Vol. 103, No. 4. pp. 242-254.
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