Facies and distribution of metamorphic rocks beneath the Muslim Bagh ophiolite, (NW Pakistan): tectonic implications
Keywords:
Intra-oceanic subduction; Metamorphic sole rocks; Mylonitic peridotites; Garnet amphibolites; GreenschistsAbstract
The Muslim Bagh ophiolite Complex comprises two massifs; Jang Tor Ghar Massif (JTGM) and Saplai Tor Ghar Massif (STGM) and shows a nearly complete ophiolite sequence that is structurally underlain by metamorphic sole rocks. The metamorphic rocks are found around both the massifs of Muslim Bagh ophiolite but, the best exposures are on the northwest side of JTGM and west of STGM. The sole rocks consist of mylonitic peridotite and sub-ophiolitic metamorphic rock series grading from (garnet-bearing) amphibolite facies to greenschist facies. A mylonitic texture in basal peridotite is the result of ductile lithospheric deformation while the sub-ophiolitic metamorphic rocks were formed during intra-oceanic subduction, i.e., the first stage of the emplacement of Muslim Bagh ophiolite. The foliation plane of the metamorphic sole rocks on the northwestern base of the JTGM strikes northeast–southwest with a dip ranging from 20o –75o to the east, while on the western side of STGM, it trends north–south and dips steeply towards east. Most of the lineations display northeast–east orientations which suggest that the ophiolite was obducted from west to east in the frame of today’s geographic co-ordinates. During intra-oceanic subduction various parts of the subducted plate were accreted to the base of the overriding slab and subjected to a temperature between about 900–1,000 °C, forming mylonitic peridotite and then continued downwards to form the sub-ophiolitic metamorphic rocks.
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