OPHIOLITES OF PAKISTAN

OPHIOLITE• The characteristic assemblage

of rocks which form at spreading ridges is called an ophiolites sequence. which laterally emplaced on continental lithosphere.

• The typical rock types are ocean sediments, mafic extrusive and intrusive igneous rocks, and ultramafic rocks.

• These sequences are commonly revelaled in areas characterized by accretionary tectonics, such as the western margin of North America.

OPHIOLITES OF PAKISTAN

1. MUSLIM BAGH OPHIOLITES.2. ZHOB OPHIOLITES.

3. WAZIRISTAN(KHOST OPHIOITES).4. RASKOH OPHIOLITES.

5. INDUS SUTURE OPHIOLITES.6. MALAKAND OPHIOITE.

7. SWAT OPHIOLITE8. BELA OPHIOLITES.

TECTONIC SETTINGS AND ENVIROMENTS.

1. Along Chaman Transform fault (Bela, Zhob,Bagh & Waziristan)

2. Along Chagai magmatic arc formed by the subduction of Indian plate (Raskoh ophiolites)

3. Along Indus suture zone. In north of Pakistan developed along thrust faults along with subduction of Indian plate. (Swat and Malakand)

MUSLIM BAGH OPHIOLITES.

• Located in Zhob valley in Northeast of Quetta.

• Consisting of two main blocks.1. Jhang Tor Ghar(West).2. Saplai Tor Ghar(East).

• Smaller massifs in zazghai and khanozoi are found.

• Consists sedimentary and igneous rocks of Neo-Tethys ocean.

SYNONAMY AND CONTACTS.

• Abbas and Rossman(1970).• Moores(1980).• Mahmood(1994).

• CONTACTS:• Underlying masstrichtian limestone turbidities.• Overlying lower Eocene transgression.

Ophiolitic Complex sequence.

• Banded dunites and harzburgites. • Green schist to granulatic facies. assemblage

found.• Transition from mantle to crustal sequence is

only exposed in saplai Tor Ghar and Kanozai area(Mark by dunite rich zone).

• Gabbros are layered, foliated or isotropic.• Sheeted dyke complex forms the core of 4km

wide synform in saplai tor Ghar massifs.

ZHOB OPHIOLITES.

• Located in north east of the muslim bagh ophiolites.

• Located b/t Chaman transform fault & Indian shield.

• Large section of it is covered by pillow lavas.• It forms the core of four synclines.• Best exposures are found at Muslim Bagh-Nasai

area as Sapli Tor Ghar –Nasai Massif & Jang Tor Ghar Massif.

SYNONAMY AND CONTACT

• SYNONAMY:1. Hunting survey of Pakistan(1960).2. Assrarullah(1979).

• CONTACTS:1. Over lain by the sediments of unknown age.2. Under lain by marine sediments of upper

cretaceous.

Rocks of Zhob ophiolite

• Ultrmafic tectonites contain of Lherzolite ,Hurzbrgite and Dunite(Jang Tor Ghar Massif)and Dunite enrich tectonites are associated with Sapli Tor Ghar-Nasai Massif.Ultramafic to mafic cumulates consist of Olivine at base and Wehrlite pyroxinite at top,

• Mafic-trojdhjemitic dyke complex contain Dolerite gabbro,plagiogranite (Greenschist to Amphibolite facies).

COMPLEX SEQUENCE.

• The harzburgite gabbro section were thrust upon pillow lavas forming the central part of synclines with dunite veins.

• Contain doleritic dikes and granitoid intrusions.

• Most of upper section is covered by pillow lavas.

WAZIRISTAN OPHIOLITES• SYNONMAY:1. Khan(1982).2. Jan(1985).3. Beck(1996).

• CONTACTS: Overlain by red to Greyish radiolarian cherts. Underlain by the sediments of upper

masstrichtian limestone and shales.

Waziristan ophiolites.

• Third largest ophiolites sequence in Pakistan.

• Emplaced during Tertiary period.• Also named as Khost Ophiolites.• About 50% of outcrop is pillow basalts and

sheeted dikes.

OPHIOLITIC SEQUENCE• Complete but strongly dismembered sequence.• Mantle section consist of harzburgites and dunite(contain

chromite deposits).• Massive ore of chromites with pull a part texture found • Gabbros occur along with anarthosite in crustal

sequence.• Blue schist facie also found in some parts of sequence.• Most of sequence is dominated by pillow basalts and

sheeted dikes.• Some parts of sequence are more than 90ma years

older.

Rocks of Waziristan ophiolites

• Ultramafic rocks contain Hurzburgite,Dunite,Pyroxinite .

• Sheeted dykes contains labradorite,augite,pleochroic hornblende,ilminite,actinolite,chlorite,albite ,epidote,quartz and carbonates.

• Volcanic rocks contains pillow lava,tuff,agglomerate,breccia,dolerite,diorite,actionolite,epidote,calcite,ironoxide.

Dunite(contain chromite deposits).

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Raskoh ophiolite• Located in between chagai mamatic arc and

chaman transform fault.• Present in raskoh range Balouchistan.• Height of about 3000m.• Two main areas can be distinguished in Ras koh

range.• Ras Koh and Chagai region is seprated by

Dalbandin.• Sequence disappears in Hamun 1 musakhel

dipression in its west.

Rocks in Ras Koh.

• Ultramafic contains serpentininized dunite,peridotite and pyroxinite.

• Dolerit dykes intruded in the granitoids and rhyolitic flow

• Volcanic rocks consist of diorite,gabbro,norite,monzonite & aplite

Complex sequence.• Serpentized harzburgite outcrops are widely

spread in the Bunap area.

• Red conglomerates containing basalts and chert pebbles occur with serpentinites.

• Metamorphic soles contain hornblendes which formed in initial stage.

• Alkaine pillow lavas are found exposed in some places.

Indus suture ophiolites

• Indus suture zone is tectonic melange between Kohistan island arc and Indian plate.

1. Malakand mohmmand ophiolite2. Swat ophiolite

Malakand mohmmand ophiolite

• Greenschist to amphiobolite facies during early Tertiary period.

• ultramafic rocks contain (talc tremolite,talc carbonatewith green beryl & emerald)

• Mafic rocks consist of saussurite,chlorite,uralite & rodingite.

• Volcanic rocks consist of chlorite,epidote,quartz,albite,amphibolites,mica and pelites.

Swat ophiolites

• Ultramafic rocks consist of hurzburgite,dunite ,lherzolite ,websterite,diopsidite.

• Mafic rocks consist of gabbro with albite ,clinozoisite,amphibolite,with augite.

• Plagiogranite,quartz,actinoite,pargasiteepidote.

BELA OPHIOLITES

• Largest & most complete sequence• Appear as large nappe over mesozoic

sequence of lover indus basin.• Forms 10-60 km wide and 300 km long

belt between karachi and Khuzdar.• Northern part offset along a sinistral fault

and continues in south to Arabian sea.

SYNONAMY

• Vrendenburg(1909).• Hunting Corpertion(1960).• Ahsan(1979).• Sarwar(1992).

BELA OPHIOLITES

TWO MAIN UNITS.

• Upper Unit: The true ophiolite sequence found in the

sunaro region in north.

• Lower Unit: Mainly southern area of tectonically lower

accretionary wedge .

Upper Unit• Mainly most of remanents found are located in northern part of

belt.

• Most complete sequence is found between villages of wad and Sunaro.

• Section Exposed contains:1. A metamorphic Sole2. <2Km of serpentinized harzburgite mantle sequence3. 1.5 to 2km of layered peridotites/gabbros,layered,foliated and

isotropic gabbros.4. 0.5 to 1 km of sheeted dikes.5. <100m of an extrusive sequenc.

LOWER UNIT• It consists of imbricated sheets that dip 45-50 degree

west to north west.• Imbrication is consist of partial or complete sequence of

oceanic lithosphere.• The micro gabbroic intrusions and sills cover larger

sequence of about 30%.• Red granitoides and dacites are also observed.• Three sedimentary units found here(Red sediments,

blackish sediments and yellow sediments).

• LOWER UNIT MAINLY CONTAINS:1. Pillow lavas.2. Sedimentary rocks 3. Serpentinites.4. Dolerits.