Clay minerals assemblage in the neogene fluvial succession of the pishin belt,pakistan: Implications for provenance

The neogene siliciclastic succession of the pishin belt comprises the newly proposed middle to upper miocene dasht murgha group,miocene-pliocene malthanai formation and pleistocene bostan formation. sandstones of the succession have been classified as lithic arenites and their detrital modes indicate derivation of material from the pre-miocene sedimentary and meta-sedimentary terrains of the pishin belt. x-ray diffraction (xrd) analyses indicate that clay minerals in various mudstones and sandstone samples are identical and detrital in nature and include smectite,chlorite,illite,serpentine and kaolinite. smectite and chlorite are most probably derived from the metavolcanic and mafic volcanic rocks,respectively. presence of serpentine in samples of the bostan formation indicates altered ultramafic rocks as one of the source terrains. illite is probably recycled from the older sedimentary and metasedimentary successions. the source of kaolinite seems to be pedogenic or lateritic. the clay minerals assemblage in mudstones and sandstones of the dasht murgha group,malthanai formation and bostan formation appears to have been derived from the nearby-exposed pre-miocence mafic/ultramafic rocks of the cretaceous muslim bagh-zhob ophiolite and argillites of the eocene nisai and oligocene khojak formations of the pishin belt. the triassic-jurassic succession,of the wulgai and loralai formations of the adjacent sulaiman fold-thrust belt,is also believed to have provided some material,however in subordinate amount. © 2014 national centre of excellence in geology. all rights reserved.