Magmatic and deformational fabrics of the chilas gabbronorite are. Changing sources of magma generation beneath intraoceanic island arcs. The paleogeographic position of the kohistan island arc is uncertain. The karakoram kohistan suture zone kksz is the northern branch of the western continuations of the yalutsangpo suture recognised in southern tibet e. Oceanic island arcs, such as the izuogasawaramariana, tongakermadec, or kurilealeutian arcs, are believed to develop from normal oceanic crust at plate subduction boundaries. The intraoceanic kohistan island arc was a cretaceous volcanic are within tethys which first collided with asia along the. Episodic unroofing of the kohistan batholith, pakistan. The limestones was arenaceous and is highly bioturbated and shows good preservation of fossils. Our pdf merger allows you to quickly combine multiple pdf files into one single pdf document, in just a few clicks. Structures related to collision, during which the arc was thrust onto the leading edge of continental india along the. The model allows a quantitative approximation of the possible relative roles of fractional crystallization and assimilation to explain the silicarich. The complex resulted from a rising diapir during the mid. The kksz separates in nw pakistan the karakoram terrane, to the north, from the kohistan paleo island arc complex, to the south. A primitive odobenine walrus of early pliocene age from japan.
The scale of an oceanic arc is typically a few hundred kilometers across, with only a small portion rising above sea level. The kohistan island arc terrane is sandwiched between the collided indian and karakoram plates in the himalaya of north pakistan. Petrogenesis of mafic garnet granulite in the lower crust. The tectonic history of kohistan, northern pakistan, involves two collisional events. Survival of an island arc in continental collision. Accordingly, the secular evolution of magmatic arcs is crucial to the understanding of crust formation processes. Soda pdf is the solution for users looking to merge multiple files into a single pdf document. Request permission export citation add to favorites track citation. The kohistan island arc terrane and adjacent rocks of the. The utror volcanic formation forms a nesw belt with in kohistan island arc, which lies between the indian and. Geological setting the kohistan arc complex kac, fig 1a, in northern pakistan,represents the exhumed section of a cretaceous intraoceanic arc formed during the northward subduction. Geology of the northern part of the nanga parbat massif. Precollision tilt of crustal blocks in rifted island arcs. In this paper we present the first comprehensive upb, hf, nd and sr isotopic dataset documenting c.
Geological setting the kohistan arc complex western himalaya, northern pakistan. Obduction of the sapat ophiolite and kohistan arc occurred between. Pdf merge combine pdf files free tool to merge pdf online. Andesitic crust formation is only incipient in such arcs, while the fossil kohistan island arc constitutes a mature island arc with a fully developed 420km thick batholith resulting in a bulk crust composition that is andesitic jagoutz and schmidt, 2012.
The tectonic history of kohistan and its implications for. Age and isotopic constraints on magmatism along the. The areas within rectangles, located around the towns of drosh. This free online tool allows to combine multiple pdf or image files into a single pdf document. Geology of the northern part of the nanga parbat massif, northern pakistan, and its. Based on alinhornblende barometry, the batholith records intrusion pressures from 0. The closure of the shyok suture zone separating kohistan from the karakoram plate must have occurred prior to 75 ma, the age of the jutal basic dikes which crosscut the closurerelated fabrics, mainly late north directed backthrusting in the lower hunza valley. The processes active in the deep crust above an oceanic subduction zone during its evolution have been constrained through a detailed geochemical study major and trace elements and sr, nd and pb isotopes of representative samples through an. Mckenna department of vertebrate paleontology, american museum of. Pdfsam ist eine plattformunabhangige free open source. Pb mineral ages from plutonic rocks help constrain the thermal and tectonic evolution of the kohistan island arc terrane following its collision with india in early tertiary time. Cleavage and folding developed at 90100 ma along the northern suture between the kohistan island arc and the asian plate. Pdfdateien miteinander zu verbinden bezeichnet man auch als pdfmerge.
Pdf the isotopic evolution of the kohistan ladakh arc. Pdfdateien in einzelne seiten aufteilen, seiten loschen oder drehen, pdfdateien einfach zusammenfugen oder. From archaean times, the indian subcontinent was a part of. The intraoceanic kohistan island arc was initiated during the cretaceous as a result of northward movement of the indian plate. Changing sources of magma generation beneath intra. The conventional assertion that the arc was erected above a northdipping subduction zone has been challenged by an alternative hypothesis, which suggests that the arc was built above. Free web app to quickly and easily combine multiple files into one pdf online. Geological map of the cretaceous kohistan island arc. The geological field work report writing is an essential requirement for bs degree in geology. Combine pdfs in the order you want with the easiest pdf merger available. Remagnetizations and postfolding rotations in utror area, kohistan arc, northern pakistan. Magnetomineralogical changes along the kohistan karakoram collision zone in north pakistan. The southern and central kohistan batholith is primarily composed of plu.
Northward subduction of the indian plate beneath the. Existing data constrain its late cretaceous position 10080ma in the equatorial zone and close to the karakoram margin of the. Island arcs are long chains of active volcanoes with intense seismic activity found along convergent tectonic plate boundaries most island arcs originate on. Geochemical architecture of the lower to middlecrustal. Ttgtype plutonic rocks formed in a modern arc batholith by hydrous fractionation in the lower arc crust. The root of the kohistan island arc in the himalaya of northern pakistan, tectonics of the western himalayas, lawrence l.
Pdf construction of the granitoid crust of an island arc. Origin of the island arc moho transition zone via melt. The sample was transported and was not capable to be studied in thin section for this sake the sample was studied megascopically through the use of hand lens. Investigation of major geothermal fields of pakistan using isotope and chemical techniques manzoor ahmad, muhammad rafiq, naveed iqbal, waheed akram, m. During this time the kashmir basin remained exposed. This paper describes the suture zone between the asian plate and the accreted kohistan island arc in the chitral district of nw pakistan. Multiple mantle sources during island arc magmatism. Kohistan island arc is concordant and ductile, is associated with interleaving of nanga parbat and. The conventional assertion that the arc was erected above a northdipping subduction zone has been challenged by an alternative hypothesis, which suggests that the arc was built above a southdipping subduction zone. The seismic structure of island arc crust springerlink.
Often it is the case that fats will combine before accret ing onto a. Structural evidence from the kohistan arc jeanpierre burg,1 oliver jagoutz,1,2 hamid dawood,3 and s. Kohistan has experienced a prolonged tectonomagmatic history extending from the early cretaceous through the tertiary. The southern part of the asian plate consists of two tectonic units separated by the ndipping reshun fault.
The chilas complex, a large gabbronorite body enclosing kmscale ultrama. Timing of collision of the kohistanladakh arc with india. The chilas complex comprises gabbronorites, peridotites, anorthosites, troctolites, and pyroxenites. Jeanpierre burg, swiss federal institute of technology in zurich, switzerland.
The kohistan arc, located in the nw himalaya, and exposed to the west of the nanga parbat syntaxis, was initiated as an intraoceanic island arc between eurasia and india during the cretaceous. The isotopic evolution of the kohistan ladakh arc from. At the same time there was major folding and shearing of the lower part of the kohistan arc, approximately 100 km south of the suture. Results of simple model calculations that integrate cumulate compositions from the kohistan arc terrain are presented in order to develop a consistent petrogenetic model to explain the kohistan island arc granitoids. Unter dem namen hat sich ein kostenloses onlineangebot. Review article timing of collision of the kohistan ladakh arc with india and asia. Detailed petrography and mineral chemistry are presented in this paper. Sedimentation resumed in hazara and kashmir basins with the development of transgressive shoreline and hangu formation was formed in danian. Structural evolution of a crustal section in the western. The ladakh and kohistan blocks are bounded to the south by the indus suture zone, and it has. Construction of the granitoid crust of an island arc part.
Large volumes of felsic uppercrustare observed ine. Volcanostratigraphy of arc volcanic sequences in the. Construction of the granitoid crust of an island arc. Construction of the granitoid crust of an island arc part i. A back arc basin occurs on the side of the overriding plate and a fore arc basin forms toward the subducted plate side. Collision zone between the kohistan arc and the asian. Petrography and physicomechanical properties of the. The kohistan arc terrane of the western transhimalaya exposes a remarkable crosssection through an island arc sequence which developed as a result of the northward subduction of neotethyan oceanic crust beneath asia during late jurassic and early cretaceous times. The tectonic evolution of the kohistankarakoram collision. An insight from the juvenile kohistan island arc, pakistan himalaya stella m. Ttgtype plutonic rocks formed in a modern arc batholith. Multistage evolution of the jijal ultramafic mafic complex.
Pdf geology of the chaltbabusar transect, kohistan. Recent field work on the kohistan complex in the karakorum range of north pakistan has shown its stratigraphy to be repeated by several phases of tight to isoclinal folding. Origin of the island arc moho transition zone via meltrock reaction and its implications for intracrustal differentiation of island arcs. Investigation of major geothermal fields of pakistan using. Evidence from the jijal complex kohistan complex, northern pakistan.
345 555 416 1390 931 474 1299 732 743 1524 1051 160 15 246 1551 457 473 1129 988 570 1431 1235 1559 404 767 388 1611 128 319 340 473 253 136 1332 844 485 681 1259 1092