Manganese and ferromanganese ores from different tectonic settings in the NW Himalayas,Pakistan

In Pakistan manganese and ferromanganese ores have been reported from the Hazara area of North West Frontier Province, Waziristan agencies in the Federally Administered Tribal Areas and the Lasbela-Khuzdar regions of Baluchistan. This study is focused on comparison of mineralogy and geochemistry of the continental ferromanganese ores of Hazara and the ophiolitic manganese ores of the Waziristan area of Pakistan. In the Hazara area, ferromanganese ores occur at Kakul, Galdanian and Chura Gali, near Abbottabad, within the Hazira Formation of the Kalachitta-Margala thrust belt of the NW Himalayas of the Indo-Pakistan Plate. The Cambrian Hazira Formation is composed of reddish-brown ferruginous siltstone, with variable amounts of clay, shale, ferromanganese ores, phosphorite and barite. In Waziristan, manganese ores occur at Shuidar, Mohammad Khel and Saidgi, within the Waziristan ophiolite complex, on the western margin of the Indo-Pakistan Plate in NW Pakistan. These banded and massive ores are hosted by metachert and overlie metavolcanics.The ferromanganese ores of the Hazara area contain variable amount of bixbyite, partridgeite, hollandite, pyrolusite and braunite. Bixbyite and partridgeite are the dominant Mn-bearing phases. Hematite dominates in Fe-rich ores. Gangue minerals are iron-rich clay, alumino-phosphate minerals, apatite, barite and glauconite are present in variable amounts, in both Fe-rich and Mn-rich varieties. The texture of the ore phases indicates greenschist facies metamorphism. The Waziristan ores are composed of braunite, with minor pyrolusite and hollandite. Hematite occurs as an additional minor phase in the Fe-rich ores of the Shuidar area. The only silicate phase in these ores is cryptocrystalline quartz.The chemical composition of the ferromanganese ores in Hazara suggests that the Mn–Fe was contributed by both hydrogenous and hydrothermal sources, while the manganese ores of Waziristan originated only from a hydrothermal source. It is suggested that the Fe–Mn ores of the Hazara area originated from a mixed hydrothermal–hydrogenetic source in shallow water in a ontinental shelf environment due to the transgression and regression of the sea, while the Mn ores of Waziristan were formed at sea-floor spreading centers within the Neo-Tethys Ocean, and were later obducted as part of the Waziristan ophiolite complex.     

Structural evolution and asymmetric uplift of the Nanga Parbat syntaxis,Pakistan Himalya

The Nanga Parbat syntaxis, in the NW Himalaya, is a still growing crustal-scale north-trending antiformal structure in the core of which Indian Plate gneisses have been uplifted from beneath the overthrust rocks of the Kohistan island arc. Isotopic and fission track geochronology show that uplift rates within the syntaxis have increased to present day rates of > 6 mm/yr. Uplift has been accommodated by a combination of initial northwest verging thrusting on the western margin of the syntaxis, followed by crustal scale folding within the syntaxis and latterly by dextral reverse faulting on the western margin. This thrusting, folding and faulting is the effect of deformation at the north-western lateral tips of the main Himalayan thrusts where they interfere with the south-southeast verging thrusts of the northwest Himalaya.

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Zusammenfassung Nanga Parbat Konvergenz im nordwestlichen Himalaya ist eine noch im Wachsen begriffene nach Norden streichende antiformale Struktur im Krustenmaßstab. In ihrem Inneren wurden Gneisse der Indischen Platte aus der Nähe der überschobenen Gesteine des Kohistan Inselbogens herausgehoben. Isotopen- und Spaltspurengeochronologie zeigen, daß das Heraushebungsmaß innerhalb der Konvergenz zu der heutigen Rate von > 6 mm/a angestiegen ist. Die Heraushebung hat sich angepaßt an die Kombination von initialer NW-vergenter Überschiebung auf den westlichen Konvergenzrand, die gefolgt wurde von einer krustalen Faltung und lateral von dextraler antithetischer Verwerfung des westlichen Randes. Diese Deckenüberschiebung, Faltung und Verwerfung ist das Resultat der Deformation des nordwestlichen Ausstriches der Himalaya-Hauptüberschiebung, wo sie in Wechselwirkung mit der SSE-vergenten Überschiebung des NW-Himalayas steht.

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Résumé La convergence du Nanga Parbat, dans le nordouest de l'Himalaya, est une structure antiforme d'orientation nord-sud, d'échelle crustale et toujours active; son cur est occupé par des gneiss de la plaque indienne qui ont été soulevés à travers les roches charriées de l'arc insulaire du Kohistan. Les données géochronologiques obtenues à partir des isotopes et des traces de fission montrent que le taux de soulèvement a augmenté dans cette structure jusqu'à la valeur actuelle de plus de 6 mm/an. Le soulèvement s'est effectué par la combinaison d'un charriage initial, à vergence nordouest, sur la bordure ouest de la convergence, suivi d'un plissement d'échelle crustale dans la convergence et, latéralement, d'une fracturation par faille dextre inverse sur sa bordure ouest. Ce charriage, ce plissement et cette fracturation sont l'expression de la déformation à l'extrémité latérale nord-ouest des charriages principaux de l'Himalaya, où ils interfèrent avec les charriages à vergence sud- sud-est de l'Himalaya septentrional.

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Timing of Late Quaternary glaciations in the Himalayas of northern Pakistan

Optically stimulated luminescence dating of Late Quaternary glaciogenic sediments was undertaken in critical areas of the Himalayas of northern Pakistan in order to examine the timing of glaciation. The dates demonstrate that several glaciations occurred during the last glacial cycle. In Swat, the Grabral 2 Stade and the Kalam I Stade were dated at ca. 77 ka and ca. 38 ka, respectively. The error on the former date is large and it is conceivable that the moraines may have formed during the early part of Oxygen Isotope Stage 3 rather than during Oxygen Isotope Stage 4. The Kalam I Stade, however, clearly represents a glaciation during Oxygen Isotope Stage 3. The oldest moraines and those at the lowest altitude in the Indus valley at Shatial have an age of ca. 60 ka. These also relate to a major glacial advance during Oxygen Isotope Stage 3. A younger series of moraines, the Jalipur Tillite, and glaciofluvial sands at Liachar in the Indus valley, and moraines at Rampur–Tarshing have ages of ca. 27 ka, ca. 21–23 ka and ca. 15 ka, respectively. These dates show that glaciers also occupied parts of the Indus valley during Oxygen Isotope Stage 2. These dates and the morphostratigraphy show that glaciation in the Pakistani Himalaya was more extensive during the early part of the last glacial cycle and that the local last glacial maximum in Pakistan was asynchronous with the maximum extent of Northern Hemisphere ice sheets. Copyright © 2000 John Wiley & Sons, Ltd.     

Analysis of landslide causes and associated damages in the Kashmir Himalayas of Pakistan

This article deals with the analysis of landslide causes and associated damages in the Kashmir Himalayas of Pakistan. The present study is based on Muzaffarabad, which lies in the lesser Himalayas. Geologically, the Kashmir Himalaya is the young and most dynamic system in the world. In Muzaffarabad, mostly, people live on the fragile mountain slopes, and therefore, they are highly vulnerable to the risk of landslides. To achieve the objectives of the study, data were collected both from primary and secondary sources. Primary data were obtained through intensive field work and human perception survey, while secondary data were obtained from the related line agencies. The analysis reveals that in the study area, immature geology, active seismic zone, wide range of temperature and seasonal rain are the major physical factors, whereas human interventions on the fragile slopes are intensifying factors which in effect contribute to the landslide incidence. As a result, the adverse impacts on housing, sources of livelihood earnings and human casualties are escalating day-by-day. There are several implementing agencies which are responsible for reducing the risk of landsliding. So far, these agencies have not reduced the landslide damages rather their intensity and frequency have been increased especially after 2005 Kashmir earthquake.     

Morphotectonic analysis of the Hazara arc region of the Himalayas, north Pakistan and northwest India

In the Hazara arc region of northern Pakistan, some of the active basements structures buried below a thick, detached sedimentary layer are inferred from the distribution of lineaments and the drainage patterns, as viewed in Landsat satellite imagery and from river profiles.A prominent set of NW-trending lineaments seen on satellite imagery, coincides approximately with the southwest or updip side of the Indus—Kohistan seismic zone (IKSZ) —the most active basement structure of the region, even though this structure is buried beneath and decoupled from a 12 km thick sedimentary layer. The IKSZ has been interpreted as an extension of the Himalayan Basement Thrust, and is also associated with a prominent topographic “step”.Knickpoints on major rivers in the region lie on or north of the IKSZ. All Indus River tributaries, examined north of the IKSZ, show prominent knickpoints, while two tributaries draining south of the IKSZ have no knickpoints. These results suggest ongoing uplift above and north of the IKSZ, and are consistent with the tectonic model obtained from the seismic data.Another prominent lineament set is detected along the north—south section of the Indus River. This set is probably related to the Indus River horst—anticline and associated reentrant.One of the two highest lineament concentrations occurs at the intersection between the NW-trending IKSZ lineament and the N-trending Indus River lineament. The other is along the west bank of the Indus Valley, 25 km north of Tarbela Dam.A topographic ridge (Swabi—Nowshera ridge) appears to be forming along the west side of the Indus River, in the Peshawar Basin. The rising ridge is ponding the Kabul River upstream of Nowshera, where the drainage is braided.     

Focal mechanism solutions and dynamic parameters of earthquakes in the eastern Himalayas and northern Burma

Focal-mechanism solutions of four earthquakes in the eastern Himalayas and northern Burma are determined using the first motion of compressional waves. Two possible solutions thus obtained for each event reveal steeply dipping fault with predominantly strike-slip motion. The stress directions inferred from the focal mechanism solutions are interpreted in the light of predictions of the plate tectonics theory, viz., the underthrusting of the Indian plate in the Burma region in an easterly direction.Dynamic parameters (seismic moment, apparent stress and average dislocations) are obtained using the corrected spectra of Love waves. The earthquakes are found to possess low seismic moment and apparent stress values. A comparison of these estimates with values for intraplate earthquakes is given. It is suggested that these earthquake might be a consequence of a nonhomogeneous rupture process.     

Petrology and geochemistry of Jura granite and granite gneiss in the Neelum Valley,Lesser Himalayas (Kashmir,Pakistan)

Late Proterozoic rocks of Tanol Formation in the Lesser Himalayas of Neelum Valley area are largely green schist to amphibolite facies rocks intruded by early Cambrian Jura granite gneiss and Jura granite representing Pan-African orogeny event in the area. These rocks are further intruded by pegmatites of acidic composition, aplites, and dolerite dykes. Based on field observations, texture, and petrographic character, three different categories of granite gneiss (i.e., highly porphyritic, coarse-grained two micas granite gneiss, medium-grained two micas granite gneiss, and leucocratic tourmaline-bearing muscovite granite gneiss), and granites (i.e., highly porphyritic coarse-grained two micas granite, medium-grained two micas granite, and leucocratic tourmaline-bearing coarse-grained muscovite granite) were classified. Thin section studies show that granite gneiss and granite are formed due to fractional crystallization, as revealed by zoning in plagioclase. The Al saturation index indicates that granite gneiss and granite are strongly peraluminous and S-type. Geochemical analysis shows that all granite gneisses are magnesian except one which is ferroan whereas all granites are ferroan except one which is magnesian. The CaO/Na₂O ratio (>0.3) indicates that granitic melt of Jura granite gneiss and granite is pelite-psammite derived peraluminous granitic melt formed due to partial melting of Tanol Formation. The rare earth element (REE) patterns of the Jura granite and Jura granite gneiss indicate that granitic magma of Jura granite and Jura granite gneiss is formed due to partial melting of rocks that are similar in composition to that of upper continental crust.     

Changes in the depositional system of the Paleo-Kathmandu Lake caused by uplift of the Nepal Lesser Himalayas

Sedimentological and palynological studies on a series of slimes taken from a drill-well in the central part of the Kathmandu Basin and the Lukundol Formation at the southern margin of the basin indicate that the depositional environments of the Paleo-Kathmandu Lake changed at around 1 Ma. In the central part of the basin, the abrupt appearance of a fossiliferous 4 m thick sand bed, containing abundant fish teeth and gastropod opercula, and shell fragments, in an otherwise open-lacustrine mud sequence, suggests that a lowering of the water level occurred at about 1 Ma. The common occurrence of the green alga Pediastrum in the overlying mud beds implies that the lake remained shallow after the deposition of the sand bed. Changes in the depositional system of the Paleo-Kathmandu Lake at about 1 Ma are also recorded in the Lukundol Formation. Granitic gravel and detrital muscovite flakes, which are common in the Lower and Middle Members, disappear from the Upper Member. Paleocurrent directions in the Lower and Middle Members show flow from the north and east, whilst in the Upper Member they change to flow from the south. Sedimentary facies change from marginal lacustrine in the Middle Member, to a braided river facies in the Upper Member. These changes occurred at around 1 Ma, at the base of the Upper Member. They seem to have been caused by the initiation of rapid uplift of the Mahabharat Lekh, which was due to faulting and underthrusting along the Main Boundary Thrust System.     

Petrography,provenance, diaganesis and depositional environment of Murree Formation in Jhelum Valley,Sub Himalayas,Azad Jammu and Kashmir,Pakistan

The clastic sediments of the Murree Formation of Miocene age are exposed in Jhelum valley areas of Azad Jammu and Kashmir Pakistan. Field observations revealed the cyclic deposition in the Murree Formation. The sandstone, siltstone, and shale constitute a single cycle within the formation. This single unit is divided into five different lithofacies which constitute the Bouma sequence in the Murree Formation. The Murree Formation shows faulted contacts with Panjal Formation and Nagri Formation in the study area. The modal mineralogy data obtained from the petrography of sandstone indicates that sandstone is litharenite and lithic greywacke. The mineralogical and textural data suggests that sandstone is compositionally mature and poorly to moderately sorted. The dominantly angular to sub angular quartz grains show nearness of the source area. Fractured and sutured quartz grain reveals tectonodiagentic changes that occurred in Murree Formation. The sandstone experienced diagenetic changes. The pressure solution and cementation reduced the primary porosity of sandstone. However, alteration of feldspar and fractures in grains have produced secondary porosity. The X-ray diffraction (XRD) of the shale samples indicates that shale of the Murree Formation is argillaceous and dominated by illite clay mineral. The illite crystallinity values indicate very low grade metamorphism of Murree Formation in core of Hazara Kashmir Syntaxis. The petrographic data suggests that the provenance of sandstone is recycled orogen. Quartz is of igneous and metamorphic origin. Feldspar (albite and microcline) composition suggests its derivation from acidic igneous rocks. The rock fragments of volcanics, slate, phyllite, and schist suggest igneous and metamorphic provenance. The petrographic data suggests that at the time of deposition of Murree Formation, igneous and low grade metamorphic rocks were exposed. However, presence of some clasts of carbonates indicates that sedimentary rocks were also exposed in the source region. The quartz content and clay minerals in the shale revealed that source region was igneous and metamorphic rocks. Cyclic deposition, lithofacies, and various sedimentary structures like cross bedding, ripple marks, and calcite concretions suggest that deposition of Murree Formation occurred in fluviatile environment by meandering river system having decreasing turbidity current.     

Evidence for the recurrence of large-magnitude earthquakes along the Makran coast of Iran and Pakistan

The presence of raised beaches and marine terraces along the Makran coast indicates episodic uplift of the continental margin resulting from large-magnitude earthquakes. The uplift occurs as incremental steps similar in height to the 1–3 m of measured uplift resulting from the November 28, 1945 (M 8.3) earthquake at Pasni and Ormara, Pakistan. The data support an E—W-trending, active subduction zone off the Makran coast.The raised beaches and wave-cut terraces along the Makran coast are extensive with some terraces 1–2 km wide, 10–15 m long and up to 500 m in elevation. The terraces are generally capped with shelly sandstones 0.5–5 m thick. Wave-cut cliffs, notches, and associated boulder breccia and swash troughs are locally preserved. Raised Holocene accretion beaches, lagoonal deposits, and tombolos are found up to 10 m in elevation. The number and elevation of raised wave-cut terraces along the Makran coast increase eastward from one at Jask, the entrance to the Persian Gulf, at a few meters elevation, to nine at Konarak, 250 km to the east. Multiple terraces are found on the prominent headlands as far east as Karachi. The wave-cut terraces are locally tilted and cut by faults with a few meters of displacement.Long-term, average rates of uplift were calculated from present elevation, estimated elevation at time of deposition, and ¹⁴C and U–Th dates obtained on shells. Uplift rates in centimeters per year at various locations from west to east are as follows: Jask, 0 (post-Sangamon); Konarak, 0.031–0.2 (Holocene), 0.01 (post-Sangamon); Ormara 0.2 (Holocene).     

Application of gravity and magnetic methods for the crustal study and delineating associated ores in the western limb of Hazara Kashmir Syntaxis,Northwest Himalayas,Pakistan

The present geophysical study deals with the ores and crustal demonstration of southeastern Hazara and its adjoining areas of Azad Jammu and Kashmir, Pakistan, on the basis of terrestrial gravity and magnetic data. Tectonically, the study area lies in the Lesser Himalayas as well as to an extent in the sub-Himalaya, more specifically in the western limb of Hazara Kashmir Syntaxis. In this study, 567 gravity and 508 magnetic stations have been measured with CG-5 gravimeter and proton precession magnetometer, respectively. The collected data have been processed by applying standard corrections and then different types of maps were prepared. The ores in the area have been delineated by the qualitative interpretation of residual Bouguer anomaly and reduction to pole total magnetic intensity maps, whereas regional structures are demarcated by the Bouguer anomaly and regional Bouguer anomaly maps. The positive contour closures on the residual Bouguer anomaly map indicate the iron ore and phosphate, whereas negative contour closures are the effects of low-density material which consists of gypsum and soapstone. The pole-reduced total intensity map also shows the negative and positive contour closures almost in the same localities and confirms the residual Bouguer anomaly map. The geological model computed on the basis of Bouguer anomaly demarcated a series of faults between different rock units in the study area. The Kashmir Boundary Thrust cuts the western limb of Hazara Kashmir Syntaxis near the apex in the north of Muzaffarabad and marks the boundary between Murree Formation and carbonates of Abbottabad Formation. The gravity model also suggests that the thickness of the crust increases towards the northeast.     

Cooling and uplift histories of the crystalline thrust stack of the Indian Plate internal zones west of Nanga Parbat, Pakistan Himalaya

Amphibole and mica K-Ar, Ar-Ar and Rb-Sr geochronology for the crystalline internal zones of the Indian Plate define both an extensive pre-Himalayan thermal history and a post-Himalayan metamorphism cooling history. South of the Main Mantle Thrust, near Besham, hornblende Ar-Ar ages from basement gneisses record an ca. 1850 Ma mid-Proterozoic thermal event. Hornblende, muscovite and biotite cooling ages from cover sequences metamorphosed during the Himalayan orogeny are 35 ± 4, 30 to 24, and 29 to 22 Ma respectively. The mica ages, together with those derived from zircon and apatite fission track data (Zeitler, 1985) demonstrate a rate of cooling, of about 30°C/Ma, during the late Oligocene to early Miocene that was greater than that either before or since. This rapid cooling was initiated during the post-metamorphic evolution of the Indian Plate south-verging crustal-scale thrust stack, during which cover sequences metamorphosed during the Himalayan orogeny were imbricated with basement rocks thermally unaffected during that event. Most of the cooling, which happened during the stripping of some 10 ± 2 km of overburden, reflects exhumation due to a combination of erosion, recorded in the Miocene molasse sediments of the foreland basin, and major crustal extension within the MMT zone. Both erosion and extension were the direct consequence of the evolution of the thrust stack.     

Erosion and uplift uncertainties in the Barents Sea, Norway

Three different types of methods are used to assess the ability to determine erosion amounts and to provide estimates of uncertainty. In the situation of dynamical indicator methods, such as seismic velocity, sonic logs, density logs, or drilling exponent methods, intrinsic assumptions and parameter values used provide only a broad statement on the resolution of uplift/erosion events. None of the methods is more accurate, at best, to better than ± 1 km and likely much worse. For geological model procedures, exemplified by considerations of Airy isostasy and by bed upturning near a salt dome in the Nordkapp Basin of the Barents Sea, the uncertainties are again of the order of ± 500–1000 m. With thermal indicator procedures, the bulk of the constraint information from available data is needed to determine paleoheat flux with little left over to constrain the erosion, implying a minimum uncertainty of ± 500 m on erosion determinations. No method seems capable of resolving erosional events to better than a minimum uncertainty of ± 500 m, and likely no better than ± 1 km.     

Geochemistry and petrogenesis of the mandidarla volcanics,northwestern Himalayas

The Proterozoic Mandi-Darla Volcanics (MDV) occur as flows intercalated with the low-grade metasediments of the Sundarnagar Group of the Lesser Himalayas. These volcanics are aphyric and have quenched textures with plagioclase-clinopyroxene skeletal microphenocrysts. They are of tholeiitic composition, and are enriched in FeO^t, TiO₂, incompatible trace and rare earth elements. They have relatively high SiO₂ abundances for their MgO levels, which are attributed to high PH₂O pertaining during melt generation. Fractional crystallisation does not appear to have played any major role in the evolution of their bulk chemistry. Instead, they appear to have been generated by different extents of isobaric partial melting of a non-pyrolitic and heterogeneous source with enriched and variable Fe/Mg ratios. REE modelling suggests that the REE enriched source consisted of variable proportions of at least two end members differing in their MREE and HREE contents, but with similar LREE abundances. The enrichment of the source is attributed to mantle metasomatism by a melt-dominated phase penecontemporaneous with magma generation.     

东喜马拉雅南迦巴瓦地区区域地质特征及构造演化

研究区位于喜马拉雅造山带的东构造结。本文以区域地质填图成果为基础 ,结合前人资料 ,首先对研究区进行了构造单元划分 ,其次对各构造单元的地质特征进行了总结 ,最后对构造演化和有关问题进行了探讨。结论为 :1南迦巴瓦地区可以划分为冈底斯—拉萨陆块、雅鲁藏布江缝合带和印度陆块 3个一级构造单元。以蛇绿混杂岩为代表的雅鲁藏布江缝合带呈向 NE凸的马蹄状连续分布 ;印度陆块由被称为南迦巴瓦岩群的高喜马拉雅结晶岩系单独构成 ,南迦巴瓦岩群由以含高压麻粒岩透镜体为标志的直白岩组、派乡岩组和多雄拉混合岩组成。2印度—欧亚板块碰撞的时间早于 70 Ma;2 3Ma以来主要断层的运动性质以伸展拆离作用为主 ;大约 5 Ma时发生了大规模的混合岩化和深熔作用。3地幔上隆是本区快速隆升的关键因素 ,但河流的作用同样功不可没