Engineering Geology: Engineering Geology: Engineering Geology: Work Methodology of Cable Anchors

Engineering Geology: Engineering Geology: Engineering Geology: Work Methodology of Cable Anchors

Engineering Geology: Geology Of Himalayas, Jammu & Kashmir

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Geology Of Himalayas, Jammu & Kashmir

Introduction The closing and subduction of the Tethyan Ocean, located between India and Asia during the Paleozoic, followed by collision of continents produced the structures and lithologies we see today in the Himalayas. Consequently, the mountains and surrounding regions are characterized by astounding complexity,represented by a variety of deformed and collision-produced lithologies and representing several phases of tectonic and deformational events. The Himalayas can be divided into six primary lithotectonic zones that occur in parallel belts. These zones consist of the Trans-Himalayan batholith, Indus-Tsangpo suture zone, Tethyan(Tibetan) Himalaya, Higher(Greater) Himalaya, Lesser(Lower) Himalaya, and Sub-Himalaya. Tectonic environments within these zones also vary. The emense collision of plates at 45 million years gave rise to an island-arc margin in the western Himalayas and an Andean-type margin in central-to-eastern Himalayan regions (Windley 1995). Trans-Himalayan Batholith The Trans-Himalaya zone is a linear plutonic complex. It is partly covered by forearc rocks and continental molasse sedimentary rocks. These assemblages are derived from uplift of magmatic rocks and their subsequent erosion. The igneous complex consists of I-type lithologies, including gabbros,diorites, and granites. Formation of the complex is thought to have occured in several phases, between 110 and 40 million years. Partial melting of a subducting NeoTethyan slab beneath the Asian plate is thought to have resulted in these magmas (Sorkhabi 1999). This zone varies in a west-east direction. To the west, plutons were emplaced into an area, called the Kohistan-Ladakh region, and represent an island arc environement. Contrastly, eastern igneous rocks represent an Andean-type environment(Windley 1995). Western Trans-HimalayaAn island arc formed on the northern side of the NeoThethys and became trapped in between Asia and India. This allowed for two stages of deformation. The first consisted of collision of the arc with Eurasia, followed by collision with India, as the Tethys began to subduct under Asia (Windley 1995). The area is dominated by granodiorites and tonalite composed of a quartz+K-spar+biotite+hornblende+ sphene mineral assemblage. U-Pb in monazite and allunite dated the granitic rocks at 60.7 plus or minus 0.04 million years. Late stage bodies of pegmatite and leucogranitic dikes are also present. Pre-collision phases, consisting of felsic intrusions, have been dated by U-Pb in zircon techniques and record a date of 101 plus or minus 2 million years (Searle 1991).Eastern Trans-HimalayaThe Kangdese sub-alkaline batholith extends along the north side of the Indus-Tsangpo Suture and represents the Andean style tectonic environment. Rock types in this zone include slates, phyllites,schists, gneisses, amphibolites, and migmatites of Ordovician-Cretaceous age (Windley 1995). Indus-Tsangpo Suture Zone The Indus-Tsangpo Suture Zone (ITZS) defines the areas of collision between the Indian plate and the Kohistan-Ladakh arc in the western Himalayas and the Tibetan Lhasa block in the east (Windley 1995). It also marks the zone along which the Tethys Ocean was consumed by subduction processes. The ITSZ can be traced for more than 2000km (Searle 1991) between these regions and host a variety of rock types that tell us quite a bit about the orogen. Complete successions of ophiolites occur, some containing diamonds as well, suggesting high pressures during subduction and rapid extrusion along the suture zone. Glaucophane schists also occur in narrow belts along the ITSZ in Pakistan. Olistoliths occur in northwestern India and consist of reef and and continental slope sediments in abyssal tubidite deposits. Mafic to felsic lavas as well as cherts, serpentinites, and dunites are also observed. Limestones and red sandstones are associated with Tethys Ocean sediments and found in the Ladakh region (Windley 1995). Such a wide variety of rock types along the ITSZ further indicates that the collision of plate boundaries was a complex one, effecting many terraines in many ways. Their one commonality is that this great structure separates Asian lithosphere from the Indian plate. Tethyan(Tibetan) Himalaya The Tethyan Himalayas are located to the south of the ITSZ. They consist of thick, 10-17km, marine sediments that were deposited on the continental shelf and slope of the Indian continent. This occured as India was drifting but still in the southern hemisphere (Verma 1997). Sediments are largely unmetamorphosed, which has made for excellent preservation of fossils and occur in synclinorium-type basins. Some however, have experienced greenschist facies deformation (Windley 1995). Fossils occur in this east-west zone within strata that are very clearly known. The large variety of size and distribution of fauna suggest that life was flourishing in this area before the orogen. Such success in biological diversity is accounted for by the relatively stationary position of the Tehthyan Zone between mid-Proterozoic and Eocene time. Episodic formation of land barriers enabled life to grow and diversify (Sorkhabi 1999). Higher(Greater) HimalayasThe Higher Himalayas are also known as the Central Crystalline zone, comprised of ductily deformed metamorphic rocks and mark the axis of orogenic uplift. Mica schist, quartzite, paragneiss, migmatite, and leucogranite bodies characterize this uppermost Himalayan zone. They represent a multiphase deformation event, the first being Barrovian type, or normal geothermal gradient conditions. There was then a shift to Buchan-type metamorphism, low pressure and high temperature conditions, with temperatures greatly exceeding normal gradient temperatures(Sorkhabi 1999). Local retrograde events have also been noted. Analyses show that peak orogenic temperatures and pressures were 475-825 degrees Celsius and 500-800 megapascals. Corresponding minerals assemblages are dominated by biotite to sillmanite, representing greenschist to amphibolite facies deformation. Deformation seems to have occured in a north to south direction and is associated with the Main Central Thrust Fault (MCT) which brings the higher Himalayas on top of the lower Himalayas (Sorkhabi 1999). Initially, it was thought that approximately 350km of shortening had occured in the Greater Himalayan sequence of rocks. However, through studies by DeCelles etal. (1998), a major thrust fault within the zone was discovered. As a result, it is now estimated that between 600 and 650km of shortening occured here. There was also a question of provenance for Great Himalayan rocks. Previous work suggested that lower Indian crust comprised this area. New interpretations of rocks there indicate that the higher Himalayas are actually made of supercrustal rock. This idea states that upper crustal material of India accreted northward onto the Asian continent and that crustal material was origanlly an appendage of India that was, itself, accreted to India during Paleozoic time. This study implies that India probably had significantly more continental crust than previously thought, much more crust to be shortened in the formation of the Greater Himalayas. Lesser(Lower) Himalayas The Lesser Himalayan zone is bounded the Main Central Thrust(MCT) in the north and Main Boundary Thrust(MBT) to the south. Unlike the higher Himalayas, the lessers only experienced up to greenschist facies metamorphism. The rock types present here are also different. They are primarily sedimentary rocks from the Indian platform. Rock units here also show a series of anticlines and synclines that are in many cases quite sheared. Fossils have been documented in this zone, but they do not occur at the same frequency as Tehtyan zone fossils. Main Central Fault (MCT)This thrust fault was first described by Heim and Gansser (1939) when they noted a contact between terrigenous carbonate rocks and thick overlying metamorphic rocks, mica schists and gneiss (Sinha 1987). The Main Central fault marks the boundary between the higher and lesser Himalayan mountains. It is a longitudinal thrust fault, and in many places is marked by a several kilometer thick zone of deformed rocks with varying degrees of shearing and imbrication (Sorkhabi 1999). Mylonitization and retrograde metamorphic assemblages also occur here. The MCT is the actual suture between Gondwanaland (India) and the Proto-Tehtys microcontinent to the north (Spikantia 1987). Movement along the fault has brought crystalline rock from the Higher Himalayan zone on top of Lesser Paleozoic sediments in the form of klippen in synclines (Windley 1995). These units are called the Outer Crystallines, as noted above on the map. Outer crystalline rocks, garnet and kyanite-bearing, were exposed by slip along the MCT followed by uplift and erosion of 10km of overlying rock (Molnar 1986). Sub-HimalayaThis foreland zone consists of clastic sediments that were produced by the uplift and subsequent erosion of the Himalayas and deposited by rivers. These rocks have been folded and faulted to produce the Siwalik Hills that are at the foot of the great mountains. Sub-Himalayan rocks have been overthrust by the Lesser Himalayas along the Main Boundary Thrust Fault. This steep thrust flattens with depth, dveloped during the Pliocene time and has been shown as active through the Pliestocene (Ni 1984). In turn, the Sub-Himalayas are bounded by a thrust fault to the south and are forced over sediments on the Indian plate. This fault system is called the Himalayan Frontal thrust (Sorkhabi 1999). Home

Grouting in Closer Dyke Area

Method Statement The area of closer Dyke is very susceptible means high seepage zone by which water flows through the voids or by filled loose materials and enter into the excavated portion of Dam. The entering of water through such materials creating lots of problem in many cases like excavation which is one of the most important activities hampered by seepage of water. To stop the seepage of water Grouting is only the suggestive method .The main purpose of Grouting in this part is 1) creating a seepage barrier to reduce uplift 2) consolidating the loose or filled material sufficiently to make it act as a monolith. Grouting Materials: The type of Grout used here is the mixture of Portland cement and water in the ratio of 1:4. The grout is forced through holes that having the depth of 3.0m and is oblique to the surface. As it is the primary stage of grouting so no chemicals to be added. Grouting Equipment: Unigrout pumps are used to inject grout in this area. This consists of a tank filled with grout; which is cautiously squeezed out into the holes by means of compressed air (ROC, Atlas Copco). Pressure gauge is installed in the grout pump in order to maintain proper line pressures. Grout Holes: The grout is forced into oblique holes varying from 50 to 80, the diameter of which is 64mm. The holes are drilled with ROC equipment with the pressure of 5kg/sq.cm. The length of the holes are 3.0m and are staggered.The holes pattern are shown below: Grouting Method: The method used for grouting in the closer Dyke area is stage method. In this method the holes are drilled to the seam closest to the surface and then the holes are grouted. The process is repeated, using increasing grouting pressure, until the plan grouting depth is reached. Once the primary holes are grouted successfully then go for the holes of larger depth using the same machine and after increasing the hole depth or by reaching the water table Packer method come in view. In this method the holes are drilled to the full planned depth. A zone of certain thickness then is grouted, and packer is inserted into the hole corresponding to the top of the grouted zone. The overlying zone for a certain thickness then is grouted using decreased pressure. The process is repeated until the hole is grouted.

Engineering Geology: Engineering Geology: Work Methodology of Cable Anchors

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Engineering Geology: Work Methodology of Cable Anchors

tEngineering Geology: Work Methodology of Cable Anchors

Work Methodology of Cable Anchors

Introduction: To work in a Hydro sector support system plays very important role. Either to support the rock or slope some of the most important method are Rock Bolting, Rock Anchoring, shotcreting, wiremesh etc. Out of which Cable Anchoring lays very important role, some people also termed as Tendons. Working methodology for cable Anchoring are described here: 1) Drilling 2) Fabrication of Anchors 3) Lowering of Cables 4) Anchor Grouting 5) Stressing

1. Drilling:

Drilling of Anchor holeswill be completed upto the required depth (Fixed length+Free length) and at require inclination with the help of percussion drilling method.

2. Fabrication of Anchors:

• 7 nos. of 12mm dia. Un-oiled strands shall be cut to the 16m length. Cutting of cable is to bederived as fixed length@9m and free length@6m + extra 1m for stressing purpose.
• Strands are cleaned throughly and dust on the surface is removed 1st coat of epoxy paint is to be appklied uniformly on the strands and it is allow to dry for a period of 2-3hrs. The second coat is applied thereafter and the same is allow to dry for 24hrs. The third coat is applied uniformly thereafter. Quartz sand is to be sprinkled on fix zone of strands when third coat is tacky.
• Place the 100mm ID, 2mm thich flexible HDPE pipe on Free length portion.
• The Pre-stressing strands, greased for the free length portion should be enclosed in 16mm ID HDPE sleeves, 2mm encasing individual strand.
• Fix length of cable is then provided with 84mm ID corrugated HDPE sheathing 2mm thick.
• Fabrication: Fix shoe with the help of brazing at bottom of the cable. Then tie spacer at 1.0m c/c through out the length of the cable.
• Shifting of cable at site: Prepare bundle of suitable diameter so that the same can be loaded and off-loaded in trailer. Keep all cables above ground levels with the help of wooden sleepers.

3. Lowering of Cables:

• A lowering of anchors, check the depth of the hole by inserting a strands piece of similar length.
• After checking depth of holder lower fabricated cable into the hole, while lowering ensure that cable is in suspended position be keeping about 300mm from bottom of the hole and of the cable.

4. Anchor Grouting:

• Grouting of cables will be carried out by using MI-pump which is having output capicity of 1200lit/hr. and working pressure of 30 kg/sq.cm. Prepare cement grout mix of 1;0.4 by calculating volume of grout to be poured in an anchoe length zone. If possible dry cement should be seived to remove lumps or stone from the cement.
• Grout the entire hole (Fix length+Free length) with the help of cement grout. Whilr grouting the grouting operation should be in one go only. There should not be any stoppage in between and no air entrap in between the grout.

5. Stressing:

Stressing of anchor will be carried out when grout has attained required strength. The stressing will be carried out by using hydraulic jack. Use load cell to measure the residual forces on the anchors. After 24 hrs. of stressing, the extra length of the cable above anchor head should be cut by keeping 2'' projection above anchor head with the help of grinder.

Bermuda Triangle -A Mystery

The Bermuda Triangle or "Devil's Triangle" is a triangular-shaped area off the coast of Florida that is famous for reports in which strange disappearances occur and magnetic compasses go haywire. The area is situated in the Atlantic Ocean and is generally thought of as having apexes at Miami, Bermuda, and San Juan. This area contains some of the deepest sub-oceanic trenches in the world, encompasses the fast-moving waters of the Gulf Stream, and has frequent strong water spouts and violent storms, making at least some of the reported odd phenomena attributable to human error or mishap. The US Coast Guard acknowledges the fact that there are definite environmental anomalies in this area, but goes on to say that human error is by far the more bizarre phenomena that happens in these waters. The area sustains heavy traffic, both by air and by sea, and certainly accidents are bound to happen. Inexperienced mariners or pilots who don't take into account variations in compass readings or environmental anomalies in the area can and do get into serious trouble, accounting for many of the unexplained disappearances in the area. However, even if every one of these stories were found to be attributable to human error or natural phenomena, the area is still fascinating for other reasons, not the least of which includes speculation that it encompasses the lost continent of Atlantis, and that it is a doorway to other dimensions. There is also speculation that the seabed in this area contains huge amounts of methane gas that is released suddenly due to changes in the sea bed, releasing large, unpredictable plumes of gas that have the capability to swallow ships or planes within minutes - without a trace. One interesting theory is that the Bermuda Triangle is just one of many "vile vortices" that exist in both hemispheres all over the globe, a subject that we are researching and will publish more information on very soon. Rather than dredging through the reports of disappearances, we are going to attempt to look at the area of the Bermuda Triangle with all it's anomalies and try to make some sense of it all on this page. There are several interesting aspects of the area that warrant a closer look: Triangular Shape: The triangle has had mystical and magical connotations attached to it since before written history - after all, the Great Pyramid is sitting out there for all to see - and it is a perfect triangle with a whole slew of unknowns surrounding it. Having said that, is the triangular shape of the Bermuda Triangle of any significance? Yes, but not like one might think........it indeed does appear to be on a strong energy line or vortex in addition to all the variations described above, but this appears to be more relevant to its placement on earth than the actual triangular shape made by the 3 reference points by which we identify it. Electromagnetism: Certainly electromagnetism has played a role in the mystery surrounding the Bermuda Triangle. This is one of only two places in the world where the compass points true north. However, the fact is that as you circumnavigate the earth you find compass variations of up to 22 percent at various locations. At first glance, this does not seem significant in any real sense, but again, if one looked worldwide very closely, this points to a strong vortex of some sort within the Bermuda Triangle area. We are continuing research in this area and will post updates soon. The Lost Continent of Atlantis: Speculation that Atlantis was located in or very near the area of the Bermuda Triangle is probably the most interesting aspect of the Bermuda Triangle phenomena. Mainly because of psychic Edgar Cayce's revelations, the Bahamas and surrounding sea in particular have been pinpointed as a likely site for this lost continent. Speculation has it that if the water was lowered in the area by 300 feet or so, the dimensions and topology originally described by Plato would match almost exactly. Indeed, a report in 2001 of an underwater city that has been found off the western tip of Cuba may shed some light on this mystery. It could be that the continent encompassed the entire Caribbean area and that the land forms we know today are the highest mountain peaks of that lost civilization. Unexplained variations in compass readings other than those attributable to normal compass variation discussed above have been reported in the Caribbean area, and most agree that psychic energy is very high here. Some suggest that the Bermuda Triangle phenomena is directly related to sunken batteries or crystals from the lost continent of Atlantis still emitting energies from the ocean floor. Portal to Another Dimension: Another interesting theory about the Bermuda Triangle area is that certain places there serve as portals to other dimensions. The sheer number of credible eyewitness UFO reports makes this an area warranting serious further study with respect to either permanent or ever-changing possible portal sites. Credible scientists making careful observations in the area have reported anomalies in magnetism and gravitational forces here that cannot be explained by conventional physics, introducing the possibility that there is a dynamic opening and closing of other dimensional doorways in the vicinity. In summary, the Bermuda Triangle is a fascinating area with a rich history that does seem to be conducive to supernatural phenomena in some respects, though further analytical study is definitely needed. There is speculation that the US government is already conducting covert tests in the Bahamas area, specifically Bimini, though exactly what they are looking for is as much a mystery as the area itself. Indeed, the famous "Bimini Road" is located on this island, where some say portions of the ruins of Atlantis can be seen in the clear shallow water. The National Geographic Society is reportedly investigating the reports of the lost city beneath the waters off Cuba, but they have not made any public announcements about what they have found to date. We will be keeping an eye on this development, so do check back often for further information.

Making of Himalayas

The geology of the Himalaya is a record of the most dramatic and visible creations of modern plate tectonic forces. The Himalayas, which stretch over 2400 km, are the result of an ongoing orogeny — the result of a collision between two continental tectonic plates. This immense mountain range was formed by huge tectonic forces and sculpted by unceasing denudation processes of weathering and erosion. The Himalaya-Tibet region is virtually the water tower of Asia: it supplies freshwater for more than one-fifth of the world population, and it accounts for a quarter of the global sedimentary budget. Topographically, the belt has many superlatives: the highest rate of uplift (nearly 1 cm/year at Nanga Parbat), the highest relief (8848 m at Mt. Everest Chomolangma), the source of some of the greatest rivers and the highest concentration of glaciers outside of the polar regions. This last feature earned the Himalaya its name, originating from the Sanskrit for "the abode of the snow". Contents[hide] 1 The making of the Himalaya 2 Major tectonic subdivisions of the Himalaya 3 Future of the Himalaya 4 Notes 5 References 6 External links // [edit] The making of the Himalaya During Late Precambrian and the Palaeozoic, the Indian sub-continent, bounded to the north by the Cimmerian Superterranes, was part of Gondwana and was separated from Eurasia by the Paleo-Tethys Ocean (Fig. 1). During that period, the northern part of India was affected by a late phase of the so-called "Cambro-Ordovician Pan-African event", which is marked by an unconformity between Ordovician continental conglomerates and the underlying Cambrian marine sediments. Numerous granitic intrusions dated at around 500 Ma are also attributed to this event. In the Early Carboniferous, an early stage of rifting developed between the Indian continent and the Cimmerian Superterranes. During the Early Permian, this rift developed into the Neotethys ocean (Fig. 2). From that time on, the Cimmerian Superterranes drifted away from Gondwana towards the north. Nowadays, Iran, Afghanistan and Tibet are partly made up of these terranes. In the Norian (210 Ma), a major rifting episode split Gondwana in two parts. The Indian continent became part of East Gondwana, together with Australia and Antarctica. However, the separation of East and West Gondwana, together with the formation of oceanic crust, occurred later, in the Callovian (160-155 Ma). The Indian plate then broke off from Australia and Antarctica in the Early Cretaceous (130 - 125 Ma) with the opening of the "South Indian Ocean" (Fig. 3). In the Upper Cretaceous (84 Ma), the Indian plate began its very rapid northward drift at an average speed of 16 cm/year, covering a distance of about 6000 km, until the collision of the northwestern part of the Indian passive margin with Eurasia in early Eocene time (48-52 Ma). Since that time and until today, the Indian continent continues its northwards movement at a slower but still surprisingly fast rate of ~ 5 cm/year, indenting Eurasia by about 2400 km and rotating by just over 33° in an anticlockwise direction (Fig. 4). Whilst most of the oceanic crust was "simply" subducted below the Tibetan block during the northward motion of India, at least three major mechanisms have been put forward, either separately or jointly, to explain what happened, since collision, to the 2400 km of "missing continental crust". The first mechanism also calls upon the subduction of the Indian continental crust below Tibet. Second is the extrusion or escape tectonics mechanism (Molnar and Tapponier, 1975) which sees the Indian plate as an indenter that squeezed the Indochina block out of its way. The third proposed mechanism is that a large part (~1000 km; Dewey et al. 1989) of the 2400 km of crustal shortening was accommodated by thrusting and folding of the sediments of the passive Indian margin together with the deformation of the Tibetan crust. Even though it is more than reasonable to argue that this huge amount of crustal shortening most probably results from a combination of these three mechanisms, it is nevertheless the last mechanism which created the high topographic relief of the Himalaya. [edit] Major tectonic subdivisions of the Himalaya One of the most striking aspects of the Himalayan orogen is the lateral continuity of its major tectonic elements. The Himalaya is classically divided into four tectonic units that can be followed for more than 2400 km along the belt (Fig. 5 and Fig. 7)2. The Subhimalaya forms the foothills of the Himalayan Range and is essentially composed of Miocene to Pleistocene molassic sediments derived from the erosion of the Himalaya. These molasse deposits, known as the Muree and Siwaliks Formations, are internally folded and imbricated. The Subhimalaya is thrust along the Main Frontal Thrust over the Quaternary alluvium deposited by the rivers coming from the Himalaya (Ganges, Indus, Brahmaputra and others), which demonstrates that the Himalaya is still a very active orogen. The Lesser Himalaya (LH) is mainly formed by Upper Proterozoic to lower Cambrian detrital sediments from the passive Indian margin intercalated with some granites and acid volcanics (1840± 70 Ma; Frank et al., 1977). These sediments are thrust over the Subhimalaya along the Main Boundary Thrust (MBT). The Lesser Himalaya often appears in tectonic windows (Kishtwar or Larji-Kulu-Rampur windows) within the High Himalaya Crystalline Sequence. The Central Himalayan Domain, (CHD) or High Himalaya, forms the backbone of the Himalayan orogen and encompasses the areas with the highest topographic relief. It is commonly separated into four zones. The High Himalayan Crystalline Sequence, HHCS (approximately 30 different names exist in the literature to describe this unit; the most frequently found equivalents are Greater Himalayan Sequence, Tibetan Slab and High Himalayan Crystalline) is a 30-km-thick, medium- to high-grade metamorphic sequence of metasedimentary rocks which are intruded in many places by granites of Ordovician (~ 500 Ma) and early Miocene (~ 22 Ma) age. Although most of the metasediments forming the HHCS are of late Proterozoic to early Cambrian age, much younger metasediments can also be found in several areas (Mesozoic in the Tandi syncline and Warwan region, Permian in the Tschuldo slice, Ordovician to Carboniferous in the Sarchu Area). It is now generally accepted that the metasediments of the HHCS represent the metamorphic equivalents of the sedimentary series forming the base of the overlying Tethys Himalaya. The HHCS forms a major nappe which is thrust over the Lesser Himalaya along the Main Central Thrust (MCT). The Tethys Himalaya (TH) is an approximately 100-km-wide synclinorium formed by strongly folded and imbricated, weakly metamorphosed sedimentary series. Several nappes, termed North Himalayan Nappes (Steck et al., 1993) have also been described within this unit. An almost complete stratigraphic record ranging from the Upper Proterozoic to the Eocene is preserved within the sediments of the TH. Stratigraphic analysis of these sediments yields important indications on the geological history of the northern continental margin of the Indian continent from its Gondwanian evolution to its continental collision with Eurasia. The transition between the generally low-grade sediments of the Tethys Himalaya and the underlying low- to high-grade rocks of the High Himalayan Crystalline Sequence is usually progressive. But in many places along the Himalayan belt, this transition zone is marked by a major extensional structure, the Central Himalayan Detachment System (also known as South Tibetan Detachment System or North Himalayan Normal Fault). The Nyimaling-­Tso Morari Metamorphic Dome, NTMD: In the Ladakh region, the Tethys Himalaya synclinorium passes gradually to the north in a large dome of greenschist to eclogitic metamorphic rocks. As with the HHCS, these metamorphic rocks represent the metamorphic equivalent of the sediments forming the base of the Tethys Himalaya. The Precambrian Phe Formation is also here intruded by several Ordovician (~480 Ma; Girard and Bussy, 1998) granites. The Lamayuru and Markha Units (LMU) are formed by flyschs and olistholiths deposited in a turbiditic environment, on the northern part of the Indian continental slope and in the adjoining Neotethys basin. The age of these sediments ranges from Late Permian to Eocene. The Indus Suture Zone (ISZ) (or Indus-Yarlung-Tsangpo Suture Zone) defines the zone of collision between the Indian Plate and the Ladakh Batholith (also Transhimalaya or Karakoram-Lhasa Block) to the north. This suture zone is formed by: the Ophiolite Mélanges, which are composed of an intercalation of flysch and ophiolites from the Neotethys oceanic crust the Dras Volcanics, which are relicts of a Late Cretaceous to Late Jurassic volcanic island arc and consist of basalts, dacites, volcanoclastites, pillow lavas and minor radiolarian cherts the Indus Molasse, which is a continental clastic sequence (with rare interbeds of marine saltwater sediments) comprising alluvial fan, braided stream and fluvio-lacustrine sediments derived mainly from the Ladakh batholith but also from the suture zone itself and the Tethyan Himalaya. These molasses are post-collisional and thus Eocene to post-Eocene. The Indus Suture Zone represents the northern limit of the Himalaya. Further to the North is the so-called Transhimalaya, or more locally Ladakh Batholith, which corresponds essentially to an active margin of Andean type. Widespread volcanism in this volcanic arc was caused by the melting of the mantle at the base of the Tibetan bloc, triggered by the dehydration of the subducting Indian oceanic crust. [edit] Future of the Himalaya Over periods of 5-10 million years, the plates will probably continue to move at the same rate. In 10 million years India will plow into Tibet a further 180 km. This is about the width of Nepal. Because Nepal's boundaries are marks on the Himalayan peaks and on the plains of India whose convergence we are measuring, Nepal will technically cease to exist. But the mountain range we know as the Himalaya will not go away. This is because the Himalaya will probably look much the same in profile then as it does now. There will be tall mountains in the north, smaller ones in the south, and the north/south width of the Himalaya will be about the same. What will happen is that the Himalaya will have advanced across the Indian plate and the Tibetan plateau will have grown by accretion. One of the few clues about the rate of collision between India and Tibet before the GPS measurements were made was the rate of advance of Himalayan sediments across the Ganges plain. There is an orderly progression of sediments in front of the foothills. Larger boulders appear first, followed by pebbles, and further south, sand-grains, silts, and finally very fine muds. This is what you see when you drive from the last hills of the Himalaya southward 100 km. The present is obvious, but the historical record cannot be seen on the surface because the sediments bury all former traces of earlier sediments. However, in drill holes in the Ganges plain, the coarser rocks are always on the top and the finer pebbles and muds are on the bottom, showing that the Himalaya is relentlessly advancing on India.