oman ophiolite pdf

14 Mar oman ophiolite pdf

Study of deformation processes from subgrain scale to plate scale with specific focus on the Himalayan orogen and North American Cordillera. They are also very low in large ion lithophile elements such as K and Rb, but relatively enriched in Ba and Pb. rodingites composed of hydrogrossular, diopside, micas, and calcite. are reported within the Upper Campanian–Maastrichtian successions. Subduction of the leading edge of the Ara-, bian continental crust to depths of about 78–, 90 km occurred beneath the Semail ophiolite, during obduction, forming metabasaltic (sodic, clinopyroxene + garnet + glaucophane + phen-, gite) and metapelitic (garnet + chloritoid) eclog-, ites (Fig. Using the same spreading rate, one can calculate a minimum half width of 300 to 750 km for the Tethyan Ocean during the Late Cretaceous. Abundant cataclasites overprint previously formed listvenite in the Oman Drilling Hole BT1B; Cataclasis was related to fluid flow, which caused Mg loss and/or Si enrichment, and local redistribution of Cr; The multistage tectonic overprint after peridotite carbonation in the Oman ophiolite should be excluded when analyzing early structures The, normal metamorphic sole comprising amphibo-, lites and greenschists is exposed in the Asimah-, Masafi corridor beneath the ophiolite and has, been structurally imbricated within the Dibba, zone (Searle, 1980, 1988a; Gnos, 1992). This metamorphism affects the allochtho-, nous thrust sheets beneath the ophiolite, the entire, shelf carbonate sequence, as well as the pre-Per-, mian basement along the north margin of the Saih, Hatat dome. The largest extensional fault is the contact between the Hulw and As Sifah unit that shows around 16 kbar of pressure difference across it. 10.1130/0016-7606(1999)111<0104:TSOAOO>2.3.CO;2, Extrusion of subducted crust explains the emplacement of far-travelled ophiolites, Groundwater characterization in arid regions using seismic and gravity attributes: Al Jaww Plain, UAE, Structural and thermal evolution of an infant subduction shear zone: Insights from sub-ophiolite metamorphic rocks recovered from Oman Drilling Project Site BT-1B, Microfacies, Biostratigraphy, Depositional Environment, Seismic Refraction and Correlation of Coralline Limestones of the Barzaman Formation (Oligocene-Pliocene? Exhumation of the eclogites oc-, curred in two stages, first by rapid emplace-, ment against intermediate units of garnet +, crossite ± chloritoid blueschists at 20–25 km, depth, and second by exhumation of the entire, high-pressure zone along extensional shear, In the northern Oman Mountains intermediate, medium-pressure rocks have been reported in the, form of crossite- and glaucophane-bearing meta-, basalts in the Dibba zone (Searle, 1980), and, high-pressure kyanite-bearing assemblages were, reported by Gnos (in press) from garnet amphibo-, rates. T. peratures of metamorphism reached 670–740 °C, although temperatures could have reached ~800, °C to produce the tonalitic partial melts within the. The gabbros are slightly alkaline rocks of transitional to tholeiitic affinity that intruded the Hawasina-like pelagic sediments, forming small bodies and dykes. As thrusting and exhumation, progressed, greenschist facies metamorphism at, higher structural levels was imposed on Haybi, volcanic rocks, manganiferous cherts, exotic, limestones, and shales, which were welded onto, the base of the amphibolites. ridge either (MacLeod and Rothery, 1992). The approximate po-, sitions and depths of the high pressure units in the, United Arab Emirates is shown on the reconstruc-, tion sections in Figure 7. They are clearly intrusive. (1988) and El-Shazly, et al. In addition, ~4–5 km of, erosion of the obducting ophiolite sequence oc-, curred in the Muscat area, where crustal levels, ity lies above harzburgites of the mantle se-, quence. EPR microplates, a model for the Oman Ophiolite F Boudier eta/ Terra Nova, Vol 9, No 2 79-82 Fig. 1) is not only probably the largest, and best exposed such ophiolite anywhere, but it is, also the most extensively studied (e.g., Glennie. Obduction of the Oman ophiolite controlled the palaeo-configuration rocks, followed by banded marbles, rare pelites, greenschist facies rocks have been thrust over un-, metamorphosed sedimentary rocks, Haybi vol-, canic rocks, and melanges along a brittle thrust, fault. (b) Simplified map of the Samail ophiolite. The normal metamorphic sole of the Semail ophiolite comprises a highly condensed sequence of hornblende + plagioclase ± garnet amphibolites with small, Two localities where the inverted metamorphic sole of the Oman Ophiolite are best exposed, Sumeini Window and Wadi Tayyin, have been mapped and sampled in greater detail. However, the link between continental subduction-exhumation dynamics and far-travelled ophiolite emplacement remains poorly understood. It is possible that the earlier oceanic ridge, tectonic setting was superseded by a later sub-, duction-zone tectonic setting. Such interactions are also responsible for the 3 formation of a thin dunite envelope. The Samail ophiolite is one of the largest thrust sheets on Earth, with a length of >400 km and a width of 150 km (Figure 1). Higher temperatures and pressures in the United Arab Emirates sector, possibly due to a thicker or double-thickness ophiolite section, led to blueschist, amphibolite, and granulite facies conditions in the metamorphic sole, and crustal melting in the subophiolite basement produced leucocratic granites that intruded up as dikes through the obducted ophiolite. ]: Berne, Switzerland, University, Gnos, E., in press, Inverted pressure gradient in subophiolite, metamorphic rocks of the Semail ophiolite: Journal of, Gnos, E., and Kurz, D., 1994, Sapphirine-quartz and sap-, phirine-corundum assemblages in metamorphic rocks as-, sociated with the Semail ophiolite (United Arab Emi-. (Searle, 1980; Searle and Malpas, 1980, 1982). Berne, Switzerland, University of Berne, 293 p. Tilton, G. R., Hopson, C. A., and Wright, lead isotopic ages of the Samail ophiolite, Oman, with ap-, plication to Tethyan ocean ridge tectonics: Journal of. Ero-, sion was not the primary factor leading to ex-, humation although some extreme deformation of, the shelf carbonate and pre-Permian basement, sequence must have occurred along the northern, margin of Saih Hatat. In Oman, the most complete and intact section through the, metamorphic sole is in the Sumeini window, Some 80 m of fine- to medium-grained horn-, blende + plagioclase amphibolites are immedi-, ately below the basal harzburgites of the ophiolite, sequence in the Sumeini window (Fig. duction-obduction–related fabrics marking the early high-temperature shearing during the emplacement process. (1974) and, Robertson (1987), but its rock types, structural, position, and metamorphism all suggest that it, more likely forms part of the Haybi complex, the, thrust slice immediately underlying the Semail, peridotites (Searle and Malpas, 1980). The along-strike continuity of, the cumulate sequence peridotites and gabbros, hjemites or plagiogranites, composed of quartz, and plagioclase with minor ferromagnesian min-, erals, represent the final end product of magmatic. 0000001478 00000 n There is no evidence of a, paleo-transform fault juxtaposing Haybi complex. All the units are affected by v. able degrees of greenschist facies overprinting. Their mineralogy is characterised by the absence of clinopyroxene combined with a high proportion of Al-rich phases, especially plagioclase and garnet together with subordinate spinel, sphene, rutile, orthopyroxene and quartz. quartzites, clinopyroxene + garnet calc-silicates, clinopyroxene amphibolites). age strata. These amphibolites, were welded onto the base of the mantle se-, quence peridotites. Tnjectories ofthe diabase dykes define a NE-SW and a NW-SE ridge systems. The subophiolite amphibolites, were dominantly basalts, which together with, distal oceanic sedimentary rocks, were rapidly. Initial 87Sr/86Sr ratios of analysed dykes vary between 0.710 and 0.706 at initial ɛNd values of between −6.3 and −0.5. 0000010748 00000 n 10 km separates the units on the ground today. Subsequent work, particularly by Goffé et al. 4, along wadis where alteration facies have been studied. Unmetamorphosed sediments in contact with the basal metamorphic sheet do not show evidence of polyphase deformation. A minimum of 130 km shortening is recorded by restoration of the major folds within the Bani Hamid thrust sheet, and more than 30 km offset has occurred along the west-directed breaching out-of-sequence Bani Hamid thrust. The dominant regional folia-, tion is defined by high-pressure phases (om-, phacite, phengite), and is folded into D2 asym-, metric folds that verge northeast, and were, formed after the growth of garnet, but before all.

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