A backarc basin is a geological formation that occurs on the ocean floor. Slowly opening backarcs, such as the mariana trough, may perpetuate threedimensional patterns of mantle flow, crustal magmatism and heterogeneiity. The chilas complex is a 40 wide and 300 long composite plutonic body exposed in the central part of kohistan island arc, which formed first as intraoceanic island arc in the neotethyan oceanic crust and later transformed into andeantype continental margin after the closure of backarc basin. Dominant structural trend in south lut province figure 2 is ew. The area behind a volcanic arc and within the overriding plate in a subduction zone environment. Abstract the salin subbasin of myanmar part of the larger central basin is a forearcbackarc basin couplet situated between an oblique subduction zone to the west and a major rightlateral strikeslip fault to the east.
Backarc basin, submarine basin that forms behind an island arc. Caltex pacific indonesia area of operations, situated largely between the bila river to the north and the kampar river to the south, are. Laubasin, mariana troughand east scotia basin averages in 1,2, the global compositional variation of bab lavas has not been investigated previously. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Modern island arcs and attendant backarc basins form mainly by trench rollback caused by progressive subduction of negatively buoyant thick. Ldeo seismology student workshop, columbia university, palisade, ny invited talk seismic attenuation beneath the lau backarc basin. Backarc extension or compression is often related to a particular behavior of the slab dip. Crosssection sketch showing the development of a back arc basin by rifting the arc longitudinally. Backarc basalts in many respects marginal basin basalts mbb are similar to normal midocean ridge basalts ntype morb. Plate motions, slab dynamics and backarc deformation. Some of the betterknown geological basins are the southern michigan basin of gently downwarped paleozoic rocks. Delineation of mahanadi river basin by using gis and arcswat.
The jaglot group derives from back arc basin assemblages and the chilas complex is a magmatic diapir emplaced in. Data from mcdonald 1968 gsa memoir 116 basalt tetrahedron is based on normative minerals computed from chemical analysis. Backarc basin basalts babbs affected by different contributions of subducted materials have various geochemical compositions ranging from morblike to arclike, so that they are ideal media to investigate the behavior of ca isotopes during plate subduction. Backarc basin submarine features associated with island arcs and subduction zones. Active backarc spreading can result in a phase of less or no activity at the arc. Basin, in geology, a broad shallow trough or syncline, a structure in the bedrock, not to be confused with a physiographic river basin, although the two may coincide. The western mediterranean basin formed from oligocene to.
Backarc basins are sites of significant hydrothermal activity, and the deepsea vents that occur in these. The tectonics and the tertiary structural history of the central sumatra backarc basin in the p. Two suture zones, i the northern suture mkt and the southern suture mmt mark tectonic. Rock expansion along the long axis of backarc basin is attributed to lower part of continental crust melting underplating on the dehydration belt. Subduction occurs beneath only one side at a time of an internally rigid plate, and the common regime in an overriding plate, behind a surficial accretionary wedge, is extensional, except where a collision is underway. The composition of backarc basin lower crust and upper. The shape of island arc is formed by changing the axis of backarc basin caused by rock expansion along the long axis of backarc basin. This includes an asymmetric distribution of horst and graben structures in the backarc basin, the distribution and spacing of which is related to. However during the early stages of backarc spreading, when the uprising mantle diapir splits the volcanic arc, the basalt magmas are derived from the subarc mantle. Okinawa trough backarc basin early tectonic and magmatic evolution. Subsequent closure of this basin in the late cretaceous and the low angle of plate convergence during the tertiary has resulted in severe deformation of the ophiolitic portion of the woyla group. Transition from backarc to foreland basin development in. In this frame, the marine areas to the w of italy represent a set of eastward younging backarc basins.
Although analyses of some basalts from backarc basin bab spreading centers were included intheinitialglobalcompilationse. The tyrrhenian backarc basin and subduction of the ionian. Pdf development of an ancient backarc basin overlying. There is a sharp contrast between the main spreading area of the fonualei spreading center fsc and its northernmost termination, the mangatolu triple junction mtj. Mark harrison center for lithospheric studies, university of texas at dallas, richardson tx 750830688, usa. Jaj f transform 20 mmyr 25 mrnyr foreland j, peripheral foreland, retroarc foreland r. Sedimentary basins range in size from as small as hundreds of meters to large parts of ocean.
With the emerging deepsea mining industry focused on south pacific backarc basin hydrothermal systems, this lack of baseline data is a major impediment to informed decisionmaking. The boundary for this basin is derived primar ily from the basin outline shown on frezon and finn 1988. The espanola basin is a medium rift basin that is part of the rio grande rift system. New species of scale worms polychaeta, polynoidae from. Basins associated with subduction processes prepared by dr. Intracontinental backarc basin inversion and late carboniferous. Imaging partial melt beneath the lau backarc basin. However, the reasons why backarc basins are associated with some subduction systems but not all has remained elusive.
The island arc 1996 5, 354372 research article the composition of backarc basin lower crust and upper mantle in the mariana trough. Models of mediterranean backarc basin formation royal society. Along the spreading axes of the lau basin, there is a firstorder progression from arclike to morblike lava compositions with increasing distance away from the tofua arc e. To the east, the plate is bounded by the south sandwich trench formed by the subduction of the south american plate beneath the south sandwich plate pearce et al. In the present work, the basin area of mahanadi river framework lying in orissa is taken as study territory. Preliminary catalog of the sedimentary basins of the united states by james l. Backarc basins are extensional basins formed behind subduction zones by rifting. Preliminary catalog of the sedimentary basins of the. Back arc basin assemblages in kohistan, northern pakistan. Although analyses of some basalts from back arc basin bab spreading centers were included intheinitialglobalcompilationse. When fast backarc spreading develops, as in the lau and manus basins, the backarc flow patterns and crustal melt lenses will become more twodimensional. Sedimentation in backarc basins can be very varied, ranging from pelagic through turbidites to alluvial fans, although volcaniclastics see clast are common.
Any theory for the genesis of backarc basins must account for this fact. Physiographictectonic zoning of iran s sedimentary basins. Such basins are typically found along the western margin of the pacific ocean near the convergence of two tectonic plates. Surface and subsurface expressions of folds and faults suggest that the basin experienced northnorthwestdirected. Therefore we infer that all the subductionrelated magmatism is captured by the back arc as the adjacent arc is shut off. Calcium isotopic fractionation during plate subduction. Mafic magma types chemical distinction alkalis vs silica plot basalt tetrahedron alkali versus silica plot was originally proposed to distinguish different types of hawaiian basalts. Polynoidae from the hydrothermal rift area of the mariana back arc basin in the western central pacific by m. Backarc basins by fer nan d o m arti n ez, kyo ko o ki n o, ya s u h i ko o h a r a, a n n a lo u i s e r e y s e n b a c h, and. The larger mergui north sumatera basin is an extensional basin that initaly formed in late paleogene and mostly developed during neogene time.
A backarc basin is formed by the process of backarc spreading, which begins when one tectonic plate subducts under underthrusts another. All structured data from the file and property namespaces is available under the creative commons cc0. The effects of backarc spreading on arc magmatism sciencedirect. The late mesozoic woyla group includes a volcanic arc assemblage and portions of a dismembered ophiolite together with a cover sequence which formed in a backarc basin. In island volcanic arcs it consists of backarc basins of oceanic crust with abyssal depths, which may be separated by remnant arcs, similar to island arcs. Central sumatra basin is the shallowest and exhibits the highest geothermal gradient of the backarc basins along the sunda margin.
Slab roll back and back arc extension arcuate shape of arctrench systems corner flow or wedge flow or induced asthenospheric convection sea anchor model observed features of subduction processes non subductionrelated driving mechanisms extrusion model mediterranean area balearic basin circumpacific zones circumpacific zones. New species of scale worms polychaeta, polynoidae from the hydrothermal rift area of the mariana back arc basin in the western central pacific. Intra arc basin foreland basin fore arc basin back arc basin h. The eastern lau spreading centre, located on the lau backarc basin hydrothermal vent system between fiji and tonga, is a focus site of the ridge 2000. I propose that those basins be compared to the black sea and caspian basins, and suggest that junggar was formed during the carboniferous period, and tarim and qaidam during the permian period, as backarc basins behind volcanic arcs on the southern active margin of paleozoic asia.
Basalts above subduction zones typically have higher oxygen fugacity f. Cahan the text accompanying this catalog gives a very brief synopsis of the age and style of the listed sedimentary basins. However, the longterm natural variability of backarc basin hydrothermal vents is largely unstudied boschen et al. Most tectonic elements in the north sumatera basin has relatively ns and nwse trends. In a word, in the formation mechanism of island arc, the factors such as the dehydration of subducted oceanic crust, substrate melting of backarc basin, temperature rise of rocks, rock expansion, the deformation of long. Subduction zones and island arcs university of leicester. At that point the aggregate region or the shapefile is to be kept in the projected coordinate system framework in. During the mesozoic evolution of the southernmost andes, backarc basin formation in an extensional setting was followed by foreland basin development in a compressional setting.
For 500 km along the strike of the mountains, this tectonic transition is marked by a sandstone. The san plate is composed of oceanic lithosphere that forms from the east side of the east scotia ridge esr, a backarc spreading center that sets the western boundary of the plate. Backarc basin assemblages in kohistan, northern pakistan. South luthelmand back arc basin has formed on south part of eastcentral iran microcontinent and it. This region is to be first made a polygon shapefile with the utilization of arc catalog which is a tool of arcgis. Backarcbasin lithosphere is built behind, or by, migrating island arcs, which lengthen and increase their curvatures. From tectonics view, it contains a retro arc back arc basin that has continued to helmand plain in pakistan. Backarc basin article about backarc basin by the free. View notes backarc basins from epse 350 at mcgill university. This marine formation is most commonly identified along subduction zones, which occur where one tectonic plate moves beneath another, and island arcs, which are a kind of archipelago made up primarily of volcanos. Mediterranean backarc basins are characterized by a hot upper mantle, overlain by crust transitional from continental to.
Media in category backarc basins the following 7 files are in this category, out of 7 total. It also includes the east flank of the volcanic and volcanosedimentary rocks of the jemez volcanic field. The backarc region is the area behind a volcanic arc. The subduction of old oceanic lithosphere may make the volcanic arc move toward the trench and produce an extensional backarc basin behind the arc. The process of backarc basin formation appears to be inactive at present in some arcs as in the case of the japan sea, whereas others are believed to have an actively opening backarc basin, for example, the m ariana trough karig, 1971a. Pdf backarc basin assemblages in kohistan, northern. The north sumatera backarc basin itself is the southern part of the larger mergui north sumatera basin. Samples from the arcproximal and shallow valu fa ridge vfr and southern east lau spreading center selsc have the lowest na8 and ti8, and the highest bala and h 2 o8 fig. Subduction creates a trench between the two plates and melts the mantle in the overlying plate, which causes magma to rise toward the surface. The rift matures to the point of seafloor spreading, allowing a new magmatic arc to form on the trenchward side of the basin to the right in this image and stranding a remnant arc on the far side of the basin to the left in this image. The shaquanzi formation volcanic rocks could have formed in an intra continental backarc basin setting, probably via the southward subduction of the. In continental arcs the backarc region is part of continental platform, either dry land or forming shallow marine basins.
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