Permiantriassic backarc basin development in response to. Such basins are typically found along the western margin of the pacific ocean near the convergence of two tectonic plates. Large gas reservoir along the rift axis of a continental. Compared with intraoceanic mature backarc basins, which primarily have mantlelike or slightly high whole rock. The basin displays only one producing gas condensate field and several gascondensate shows. Another argument put forward is that the process of seafloor spreading is the same but the movement of seafloor spreading centers in the basin causes the asymmetry in the magnetic anomalies. Evolution of faulting and volcanism in a backarc basin.
The age need to establish back arc spreading is oceanic lithosphere that is 55 million years old or older. The ne lau basin in the southwest pacific ocean is a complex back arc region of widespread hydrothermal activity. It is bounded by the ryukyu ridge and trench to the south and east, and by the east china sea contribution of the scripps institution of oceanography, new series. Magmas in the central part of the basin are back arc basin basalts. Mantle hotspot neon in basalts from the northwest lau back. In the okinawa trough off southwestern japan, hydrothermal circulation due to back. However, the longterm natural variability of backarc basin hydrothermal vents is largely unstudied boschen et al. Backarc basalts in many respects marginal basin basalts mbb are similar to normal midocean ridge basalts ntype morb. Fresh volcanic rocks occur on numerous submarine features distributed along the rift axis, including a discontinuous neovolcanic ridge similar to the nascent spreading centers seen in some other back arc basins. Implications for the tectonomagmatic evolution of the caribbean plate alan r. Earthbyte group and school of geosciences, university of sydney. As illustrated in this book, oceanic basalts are compositionally diverse. The okinawa trough, lying between japan and taiwan, is a backarc basin formed by extension within the continental lithosphere. Back arc basins are found in areas where the subducting plate of oceanic crust is very old.
Trace element and isotope perspectives article pdf available in geophysical monograph series 166. Geochemistry of compositionally distinct late cretaceous backarc basin lavas. These were first described from the east scotia sea, an active back arc basin behind the south sandwich island arc in the south atlantic barker 1972, and have subsequently been documented from the lau, mariana, south fiji and west philippine basins. New species of scale worms polychaeta, polynoidae from the hydrothermal rift area of the mariana back arc basin in the western central pacific. A backarc basin is formed by the process of backarc spreading, which begins when one tectonic plate subducts under underthrusts another. Hydrocarbon exploration history began in the late 19 th century. Hydrothermal activity and metallogenesis in the lau back. Back arc basins are geologic basins, submarine features associated with island arcs and subduction zones. The neon isotope compositions of basalts from the northwest lau backarc basin reflect threecomponent mixing between an ocean island basalt oib mantle hotspot component, midocean ridge basalt morb mantle, and atmosphere. 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. Okinawa trough backarc basin early tectonic and magmatic evolution. However, the longterm natural variability of back arc basin hydrothermal vents is largely unstudied boschen et al. Okinawa trough, also known as the nanseishoto trough, is the back arc basin of the ryukyu trench arc back arc system.
In continental arcs the backarc region is part of continental platform, either dry land or forming shallow marine basins. Probable modern analogue of kurokotype massive sulphide deposits in the okinawa trough backarc basin. The chemical similarity between the east sulawesi ophiolite lavas and those from the eocene celebes sea backarc basin crust together with their identical age strongly suggest a backarc tectonic environment for this ophiolite, which represents a fragment of the eurasian plate obducted onto the east sulawesi basement of australian origin. The neon isotope compositions of basalts from the northwest lau back arc basin reflect threecomponent mixing between an ocean island basalt oib mantle hotspot component, midocean ridge basalt morb mantle, and atmosphere. 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 back arc basin. Most of them result from tensional forces caused by oceanic trench rollback the oceanic trench is wandering in the seafloor direction and the collapse of the edge of the continent. The mtj samples are characteristic back arc basin basalts babb.
The basin extends from 12 nto23 n and is characterized by a crescent shape. View enhanced pdf access article on wiley online library html view download pdf for offline viewing. Previous models for intraoceanic backarc basin sedimentation are static in that they focus on a longlived, stationary. Three key tectonic domains of western north america, the walker lane fault zone wlfz, northwestern basin and range nwbr, and cascade arc, intersect in southcentral oregon. This geologic formation is located in the western region of the pacific ocean, where it is surrounded by the inactive west mariana ridge and the stillactive mariana volcanic arc to the east. Most of them result from tensional forces caused by oceanic trench rollback and the collapse of the edge of the continent. Biogenic ch 4 in discharging hydrothermal fluids at the iheya north knoll is derived from outside the knoll. By comparing detrital zircon upb age spectra of coeval fore. Manus basin the spreading axes of the manus basin also show a systematic variation from arc like to morblike lava compositions withincreasing distance away from the new britain arc 37, though in this case gps measurements. Two suture zones, i the northern suture mkt and the southern suture mmt mark tectonic. Large gas reservoir along the rift axis of a continental back. Bounded by cascade arc volcanoes in the west, the klamath graben is traditionally regarded as the westernmost extent of the basin and range extensional province at the. 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. Deep structural graben are found in a region of low heat flow, and we interpret these to manifest a low.
Shear development and overprinting in a back arc basin. Subduction creates a trench between the two plates and melts the mantle in the overlying plate, which causes magma to rise toward the surface. 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. March 1979, backarc opening and the mode of subduction pdf, journal of geophysical research. Backarc basins are geologic basins, submarine features associated with island arcs and subduction zones. Seismic imaging of late miocene messinian evaporites. Backarc basin article about backarc basin by the free. A back arc system represents an important geological response to the nature of the oceanic lithosphere and the mantle dynamics along a plate boundary e. Media in category back arc basins the following 7 files are in this category, out of 7 total. Compared with intraoceanic mature back arc basins, which primarily have mantlelike or slightly high whole rock.
Dacite debris avalanche debris dam deformation diamict dike directed blast doas dome drainage. Therefore we infer that all the subductionrelated magmatism is captured by the back arc as the adjacent arc is shut off. Backarc basin basalt basaltic andesite base surge batholith benchmark bishop tuff block and ash flow bomb breadcrust bomb. New species of scale worms polychaeta, polynoidae from. Mark4 school of geography, geology, and the environment, kingston university, penrhyn road. Our results suggest that back arc basin formation is always preceded by an absolute motion of the overriding plate away from the. Sedimentation in backarc basins can be very varied, ranging from pelagic through turbidites to alluvial fans, although volcaniclastics see clast are common. Transition from continental rift to backarc basin in the. They are found at some convergent plate boundaries, presently concentrated in the western pacific ocean. The backarc region is the area behind a volcanic arc. Back arc basin, submarine basin that forms behind an island arc.
The area behind a volcanic arc and within the overriding plate in a subduction zone environment. In 1989, the submersible nautile discovered one of the most active hydrothermal fields on the modern ocean floor, in the lau back arc basin fig. Tectonic and magmatic controls on backarc basin sedimentation. Various convective systems have been postulated to explain extension, which is oriented parallel to the compression in a. View notes backarc basins from epse 350 at mcgill university. In island volcanic arcs it consists of backarc basins of oceanic crust with. Probable modern analogue of kurokotype massive sulphide. Geochemistry of compositionally distinct late cretaceous back arc basin lavas. These results indicate that geodynamic systems associated with backarc spreading are related to. 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. Petroleum system analysis for a back arc basin offshore. These were first described from the east scotia sea, an active backarc basin behind the south sandwich island arc in the south atlantic barker 1972, and have subsequently been documented from the lau, mariana, south fiji and west philippine basins.
Marginal basin oceanic island basalt oceanic basalt guaymas basin. Fresh volcanic rocks occur on numerous submarine features distributed along the rift axis, including a discontinuous neovolcanic ridge similar to the nascent spreading. Back arc basins form because the subduction of old oceanic lithosphere may make the volcanic arc move toward the trench and produce an extensional basin behind the arc 2 necessary steps in the formation of a volcanic arc. Hydrothermal activity and metallogenesis in the lau backarc. For back arc extension to form, a subduction zone is required, but not all subduction zones have a back arc extension feature. In 1989, the submersible nautile discovered one of the most active hydrothermal fields on the modern ocean floor, in the lau backarc basin fig. Back arc basalts in many respects marginal basin basalts mbb are similar to normal midocean ridge basalts ntype morb. A backarc basin is formed by the process of back arc spreading, which begins when one tectonic plate subducts under underthrusts another. Bransfield strait is a quaternary, ensialic back arc basin at the transition from rifting to spreading. The continental backarc basins formed by multiaxial extensional opening since the oligocene chough and barg, 1987. Backarc basins are extensional basins formed behind subduction zones by rifting.
The sequence of backarc basin development in the southwestern part of okinawa trough has apparently been crustal thinning, involving normal faulting and fault block rotation, rifting, and crustal separation with associated magmatic intrusion. Manus basin the spreading axes of the manus basin also show a systematic variation from arclike to morblike lava compositions withincreasing distance away from the new britain arc 37, though in this case gps measurements. Abstract the black sea is traditionally thought to be a backarc basin with active rifting beginning in the middle cretaceous. Geochemistry of compositionally distinct late cretaceous. Tethyan oceanic slab due to the southward migration of arc magmatism at ca. This diversity arises not only from low pressure fractionation in subvolcanic magma chambers, but also during the solidliquid fractionation that accompanies melting of the mantle. Caldera ce cinder cone cirque composite volcano coulee crust cryptodome cumulovolcano. The kuril backarc basin is a 3300mdeep basin located behind the kuril island. The distribution of hydrothermal venting reveals important clues about the presence of magma in submarine settings.
Seismic imaging of late miocene messinian evaporites from. Backarc basin origin for the east sulawesi ophiolite. North sumatera basin is a backarc basin that occupies an area of 60,0000 sq. Source lithology and crustal assimilation recorded in low. Implications for the origin of back arc basin basalts. Back arc basins are sites of significant hydrothermal activity, and the deepsea vents that occur in these regions often harbour diverse biological communities. Article geochemistry of back arc basin volcanism in. 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 sardoprovencal basin is therefore considered a backarc basin confined between the conjugated passive margins of the corsosardinian microplate to the east and of the gulf of lions and provence to the nw rehault et al. In continental arcs the back arc region is part of continental platform, either dry land or forming shallow marine basins. Paralvinella hessleri, new species of alvinellidae. Geochemistry of compositionally distinct late cretaceous back.
The pwave velocity distribution in the crust of the southern yamato basin is missing a typical continental upper crust with pwave velocities of 5. Trenchslope basin trench forearc basin intra arc basin backarc basin trenches. Seismic tomography and wave form inversion revealed that very slow velocity anomalies 5 to 7 percent beneath the active lau spreading center extend to 100kilometer depth and are connected to moderately slow anomalies 2 to 4 percent in the mantle wedge to 400kilometer depth. It includes spreading ridges, arc volcanoes, and intraplate volcanoes that provide a perhaps unique laboratory for studying interactions between hydrothermal.
Backarc basin assemblages in kohistan, northern pakistan. With the emerging deepsea mining industry focused on south pacific back arc basin hydrothermal systems, this lack of baseline data is a major impediment to informed decisionmaking. New species of scale worms polychaeta, polynoidae from the. Rising magma increases the pressure at the top of the overlying plate that creates rifts in the crust above and. Crustal thickness varies from 4 to 7 km in its central part, with a velocity structure typical of slowspreading ridges e. Several lines of evidence indicate that these rocks are similar to typical back.
Opening of the sea of japan backarc basin by asthenospheric. Kohistan can be divided into three tectonic zones, i the southern kamila zone comprises amphibolitized basalts, and mafic and ultramafic rocks, ii the central chilas complex, and iii the northern. North sumatera basin is a back arc basin that occupies an area of 60,0000 sq. A backarc system represents an important geological response to the nature of the oceanic lithosphere and the mantle dynamics along a plate boundary e. The northern part of the trough is now rifting, with extension accommodated by combined stretching and igneous intrusion. Faulting and volcanism in the axial valley of the slow. The understanding of the messinian salinity crisis msc as a mediterranean basinwide event requires an improved knowledge of the stratigraphy in the deep basins and continental margins e.
Backarc basins form because the subduction of old oceanic lithosphere may make the volcanic arc move toward the trench and produce an extensional basin behind the arc 2 necessary steps in the formation of a volcanic arc. Subduction zones and island arcs university of leicester. However during the early stages of back arc spreading, when the uprising mantle diapir splits the volcanic arc, the basalt magmas are derived from the sub arc mantle. The idea that back arc basin spreading is inherently different that midocean ridge spreading has been debated though the years. This petroleum system analysis of the tertiary ulleung basin offshore south korea is part of the korea national oil cooperation knoc active exploration program. The ne lau basin in the southwest pacific ocean is a complex backarc region of widespread hydrothermal activity. Due to the lack of lithological information from scientific and industrial wells, improvement of seismic imaging is currently the key element used to study the msc stratigraphy in the. The effects of backarc spreading on arc magmatism sciencedirect. Depth extent of the lau backarc spreading center and its. The back arc region is the area behind a volcanic arc. The mariana trough is one of the most wellknown back arc basins in the world. 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. 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. Unlimited viewing of the articlechapter pdf and any associated supplements and.
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