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80-475: The continuously spreading Chile Ridge collides with the southern South American plate to the east, and the ridge has been subducting underneath the Taitao Peninsula since 14 million years ago (Ma). The ridge-collision has generated a slab window beneath the overlying South America Plate, with smaller volume of upper mantle magma melt, proven by an abrupt low velocity of magma flow rate below

160-400: A central role in plate tectonic theory and the interpretation of ancient mountain belts. The stratigraphic -like sequence observed in ophiolites corresponds to the lithosphere -forming processes at mid-oceanic ridges . From top to bottom, the layers in the sequence are: A Geological Society of America Penrose Conference on ophiolites in 1972 defined the term "ophiolite" to include all of

240-451: A few magma chambers beneath ridges, and these are quite thin. A few deep drill holes into oceanic crust have intercepted gabbro, but it is not layered like ophiolite gabbro. The circulation of hydrothermal fluids through young oceanic crust causes serpentinization , alteration of the peridotites and alteration of minerals in the gabbros and basalts to lower temperature assemblages. For example, plagioclase , pyroxenes , and olivine in

320-574: A green color. The origin of these rocks, present in many mountainous massifs , remained uncertain until the advent of plate tectonic theory. Their great significance relates to their occurrence within mountain belts such as the Alps and the Himalayas , where they document the existence of former ocean basins that have now been consumed by subduction . This insight was one of the founding pillars of plate tectonics , and ophiolites have always played

400-457: A layered velocity structure that implies a layered rock series similar to that listed above. But in detail there are problems, with many ophiolites exhibiting thinner accumulations of igneous rock than are inferred for oceanic crust. Another problem relating to oceanic crust and ophiolites is that the thick gabbro layer of ophiolites calls for large magma chambers beneath mid-ocean ridges. However, seismic sounding of mid-ocean ridges has revealed only

480-946: A passive continental margin. They include the Coast Range ophiolite of California, the Josephine ophiolite of the Klamath Mountains (California, Oregon), and ophiolites in the southern Andes of South America. Despite their differences in mode of emplacement, both types of ophiolite are exclusively supra-subduction zone (SSZ) in origin. Based on mode of occurrences, the Neoproterozoic ophiolites appear to show characteristics of both mid-oceanic ridge basalt (MORB)-type and SSZ-type ophiolites and are classified from oldest to youngest into: (1) MORB intact ophiolites (MIO); (2) dismembered ophiolites (DO); and (3) arc-associated ophiolites (AAO) (El Bahariya, 2018). Collectively,

560-696: A problem arises concerning compositional differences of silica (SiO 2 ) and titania (TiO 2 ). Ophiolite basalt contents place them in the domain of subduction zones (~55% silica, <1% TiO 2 ), whereas mid-ocean ridge basalts typically have ~50% silica and 1.5–2.5% TiO 2 . These chemical differences extend to a range of trace elements as well (that is, chemical elements occurring in amounts of 1000  ppm or less). In particular, trace elements associated with subduction zone (island arc) volcanics tend to be high in ophiolites, whereas trace elements that are high in ocean ridge basalts but low in subduction zone volcanics are also low in ophiolites. Additionally,

640-659: A type of geosyncline called eugeosynclines were characterized by producing an "initial magmatism" that in some cases corresponded to ophiolitic magmatism. As plate tectonic theory prevailed in geology and geosyncline theory became outdated ophiolites were interpreted in the new framework. They were recognized as fragments of oceanic lithosphere , and dykes were viewed as the result of extensional tectonics at mid-ocean ridges . The plutonic rocks found in ophiolites were understood as remnants of former magma chambers. In 1973, Akiho Miyashiro revolutionized common conceptions of ophiolites and proposed an island arc origin for

720-416: A very little amount of magma is produced underneath the slab window. The mantle in the slab window is rather hotter than the mantle that melts from the lithospheric crust, and the generation of magma is very slow. This is due to low-extent of hydration to the subduction zone, decreasing mantle convection velocity, as the production of magma in the subduction zone is mainly driven by the hydration that lowers

800-478: Is a section of Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed, and often emplaced onto continental crustal rocks. The Greek word ὄφις, ophis ( snake ) is found in the name of ophiolites, because of the superficial texture of some of them. Serpentinite especially evokes a snakeskin. (The suffix -lite is from the Greek lithos , meaning "stone".) Some ophiolites have

880-632: Is also silica-rich. The partial melting causes the alteration of the subducted basalts into eclogite and amphibolite which contains garnet . Along the axis in the Chile ridge, magmatic rocks which are mafic to ultramafic are emplaced. For instance, the Taitao ophiolite complex is discovered in the westernmost of the Taitao Peninsula (east of the Chile Ridge), about 50 km southeast of

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960-602: Is an intraplate seismicity gap between 47° and 50°S (area with abnormal high heat flow), which coincides with the Patagonian slab window , disrupting most seismic events . The local seismic data only reveals a low-magnitude (magnitude lower than 3.4) seismic event, which is not related to tectonic process. The reason behind this is that the Antarctica Plate undergoes shallow subduction which causes very limited seismic deformation. (Fig-5) The most obvious impact of

1040-583: Is relatively low-extent (20%) of partial melting of the lithosphere, the pressure and the temperature of the partial melting is less than 10 kbar and higher than 650° respectively. This is because the warm young Nazca plate has hindered high rate of cooling and dehydration . The partial melting of the Taitao granite creates plutons like the Cabo Raper adakitic pluton. Adakite is a felsic to intermediate rock and are usually calc-alkaline in composition. It

1120-579: Is shown from the north to the south of the triple junction. Also, the hypothesized conductive heat flow is consistent with the heat flow data from BSR. Understanding the spreading ridge subduction is crucial as it controls the evolution of continental crust. The subduction of the Chile Ridge beneath the Chile Trench provides a suitable analog for the initiation of the Archean continental crust via

1200-827: Is subducting under the western edge of the South American plate, along the continent's Pacific coast, at a rate of 77 mm (3.0 in) per year. The collision of these two plates is responsible for lifting the massive Andes Mountains and for creating the numerous volcanoes (including both stratovolcanoes and shield volcanoes ) that are strewn throughout the Andes.       Gómez Tapias, Jorge; Montes Ramírez, Nohora E.; Almanza Meléndez, María F.; Alcárcel Gutiérrez, Fernando A.; Madrid Montoya, César A.; Diederix, Hans (2015). Geological Map of Colombia . Servicio Geológico Colombiano . pp. 1–212 . Retrieved 2019-10-29 . Ophiolite An ophiolite

1280-590: Is uplifted onto continental margins despite the relatively low density of the latter. All emplacement procedures share the same steps nonetheless: subduction initiation, thrusting of the ophiolite over a continental margin or an overriding plate at a subduction zone, and contact with air. A hypothesis based on research conducted on the Bay of Islands complex in Newfoundland as well as the East Vardar complex in

1360-479: Is worth studying because it explains how the Archean continental crust initiation formed from deep oceanic crust. From approximately 14 to 3 million years ago, a series of trenches collided the Chile Trench, forming what is part of the Chile Ridge. In the 2010 Concepcion earthquake (magnitude 8.8) struck the ridge. The geology of the Chile ridge is closely related to the geology of the Taitao Peninsula (East of

1440-650: The Aysén Region , southern Chile. There is only an event of seismic magnitude higher than 7 happening in 1927. This hinders the finding in seismicity near the Chile Ridge. Nevertheless, in 2007, the Liquiñe-Ofqui fault system releases the accumulated stress brought by the subduction of Nazca underneath the South America Plate with seismicity magnitude reaching 7 in an earthquake. Recently, 274 seismic events have been detected in 2004–2005. There

1520-553: The Chile Rise is actively subducting under the South American plate. Geological research suggests that the South American plate is moving west away from the Mid-Atlantic Ridge: "Parts of the plate boundaries consisting of alternations of relatively short transform fault and spreading ridge segments are represented by a boundary following the general trend." As a result, the eastward-moving and more dense Nazca plate

1600-643: The closure of the Tethys Ocean . Ophiolites in Archean and Paleoproterozoic domains are rare. Most ophiolites can be divided into one of two groups: Tethyan and Cordilleran. Tethyan ophiolites are characteristic of those that occur in the eastern Mediterranean sea area, e.g. Troodos in Cyprus, and in the Middle East, such as Semail in Oman, which consist of relatively complete rock series corresponding to

1680-441: The crystallization order of feldspar and pyroxene (clino- and orthopyroxene) in the gabbros is reversed, and ophiolites also appear to have a multi-phase magmatic complexity on par with subduction zones. Indeed, there is increasing evidence that most ophiolites are generated when subduction begins and thus represent fragments of fore-arc lithosphere. This led to introduction of the term "supra-subduction zone" (SSZ) ophiolite in

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1760-409: The emplacement of ophiolite complex . The Chile triple junction is the intersection of Nazca, Antarctica and South American plate. The position of the junction shifts over time, and depends whether the spreading ridge subducts or the transform fault subducts beneath the South American plate. When the spreading ridge subducts, the triple junction shifts northwards; but if the fracture zone subducts,

1840-406: The emplacement of the alkaline basalts. (5.19 Ma) Bathymetry of the Chile ridge is inspected, which is the submarine topography that studies the depths of landforms under the water level. It is discovered that there are large abyssal hills extend along two sides of the ridge. The abyssal hills grow cyclically which is caused by the cyclic fault growth. During faulting cycles, the extension of

1920-555: The geosyncline concept. He held that Alpine ophiolites were "submarine effusions issuing along thrust faults into the active flank of an asymmetrically shortening geosyncline". The apparent lack of ophiolites in the Peruvian Andes , Steinmann theorized, was either due to the Andes being preceded by a shallow geosyncline or representing just the margin of a geosyncline. Thus, Cordilleran-type and Alpine-type mountains were to be different in this regard. In Hans Stille 's models

2000-433: The metal-ore deposits present in and near ophiolites and from oxygen and hydrogen isotopes suggests that the passage of seawater through hot basalt in the vicinity of ridges dissolved and carried elements that precipitated as sulfides when the heated seawater came into contact with cold seawater. The same phenomenon occurs near oceanic ridges in a formation known as hydrothermal vents . The final line of evidence supporting

2080-411: The partial melting of the crust. A volcanic arc gap is formed above the slab window as the magma melted from the crust convects slowly which hampers the volcanism . The ridge segment between Taitao and Darwin transform faults are currently located near the Chile Trench and collide with the South American plate. The presence of slab window underneath southern South America Plate has been proven by

2160-539: The "Steinmann Trinity": the mixture of serpentine , diabase - spilite and chert . The recognition of the Steinmann Trinity served years later to build up the theory around seafloor spreading and plate tectonics . A key observation by Steinmann was that ophiolites were associated to sedimentary rocks reflecting former deep sea environments. Steinmann himself interpreted ophiolites (the Trinity) using

2240-516: The 1980s to acknowledge that some ophiolites are more closely related to island arcs than ocean ridges. Consequently, some of the classic ophiolite occurrences thought of as being related to seafloor spreading (Troodos in Cyprus , Semail in Oman ) were found to be "SSZ" ophiolites, formed by rapid extension of fore-arc crust during subduction initiation. A fore-arc setting for most ophiolites also solves

2320-868: The African plate; the southerly edge is a complex boundary with the Antarctic plate , the Scotia plate , and the Sandwich Plate ; the westerly edge is a convergent boundary with the subducting Nazca plate ; and the northerly edge is a boundary with the Caribbean plate and the oceanic crust of the North American plate . At the Chile Triple Junction , near the west coast of the Taitao – Tres Montes Peninsula , an oceanic ridge known as

2400-478: The Apuseni Mountains of Romania suggest that an irregular continental margin colliding with an island arc complex causes ophiolite generation in a back-arc basin and obduction due to compression. The continental margin, promontories and reentrants along its length, is attached to the subducting oceanic crust, which dips away from it underneath the island arc complex. As subduction takes place,

2480-513: The Chile Ridge segments were subducted beneath the Southern Patagonian Peninsula (located between 48° and 54°S) subsequently. From 10 Ma to the present, Chile Ridge was separated into several short segments by the fracture zones , and the segments of the ridge are subducted between 46° and 48° S. The above findings have proven that Chile Ridge has been encountered a northward migration. Thus it has been found that

Chile Ridge - Misplaced Pages Continue

2560-515: The Chile Ridge. The subduction of the ridge started is an oblique subduction with 10° – 12° oblique to the Chile trench since 14 Ma, which subducts beneath the southeastern Southern Patagonia. Thus it is found that both the Nazca-South American plate collision and Antarctic-South American plate collision have been taken place at the same time when the Chile ridge is separating, i.e. segments of Chile Ridge have been subducting beneath

2640-415: The Chile ridge brought about 'diffusion' tectonic deformation which forms numerous tiny faults. The continuous divergence of the ridge causes the extensional strain to concentrate, the tiny faults to link together to generate tall and long abyssal-hill-scale faults. The huge faults push the old and inactive faults away from the ridge axis by extensional force. This process would repeat again. Therefore,

2720-454: The Chile ridge). This is because the Chile ridge subducts beneath the Taitao Peninsula, which give rise to unique lithologies there. The lithological units would be discussed from youngest to oldest, and Taitao Granites and Taitao Ophiolite would be our main focus. Adakite magmatism is formed by the melting of the Nazca plate's trailing edge. Due to the subduction of the Chile Ridge beneath

2800-425: The Chile ridge. It is proved that Chiloe Microplate (Fig-5, 6) is migrated northwards relative to the South American plate which is rather immobile. The Golfo de Penas basin is formed because of the northward movement of Chiloe Microplate. The Liquiñe-Ofqui fault system is a right-lateral strike-slip fault separating Chiloe Microplate and the South America Plate. The northward migration of Chiloe Microplate along

2880-430: The Chile triple junction (CTJ). The tectonic activity and seismicity are mainly driven by the subduction of Chile Ridge. A slab window is formed as the Nazca and Antarctica Plate continues to diverge when colliding with Chile trench, a gap is created as new lithosphere production is becomes very slow. Moderate to high offshore seismicities for magnitude higher than 4 is detected in the segmented Chile Ridge as well as

2960-453: The Chile triple junction. This is contributed by the obduction of the Nazca plate produced due to the convergence of the overriding South America Plate and the Chile ridge Tres Montes segment. The obduction and the thrusting causes low-pressure metamorphism and forms the ophiolite complex. This metamorphism indicates the onset of hydrothermal alteration in a spreading ridge environment. There are also recent activities of acidic magmas in

3040-490: The Coast Range ophiolite of California and Baja California, by a change in subduction location and polarity. Oceanic crust attached to a continental margin subducts beneath an island arc. Pre-ophiolitic ocean crust is generated by a back-arc basin. The collision of the continent and island arc initiates a new subduction zone at the back-arc basin, dipping in the opposite direction as the first. The created ophiolite becomes

3120-539: The E-W direction. There are six fault zones between the Valdivia Fault Zone. Ridge -parallel abyssal hills present on both sides of the axial valley Geophysical and geothermal analysis in the southern Chile triple junction has been examined. Magnetic and bathymetric data have been recorded across the Chile Ridge which recognizes a slight transformation in the configuration of the spreading ridge when

3200-497: The Liquiñe-Ofqui fault creates the Golfo de Penas basin in the late Miocene period. The Liquiñe-Ofqui fault is a fast-slipping fault (with a geodetic rate of 6.8–28 mm/yr). Intraplate seismicity has mainly been taken place in this fault system. Also, enormous stress from the Nazca plates and South American plate collision has accumulated along the fault system. Throughout history, only limited seismic studies have been conducted in

3280-415: The South American plate, there were intrusive magmatism which generates granite. This is also formed by the partial melting of the subducted oceanic crust. The young Nazca crust (less than 18 Myr old) are warmer so that the metamorphosed subducted basalts are melted. In normal mid-oceanic ridge , the presence of volatiles like water also reduces the solidus temperature. However, in Chile Ridge, there

Chile Ridge - Misplaced Pages Continue

3360-470: The South American plate. Due to the difference in the convergence rate, the formation of a slab window is favoured. Slab window is a gap underneath the South America Plate, where the overriding South America Plate has only little lithospheric mantle supporting it and is directly exposed to the hot asthenospheric mantle . The experimental results from the magnetic anomalies within the oceanic crust suggest that about in 14–10 Ma (late-Miocene), some of

3440-441: The Taitao Peninsula which allows the comparison between the past composition and current composition, history of the magma can be determined. Taitao ophiolite lithosphere forms a special sequence from the top to bottom: pillow lavas , sheeted dike complex, gabbros and ultramafic rock units. For the ultramafic rock units, it proved that there are at least two melting events that happened before. The thermal configuration and

3520-449: The alteration in the thermal configuration and the geometry of the sub-arc mantle wedge, creating a distinct chemical composition of magma generations. That means by understanding the composition of the magma, specific conditions of subduction systems can be known. This has found that the slab window produced by the subduction of the ridge causes the generation of alkali basalt . The ridge-trench convergence and slab window generation aids

3600-495: The buoyant continent and island arc complex converge, initially colliding with the promontories. However, oceanic crust is still at the surface between the promontories, not having been subducted beneath the island arc yet. The subducting oceanic crust is thought to split from the continental margin to aid subduction. In the event that the rate of trench retreat is greater than that of the island arc complex's progression, trench rollback will take place, and by consequence, extension of

3680-477: The classic ophiolite assemblage and which have been emplaced onto a passive continental margin more or less intact (Tethys is the name given to the ancient sea that once separated Europe and Africa). Cordilleran ophiolites are characteristic of those that occur in the mountain belts of western North America (the " Cordillera " or backbone of the continent). These ophiolites sit on subduction zone accretionary complexes (subduction complexes) and have no association with

3760-432: The current knowledge of the oceanic crust's composition. For this reason, researchers carried out a seismic study on an ophiolite complex ( Bay of Islands, Newfoundland ) in order to establish a comparison. The study concluded that oceanic and ophiolitic velocity structures were identical, pointing to the origin of ophiolite complexes as oceanic crust. The observations that follow support this conclusion. Rocks originating on

3840-497: The first, he used ophiolite for serpentinite rocks found in large-scale breccias called mélanges . In the second publication, he expanded the definition to encompass a variety of igneous rocks as well such as gabbro , diabase , ultramafic and volcanic rocks. Ophiolites thus became a name for a well-known association of rocks occurring in the Alps and Apennines of Italy. Following work in these two mountains systems, Gustav Steinmann defined what later became known as

3920-499: The following section, 7 segments will be discussed. From the table below, it reveals that the spreading ridge segments range in length from about 20 to 200 km, the offsets within segments are about 10 to 1100 km. There are actually a total of 10 first-order ridge segments in the northern ridge (N1-N10), 5 first-order ridge segments (V1-V5) in Valdivia Fracture Zone , 5 first-order ridge segments (S1-S5) are in

4000-455: The further the abyssal hill to the ridge axis, the older the age it is. The Chile Ridge is formed by the divergence of the Nazca and Antarctica plates. It is spreading actively at the rate of about 6.4 – 7.0 cm/year since 5 Ma to present. The Late Miocene Nazca-Antarctic spreading ridge formation creates about 550 km-long Chile Ridge as there are differences in the convergence rates between Nazca and Antarctica plates. According to

4080-540: The generation of the slab window, the Chile Ridge subduction into the Chile triple junction also influences the Taitao Peninsula . First of all is the tectonic erosion , Neogene basaltic volcanism and tectonic uplift in Late Cretaceous. Obduction and thrusting of Nazca plate produced due to the convergence of the overriding South America Plate and the Chile ridge, causing low-pressure metamorphism, facilitated

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4160-591: The investigated ophiolites of the Central Eastern Desert (CED) fall into both MORB/back-arc basin basalt (BABB) ophiolites and SSZ ophiolites. They are spatially and temporally unrelated, and thus, it seems likely that the two types are not petrogenetically related. Ophiolites occur in different geological settings, and they represent change of the tectonic setting of the ophiolites from MORB to SSZ with time. The term ophiolite originated from publications of Alexandre Brongniart in 1813 and 1821. In

4240-589: The layers listed above, including the sediment layer formed independently of the rest of the ophiolite. This definition has been challenged recently because new studies of oceanic crust by the Integrated Ocean Drilling Program and other research cruises have shown that in situ ocean crust can be quite variable in thickness and composition, and that in places sheeted dikes sit directly on peridotite tectonite , with no intervening gabbros . Ophiolites have been identified in most of

4320-655: The magmatism of the North American boundary. South American plate The South American plate is a major tectonic plate which includes the continent of South America as well as a sizable region of the Atlantic Ocean seabed extending eastward to the African plate , with which it forms the southern part of the Mid-Atlantic Ridge . The easterly edge is a divergent boundary with

4400-441: The melting of deep oceanic crust. This is because the Chile Ridge subduction is the only example in the world that the overriding plate is a continental one. The correlations between the rocks in the past can also be examined. The ridge trench interaction can also be studied. In addition, due to the presence of Patagonian slab window and the obduction of the Nazca plate, the geological process that happened in different period are not

4480-443: The ophiolite is emplaced onto the continental margin. Based on Sr and Nd isotope analyses, ophiolites have a similar composition to mid-ocean-ridge basalts, but typically have slightly elevated large ion lithophile elements and a Nb depletion. These chemical signatures support the ophiolites having formed in a back-arc basin of a subduction zone. Ophiolite generation and subduction may also be explained, as suggested from evidence from

4560-462: The origin of ophiolites as seafloor is the region of formation of the sediments over the pillow lavas: they were deposited in water over 2 km deep, far removed from land-sourced sediments. Despite the above observations, there are inconsistencies in the theory of ophiolites as oceanic crust, which suggests that newly generated ocean crust follows the full Wilson cycle before emplacement as an ophiolite. This requires ophiolites to be much older than

4640-425: The orogenies on which they lie, and therefore old and cold. However, radiometric and stratigraphic dating has found ophiolites to have undergone emplacement when young and hot: most are less than 50 million years old. Ophiolites therefore cannot have followed the full Wilson cycle and are considered atypical ocean crust. There is yet no consensus on the mechanics of emplacement, the process by which oceanic crust

4720-671: The otherwise-perplexing problem of how oceanic lithosphere can be emplaced on top of continental crust. It appears that continental accretion sediments, if carried by the downgoing plate into a subduction zone, will jam it up and cause subduction to cease, resulting in the rebound of the accretionary prism with fore-arc lithosphere (ophiolite) on top of it. Ophiolites with compositions comparable with hotspot -type eruptive settings or normal mid-oceanic ridge basalt are rare, and those examples are generally strongly dismembered in subduction zone accretionary complexes. Ophiolites are common in orogenic belts of Mesozoic age, like those formed by

4800-455: The overriding plate will occur to allow the island arc complex to match the trench retreat's speed. The extension, a back-arc basin, generates oceanic crust: ophiolites. Finally, when the oceanic lithosphere is entirely subducted, the island arc complex's extensional regime becomes compressional. The hot, positively buoyant ocean crust from the extension will not subduct, instead obducting onto the island arc as an ophiolite. As compression persists,

4880-462: The research which aims at determining the lithosphere and upper mantle structure proximate to the Chile Ridge. An intraplate seismic gap is recorded which coincides with the Patagonian slab window location. The experimental results of the P wave travel-time tomography show there is low-velocity zone in the predicted slab window location, migrating eastward with increasing depth. Other than

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4960-528: The results from space geodetic observations, Nazca-South America converges four times faster than that of Antarctica-South America. In addition, the direction of the Nazca plate migration is different from the Antarctica plate migration since 3 Ma. The direction that Nazca plate moves is ENE, while the Antarctic plate is ESE. The net diverging movement of the two plates contributes to the spreading of

5040-477: The ridge axes. It is also named as fault zones . They are the transform faults and separate the Chile Ridge into segments, causing the entire ridge axis to trend southeastward. Fracture zones are trending east-northeast (ENE). The total length of the Chile ridge axis offset is 1380 km caused by the 18 fault zones, among the fault zones, there are also 2 complex fault systems. The longest fault zones are Chiloe fault with 234 km long, and Guafo fault being

5120-512: The ridge converges with the trench. The overriding South America Plate is dominantly impacted by the ridge collision. The Chile-Peru Trench becomes steeper and narrower when the Chile Ridge is subducting. Chile Ridge segment within the Taitao Fracture Zone collides with the southern end of the trench. The collision of the ridge may also be associated with the obduction process onto the landward trench slope. Geothermal data along

5200-472: The same. Therefore, the Chile Ridge subduction is not conformable with the uniformitarian principle (geological process happened now is the same with that in the past). The subduction of Kula-Farallon/Resurrection ridge started during Late Cretaceous-Paleocene, this is currently located at the Chugach complex, Alaska where mafic-ultramafic high grade metamorphism is found nowadays. The ridge subduction controls

5280-460: The seafloor show chemical composition comparable to unaltered ophiolite layers, from primary composition elements such as silicon and titanium to trace elements. Seafloor and ophiolitic rocks share a low occurrence of silica-rich minerals; those present have a high sodium and low potassium content. The temperature gradients of the metamorphosis of ophiolitic pillow lavas and dykes are similar to those found beneath ocean ridges today. Evidence from

5360-406: The segment ends are wider. This forms an hourglass morphology. (Fig-8) It is located in the middle of the Chile ridge (Fig-1, 2, 7), and separates the ridge into northern and southern sections, discovered by the bathymetry and magnetic profiles study, as well as the gravity anomaly detection. The Valdivia Fault Zone has caused the offset of the north and south Chile ridge for more than 600 km in

5440-420: The separating Chile ridge. The subduction generates a special type of igneous rocks , represented by the Taitao ophiolites , which is an ultramafic rock composed of olivine and pyroxene , usually found in oceanic plates . In addition, the subduction of the Chile Ridge also creates Taitao granite in Taitao Peninsula which appeared as plutons . The Chile Ridge involves spreading ridge subduction which

5520-551: The sheeted dikes and lavas will alter to albite , chlorite , and serpentine , respectively. Often, ore bodies such as iron -rich sulfide deposits are found above highly altered epidosites ( epidote - quartz rocks) that are evidence of relict black smokers , which continue to operate within the seafloor spreading centers of ocean ridges today. Thus, there is reason to believe that ophiolites are indeed oceanic mantle and crust; however, certain problems arise when looking closer. Beyond issues of layer thicknesses mentioned above,

5600-603: The shortest (39 km). Through various research on the magnetic and bathymetry data, fracture zones' locations are located. While major fault zones are surveyed by the bathymetry method and defined as troughs. Same bathymetry data also discovered the Fault zones in East Pacific Rise as well as the low-velocity-spreading Mid-Atlantic ridge . Chile Ridge is divided into a wide range of several short spreading segments which have different lengths and offset distances, in

5680-416: The southern ridge. Moreover, both segments N9 and S5 are divided into two parts by non-transform offsets. The table above summarized the longer, more regular and less complicated faults: N1, N5, N8, N9N, N9S, N10, V4, S5N, and S5S. Deep contours are located along the segment ends while shallow contours are located at the segment center. The segment center is narrower as the while the axial valley located at

5760-437: The southern triple junction are measured. The heat flow analysis in the collision zone of the trench indicated a high value of heat pulse (345 mW/m) related to the Chile ridge subduction in the lower part of the trench. Furthermore, by the application of bottom-simulating reflectors (BSR), more convincing evidence of the existence of high heat flow underneath the trench slope , as a wider range of heat flow observations grid

5840-538: The spreading rate of Chile Ridge from 23 Ma to the present has slowed down. While the spreading rate of the ridge is correlated to time of the collisions of ridge and trench. Some studies have different discoveries in the rate of spreading which shows that the ridge may have spread uniformly for about 31 km/Myr half spreading rate starting from 5.9 Ma. In the Chile Ridge Subduction Project (CRSP), seismic stations are deployed in

5920-406: The structure of the subduction zone affects the interactions of the oceanic lithosphere , seafloor sediments, the eroded rock from the overlying South American plate, and the sub-arc mantle wedge as well as the chemical composition of the magma, that melts from the mantle. Due to the subduction of oceanic ridges (Chile Ridge) beneath the South American plate which has occurred since 16 Ma, this caused

6000-425: The subduction of the Chile ridge is the formation of slab window. It is formed when the segments of separating Chile Ridge subducts under the southern South America Plate. The trailing edge of the Nazca plate is completely melted in the subduction zone, and the leading edge of the Antarctic plate diverges, a widening gap is created between the two plates as very little crust is melted after subduction. In this case, only

6080-452: The temperature of Chile triple junction below the depth of 10 – 20 km is predicted to be 800 – 900 °C. The ridge axes are the middle part of the ridge where newer crusts are formed. The central ridge axis of Chile Ridge is trending in the direction of north-northwest (NNE). Ridge axes are also known as topographic axial rift valleys . With the help of satellite altimetry data and magnetic data, gravity lows are discovered near

6160-532: The tip of the new subduction's forearc and is uplifted (over the accretionary wedge ) by detachment and compression. Verification of the two above hypotheses requires further research, as do the other hypotheses available in current literature on the subject. Scientists have drilled only about 1.5 km into the 6- to 7-kilometer-thick oceanic crust, so scientific understanding of oceanic crust comes largely from comparing ophiolite structure to seismic soundings of in situ oceanic crust. Oceanic crust generally has

6240-424: The transform faults. It is predicted that the subduction of the spreading Chile Ridge under South America to the north of the Chile triple junction give rise to the seismic event. Furthermore, intraplate seismicity in the overriding South American plate is more likely resulted from the deformation of the Liquiñe-Ofqui fault system. This is a tiny plate between Nazca plate and South American plate, it locates east of

6320-483: The triple junction shifts southwards. The junction has shifted to the north starting from the onset of Chile Ridge subduction since 17 Ma after the rupture of the Nazca-Antarctic-Phoenix triple junction. Since then, the Chile triple junction has arrived to its current position in the western Taitao Peninsula . Prior to 10 Ma, Chile triple junction reaches the southern Taitao peninsula. Currently,

6400-410: The world's orogenic belts . However, two components of ophiolite formation are under debate: the origin of the sequence and the mechanism for ophiolite emplacement. Emplacement is the process of the sequence's uplift over lower density continental crust. Several studies support the conclusion that ophiolites formed as oceanic lithosphere . Seismic velocity structure studies have provided most of

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