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Chile Ridge

The Chile Ridge, also known as the Chile Rise, is a submarine oceanic ridge formed by the divergent plate boundary between the Nazca Plate and the Antarctic Plate. It extends from the triple junction of the Nazca, Pacific, and Antarctic plates to the Southern coast of Chile.[1][2] The Chile Ridge is easy to recognize on the map, as the ridge is divided into several segmented fracture zones which are perpendicular to the ridge segments, showing an orthogonal shape toward the spreading direction. The total length of the ridge segments is about 550–600 km.[1]

Fig-1 Map of the Chile ridge in the Pacific Ocean. The red line and red letters 'CR' represents Chile ridge. The ridge is divided into numerous segments of the fault line indicated by black lines. 'FZ' means fracture zone. The pink arrows indicate the direction of the Nazca Plate and Antarctic Plate movements as well as their rate of migration. They show that the Nazca Plate is moving in an ENE direction, which is oblique to the boundary with the South American Plate, while the Antarctica Plate is moving in an E-W direction, which is almost perpendicular to the plate boundary. In addition, the Nazca Plate migrates over four times faster than the Antarctica Plate. The dark purple circle shows the Taitao Peninsula where the Chile ridge collides to the South American Plate. The yellow line shows the plate boundary.[1]

The continuously spreading Chile Ridge collides with the southern South America Plate to the east, and the ridge has been subducting underneath the Taitao Peninsula since 14 million years ago (Ma).[1][2] 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 the separating Chile ridge.[2][1][3] 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.[4][2] In addition, the subduction of the Chile Ridge also creates Taitao granite in Taitao Peninsula which appeared as plutons.[2][5]

The Chile Ridge involves spreading ridge subduction which is worth studying because it explains how the Archean continental crust initiation formed from deep oceanic crust.[4]

History

From approximately 3-14 million years ago, a series of trenches collided the Chile Trench, forming what is part of the Chile Ridge.[citation needed]

In the 2010 Concepcion earthquake, an 8.8 magnitude struck the ridge.[citation needed]

Regional geology

Geology of the Chile ridge

The geology of the Chile ridge is closely related to the geology of the Taitao Peninsula (East of the Chile ridge). This is because the Chile ridge subducts beneath the Taitao Peninsula, which give rise to unique lithologies there.[4][5] The lithological units would be discussed from youngest to oldest, and Taitao Granites and Taitao Ophiolite would be our main focus.

Taitao Granites (Adakite-like rocks in Late-Miocene)

Adakite magmatism is formed by the melting of the Nazca Plate’s trailing edge.[2] Due to the subduction of the Chile Ridge beneath the South American Plate, there were intrusive magmatism which generates granite. [4] This is also formed by the partial melting of the subducted oceanic crust.[4] [5] The young Nazca crust (less than 18 Myr old) are warmer so that the metamorphosed subducted basalts are melted. [5][4] In normal mid-oceanic ridge, the presence of volitiles like water also reduces the solidus temperature.[4] However, in Chile Ridge, there 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.[4] 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.[4]

Characteristics of Taitao Granites
 
Fig-2 shows the geology of the Taitao Peninsula. Taitao granites and Taitao ophiolites would be mainly focused on in this part. Chile ridge is located west of the Taitao Peninsula, and the geology of Chile Ridge is closely associated with that of Taitao Peninsula.[5][6][4]

Adakite is a felsic to intermediate rock and are usually Calc-alkaline in composition. It is also silica-rich. [2] The partial melting causes the alteration of the subducted basalts into eclogite and amphibolite which contains garnet. [4]

Taitao Ophiolite (pillow lava, sheeted dikes, gabbro, ultramafic rocks in Late-Miocene)

Along the axis in the Chile ridge, magmatic rocks which are mafic to ultramafic are emplaced.[4] 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 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.[2][7] 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. [4][7] There are also recent activities of acidic magmas in the Taitao Peninsula which allows the comparison between the past composition and current composition, history of the magma can be determined.[2][8]

Characteristics of Taitao Ophiolite

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.[2][9]

The thermal configuration and 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.[2] Due to the subduction of oceanic ridges (Chile Ridge) beneath the South American plate which has occurred since 16 Ma, this caused the alteration in the thermal configuration and the geometry of the sub-arc mantle wedge, creating a distinct chemical composition of magma generations.[2] That means by understanding the composition of the magma, specific conditions of subduction systems can be known.[2] This has found that the slab window produced by the subduction of the ridge causes the generation of Alkaline basalts. The ridge-trench convergence and slab window generation aids the emplacement of the Alkaline basalts.[2][6]

Summary of the geology in Chile ridge [2]
Age of the rocks Kinds of magmatism Rock type Subduction settings Composition
Holocene / Conglomerate / Variable compositions: rock fragments from Taitao granites, ophiolite,
Late-Miocene (3.92 Ma, 5.12 Ma) Arc magmatism Taitao Granites low-extent partial melting of the altered basalt (from the trailing edge of Nazca Plate) in a hot subduction event beneath the volcanic arc intermediate to felsic, calc-alkaline, adakites: high Sr/Y and La/Yb ratio
Late-Miocene

(5.19 Ma)

Arc magmatism Taitao Ophiolite obduction and uplift of the Nazca Plate produced due to the convergence of the overriding South America Plate and the Chile ridge, causing low-pressure metamorphism mafic to ultramafic, olivine and pyroxene
Pre-Jurassic / Meta-sedimenary basement / /

Bathymetry

Bathymetry of the Chile ridge is inspected, which is the submarine topography that studies the depths of landforms under the water level.[10] 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 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, the further the abyssal hill to the ridge axis, the older the age it is.[9]

The Chile Ridge movement

 
Fig-3 shows a close up view of the spreading Chile Ridge. With difference relative plane motion of Nazca Plate and Antarctica plate, this creates an extensional force for sea floor spreading to carry out. [11]
 
Fig-4 shows the Evolutionary diagram of the Chile Ridge Movement. The magmatism of under Taitao Peninsula from about 6 Ma to 5.7–5.1 Ma is shown. CTJ stands for Chile Tripple Junction. A) The ridge is located at the edge of the Chile Trench. the Magma chambers developed and cause the upwelling of the ophiolite onto the surface of the spreading ridge. Cabo Raper pluton is also shown in the diagram. B) The old magma chamber is pushed away by the new magma chamber. Some ophiolite was also formed when the Nazca plate obducted and uplift. A new magma chamber was generated. The Chile Ridge segment subducts beneath the South American Plate.[5][4]

The spreading of the Chile Ridge

The Chile Ridge is formed by the divergence of the Nazca and Antarctica plates.[4] It is spreading actively at the rate of about 6.4 – 7.0 cm/year since 5 Ma to present.[4] 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.[2] According to the results from space geodetic observations, Nazca-South America converges four times faster than that of Antarctica-South America.[1][9]

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 the Chile Ridge.[4]

Plate motion of Nazca plate and Antarctica plate[9][2][1]
Name of the Plate Direction of movement Rate of movement
Nazca plate N77°E (ENE) 6.6–8.5 cm/year
Antarctica plate N100°E (ESE) 1.85 cm/year

Migration and subduction of the Chile ridge

The subduction of the ridge started is an oblique subduction with 10° – 12° oblique to the Chile trench since 14 Ma,[4] which subducts beneath the southeastern Southern Patagonia.[1][4] 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 the South American Plate.[1] Due to the difference in the convergence rate, the formation of a slab window is favoured.[1] 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.[1]

The experimental results from the magnetic anomalies within the oceanic crust suggest that about in 14–10 Ma (late-Miocene), some of the Chile Ridge segments were subducted beneath the Southern Patagonian Peninsula (located between 48° to 54°S) subsequently.[2] 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° to 48° S.[2][1] The above findings have proven that Chile Ridge has been encountered a northward migration.[2][9][4] Thus it has been found that 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.[1] 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.[9]

Associated seismicity

In the Chile Ridge Subduction Project (CRSP), seismic stations are deployed in the Chile Triple Junction (CTJ). [12] The tectonic activity and seismicity are mainly driven by the subduction of Chile Ridge.[13] 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.[14][3][15] Moderate to high offshore seismicities for magnitude higher than 4 is detected in the segmented Chile Ridge as well as the transform faults. [12] 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.[14][13][16]

Chiloe Microplate

This is a tiny plate between Nazca Plate and South American Plate, it locates east of 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.[16]

Seismicity of Liquiñe-Ofqui fault system in the Aysén Region

The Liquiñe-Ofqui fault system is a right-lateral strike-slip fault separating Chiloe Microplate and the South America Plate.[13] The northward migration of Chiloe Microplate along the Liquiñe-Ofqui fault creates the Golfo de Penas basin in the late Miocene period. [16]

The Liquiñe-Ofqui fault is a fast-slipping fault (with a geodetic rate of 6.8–28 mm/yr).[16] Intraplate seismicity has mainly been taken place in this fault system. Also, enormous stress from the Nazca Plates and South America Plate collision has accumulated along the fault system.[16][13] Throughout history, only limited seismic studies have been conducted in the Aysén Region, southern Chile. There is only an event of seismic magnitude higher than 7 happening in 1927.[13] 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.[16] Recently, 274 seismic events have been detected in 2004–2005.[16]

Seismicity of the Patagonian Slab Window

There is an intraplate seismicity gap between 47° to 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.[16][14] (Fig-5)

Frequency values of strike-slip faulting of different regions[16]
Regions where the seismicity is concentrated depth of focus (km) magnitude of seismic event Orientation of the maximum compressional stress
North of the Chile Triple Junction intraplate seismic events concentrated along Liquiñe-Ofqui fault system 4–21 1.5–6 ENE-WSW (oblique to the continental margin of South American Plate of N10°)
South of the Chile Triple Junction (between 46.5°-50°S) seismic events sparsely populated in Southern Patagon 12–15 5 ESE-WNW

Geological Formation related to the Chile Ridge Movement

Consequence of the Subduction of the Chile Ridge

Patagonia Slab Window

 
Fig-5 This sketch shows the cross-section of the slab window. The Nazca plate and Antarctic Plate is colliding with South American Plate.[3]

The most obvious impact of 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 a very little amount of magma is produced underneath the slab window.[3] 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 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.[15][1][2][17] The ridge segment between Taitao and Darwin transform faults are currently located near the Chile Trench and collide with the South American plate.[1][3]


The presence of slab window underneath southern South America Plate has been proven by the research which aims at determining the lithosphere and upper mantle structure proximate to the Chile Ridge.[3] An intraplate seismic gap is recorded which coincides with the Patagonian slab window location.[14][8] 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. [3]

 
Fig-6 This figure shows the slab window caused by the subduction of Chile ridge, slab window also brings about a seismic gap. The black lines are fault zones (FZ) and the red lines are Chile ridge segments. The dark blue spot is the Chile Triple Junction (CTJ).[16][14] The purple area reveals the Chiloe Microplate and Liquine-Ofqui fault zone is located between the Chiloe Microplate and the main South American Plate.[14][16]

Tectonic Erosion and Emplacement of Ophiolite

Other than 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.[2] 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 the emplacement of ophiolite complex.[13][4]

Chile Triple Junction

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, the Triple junction shifts southwards.[1]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.[2] Since then, the Chile Triple Junction has arrived to its current position in the western Taitao Peninsula.[14] Prior to 10 Ma, Chile Triple Junction reaches the southern Taitao peninsula. Currently, the temperature of Chile Triple Junction below the depth of 10 – 20 km is predicted to be 800 – 900 °C.[18][13]

Ridge Axes

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 the ridge axes.[1]

Fracture Zones

 
Fig-7 This picture shows the several segments of Chile ridge which is divided by numerous transform fault zones. The segment numbers are shown in red words next to the ridge segments. The Chiloe Microplate is located at the east of the Chile ridge and the Liquine-Ofqui fault zone is located between the Chiloe Microplate and the main South American Plate.[9] Figure made with GeoMapApp (www.geomapapp.org)

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.[9][1] 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 the shortest (39 km). [9] 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. [1][8][9]

Segmentation of Chile Ridge

Chile Ridge is divided into a wide range of several short spreading segments which have different lengths and offset distances, in the following section, 7 segments will be discussed.[9][1] 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 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.

 
Fig-8 The contour lines show the hourglass morphology of one of the segments of the Chile Ridge. Below is the cross-section of the Chile Ridge topography.[9]
Hourglass morphology

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 the segment ends are wider. This forms an hourglass morphology. (Fig-8)[9]

Valdivia Fault Zone

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.[4] The Valdivia Fault Zone has caused the offset of the north and south Chile ridge for more than 600 km in the E-W direction. There are six fault zones between the Valdivia Fault Zone.[1]

Summary of the segments of Chile Ridge (Fig-7) [9][1]
Name of the segment Length (km) Number of orders (No. of hourglass) Location relative to the Chile Ridge Morphology
N1 70 First-order Northernmost; Bounded by 1000 km-long transform fault zones in both north and south Asymmetric hourglass,

Ridge-parallel abyssal hills present on both sides of the axial valley

N5 95 First-order Offset east of N1 for 250 km; Bounded by 'pseudofaults' between the southern end of N5 and the northern end of N6, which offset 20 km east Asymmetric hourglass (located in short volcanic chains)
N8 65 First-order Offset east of N9 for 80 km, bounded by a transform fault in N7 in the north, and a transform fault with offset N9 80 km More obvious hourglass (deeper segment center, local minimum is at the shallowest part of the segment)
N9 140 Second-order (N9N and N9S) Offset east of N8 for 80 km, and offset east of N10 for 25 km, N9 are broken into two parts by a non-transform offset (N9N and N9S), bound by the transform offset in the north and a transform offset N9 by 80 km in the south
N9N 110 Bound in the south by NTO which offset east of N9S 8km Two obvious hourglasses (deep, wide axial valley)
N9S 30 Semi-hourglass (shallow hourglass structure)
N10 95 First-order Offset west of N9 for 25km, bounded by a transform fault that offsets west of N9 in the north, and Valdivia fracture Zone in the south which offset 600 km in E-W direction Hourglass (decrease in relief towards the spreading center, i.e. middle of the ridge segment)
V4 20 First-order In the Valdivia Fracture zone, bounded by N10 and S5 transform fault segments in the north and south, segment lengths are very short /
S5 115 Second-order (S5N and S5S) Bounded by Valdivia Fracture Zone transform fault in the north, and a transform fault in the south that offset next segment 60 km eastward Hourglass
S5N 70 Hourglass
S5S 45 More obvious hourglass (inside corner of southern section is more shallow than the outside corner)

Interaction between Chile Ridge and Chile Trench

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 the ridge converges with the trench.[13][8][14]

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.[8] 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 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/m2) related to the Chile ridge subduction in the lower part of the trench.[8] 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 is shown from the north to the south of the Triple Junction.[8] Also, the hypothesized conductive heat flow is consistent with the heat flow data from BSR.[8][12]

Importance of the spreading ridge subduction

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 the melting of deep oceanic crust.[4] 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.[4]

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 the same.[4] Therefore, the Chile Ridge subduction is not conformable with the uniformitarian principle (geological process happened now is the same with that in the past).[19]

Other example of spreading ridge subduction

The Kula-Farallon/Resurrection ridge subduction

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.[4] The ridge subduction controls the magmatism of the North American boundary.[4]

See also

References

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  2. ^ a b c d e f g h i j k l m n o p q r s t u v w Ramírez de Arellano, Cristóbal; Calderón, Mauricio; Rivera, Huber; Valenzuela, Mauricio; Fanning, C. Mark; Paredes, Eliot (October 2021). "Neogene Patagonian magmatism between the rupture of the Farallon plate and the Chile Ridge subduction". Journal of South American Earth Sciences. 110: 103238. Bibcode:2021JSAES.11003238R. doi:10.1016/j.jsames.2021.103238. ISSN 0895-9811.
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  4. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa Bourgois, Jacques; Lagabrielle, Yves; Martin, Hervé; Dyment, Jérôme; Frutos, Jose; Cisternas, Maria Eugenia (2016), A Review on Forearc Ophiolite Obduction, Adakite-Like Generation, and Slab Window Development at the Chile Triple Junction Area: Uniformitarian Framework for Spreading-Ridge Subduction, Pageoph Topical Volumes, Cham: Springer International Publishing, pp. 3217–3246, doi:10.1007/978-3-319-51529-8_2, ISBN 978-3-319-51528-1, retrieved 2021-11-10
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  9. ^ a b c d e f g h i j k l m n Howell, Samuel M.; Ito, Garrett; Behn, Mark D.; Martinez, Fernando; Olive, Jean‐Arthur; Escartín, Javier (June 2016). "Magmatic and tectonic extension at the Chile Ridge: Evidence for mantle controls on ridge segmentation". Geochemistry, Geophysics, Geosystems. 17 (6): 2354–2373. Bibcode:2016GGG....17.2354H. doi:10.1002/2016gc006380. ISSN 1525-2027. S2CID 53126550.
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  11. ^ Steel, Ron; Gloppen, Tor Gunnar (1980-09-11). "Late Caledonian (Devonian) Basin Formation, Western Norway: Signs of Strike‐Slip Tectonics during Infilling". Sedimentation in Oblique-Slip Mobile Zones: 79–103. doi:10.1002/9781444303735.ch6. ISBN 9780632006076.
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  19. ^ Society, National Geographic (2020-01-27). "Uniformitarianism". National Geographic Society. Retrieved 2021-11-12.

chile, ridge, also, known, chile, rise, submarine, oceanic, ridge, formed, divergent, plate, boundary, between, nazca, plate, antarctic, plate, extends, from, triple, junction, nazca, pacific, antarctic, plates, southern, coast, chile, easy, recognize, ridge, . The Chile Ridge also known as the Chile Rise is a submarine oceanic ridge formed by the divergent plate boundary between the Nazca Plate and the Antarctic Plate It extends from the triple junction of the Nazca Pacific and Antarctic plates to the Southern coast of Chile 1 2 The Chile Ridge is easy to recognize on the map as the ridge is divided into several segmented fracture zones which are perpendicular to the ridge segments showing an orthogonal shape toward the spreading direction The total length of the ridge segments is about 550 600 km 1 Fig 1 Map of the Chile ridge in the Pacific Ocean The red line and red letters CR represents Chile ridge The ridge is divided into numerous segments of the fault line indicated by black lines FZ means fracture zone The pink arrows indicate the direction of the Nazca Plate and Antarctic Plate movements as well as their rate of migration They show that the Nazca Plate is moving in an ENE direction which is oblique to the boundary with the South American Plate while the Antarctica Plate is moving in an E W direction which is almost perpendicular to the plate boundary In addition the Nazca Plate migrates over four times faster than the Antarctica Plate The dark purple circle shows the Taitao Peninsula where the Chile ridge collides to the South American Plate The yellow line shows the plate boundary 1 The continuously spreading Chile Ridge collides with the southern South America Plate to the east and the ridge has been subducting underneath the Taitao Peninsula since 14 million years ago Ma 1 2 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 the separating Chile ridge 2 1 3 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 4 2 In addition the subduction of the Chile Ridge also creates Taitao granite in Taitao Peninsula which appeared as plutons 2 5 The Chile Ridge involves spreading ridge subduction which is worth studying because it explains how the Archean continental crust initiation formed from deep oceanic crust 4 Contents 1 History 2 Regional geology 2 1 Geology of the Chile ridge 2 1 1 Taitao Granites Adakite like rocks in Late Miocene 2 1 1 1 Characteristics of Taitao Granites 2 1 2 Taitao Ophiolite pillow lava sheeted dikes gabbro ultramafic rocks in Late Miocene 2 1 2 1 Characteristics of Taitao Ophiolite 2 2 Bathymetry 3 The Chile Ridge movement 3 1 The spreading of the Chile Ridge 3 2 Migration and subduction of the Chile ridge 3 3 Associated seismicity 3 3 1 Chiloe Microplate 3 3 2 Seismicity of Liquine Ofqui fault system in the Aysen Region 3 3 3 Seismicity of the Patagonian Slab Window 4 Geological Formation related to the Chile Ridge Movement 4 1 Consequence of the Subduction of the Chile Ridge 4 2 Patagonia Slab Window 4 3 Tectonic Erosion and Emplacement of Ophiolite 4 4 Chile Triple Junction 4 5 Ridge Axes 4 6 Fracture Zones 4 6 1 Segmentation of Chile Ridge 4 6 1 1 Hourglass morphology 4 6 1 2 Valdivia Fault Zone 5 Interaction between Chile Ridge and Chile Trench 6 Importance of the spreading ridge subduction 6 1 Other example of spreading ridge subduction 6 1 1 The Kula Farallon Resurrection ridge subduction 7 See also 8 ReferencesHistory EditFrom approximately 3 14 million years ago a series of trenches collided the Chile Trench forming what is part of the Chile Ridge citation needed In the 2010 Concepcion earthquake an 8 8 magnitude struck the ridge citation needed Regional geology EditGeology of the Chile ridge Edit The geology of the Chile ridge is closely related to the geology of the Taitao Peninsula East of the Chile ridge This is because the Chile ridge subducts beneath the Taitao Peninsula which give rise to unique lithologies there 4 5 The lithological units would be discussed from youngest to oldest and Taitao Granites and Taitao Ophiolite would be our main focus Taitao Granites Adakite like rocks in Late Miocene Edit Adakite magmatism is formed by the melting of the Nazca Plate s trailing edge 2 Due to the subduction of the Chile Ridge beneath the South American Plate there were intrusive magmatism which generates granite 4 This is also formed by the partial melting of the subducted oceanic crust 4 5 The young Nazca crust less than 18 Myr old are warmer so that the metamorphosed subducted basalts are melted 5 4 In normal mid oceanic ridge the presence of volitiles like water also reduces the solidus temperature 4 However in Chile Ridge there 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 4 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 4 Characteristics of Taitao Granites Edit Fig 2 shows the geology of the Taitao Peninsula Taitao granites and Taitao ophiolites would be mainly focused on in this part Chile ridge is located west of the Taitao Peninsula and the geology of Chile Ridge is closely associated with that of Taitao Peninsula 5 6 4 Adakite is a felsic to intermediate rock and are usually Calc alkaline in composition It is also silica rich 2 The partial melting causes the alteration of the subducted basalts into eclogite and amphibolite which contains garnet 4 Taitao Ophiolite pillow lava sheeted dikes gabbro ultramafic rocks in Late Miocene Edit Main article Taitao ophiolite Along the axis in the Chile ridge magmatic rocks which are mafic to ultramafic are emplaced 4 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 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 2 7 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 4 7 There are also recent activities of acidic magmas in the Taitao Peninsula which allows the comparison between the past composition and current composition history of the magma can be determined 2 8 Characteristics of Taitao Ophiolite Edit 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 2 9 The thermal configuration and 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 2 Due to the subduction of oceanic ridges Chile Ridge beneath the South American plate which has occurred since 16 Ma this caused the alteration in the thermal configuration and the geometry of the sub arc mantle wedge creating a distinct chemical composition of magma generations 2 That means by understanding the composition of the magma specific conditions of subduction systems can be known 2 This has found that the slab window produced by the subduction of the ridge causes the generation of Alkaline basalts The ridge trench convergence and slab window generation aids the emplacement of the Alkaline basalts 2 6 Summary of the geology in Chile ridge 2 Age of the rocks Kinds of magmatism Rock type Subduction settings CompositionHolocene Conglomerate Variable compositions rock fragments from Taitao granites ophiolite Late Miocene 3 92 Ma 5 12 Ma Arc magmatism Taitao Granites low extent partial melting of the altered basalt from the trailing edge of Nazca Plate in a hot subduction event beneath the volcanic arc intermediate to felsic calc alkaline adakites high Sr Y and La Yb ratioLate Miocene 5 19 Ma Arc magmatism Taitao Ophiolite obduction and uplift of the Nazca Plate produced due to the convergence of the overriding South America Plate and the Chile ridge causing low pressure metamorphism mafic to ultramafic olivine and pyroxenePre Jurassic Meta sedimenary basement Bathymetry Edit Bathymetry of the Chile ridge is inspected which is the submarine topography that studies the depths of landforms under the water level 10 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 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 the further the abyssal hill to the ridge axis the older the age it is 9 The Chile Ridge movement Edit Fig 3 shows a close up view of the spreading Chile Ridge With difference relative plane motion of Nazca Plate and Antarctica plate this creates an extensional force for sea floor spreading to carry out 11 Fig 4 shows the Evolutionary diagram of the Chile Ridge Movement The magmatism of under Taitao Peninsula from about 6 Ma to 5 7 5 1 Ma is shown CTJ stands for Chile Tripple Junction A The ridge is located at the edge of the Chile Trench the Magma chambers developed and cause the upwelling of the ophiolite onto the surface of the spreading ridge Cabo Raper pluton is also shown in the diagram B The old magma chamber is pushed away by the new magma chamber Some ophiolite was also formed when the Nazca plate obducted and uplift A new magma chamber was generated The Chile Ridge segment subducts beneath the South American Plate 5 4 The spreading of the Chile Ridge Edit The Chile Ridge is formed by the divergence of the Nazca and Antarctica plates 4 It is spreading actively at the rate of about 6 4 7 0 cm year since 5 Ma to present 4 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 2 According to the results from space geodetic observations Nazca South America converges four times faster than that of Antarctica South America 1 9 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 the Chile Ridge 4 Plate motion of Nazca plate and Antarctica plate 9 2 1 Name of the Plate Direction of movement Rate of movementNazca plate N77 E ENE 6 6 8 5 cm yearAntarctica plate N100 E ESE 1 85 cm yearMigration and subduction of the Chile ridge Edit The subduction of the ridge started is an oblique subduction with 10 12 oblique to the Chile trench since 14 Ma 4 which subducts beneath the southeastern Southern Patagonia 1 4 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 the South American Plate 1 Due to the difference in the convergence rate the formation of a slab window is favoured 1 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 1 The experimental results from the magnetic anomalies within the oceanic crust suggest that about in 14 10 Ma late Miocene some of the Chile Ridge segments were subducted beneath the Southern Patagonian Peninsula located between 48 to 54 S subsequently 2 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 to 48 S 2 1 The above findings have proven that Chile Ridge has been encountered a northward migration 2 9 4 Thus it has been found that 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 1 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 9 Associated seismicity Edit In the Chile Ridge Subduction Project CRSP seismic stations are deployed in the Chile Triple Junction CTJ 12 The tectonic activity and seismicity are mainly driven by the subduction of Chile Ridge 13 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 14 3 15 Moderate to high offshore seismicities for magnitude higher than 4 is detected in the segmented Chile Ridge as well as the transform faults 12 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 Liquine Ofqui fault system 14 13 16 Chiloe Microplate Edit This is a tiny plate between Nazca Plate and South American Plate it locates east of 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 16 Seismicity of Liquine Ofqui fault system in the Aysen Region Edit The Liquine Ofqui fault system is a right lateral strike slip fault separating Chiloe Microplate and the South America Plate 13 The northward migration of Chiloe Microplate along the Liquine Ofqui fault creates the Golfo de Penas basin in the late Miocene period 16 The Liquine Ofqui fault is a fast slipping fault with a geodetic rate of 6 8 28 mm yr 16 Intraplate seismicity has mainly been taken place in this fault system Also enormous stress from the Nazca Plates and South America Plate collision has accumulated along the fault system 16 13 Throughout history only limited seismic studies have been conducted in the Aysen Region southern Chile There is only an event of seismic magnitude higher than 7 happening in 1927 13 This hinders the finding in seismicity near the Chile Ridge Nevertheless in 2007 the Liquine 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 16 Recently 274 seismic events have been detected in 2004 2005 16 Seismicity of the Patagonian Slab Window Edit There is an intraplate seismicity gap between 47 to 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 16 14 Fig 5 Frequency values of strike slip faulting of different regions 16 Regions where the seismicity is concentrated depth of focus km magnitude of seismic event Orientation of the maximum compressional stressNorth of the Chile Triple Junction intraplate seismic events concentrated along Liquine Ofqui fault system 4 21 1 5 6 ENE WSW oblique to the continental margin of South American Plate of N10 South of the Chile Triple Junction between 46 5 50 S seismic events sparsely populated in Southern Patagon 12 15 5 ESE WNWGeological Formation related to the Chile Ridge Movement EditConsequence of the Subduction of the Chile Ridge Edit Patagonia Slab Window Edit Fig 5 This sketch shows the cross section of the slab window The Nazca plate and Antarctic Plate is colliding with South American Plate 3 The most obvious impact of 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 a very little amount of magma is produced underneath the slab window 3 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 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 15 1 2 17 The ridge segment between Taitao and Darwin transform faults are currently located near the Chile Trench and collide with the South American plate 1 3 The presence of slab window underneath southern South America Plate has been proven by the research which aims at determining the lithosphere and upper mantle structure proximate to the Chile Ridge 3 An intraplate seismic gap is recorded which coincides with the Patagonian slab window location 14 8 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 3 Fig 6 This figure shows the slab window caused by the subduction of Chile ridge slab window also brings about a seismic gap The black lines are fault zones FZ and the red lines are Chile ridge segments The dark blue spot is the Chile Triple Junction CTJ 16 14 The purple area reveals the Chiloe Microplate and Liquine Ofqui fault zone is located between the Chiloe Microplate and the main South American Plate 14 16 Tectonic Erosion and Emplacement of Ophiolite Edit Other than 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 2 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 the emplacement of ophiolite complex 13 4 Chile Triple Junction Edit 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 the Triple junction shifts southwards 1 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 2 Since then the Chile Triple Junction has arrived to its current position in the western Taitao Peninsula 14 Prior to 10 Ma Chile Triple Junction reaches the southern Taitao peninsula Currently the temperature of Chile Triple Junction below the depth of 10 20 km is predicted to be 800 900 C 18 13 Ridge Axes Edit 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 the ridge axes 1 Fracture Zones Edit Fig 7 This picture shows the several segments of Chile ridge which is divided by numerous transform fault zones The segment numbers are shown in red words next to the ridge segments The Chiloe Microplate is located at the east of the Chile ridge and the Liquine Ofqui fault zone is located between the Chiloe Microplate and the main South American Plate 9 Figure made with GeoMapApp www geomapapp org 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 9 1 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 the shortest 39 km 9 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 1 8 9 Segmentation of Chile Ridge Edit Chile Ridge is divided into a wide range of several short spreading segments which have different lengths and offset distances in the following section 7 segments will be discussed 9 1 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 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 Fig 8 The contour lines show the hourglass morphology of one of the segments of the Chile Ridge Below is the cross section of the Chile Ridge topography 9 Hourglass morphology Edit 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 the segment ends are wider This forms an hourglass morphology Fig 8 9 Valdivia Fault Zone Edit Main article Valdivia Fracture Zone 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 4 The Valdivia Fault Zone has caused the offset of the north and south Chile ridge for more than 600 km in the E W direction There are six fault zones between the Valdivia Fault Zone 1 Summary of the segments of Chile Ridge Fig 7 9 1 Name of the segment Length km Number of orders No of hourglass Location relative to the Chile Ridge MorphologyN1 70 First order Northernmost Bounded by 1000 km long transform fault zones in both north and south Asymmetric hourglass Ridge parallel abyssal hills present on both sides of the axial valleyN5 95 First order Offset east of N1 for 250 km Bounded by pseudofaults between the southern end of N5 and the northern end of N6 which offset 20 km east Asymmetric hourglass located in short volcanic chains N8 65 First order Offset east of N9 for 80 km bounded by a transform fault in N7 in the north and a transform fault with offset N9 80 km More obvious hourglass deeper segment center local minimum is at the shallowest part of the segment N9 140 Second order N9N and N9S Offset east of N8 for 80 km and offset east of N10 for 25 km N9 are broken into two parts by a non transform offset N9N and N9S bound by the transform offset in the north and a transform offset N9 by 80 km in the southN9N 110 Bound in the south by NTO which offset east of N9S 8km Two obvious hourglasses deep wide axial valley N9S 30 Semi hourglass shallow hourglass structure N10 95 First order Offset west of N9 for 25km bounded by a transform fault that offsets west of N9 in the north and Valdivia fracture Zone in the south which offset 600 km in E W direction Hourglass decrease in relief towards the spreading center i e middle of the ridge segment V4 20 First order In the Valdivia Fracture zone bounded by N10 and S5 transform fault segments in the north and south segment lengths are very short S5 115 Second order S5N and S5S Bounded by Valdivia Fracture Zone transform fault in the north and a transform fault in the south that offset next segment 60 km eastward HourglassS5N 70 HourglassS5S 45 More obvious hourglass inside corner of southern section is more shallow than the outside corner Interaction between Chile Ridge and Chile Trench EditGeophysical 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 the ridge converges with the trench 13 8 14 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 8 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 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 m2 related to the Chile ridge subduction in the lower part of the trench 8 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 is shown from the north to the south of the Triple Junction 8 Also the hypothesized conductive heat flow is consistent with the heat flow data from BSR 8 12 Importance of the spreading ridge subduction EditUnderstanding 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 the melting of deep oceanic crust 4 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 4 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 the same 4 Therefore the Chile Ridge subduction is not conformable with the uniformitarian principle geological process happened now is the same with that in the past 19 Other example of spreading ridge subduction Edit The Kula Farallon Resurrection ridge subduction Edit 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 4 The ridge subduction controls the magmatism of the North American boundary 4 See also EditChile Triple Junction Fault zones Liquine Ofqui fault Mid ocean ridge Ophiolites Peru Chile Trench Slab Window Subduction Taitao Peninsula Valdivia Fault ZoneReferences Edit a b c d e f g h i j k l m n o p q r s t u v Tebbens S F Cande S C Kovacs L Parra J C LaBrecque J L Vergara H 1997 06 10 The Chile ridge A tectonic framework Journal of Geophysical Research Solid Earth 102 B6 12035 12059 Bibcode 1997JGR 10212035T doi 10 1029 96jb02581 ISSN 0148 0227 a b c d e f g h i j k l m n o p q r s t u v w Ramirez de Arellano Cristobal Calderon Mauricio Rivera Huber Valenzuela Mauricio Fanning C Mark Paredes Eliot October 2021 Neogene Patagonian magmatism between the rupture of the Farallon plate and the Chile Ridge subduction Journal of South American Earth Sciences 110 103238 Bibcode 2021JSAES 11003238R doi 10 1016 j jsames 2021 103238 ISSN 0895 9811 a b c d e f g Russo R M VanDecar John C Comte Diana Mocanu Victor I Gallego Alejandro Murdie Ruth E 2010 Subduction of the Chile Ridge Upper mantle structure and flow GSA Today 4 10 doi 10 1130 gsatg61a 1 ISSN 1052 5173 a b c d e f g h i j k l m n o p q r s t u v w x y z aa Bourgois Jacques Lagabrielle Yves Martin Herve Dyment Jerome Frutos Jose Cisternas Maria Eugenia 2016 A Review on Forearc Ophiolite Obduction Adakite Like Generation and Slab Window Development at the Chile Triple Junction Area Uniformitarian Framework for Spreading Ridge Subduction Pageoph Topical Volumes Cham Springer International Publishing pp 3217 3246 doi 10 1007 978 3 319 51529 8 2 ISBN 978 3 319 51528 1 retrieved 2021 11 10 a b c d e f Anma Ryo Armstrong Richard Orihashi Yuji Ike Shin ichi Shin Ki Cheol Kon Yoshiaki Komiya Tsuyoshi Ota Tsutomu Kagashima Shin ichi Shibuya Takazo November 2009 Are the Taitao granites formed due to subduction of the Chile ridge Lithos 113 1 2 246 258 Bibcode 2009Litho 113 246A doi 10 1016 j lithos 2009 05 018 hdl 2241 104215 ISSN 0024 4937 a b Veloso Eugenio E Anma Ryo Yamaji Atsushi January 2009 Ophiolite Emplacement and the Effects of the Subduction of the Active Chile Ridge System Heterogeneous 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