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M Santosh - One of the best experts on this subject based on the ideXlab platform.
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neoarchean Convergent Margin tectonics associated with microblock amalgamation in the north china craton evidence from the yishui complex
Gondwana Research, 2016Co-Authors: M Santosh, Kuang Cen, Xueming TengAbstract:Abstract Archean tectonic history of the North China Craton (NCC) involved complex processes of amalgamation of microcontinents along multiple subduction zones prior to the consolidation of the major crustal blocks and their assembly into unified cratonic architecture. Here we report a suite of granitoids, diabase, metabasalts, volcanic tuff, banded iron formations and quartzite from the Yishui Complex along the southern Margin of the Jiaoliao microblock within the Eastern Block of the NCC. The geochemical features of the magmatic suite are consistent with calc-alkaline magmatism in a Convergent Margin setting. In tectonic discrimination diagrams, the mafic suite shows variable IAB, MORB and OIB affinities typical of rocks formed in an arc-related subduction environment. Zircon grains in most of the rocks from Yishui Complex display core–rim texture with the cores showing magmatic crystallization and the narrow structureless rims corresponding to metamorphic overgrowth. The 207Pb/206Pb ages of magmatic zircons show 2504 ± 19 Ma for the volcanic tuff, 2581 ± 21 Ma for the granitoid, 2501 ± 19 Ma for the metavolcanics, 2537 ± 38 Ma for the pyroxenite, and 2506 ± 13 Ma for the diabase. Metamorphism is constrained from the 2451 ± 18 Ma and 2466 ± 23 Ma age groups in the metavolcanics and (meta-) pyroxenites. Zircons from BIF show multiple population with the oldest showing a spot age of 2503 Ma, followed by a number of distinct groups of Paleoproterozoic zircons corresponding to later thermal events. The oldest population of magmatic zircons from the quartzite shows 207Pb/206Pb mean age of 2495 ± 24 Ma. The dominantly positive eHf(t) values of the magmatic zircons from the Yishui suite are broadly consistent with a depleted mantle source with only minor input of crustal components. Their Hf crustal residence ages (TDMC) range from 2586 to 3181 Ma and Hf depleted mantle model ages (TDM) are in the range of 2548–2927 Ma. The data indicate that magma production involved Meso- to Neoarchean juvenile sources within a continental arc setting, suggesting the Jiaoliao microblock as one of the ancient continental nuclei in the NCC. We trace the continuity of a Neoarchean subduction system along the western and southern Margins of the Jiaoliao microblock with convergence of the Qianhuai and Xuhuai microblocks towards the Jiaoliao microblock with subduction–accretion–collision during the Archean–Proterozoic transition.
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mesoarchean Convergent Margin processes and crustal evolution petrologic geochemical and zircon u pb and lu hf data from the mercara suture zone southern india
Gondwana Research, 2016Co-Authors: T Amaldev, M Santosh, Toshiaki Tsunogae, Li Tang, K R Baiju, M SatyanarayananAbstract:Abstract The Mercara Shear Zone is sandwiched between the Western Dharwar Craton and the Coorg Block in the Southern Granulite Terrain of India, and is marked by steep gravity gradients interpreted to suggest the presence of underplated high-density material in the lower crust. Here we present geological, petrological and geochemical data, together with zircon U–Pb ages and Lu–Hf isotopes from a suite of metaigneous (TTG-related gneisses, charnockite, metagabbro, mafic granulite) and metasedimentary (quartz mica schist, khondalite, garnet biotite gneiss, kyanite–sillimanite bearing metapelite) rocks from this zone. Geochemical data on the magmatic suite suggests formation through subduction-related arc magmatism, whereas the metasediments represent volcano-sedimentary trench sequences. Phase equilibrium modeling of mafic granulites from the Mercara Shear Zone suggests P–T range of 10–12 kbar at 700 °C to 900 °C. The zircon data yield weighted mean 207Pb/206Pb ages of 3229 ± 80 Ma for metagabbro, 3168 ± 25 Ma for the charnockite, and 3181 ± 20 Ma for the mafic granulite. Ages ranging from 3248 ± 28 Ma to 3506 ± 26 Ma were obtained from zircons in the kyanite/sillimanite bearing metapelite, 3335 ± 44 Ma from khondalite, 3135 ± 14 Ma from garnet biotite gneiss, 3145 ± 17 Ma to 3292 ± 57 Ma from quartz mica schist and 3153 ± 15 Ma to 3252 ± 36 from TTG gneiss. The tightly defined ages of 3.1 to 3.2 Ga from igneous zircons in the magmatic suite suggest prominent Mesoarchean Convergent Margin magmatism. The timing of high grade metamorphism as constrained from metamorphic overgrowths in zircons is ca. 3.0 Ga which might mark the collisional event between the Western Dharwar Craton and the Coorg Block. Hf isotope features suggest magma derivation mostly from juvenile sources and the Lu–Hf model ages indicate that the crust building might have also involved partial recycling of basement rocks as old as ca. 3.8 Ga. Our study defines the Mercara Shear Zone as a terrane boundary, and possible Mesoarchean suture along which the Coorg Block was accreted to the Western Dharwar Craton. The accretion of these continental fragments might have coincided with the birth of the oldest supercontinent “Ur”.
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early to late neoproterozoic magmatism and magma mixing mingling in sri lanka implications for Convergent Margin processes during gondwana assembly
Gondwana Research, 2016Co-Authors: M Santosh, Toshiaki Tsunogae, Sanjeewa P K MalaviarachchiAbstract:Abstract The Sri Lankan fragment of Gondwana preserves the records of Neoproterozoic tectonothermal events associated with the final assembly of the supercontinent. Here we investigate a suite of magmatic rocks from the Wanni, Kadugannawa and Highland Complexes through geological, petrological, geochemical and zircon U–Pb and Lu–Hf isotopic techniques. The hornblende biotite gneiss, charnockites, metagabbro and metadiorites investigated in this study show geochemical features consistent with calc-alkaline affinity and subduction-related signature including LILE enrichment relative to HFSE coupled with distinct Nb–Ta depletion and weak negative Zr–Hf anomalies. The felsic suite falls in the volcanic arc granites (VAGs) field and the mafic suite shows island arc basalt affinity in tectonic discrimination plots, suggesting that the protoliths of the rocks were derived from arc-related magmas in a Convergent Margin setting. LA-ICPMS zircon U–Pb analyses show crystallization of charnockite and dioritic mafic magmatic enclave from the Highland Complex during ca. 565 and 576 Ma corresponding to bimodal magmatism. The diorite also contains metamorphic zircons of ca. 525 Ma. Hornblende–biotite gneiss from the Kadugannawa Complex shows protolith emplacement age at 973–980 Ma, followed by new zircon growth during repeated thermal events through late Neoproterozoic. The dioritic enclaves in these rocks are much younger, and form part of a deformed and metamorphosed dyke suite with emplacement ages of 559 Ma, broadly coeval with the bimodal magmatism in the Highland Complex at that time. The youngest group of zircons in this rock shows ages of 508 Ma, corresponding to the latest thermal event. A charnockite from this locality shows oldest group of zircons at 962 Ma, corresponding to emplacement age similar to that of the magmatic protolith of the hornblende biotite gneiss. This rock also shows zircon growth during repeated thermal events at 832 Ma, 780 Ma, 721 Ma and 661–605 Ma. The lower intercept age of 543 Ma marks the timing of collisional metamorphism. Charnockite from the Wanni Complex shows emplacement age at 1000 Ma, followed by thermal event at 570 Ma, the latter correlating with the bimodal magmatic event in the Highland Complex. The dioritic enclave within this charnockite shows an age of ca. 980 Ma, suggesting intrusion of mafic magma into the felsic magma chamber. Zircons in the diorite also record multiple zircon events during 950 to 750 Ma. Zircons in the Highland Complex charnockite possess negative eHf(t) values in the range − 6.7 to − 12.6 with TDMC of 2039–2306 Ma suggesting magma derivation through melting of Paleoproterozoic source. In contrast, the eHf(t) range of − 11.1 to 1.6 suggests a mixed source of both of older crustal and juvenile material. The eHf(t) values of − 4.5 to 4.5 and TDMC of 1546–1962 Ma for the hornblende biotite gneiss also shows magma derivation from mixed sources that included Paleoproterozoic components. The younger dioritic intrusive, however, has a more juvenile magma source as indicated by the mean eHf(t) value of 1.3. The associated charnockite shows a tight positive cluster of eHf(t) from 0.6 to 5.1, suggesting juvenile input. Charnockite from the Wanni Complex shows clearly positive eHf(t) values of up to 13.1, and TDMC in the range 937–1458 Ma suggesting much younger and depleted mantle source. The diorite enclave also has positive eHf(t) values with an average value of 8.5 and TDMC in the range of 709–1443 Ma clearly suggesting younger juvenile sources. The early and late Neoproterozoic bimodal suites are correlated to Convergent Margin magmatism associated with the assembly of Sri Lanka within the Gondwana supercontinent.
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precambrian iron formations from the cauvery suture zone southern india implications for sub marine hydrothermal origin in neoarchean and neoproterozoic Convergent Margin settings
Ore Geology Reviews, 2016Co-Authors: T Yellappa, T R K Chetty, M SantoshAbstract:Abstract Thick horizons of iron formations including Banded Iron Formations (BIFs) and Banded Silicate Formations (BSFs) occur as E–W trending bands in the eastern part of Cauvery Suture Zone (CSZ) in the Sothern Granulite Terrane of India. Some of these occur in close association with the Neoarchean-Neoproterozoic suprasubduction zone complexes, where as some others are associated with metamorphosed accretionary sequences including pyroxene granulites and other high grade rocks. The iron formations are highly deformed and metamorphosed under amphibolite to granulite facies conditions and are composed of quartz–magnetite–hematite–goethite–garnet–pyrite together with grunerite and pyroxene. Here we report the geochemical characteristics of twenty representative samples from the iron formations that reveal a widely varying composition with Fe2O3(t) (22–65 wt.% as total iron) total- Fe2O3/TiO2 (205–6532), MnO/TiO2 (0.25–12.66) and SiO2 (33–85 wt.%), broadly representing the two types of iron formations. These formations also show very low Al/(Al + Fe + Mn) ratio (0.001–0.01), Al2O3 (0.07–0.76 wt.%), Al2O3/TiO2 ratio (2.7–21), MgO (0.01–4.41 wt.%), CaO (0.1–1.24 wt.%), Na2O (0.01–0.05 wt.%) and K2O (0.01 wt.%) together with low total REE (3.38–31.63 ppm). The trace and REE elemental distributions show wide variation with high Ni (274 ppm), and Zn contents (up to 87 ppm) when compared to mafic volcanics of the adjoining areas. Tectonic discrimination plots indicate that the iron formations of the Cauvery Suture Zone are of hydrothermal origin. Their chondrite normalized patterns show slight positive Eu anomaly (Eu/Eu* = up to 1.77) and relatively less fractionation of REE with slight LREE enrichment compared to HREE. However, the PAAS (Post Archean Average of Australian Sediments) normalized REE patterns display significant positive Eu anomaly (Eu/Eu* up to 2.32) with well represented negative Ce anomalies (Ce/Ce* = 0.66–1.28). The above results together with petrological characteristics and available geochronology of the associated lithologies suggest that the iron formations can be correlated to Algoma-type. The Fe and Si were largely supplied by medium to high temperature sub-marine hydrothermal systems in Neoarchean and Neoproterozoic Convergent Margin settings.
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Convergent Margin magmatism and crustal evolution during archean proterozoic transition in the jiaobei terrane zircon u pb ages geochemistry and nd isotopes of amphibolites and associated grey gneisses in the jiaodong complex north china craton
Precambrian Research, 2015Co-Authors: Houxiang Shan, M Santosh, Mingguo Zhai, Elson P Oliveira, Fang WangAbstract:Abstract Mafic metavolcanic rocks and grey gneisses are the dominant components of many Archean terranes and preserve significant imprints and information of the crustal evolution. Here we present in situ zircon U–Pb geochronology, whole-rock geochemistry and Nd isotopes of the amphibolites and associated grey gneisses in the drill holes from the Jiaobei terrane, North China Craton. The LA-ICP-MS zircon U–Pb data show that the magmatic protoliths of two amphibolites and two grey gneisses crystallized at 2457–2503 Ma followed by the metamorphism at ∼1.8–1.9 Ga. These rocks exhibit heterogeneous whole-rock Nd isotopic compositions, with the most radiogenic analyses (ɛ Nd ( t ) = +3.8 to +6.9) plotting on or close to the depleted mantle evolution array and the most unradiogenic ɛ Nd ( t ) extending down to −2.4. The data suggest that both ∼2.5 Ga depleted mantle and ancient continental crust at least as old as 3.05 Ga contributed to the magma source. In combination with previous zircon Hf isotopic data, it is suggested that the ∼2.5–2.6 Ga magmatic events in the entire Jiaobei terrane were mostly derived from the reworking of the pre-existing ∼2.7–2.8 Ga crustal material. However, large variations in Hf–Nd isotopic compositions of abundant rocks at ∼2.5 Ga and ∼2.7–2.8 Ga in the Jiaobei terrane were likely to have resulted from interaction of mantle-derived juvenile magma with ancient crustal materials in the source region. Thus, the peaks of zircon Hf crustal model ages from these rocks do not represent the actual time of crustal growth, but could be artifacts of interaction of magmas from different sources. Geochemical features show that the protoliths of the amphibolites are tholeiitic basalts and can be subdivided into two groups: high-Mg tholeiite basalts (Group I) and high-Fe tholeiite basalts (Group II). Trace element systematics indicate that the Group I amphibolites show good affinity to subduction-related tholeiitic arc basalts, whereas the Group II amphibolites represent back-arc lavas modified by subduction components. The two groups of amphibolites and associated grey gneisses collectively define an arc-back-arc tectonic setting in the study area at ∼2.5 Ga. Integrated with the previous data from other areas in Jiaobei, it can be inferred that Archean-Proterozoic transition in the whole Jiaobei terrane witnessed subduction-related magmatism in a Convergent Margin.
Cesar R Ranero - One of the best experts on this subject based on the ideXlab platform.
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overriding plate structure of the nicaragua Convergent Margin relationship to the seismogenic zone of the 1992 tsunami earthquake
Geochemistry Geophysics Geosystems, 2013Co-Authors: Valenti Sallares, Cesar R Ranero, Kirk D Mcintosh, Adria Melendez, Manuel Prada, Ingo GrevemeyerAbstract:We present 2-D seismic velocity models and coincident multichannel seismic reflection images of the overriding plate and the inter-plate boundary of the Nicaragua Convergent Margin along two wide-angle seismic profiles parallel and normal to the trench acquired in the rupture area of the 1992 tsunami earthquake. The trench-perpendicular profile runs over a seamount subducting under the Margin slope, at the location where seismological observations predict large coseismic slip. Along this profile, the igneous basement shows increasing velocity both with depth and away from the trench, reflecting a progressive decrease in upper-plate rock degree of fracturing. Upper mantle-like velocities are obtained at approximate to 10 km depth beneath the fore-arc Sandino basin, indicating a shallow mantle wedge. A mismatch of the inter-plate reflector in the velocity models and along coincident multichannel seismic profiles under the slope is best explained by approximate to 15% velocity anisotropy, probably caused by subvertical open fractures that may be related to fluid paths feeding known seafloor seepage sites. The presence of a shallow, partially serpentinized mantle wedge, and the fracture-related anisotropy are supported by gravity analysis of velocity-derived density models. The downdip limit of inter-plate seismicity occurs near the tip of the inferred mantle wedge, suggesting that seismicity could be controlled by the presence of serpentinite group minerals at the fault gouge. Near the trench, the inferred local increase of normal stress produced by the subducting seamount in the plate boundary may have made this fault segment unstable during earthquake rupture, which could explain its tsunamigenic character.
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Convergent Margin structure in high quality geophysical images and current kinematic and dynamic models
2009Co-Authors: Roland Von Huene, Cesar R Ranero, Dave SchollAbstract:Understanding the mechanics of Convergent Margins is fundamental to assessing risks from earthquakes and trans-oceanic tsunamis. Marine observations of the past decade have advanced that understanding. A once commonly inferred accreted wedge extending from trench axes to shelves is now resolved into 3 domains of different mechanics in space, that vary during an earthquake cycle. The frontal prism increases weight on subducting materials elevating pore fl uid pressure and reducing interplate friction. The middle prism is moderately stable and merges into the more stable Margin framework of the inner prism beneath the upper slope and shelf. Significant accretion occurs as material from the frontal prism is added to the middle prism. Accretion is common along thickly (>1 km) sedimented trenches and slowly converging Margins. Rapid convergence enhances the effi ciency of sediment subduction and subduction erosion. The subduction channel on the lower plate accepts a fi nite amount of trench sediment and any excess is added to the frontal prism on the upper plate. Erosion beneath the middle slope contributes material to the subduction channel. Erosion and accretion can be coeval, for instance, subducted seamounts erode the upper plate as adjacent sediment accretes. The change in strain during interseismic locking that is released during coseismic slip, changes the dynamics of each segment in time. This helps explain extensional normal faults in a converging plate environment. Recent observations provide information for a unifying framework concept to aid interpretations of both accreting and eroding Margins.
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tectonic processes along the chile Convergent Margin
Ranero Cesar von Huene Roland Weinrebe Reimer Wilhelm and Reichert C. (2006) Tectonic Processes Along the Chile Convergent Margin The Andes - Active s, 2006Co-Authors: Cesar R Ranero, Roland Von Huene, Wilhelm Weinrebe, Christian ReichertAbstract:The Chile subduction zone, spanning more than 3500 km, provides a unique setting for studying, along a single plate boundary, the factors that govern tectonic processes at Convergent Margins. At large scale, the Chile trench is segmented by the subduction of the Chile Rise, an active spreading center, and by the Juan Fernandez hot spot ridge. In addition, the extreme climatic change from the Atacama Desert in the north to the glacially influenced southern latitudes produces a dramatic variability in the volume of sediment supplied to the trench. The distribution of sediment along the trench is further influenced by the high relief gradients of the segmented oceanic lithosphere.
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structure and tectonics of the erosional Convergent Margin off antofagasta north chile 23 30 s
Journal of Geophysical Research, 2005Co-Authors: Valenti Sallares, Cesar R RaneroAbstract:Subduction erosion has dominated the evolution of the north Chile Convergent continental Margin since at least the Mesozoic. We investigate the structure of the Antofagasta (23°S) sector of this Margin along a transect using coincident wide-angle and near-vertical seismic profiling and gravity data. A 2-D velocity field of the overriding and subducting plates was obtained using joint refraction and reflection travel time tomography. A velocity-derived density distribution was used to model marine gravity data and substantiate the velocity model. The gravity and velocity models imply that the overriding plate is mainly made of arc-type igneous basement. The upper plate is constructed of two main rock bodies separated by a subhorizontal layer defined by a velocity inversion, the top coincident with a reflection in near-vertical seismic images. The seismic boundary is interpreted as a detachment separating an upper extended domain with large-scale normal faulting from a lower domain apparently undergoing a different type of deformation. Velocity-derived porosity indicates that the front of the Margin is probably fluid-saturated and disaggregated by fracturation as a consequence of frontal subduction erosion. Fluids carried into the subduction channel within slope debris filling underthrusting grabens reduce basal friction and probably induce hydrofracturing and basal erosion along the underside of the overriding plate. At depths greater than ∼20 km, porosity and density values imply that most fluids have been exhausted and the lower part of the upper plate is structurally coherent and little fractured. The change in physical properties leads to increased mechanical coupling along the plate boundary and occurs at the updip limit of the distribution of aftershocks of the 1995 Antofagasta earthquake (M w = 8.0) defining the seismogenic zone.
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subduction erosion and basal friction along the sediment starved Convergent Margin off antofagasta chile
Journal of Geophysical Research, 2003Co-Authors: Roland Von Huene, Cesar R RaneroAbstract:[1] Subduction erosion is commonly associated with strong interplate coupling and a consequent abrasion of the upper plate. Northern Chile is an often cited example of a strongly coupled erosional Margin. Its crystalline basement is inferred to form a strong upper plate, the trench axis contains little detectable sediment, and the subducting lower plate has a high-relief horst-graben topography. With little water-rich sediment to reduce interplate friction, the high relief of an igneous ocean crust thrust beneath continental basement should generate high friction interplate abrasion. However, a prestack depth-migrated seismic record images slope debris that collects in a frontal prism. This debris, including ∼30% pore fluid, fills subducting grabens and is subsequently incorporated into an ∼1.5-km-thick interplate reflective layer. The subduction zone thrust passes through the upper part of this layer. Interplate seismicity and taper analyses indicate basal friction at levels that are common in sedimented Convergent Margins. The continued growth of lower plate grabens after subduction probably accommodates upper plate material, a process that erodes the upper plate. Erosion is aided by weakening of the upper plate rock framework beneath the continental slope. This erosion undermines the upper plate and tips it seaward thereby steepening the continental slope which induces midslope gravity tectonics. Despite sediment starvation, a frontal prism constructed of remolded slope debris elevates pore pressure to reduce interplate friction. Coeval erosion and prism building control the size of the frontal prism. Processes other than high friction abrasion best explain subduction erosion along northern Chile.
M J Hernandez - One of the best experts on this subject based on the ideXlab platform.
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the esmeraldas canyon a helpful marker of the pliocene pleistocene tectonic deformation of the north ecuador southwest colombia Convergent Margin
Tectonics, 2019Co-Authors: Jeanyves Collot, Gueorgui Ratzov, P Silva, Jeannoel Proust, Sebastien Migeon, M J HernandezAbstract:Deciphering the migration pattern of the Esmeraldas submarine Canyon (EC) and its history of cut‐and‐fill allows constraining the Pliocene‐Pleistocene tectonic evolution of the Ecuador‐Colombia Convergent Margin. Swath bathymetry, multichannel seismic reflection, and chronological data show that the EC is a 143‐km‐long, shelf‐incising, river‐connected canyon that started incising slope apron deposits in the Manglares fore‐arc basin ~5.3 Ma ago. The EC inception appears contemporaneous with the subduction of the Carnegie Ridge that is believed to have initiated 5–6 Myr ago and is considered an indirect cause of the EC formation. During its two‐stage left‐lateral migration, the EC upper‐half scoured deep incisions providing evidences for uplift episodes in the Manglares Basin that are correlated with mid‐Pliocene and Pleistocene regional tectonic events. Glacioeustatic variations contributed significantly to shape the EC and its upslope tributaries by increasing the rate of canyon incision during rapid sea level falls. Faults, folds, and diapirs have structurally controlled the location of the EC and of its tributary canyons, including the Ancon Canyon, which served as the main spillway of the Manglares Basin prior to be cut from its source ~170 kyr ago by the growth of a fault‐related anticline. The Margin wedge that hosts the EC is highly unstable as it is cut by active faults and shaken by large subduction earthquakes. Several mass transport deposits have dammed the EC, one of them between >~65 and ~37 kyr causing an impoverishment of detrital material in the trench sedimentation and a possible interruption of the paleoseismological record.
Bryan Davy - One of the best experts on this subject based on the ideXlab platform.
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rotation and offset of the gondwana Convergent Margin in the new zealand region following cretaceous jamming of hikurangi plateau large igneous province subduction
Tectonics, 2014Co-Authors: Bryan DavyAbstract:Jamming of the Hikurangi Plateau (large igneous province) subduction, within the Chatham Rise Convergent Margin of Gondwana at circa 105 Ma, led to offset and rotation of the Convergent Margin before subduction ceased in the New Zealand region at circa 100 Ma. The southern limit of the plateau, following leading slab break off, is highlighted by a lineament of prominent horst blocks in the southern Bounty Trough. Subduction jamming of the Gondwana Margin, and accompanying compression of the onshore Margin and/or extension of the offshore Margin, has led to two 60 km left-lateral SSE offsets of the Chatham Rise Convergent Margin at the coast and in inland Canterbury. Recognition of the onshore Chatham Rise using the gravity data also highlights the correlation of the inland Chatham Rise and central South Island seismicity. In a similar manner to the rotation of Cretaceous spreading-ridge and transform-fault fabric adjacent to the Osbourn Trough spreading ridge, the convergence direction at the Gondwana Margin was rotated anticlockwise to N-S between 105 and 100 Ma. Most of this rotation has been accommodated by offshore extension and Margin offset. The divergence between the anticlockwise rotation of offshore crustal structure and the jammed onshore Margin led to the development of the Great South Basin at 105–100 Ma. Further offshore in the Bounty Trough, extensional zones, formed between crustal blocks rotated to adjust to a changed Cretaceous direction of subduction, are evident in gravity and seismic profiles.
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hikurangi plateau crustal structure rifted formation and gondwana subduction history
Geochemistry Geophysics Geosystems, 2008Co-Authors: Bryan Davy, Kaj Hoernle, Reinhard WernerAbstract:[1] Seismic reflection profiles across the Hikurangi Plateau Large Igneous Province and adjacent Margins reveal the faulted volcanic basement and overlying Mesozoic-Cenozoic sedimentary units as well as the structure of the paleoConvergent Gondwana Margin at the southern plateau limit. The Hikurangi Plateau crust can be traced 50–100 km southward beneath the Chatham Rise where subduction cessation timing and geometry are interpreted to be variable along the Margin. A model fit of the Hikurangi Plateau back against the Manihiki Plateau aligns the Manihiki Scarp with the eastern Margin of the Rekohu Embayment. Extensional and rotated block faults which formed during the breakup of the combined Manihiki-Hikurangi plateau are interpreted in seismic sections of the Hikurangi Plateau basement. Guyots and ridge-like seamounts which are widely scattered across the Hikurangi Plateau are interpreted to have formed at 99–89 Ma immediately following Hikurangi Plateau jamming of the Gondwana Convergent Margin at ∼100 Ma. Volcanism from this period cannot be separately resolved in the seismic reflection data from basement volcanism; hence seamount formation during Manihiki-Hikurangi Plateau emplacement and breakup (125–120 Ma) cannot be ruled out. Seismic reflection data and gravity modeling suggest the 20-Ma-old Hikurangi Plateau choked the Cretaceous Gondwana Convergent Margin within 5 Ma of entry. Subsequent uplift of the Chatham Rise and slab detachment has led to the deposition of a Mesozoic sedimentary unit that thins from ∼1 km thickness northward across the plateau. The contrast with the present Hikurangi Plateau subduction beneath North Island, New Zealand, suggests a possible buoyancy cutoff range for LIP subduction consistent with earlier modeling.
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hikurangi plateau crustal structure rifted formation and gondwana subduction history
Geochemistry Geophysics Geosystems, 2008Co-Authors: Bryan Davy, Kaj Hoernle, Reinhard WernerAbstract:Seismic reflection profiles across the Hikurangi Plateau Large Igneous Province and adjacent Margins reveal the faulted volcanic basement and overlying Mesozoic-Cenozoic sedimentary units as well as the structure of the paleoConvergent Gondwana Margin at the southern plateau limit. The Hikurangi Plateau crust can be traced 50–100 km southward beneath the Chatham Rise where subduction cessation timing and geometry are interpreted to be variable along the Margin. A model fit of the Hikurangi Plateau back against the Manihiki Plateau aligns the Manihiki Scarp with the eastern Margin of the Rekohu Embayment. Extensional and rotated block faults which formed during the breakup of the combined Manihiki-Hikurangi plateau are interpreted in seismic sections of the Hikurangi Plateau basement. Guyots and ridge-like seamounts which are widely scattered across the Hikurangi Plateau are interpreted to have formed at 99–89 Ma immediately following Hikurangi Plateau jamming of the Gondwana Convergent Margin at ∼100 Ma. Volcanism from this period cannot be separately resolved in the seismic reflection data from basement volcanism; hence seamount formation during Manihiki-Hikurangi Plateau emplacement and breakup (125–120 Ma) cannot be ruled out. Seismic reflection data and gravity modeling suggest the 20-Ma-old Hikurangi Plateau choked the Cretaceous Gondwana Convergent Margin within 5 Ma of entry. Subsequent uplift of the Chatham Rise and slab detachment has led to the deposition of a Mesozoic sedimentary unit that thins from ∼1 km thickness northward across the plateau. The contrast with the present Hikurangi Plateau subduction beneath North Island, New Zealand, suggests a possible buoyancy cutoff range for LIP subduction consistent with earlier modeling.
Reinhard Werner - One of the best experts on this subject based on the ideXlab platform.
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hikurangi plateau crustal structure rifted formation and gondwana subduction history
Geochemistry Geophysics Geosystems, 2008Co-Authors: Bryan Davy, Kaj Hoernle, Reinhard WernerAbstract:[1] Seismic reflection profiles across the Hikurangi Plateau Large Igneous Province and adjacent Margins reveal the faulted volcanic basement and overlying Mesozoic-Cenozoic sedimentary units as well as the structure of the paleoConvergent Gondwana Margin at the southern plateau limit. The Hikurangi Plateau crust can be traced 50–100 km southward beneath the Chatham Rise where subduction cessation timing and geometry are interpreted to be variable along the Margin. A model fit of the Hikurangi Plateau back against the Manihiki Plateau aligns the Manihiki Scarp with the eastern Margin of the Rekohu Embayment. Extensional and rotated block faults which formed during the breakup of the combined Manihiki-Hikurangi plateau are interpreted in seismic sections of the Hikurangi Plateau basement. Guyots and ridge-like seamounts which are widely scattered across the Hikurangi Plateau are interpreted to have formed at 99–89 Ma immediately following Hikurangi Plateau jamming of the Gondwana Convergent Margin at ∼100 Ma. Volcanism from this period cannot be separately resolved in the seismic reflection data from basement volcanism; hence seamount formation during Manihiki-Hikurangi Plateau emplacement and breakup (125–120 Ma) cannot be ruled out. Seismic reflection data and gravity modeling suggest the 20-Ma-old Hikurangi Plateau choked the Cretaceous Gondwana Convergent Margin within 5 Ma of entry. Subsequent uplift of the Chatham Rise and slab detachment has led to the deposition of a Mesozoic sedimentary unit that thins from ∼1 km thickness northward across the plateau. The contrast with the present Hikurangi Plateau subduction beneath North Island, New Zealand, suggests a possible buoyancy cutoff range for LIP subduction consistent with earlier modeling.
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hikurangi plateau crustal structure rifted formation and gondwana subduction history
Geochemistry Geophysics Geosystems, 2008Co-Authors: Bryan Davy, Kaj Hoernle, Reinhard WernerAbstract:Seismic reflection profiles across the Hikurangi Plateau Large Igneous Province and adjacent Margins reveal the faulted volcanic basement and overlying Mesozoic-Cenozoic sedimentary units as well as the structure of the paleoConvergent Gondwana Margin at the southern plateau limit. The Hikurangi Plateau crust can be traced 50–100 km southward beneath the Chatham Rise where subduction cessation timing and geometry are interpreted to be variable along the Margin. A model fit of the Hikurangi Plateau back against the Manihiki Plateau aligns the Manihiki Scarp with the eastern Margin of the Rekohu Embayment. Extensional and rotated block faults which formed during the breakup of the combined Manihiki-Hikurangi plateau are interpreted in seismic sections of the Hikurangi Plateau basement. Guyots and ridge-like seamounts which are widely scattered across the Hikurangi Plateau are interpreted to have formed at 99–89 Ma immediately following Hikurangi Plateau jamming of the Gondwana Convergent Margin at ∼100 Ma. Volcanism from this period cannot be separately resolved in the seismic reflection data from basement volcanism; hence seamount formation during Manihiki-Hikurangi Plateau emplacement and breakup (125–120 Ma) cannot be ruled out. Seismic reflection data and gravity modeling suggest the 20-Ma-old Hikurangi Plateau choked the Cretaceous Gondwana Convergent Margin within 5 Ma of entry. Subsequent uplift of the Chatham Rise and slab detachment has led to the deposition of a Mesozoic sedimentary unit that thins from ∼1 km thickness northward across the plateau. The contrast with the present Hikurangi Plateau subduction beneath North Island, New Zealand, suggests a possible buoyancy cutoff range for LIP subduction consistent with earlier modeling.