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Ian E M Smith - One of the best experts on this subject based on the ideXlab platform.
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geochemistry of the early miocene volcanic succession of Northland new zealand and implications for the evolution of subduction in the southwest pacific
Journal of Volcanology and Geothermal Research, 2011Co-Authors: Mathijs A Booden, Philippa M Black, Ian E M Smith, Jeffrey L MaukAbstract:Abstract Latest Oligocene and Early Miocene volcanic rocks occur on the Northland Peninsula, New Zealand, and record the inception of Cenozoic subduction-related volcanism in the North Island that eventually evolved to its present manifestation in the Taupo Volcanic Zone. This NW-striking Northland Arc is continuous with the Reinga Ridge and comprises two parallel belts of volcanic centres ca. 60 km apart. A plethora of tectonic models have been proposed for its origins. We acquired new trace element and Sr–Nd isotope data to better constrain such models. All Northland Arc rocks carry an arc-type trace element signature, however distinct differences exist between rocks of the eastern and western belt. Eastern belt rocks are typically andesites and dacites and have relatively evolved isotope ratios indicating assimilated crustal material, and commonly contain hornblende. Additionally some eastern belt rocks with highly evolved isotope compositions show fractionated REE compositions consistent with residual garnet, and some contain garnetiferous inclusions in addition to schistose crustal fragments. In contrast, western belt rocks are mostly basalts or basaltic andesites with relatively primitive Sr–Nd isotope compositions, do not contain hornblende and show no rare earth element evidence for cryptic amphibole fractionation. Eastern and western belt rocks contain comparable slab-derived fractions of fluid-mobile trace elements and invariably possess an arc signature. Therefore the difference between the belts may be best explained as due to variation in crustal thickness across the Northland Peninsula, where western belt centres erupted onto a thinner crustal section than eastern belt rocks. The consistent arc signature throughout the Northland arc favours an origin in response to an actual, if short-lived subduction event, rather than slab detachment as proposed in some models. No Northland Arc rocks possess a convincing adakite-like composition that might reflect the subduction of very young oceanic lithosphere such as that of the Oligocene South Fiji Basin. Therefore we favour a model in which subduction of old (Cretaceous) lithosphere drove subduction.
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link between ssz ophiolite formation emplacement and arc inception Northland new zealand u pb shrimp constraints cenozoic sw pacific tectonic implications
Earth and Planetary Science Letters, 2006Co-Authors: Scott A Whattam, John Malpas, Ian E M Smith, Jason R AliAbstract:Abstract New U–Pb age-data from zircons separated from a Northland ophiolite gabbro yield a mean 206 Pb/ 238 U age of 31.6 ± 0.2 Ma, providing support for a recently determined 28.3 ± 0.2 Ma SHRIMP age of an associated plagiogranite and ∼ 29–26 Ma 40 Ar/ 39 Ar ages ( n = 9) of basalts of the ophiolite. Elsewhere, Miocene arc-related calc-alkaline andesite dikes which intrude the ophiolitic rocks contain zircons which yield mean 206 Pb/ 238 U ages of 20.1 ± 0.2 and 19.8 ± 0.2 Ma. The ophiolite gabbro and the andesites both contain rare inherited zircons ranging from 122–104 Ma. The Early Cretaceous zircons in the arc andesites are interpreted as xenocrysts from the Mt. Camel basement terrane through which magmas of the Northland Miocene arc lavas erupted. The inherited zircons in the ophiolite gabbros suggest that a small fraction of this basement was introduced into the suboceanic mantle by subduction and mixed with mantle melts during ophiolite formation. We postulate that the tholeiitic suite of the ophiolite represents the crustal segment of SSZ lithosphere (SSZL) generated in the southern South Fiji Basin (SFB) at a northeast-dipping subduction zone that was initiated at about 35 Ma. The subduction zone nucleated along a pre-existing transform boundary separating circa 45–20 Ma oceanic lithosphere to the north and west of the Northland Peninsula from nascent back arc basin lithosphere of the SFB. Construction of the SSZL propagated southward along the transform boundary as the SFB continued to unzip to the southeast. After subduction of a large portion of oceanic lithosphere by about 26 Ma and collision of the SSZL with New Zealand, compression between the Australian Plate and the Pacific Plate was taken up along a new southwest-dipping subduction zone behind the SSZL. Renewed volcanism began in the oceanic forearc at 25 Ma producing boninitic-like, SSZ and within-plate alkalic and calc-alkaline rocks. Rocks of these types temporally overlap ophiolite emplacement and subsequent Miocene continental arc construction.
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formation and emplacement of the Northland ophiolite northern new zealand sw pacific tectonic implications
Journal of the Geological Society, 2005Co-Authors: Scott A Whattam, John Malpas, Jason R Ali, Ian E M SmithAbstract:Petrological, geochemical, geochronological and palaeomagnetic data for rocks of the Northland ophiolite terrane of northern New Zealand suggest that it formed in a suprasubduction-zone setting between c . 29 and 26 Ma, at c . 35°S, close to its Late Oligocene obduction site. Cretaceous igneous rocks formerly considered to be part of the ophiolite probably represent the basement upon which the ophiolite was emplaced, and are probably part of the Mount Camel arc-related terrane. The ophiolite is believed to have been generated in the southeastern South Fiji Basin, close to a NW–SE-oriented transform fault located to the SW of the Vening Meinesz Fracture Zone, and was probably emplaced in response to the collision of the Hikurangi Plateau with eastern New Zealand at the end of the Oligocene. This collision would have involved a major adjustment on the transform fault, thereby allowing a portion of the upper-crustal section of the southern South Fiji Basin to be emplaced southwestward onto northern New Zealand as well as the coeval emplacement of the East Cape Allochthon to the south. Concomitant subduction of the lower crust–mantle section led to the initiation of arc volcanism that resulted in the Northland Lower Miocene volcanic–plutonic suite.
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origin of the Northland ophiolite northern new zealand discussion of new data and reassessment of the model
New Zealand Journal of Geology and Geophysics, 2004Co-Authors: Scott A Whattam, John Malpas, Jason R Ali, Ian E M SmithAbstract:Abstract This paper discusses new results from the Northland Ophiolite in northern New Zealand that indicate that it formed in a supra‐subduction zone setting, c. 26–29 m.y. ago, and very near to its late Oligocene obduction site. This is in contrast to previous studies which have suggested that the ophiolite is a far‐travelled igneous Cretaceous‐Paleocene terrane. Cretaceous rocks formerly mapped as part of the ophiolite are minor and represent an autochthonous Late Cretaceous‐Paleocene volcanic arc. The tectonic setting, age, and location of formation suggest that the ophiolite formed as part of the southernmost South Fiji Basin crust. Obduction of the Northland Ophiolite initiated subduction and volcanism resulting in the development of the Northland volcanic arc during the early Miocene.
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geochemistry of late cenozoic basaltic volcanism in Northland and coromandel new zealand implications for mantle enrichment processes
Chemical Geology, 2000Co-Authors: Yiming Huang, Ian E M Smith, C J Hawkesworth, Peter Van Calsteren, Philippa M BlackAbstract:New major and trace element, and Sr, Nd and Pb isotope results are presented for selected basaltic rocks from young volcanic fields (<10 Ma) in the Northland province of the Northland–Auckland Peninsula, and Mercury Island on the eastern side of the Coromandel Peninsula, North Island, New Zealand. The rocks are mainly alkali basalts and tholeiites which are different from those in the adjacent Auckland volcanic field. Samples from Kaikohe–Bay of Islands (KBI) tend to have low silica contents and high Nb/La ratios (1.05–1.62), low Sr (0.7027–0.7030) and high Nd (0.51299–0.51304) isotope ratios and relatively high /, but low / and /, and so low Δ/ (4.1±2.2) and Δ/ (10.7±6.7). Ti Point and Stony Batter samples (TPSB) and Mercury Island basalts (MIB) have similar compositions, relatively high silica contents and low Nb/La ratios (0.23–0.58), high Sr (0.7039–0.7048) and low Nd (0.51278–0.51293) isotope ratios, with higher Δ/ and Δ/ (8.1±1.6 and 30.9±5.0, respectively). The rocks from Whangarei–Puhipuhi field (WHP) have intermediate compositions, in that their Sr and Nd isotope ratios are similar to KBI, but their Pb isotope ratios are more similar to the TPSB and MIB. Furthermore, the WHP rocks have similar large ion lithophile element (LILE) abundances to KBI but with negative Nb anomalies which are a feature of TPSB and MIB. Although AFC processes could explain co-variations of isotope ratios in the samples from the different fields they are difficult to reconcile with the observed relationships between isotope ratios, major elements and Nb/La. Thus, the major differences in the geochemical features of the Northland volcanic rocks are more likely to represent source variations in the underlying mantle. The KBI samples have isotope and trace element compositions similar to the Auckland basalts, and to many ocean island basalts (OIB). In contrast, negative Nb anomalies and high Δ/ and Δ/, high Sr and low Nd isotope ratios are features of subduction-related volcanism. Therefore, two very different mantle enrichment processes have been identified in the mantle beneath the Northland–Auckland peninsula, reflecting changes in the tectonic setting from plate convergence to intraplate over the last 30 Ma. The KBI, WHP, TPSB and MIB have similar MgO and FeOt (total iron as FeO) contents at mg# ∼0.70 indicating that they were generated at similar depths and temperatures. However, the Auckland basalts have significantly higher FeOt and MgO contents, and they are therefore considered to have been derived from greater depths and higher temperatures. This constrains the spatial relationships between the two mantle domains with intraplate sources dominant at depth and the subduction related enrichment processes at shallower levels in the mantle underlying the Northland Peninsula.
Philippa M Black - One of the best experts on this subject based on the ideXlab platform.
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geochemistry of the early miocene volcanic succession of Northland new zealand and implications for the evolution of subduction in the southwest pacific
Journal of Volcanology and Geothermal Research, 2011Co-Authors: Mathijs A Booden, Philippa M Black, Ian E M Smith, Jeffrey L MaukAbstract:Abstract Latest Oligocene and Early Miocene volcanic rocks occur on the Northland Peninsula, New Zealand, and record the inception of Cenozoic subduction-related volcanism in the North Island that eventually evolved to its present manifestation in the Taupo Volcanic Zone. This NW-striking Northland Arc is continuous with the Reinga Ridge and comprises two parallel belts of volcanic centres ca. 60 km apart. A plethora of tectonic models have been proposed for its origins. We acquired new trace element and Sr–Nd isotope data to better constrain such models. All Northland Arc rocks carry an arc-type trace element signature, however distinct differences exist between rocks of the eastern and western belt. Eastern belt rocks are typically andesites and dacites and have relatively evolved isotope ratios indicating assimilated crustal material, and commonly contain hornblende. Additionally some eastern belt rocks with highly evolved isotope compositions show fractionated REE compositions consistent with residual garnet, and some contain garnetiferous inclusions in addition to schistose crustal fragments. In contrast, western belt rocks are mostly basalts or basaltic andesites with relatively primitive Sr–Nd isotope compositions, do not contain hornblende and show no rare earth element evidence for cryptic amphibole fractionation. Eastern and western belt rocks contain comparable slab-derived fractions of fluid-mobile trace elements and invariably possess an arc signature. Therefore the difference between the belts may be best explained as due to variation in crustal thickness across the Northland Peninsula, where western belt centres erupted onto a thinner crustal section than eastern belt rocks. The consistent arc signature throughout the Northland arc favours an origin in response to an actual, if short-lived subduction event, rather than slab detachment as proposed in some models. No Northland Arc rocks possess a convincing adakite-like composition that might reflect the subduction of very young oceanic lithosphere such as that of the Oligocene South Fiji Basin. Therefore we favour a model in which subduction of old (Cretaceous) lithosphere drove subduction.
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geochemistry of late cenozoic basaltic volcanism in Northland and coromandel new zealand implications for mantle enrichment processes
Chemical Geology, 2000Co-Authors: Yiming Huang, Ian E M Smith, C J Hawkesworth, Peter Van Calsteren, Philippa M BlackAbstract:New major and trace element, and Sr, Nd and Pb isotope results are presented for selected basaltic rocks from young volcanic fields (<10 Ma) in the Northland province of the Northland–Auckland Peninsula, and Mercury Island on the eastern side of the Coromandel Peninsula, North Island, New Zealand. The rocks are mainly alkali basalts and tholeiites which are different from those in the adjacent Auckland volcanic field. Samples from Kaikohe–Bay of Islands (KBI) tend to have low silica contents and high Nb/La ratios (1.05–1.62), low Sr (0.7027–0.7030) and high Nd (0.51299–0.51304) isotope ratios and relatively high /, but low / and /, and so low Δ/ (4.1±2.2) and Δ/ (10.7±6.7). Ti Point and Stony Batter samples (TPSB) and Mercury Island basalts (MIB) have similar compositions, relatively high silica contents and low Nb/La ratios (0.23–0.58), high Sr (0.7039–0.7048) and low Nd (0.51278–0.51293) isotope ratios, with higher Δ/ and Δ/ (8.1±1.6 and 30.9±5.0, respectively). The rocks from Whangarei–Puhipuhi field (WHP) have intermediate compositions, in that their Sr and Nd isotope ratios are similar to KBI, but their Pb isotope ratios are more similar to the TPSB and MIB. Furthermore, the WHP rocks have similar large ion lithophile element (LILE) abundances to KBI but with negative Nb anomalies which are a feature of TPSB and MIB. Although AFC processes could explain co-variations of isotope ratios in the samples from the different fields they are difficult to reconcile with the observed relationships between isotope ratios, major elements and Nb/La. Thus, the major differences in the geochemical features of the Northland volcanic rocks are more likely to represent source variations in the underlying mantle. The KBI samples have isotope and trace element compositions similar to the Auckland basalts, and to many ocean island basalts (OIB). In contrast, negative Nb anomalies and high Δ/ and Δ/, high Sr and low Nd isotope ratios are features of subduction-related volcanism. Therefore, two very different mantle enrichment processes have been identified in the mantle beneath the Northland–Auckland peninsula, reflecting changes in the tectonic setting from plate convergence to intraplate over the last 30 Ma. The KBI, WHP, TPSB and MIB have similar MgO and FeOt (total iron as FeO) contents at mg# ∼0.70 indicating that they were generated at similar depths and temperatures. However, the Auckland basalts have significantly higher FeOt and MgO contents, and they are therefore considered to have been derived from greater depths and higher temperatures. This constrains the spatial relationships between the two mantle domains with intraplate sources dominant at depth and the subduction related enrichment processes at shallower levels in the mantle underlying the Northland Peninsula.
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age relationships and tectonic implications of late cenozoic basaltic volcanism in Northland new zealand
New Zealand Journal of Geology and Geophysics, 1993Co-Authors: Ian E M Smith, T Okada, Tetsumaru Itaya, Philippa M BlackAbstract:An episode of late Miocene ‐ Recent essentially basaltic volcanism is the latest in a sequence of magmatic events recognised in the tectonically complex geological development of the Northland Peni...
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Northland ophiolite new zealand and implications for plate tectonic evolution of the southwest pacific
Geology, 1992Co-Authors: Jeff Malpas, Philippa M Black, K B Sporli, Iem SmithAbstract:The Northland ophiolite and coeval ocean-floor sedimentary rock form the Northland allochthon obducted from the northeast onto New Zealand in the late Oligocene. The ophiolite was probably emplaced as a single sheet and separated into individual massifs during subse quent movement of the allochthon. Chemically, the bulk of the igneous rocks are normal mid-ocean-ridge basalts, but the ophiolite also includes a younger suite of hornblende modal within-plate alkalic rocks believed to represent seamounts. Two alternative models, one involving a subduction flip, the other involving continuous westward subduction, are proposed to account for the obduction of the upper part of the Northland ophiolite. The oceanic crust from which the ophiolite originated was formed simultaneously with Tasman Sea spreading on the western rim of a once much larger South Fiji plate assemblage.
Scott A Whattam - One of the best experts on this subject based on the ideXlab platform.
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link between ssz ophiolite formation emplacement and arc inception Northland new zealand u pb shrimp constraints cenozoic sw pacific tectonic implications
Earth and Planetary Science Letters, 2006Co-Authors: Scott A Whattam, John Malpas, Ian E M Smith, Jason R AliAbstract:Abstract New U–Pb age-data from zircons separated from a Northland ophiolite gabbro yield a mean 206 Pb/ 238 U age of 31.6 ± 0.2 Ma, providing support for a recently determined 28.3 ± 0.2 Ma SHRIMP age of an associated plagiogranite and ∼ 29–26 Ma 40 Ar/ 39 Ar ages ( n = 9) of basalts of the ophiolite. Elsewhere, Miocene arc-related calc-alkaline andesite dikes which intrude the ophiolitic rocks contain zircons which yield mean 206 Pb/ 238 U ages of 20.1 ± 0.2 and 19.8 ± 0.2 Ma. The ophiolite gabbro and the andesites both contain rare inherited zircons ranging from 122–104 Ma. The Early Cretaceous zircons in the arc andesites are interpreted as xenocrysts from the Mt. Camel basement terrane through which magmas of the Northland Miocene arc lavas erupted. The inherited zircons in the ophiolite gabbros suggest that a small fraction of this basement was introduced into the suboceanic mantle by subduction and mixed with mantle melts during ophiolite formation. We postulate that the tholeiitic suite of the ophiolite represents the crustal segment of SSZ lithosphere (SSZL) generated in the southern South Fiji Basin (SFB) at a northeast-dipping subduction zone that was initiated at about 35 Ma. The subduction zone nucleated along a pre-existing transform boundary separating circa 45–20 Ma oceanic lithosphere to the north and west of the Northland Peninsula from nascent back arc basin lithosphere of the SFB. Construction of the SSZL propagated southward along the transform boundary as the SFB continued to unzip to the southeast. After subduction of a large portion of oceanic lithosphere by about 26 Ma and collision of the SSZL with New Zealand, compression between the Australian Plate and the Pacific Plate was taken up along a new southwest-dipping subduction zone behind the SSZL. Renewed volcanism began in the oceanic forearc at 25 Ma producing boninitic-like, SSZ and within-plate alkalic and calc-alkaline rocks. Rocks of these types temporally overlap ophiolite emplacement and subsequent Miocene continental arc construction.
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formation and emplacement of the Northland ophiolite northern new zealand sw pacific tectonic implications
Journal of the Geological Society, 2005Co-Authors: Scott A Whattam, John Malpas, Jason R Ali, Ian E M SmithAbstract:Petrological, geochemical, geochronological and palaeomagnetic data for rocks of the Northland ophiolite terrane of northern New Zealand suggest that it formed in a suprasubduction-zone setting between c . 29 and 26 Ma, at c . 35°S, close to its Late Oligocene obduction site. Cretaceous igneous rocks formerly considered to be part of the ophiolite probably represent the basement upon which the ophiolite was emplaced, and are probably part of the Mount Camel arc-related terrane. The ophiolite is believed to have been generated in the southeastern South Fiji Basin, close to a NW–SE-oriented transform fault located to the SW of the Vening Meinesz Fracture Zone, and was probably emplaced in response to the collision of the Hikurangi Plateau with eastern New Zealand at the end of the Oligocene. This collision would have involved a major adjustment on the transform fault, thereby allowing a portion of the upper-crustal section of the southern South Fiji Basin to be emplaced southwestward onto northern New Zealand as well as the coeval emplacement of the East Cape Allochthon to the south. Concomitant subduction of the lower crust–mantle section led to the initiation of arc volcanism that resulted in the Northland Lower Miocene volcanic–plutonic suite.
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origin of the Northland ophiolite northern new zealand discussion of new data and reassessment of the model
New Zealand Journal of Geology and Geophysics, 2004Co-Authors: Scott A Whattam, John Malpas, Jason R Ali, Ian E M SmithAbstract:Abstract This paper discusses new results from the Northland Ophiolite in northern New Zealand that indicate that it formed in a supra‐subduction zone setting, c. 26–29 m.y. ago, and very near to its late Oligocene obduction site. This is in contrast to previous studies which have suggested that the ophiolite is a far‐travelled igneous Cretaceous‐Paleocene terrane. Cretaceous rocks formerly mapped as part of the ophiolite are minor and represent an autochthonous Late Cretaceous‐Paleocene volcanic arc. The tectonic setting, age, and location of formation suggest that the ophiolite formed as part of the southernmost South Fiji Basin crust. Obduction of the Northland Ophiolite initiated subduction and volcanism resulting in the development of the Northland volcanic arc during the early Miocene.
Jason R Ali - One of the best experts on this subject based on the ideXlab platform.
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link between ssz ophiolite formation emplacement and arc inception Northland new zealand u pb shrimp constraints cenozoic sw pacific tectonic implications
Earth and Planetary Science Letters, 2006Co-Authors: Scott A Whattam, John Malpas, Ian E M Smith, Jason R AliAbstract:Abstract New U–Pb age-data from zircons separated from a Northland ophiolite gabbro yield a mean 206 Pb/ 238 U age of 31.6 ± 0.2 Ma, providing support for a recently determined 28.3 ± 0.2 Ma SHRIMP age of an associated plagiogranite and ∼ 29–26 Ma 40 Ar/ 39 Ar ages ( n = 9) of basalts of the ophiolite. Elsewhere, Miocene arc-related calc-alkaline andesite dikes which intrude the ophiolitic rocks contain zircons which yield mean 206 Pb/ 238 U ages of 20.1 ± 0.2 and 19.8 ± 0.2 Ma. The ophiolite gabbro and the andesites both contain rare inherited zircons ranging from 122–104 Ma. The Early Cretaceous zircons in the arc andesites are interpreted as xenocrysts from the Mt. Camel basement terrane through which magmas of the Northland Miocene arc lavas erupted. The inherited zircons in the ophiolite gabbros suggest that a small fraction of this basement was introduced into the suboceanic mantle by subduction and mixed with mantle melts during ophiolite formation. We postulate that the tholeiitic suite of the ophiolite represents the crustal segment of SSZ lithosphere (SSZL) generated in the southern South Fiji Basin (SFB) at a northeast-dipping subduction zone that was initiated at about 35 Ma. The subduction zone nucleated along a pre-existing transform boundary separating circa 45–20 Ma oceanic lithosphere to the north and west of the Northland Peninsula from nascent back arc basin lithosphere of the SFB. Construction of the SSZL propagated southward along the transform boundary as the SFB continued to unzip to the southeast. After subduction of a large portion of oceanic lithosphere by about 26 Ma and collision of the SSZL with New Zealand, compression between the Australian Plate and the Pacific Plate was taken up along a new southwest-dipping subduction zone behind the SSZL. Renewed volcanism began in the oceanic forearc at 25 Ma producing boninitic-like, SSZ and within-plate alkalic and calc-alkaline rocks. Rocks of these types temporally overlap ophiolite emplacement and subsequent Miocene continental arc construction.
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formation and emplacement of the Northland ophiolite northern new zealand sw pacific tectonic implications
Journal of the Geological Society, 2005Co-Authors: Scott A Whattam, John Malpas, Jason R Ali, Ian E M SmithAbstract:Petrological, geochemical, geochronological and palaeomagnetic data for rocks of the Northland ophiolite terrane of northern New Zealand suggest that it formed in a suprasubduction-zone setting between c . 29 and 26 Ma, at c . 35°S, close to its Late Oligocene obduction site. Cretaceous igneous rocks formerly considered to be part of the ophiolite probably represent the basement upon which the ophiolite was emplaced, and are probably part of the Mount Camel arc-related terrane. The ophiolite is believed to have been generated in the southeastern South Fiji Basin, close to a NW–SE-oriented transform fault located to the SW of the Vening Meinesz Fracture Zone, and was probably emplaced in response to the collision of the Hikurangi Plateau with eastern New Zealand at the end of the Oligocene. This collision would have involved a major adjustment on the transform fault, thereby allowing a portion of the upper-crustal section of the southern South Fiji Basin to be emplaced southwestward onto northern New Zealand as well as the coeval emplacement of the East Cape Allochthon to the south. Concomitant subduction of the lower crust–mantle section led to the initiation of arc volcanism that resulted in the Northland Lower Miocene volcanic–plutonic suite.
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origin of the Northland ophiolite northern new zealand discussion of new data and reassessment of the model
New Zealand Journal of Geology and Geophysics, 2004Co-Authors: Scott A Whattam, John Malpas, Jason R Ali, Ian E M SmithAbstract:Abstract This paper discusses new results from the Northland Ophiolite in northern New Zealand that indicate that it formed in a supra‐subduction zone setting, c. 26–29 m.y. ago, and very near to its late Oligocene obduction site. This is in contrast to previous studies which have suggested that the ophiolite is a far‐travelled igneous Cretaceous‐Paleocene terrane. Cretaceous rocks formerly mapped as part of the ophiolite are minor and represent an autochthonous Late Cretaceous‐Paleocene volcanic arc. The tectonic setting, age, and location of formation suggest that the ophiolite formed as part of the southernmost South Fiji Basin crust. Obduction of the Northland Ophiolite initiated subduction and volcanism resulting in the development of the Northland volcanic arc during the early Miocene.
N Mortimer - One of the best experts on this subject based on the ideXlab platform.
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detrital zircon geochronology and sandstone provenance of basement waipapa terrane triassic cretaceous and cretaceous cover rocks Northland allochthon and houhora complex in northern north island new zealand
Geological Magazine, 2013Co-Authors: C J Adams, N Mortimer, H J Campbell, W L GriffinAbstract:Detrital zircon U-Pb ages are reported for 14 sandstones of mainly Cretaceous age from the Northland Allochthon, Houhora Complex and Waipapa Terrane of northern North Island, New Zealand. Results from the Waipapa Terrane samples, selected from sequences in the Bay of Plenty, Coromandel Peninsula and Great Barrier Island, show that deposition continued into late Early Cretaceous time and, as in the Torlesse Composite Terrane, finally waned at c. 110-114 Ma. Upper Lower Cretaceous and Upper Cretaceous sedimentary successions in the Houhora Complex and Northland Allochthon have dominant sediment sources derived from local, contemporary volcanism, with a minor older contribution from the Murihiku Terrane to the west. As in eastern North Island, upper Upper Cretaceous sandstones lack major Albian magmatic components and their sources are solely in the Murihiku Terrane, and possibly the Western Province. We propose a Cretaceous palaeogeographic model that invokes a recently extinct orogen and a partially submerged continental borderland, dissected by rivers supplying submarine fans.
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Seismic stratigraphy and structure of the Northland Plateau and the development of the Vening Meinesz transform margin, SW Pacific Ocean
Marine Geophysical Researches, 2009Co-Authors: R. H. Herzer, N Mortimer, B. W. Davy, P. G. Quilty, G. C. H. Chaproniere, C. M. Jones, A. J. Crawford, C. J. HollisAbstract:The Northland Plateau and the Vening Meinesz “Fracture” Zone (VMFZ), separating southwest Pacific backarc basins from New Zealand Mesozoic crust, are investigated with new data. The 12–16 km thick Plateau comprises a volcanic outer plateau and an inner plateau sedimentary basin. The outer plateau has a positive magnetic anomaly like that of the Three Kings Ridge. A rift margin was found between the Three Kings Ridge and the South Fiji Basin. Beneath the inner plateau basin, is a thin body interpreted as allochthon and parautochthon, which probably includes basalt. The basin appears to have been created by Early Miocene mainly transtensive faulting, which closely followed obduction of the allochthon and was coeval with arc volcanism. VMFZ faulting was eventually concentrated along the edge of the continental shelf and upper slope. Consequently arc volcanoes in a chain dividing the inner and outer plateau are undeformed whereas volcanoes, in various stages of burial, within the basin and along the base of the upper slope are generally faulted. Deformed and flat-lying Lower Miocene volcanogenic sedimentary rocks are intimately associated with the volcanoes and the top of the allochthon; Middle Miocene to Recent units are, respectively, mildly deformed to flat-lying, calcareous and turbiditic. Many parts of the inner plateau basin were at or above sea level in the Early Miocene, apparently as isolated highs that later subsided differentially to 500–2,000 m below sea level. A mild, Middle Miocene compressive phase might correlate with events of the Reinga and Wanganella ridges to the west. Our results agree with both arc collision and arc unzipping regional kinematic models. We present a continental margin model that begins at the end of the obduction phase. Eastward rifting of the Norfolk Basin, orthogonal to the strike of the Norfolk and Three Kings ridges, caused the Northland Plateau to tear obliquely from the Reinga Ridge portion of the margin, initiating the inner plateau basin and the Cavalli core complex. Subsequent N115° extension and spreading parallel with the Cook Fracture Zone completed the southeastward translation of the Three Kings Ridge and Northland Plateau and further opened the inner plateau basin, leaving a complex dextral transform volcanic margin.
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Oligocene-Miocene tectonic evolution of the South Fiji Basin and Northland Plateau, SW Pacific Ocean: Evidence from. petrology and dating of dredged rocks
Marine Geology, 2007Co-Authors: N Mortimer, R. H. Herzer, P. B. Gans, C. Laporte-magoni, A. T. Calvert, Delphine BoschAbstract:We present new analytical data from lavas and associated rocks dredged and/or drilled from the South Fiji Basin, Northland Plateau, Colville Ridge and Havre Trough. These results provide much-needed ground truth about the geology, age and tectonic evolution of the Cenozoic submarine ridges and basins between the active intraoceanic TongaKermadec arc, and rifted continental borderlands of New Zealand, the Norfolk Ridge and New Caledonia. Key results from this study include: (1) ArAr dates on Minerva Abyssal Plain oceanic crust suggest that the ages of magnetic anomalies in the South Fiji Basin have been overestimated by earlier workers; (2) subduction-related lavas are widespread across the region, are not presently organised into arc-like chains, and cluster in the age range 2218 Ma (Early Miocene); (3) the oldest subduction-related lavas occur in the western part of the region (3226 Ma: Norfolk and Three Kings Ridge); (4) shoshonites, interpreted as rifted arc lavas, were erupted in a narrow 2021 Ma interval over a wide area. Put together, these results indicate high magmatic flux and large and rapid horizontal tectonic translations and basin opening from 1823 Ma in the region immediately north of New Zealand. We explain the Miocene tectonomagmatic development of the region by a model of rapid rollback of a single, east-facing Pacific arctrench system that became established after Northland Allochthon emplacement. Critical testing of this, versus other, tectonic models must await drilling and dating of thus-far unsampled Kupe Abyssal Plain crust.