New SW Pacific tectonic model

Cyclical intraoceanic magmatic arc construction and near-coeval emplacement along the Australia-Pacific margin in the Cenozoic

Scott A. Whattam, John Malpas, Jason R. Ali, Ian E M Smith

Research output: Contribution to journalArticle

42 Citations (Scopus)

Abstract

Various reconstructions of the SW Pacific for the Late Cretaceous and Cenozoic suggest that northeast dipping subduction began in the South Loyalty Basin (SLB) at 55-50 Ma and that subsequent closure of the SLB resulted in the diachronous emplacement of Cretaceous-Paleocene ophiolitic nappes onto the Norfolk Ridge in New Caledonia at 40-34 Ma and in Northland, New Zealand, around 24-21 Ma. A fundamental problem with these models is that they do not account for the fact that NE dipping subduction had already been established offshore Papua New Guinea by at least 65-60 Ma which resulted in the emplacement of the Papuan Ultramafic Belt (PUB) ophiolite at 59-58 Ma. A second issue is that the reconstructions are based largely upon unfounded assumptions as to the age and nature of the basement beneath the Loyalty arc and Three Kings Ridge. Finally, reconstructions of the Northland region are based upon the erroneous assumption that the age of the majority of the igneous component comprising the Northland allochthon is Late Cretaceous-Paleocene, when in fact it is Oligocene. A new model is presented whereby the PUB, New Caledonia, and Northland ophiolites formed and were emplaced in a cyclical fashion above an extensive NE dipping Cenozoic intraoceanic arc system which diachronously propagated (N-S) along the entire eastern margin of the Australian Plate. These "infant arc" ophiolites represent fragments of suprasubduction zone lithosphere (SSZL) generated in the earliest stages of magmatic arc formation that were emplaced shortly after (<20 m.y.) as a result of forearc-Australian Plate collision. Subduction inception was the result of subsidence of older MORB-like lithosphere generated within an extensive "back arc basin" to the east of the Norfolk Ridge during the earliest stages of SLB formation above a southwest dipping Pacific Plate. During emplacement of each ophiolite, a crustal fragment of the older lithosphere was scraped off the NE dipping slab and subsequently back-thrust beneath each ophiolite during its emplacement.

Original languageEnglish
Article numberQ03021
JournalGeochemistry, Geophysics, Geosystems
Volume9
Issue number3
DOIs
Publication statusPublished - 2008 Mar 1
Externally publishedYes

Fingerprint

Tectonics
dipping
margins
tectonics
emplacement
arcs
ophiolite
Australian plate
lithosphere
subduction
Subsidence
ridges
Cretaceous
Paleocene
basin
allochthon
fragments
Papua New Guinea
Pacific plate
folds (geology)

Keywords

  • Cenozoic
  • New Caledonia ophiolite
  • Northland ophiolite
  • Papuan Ultramafic Belt (PUB) ophiolite
  • Suprasubduction zone lithosphere (SSZL)
  • SW Pacific

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

New SW Pacific tectonic model : Cyclical intraoceanic magmatic arc construction and near-coeval emplacement along the Australia-Pacific margin in the Cenozoic. / Whattam, Scott A.; Malpas, John; Ali, Jason R.; Smith, Ian E M.

In: Geochemistry, Geophysics, Geosystems, Vol. 9, No. 3, Q03021, 01.03.2008.

Research output: Contribution to journalArticle

@article{3f6b3d6a23f14fe580600a9667417bea,
title = "New SW Pacific tectonic model: Cyclical intraoceanic magmatic arc construction and near-coeval emplacement along the Australia-Pacific margin in the Cenozoic",
abstract = "Various reconstructions of the SW Pacific for the Late Cretaceous and Cenozoic suggest that northeast dipping subduction began in the South Loyalty Basin (SLB) at 55-50 Ma and that subsequent closure of the SLB resulted in the diachronous emplacement of Cretaceous-Paleocene ophiolitic nappes onto the Norfolk Ridge in New Caledonia at 40-34 Ma and in Northland, New Zealand, around 24-21 Ma. A fundamental problem with these models is that they do not account for the fact that NE dipping subduction had already been established offshore Papua New Guinea by at least 65-60 Ma which resulted in the emplacement of the Papuan Ultramafic Belt (PUB) ophiolite at 59-58 Ma. A second issue is that the reconstructions are based largely upon unfounded assumptions as to the age and nature of the basement beneath the Loyalty arc and Three Kings Ridge. Finally, reconstructions of the Northland region are based upon the erroneous assumption that the age of the majority of the igneous component comprising the Northland allochthon is Late Cretaceous-Paleocene, when in fact it is Oligocene. A new model is presented whereby the PUB, New Caledonia, and Northland ophiolites formed and were emplaced in a cyclical fashion above an extensive NE dipping Cenozoic intraoceanic arc system which diachronously propagated (N-S) along the entire eastern margin of the Australian Plate. These {"}infant arc{"} ophiolites represent fragments of suprasubduction zone lithosphere (SSZL) generated in the earliest stages of magmatic arc formation that were emplaced shortly after (<20 m.y.) as a result of forearc-Australian Plate collision. Subduction inception was the result of subsidence of older MORB-like lithosphere generated within an extensive {"}back arc basin{"} to the east of the Norfolk Ridge during the earliest stages of SLB formation above a southwest dipping Pacific Plate. During emplacement of each ophiolite, a crustal fragment of the older lithosphere was scraped off the NE dipping slab and subsequently back-thrust beneath each ophiolite during its emplacement.",
keywords = "Cenozoic, New Caledonia ophiolite, Northland ophiolite, Papuan Ultramafic Belt (PUB) ophiolite, Suprasubduction zone lithosphere (SSZL), SW Pacific",
author = "Whattam, {Scott A.} and John Malpas and Ali, {Jason R.} and Smith, {Ian E M}",
year = "2008",
month = "3",
day = "1",
doi = "10.1029/2007GC001710",
language = "English",
volume = "9",
journal = "Geochemistry, Geophysics, Geosystems",
issn = "1525-2027",
publisher = "American Geophysical Union",
number = "3",

}

TY - JOUR

T1 - New SW Pacific tectonic model

T2 - Cyclical intraoceanic magmatic arc construction and near-coeval emplacement along the Australia-Pacific margin in the Cenozoic

AU - Whattam, Scott A.

AU - Malpas, John

AU - Ali, Jason R.

AU - Smith, Ian E M

PY - 2008/3/1

Y1 - 2008/3/1

N2 - Various reconstructions of the SW Pacific for the Late Cretaceous and Cenozoic suggest that northeast dipping subduction began in the South Loyalty Basin (SLB) at 55-50 Ma and that subsequent closure of the SLB resulted in the diachronous emplacement of Cretaceous-Paleocene ophiolitic nappes onto the Norfolk Ridge in New Caledonia at 40-34 Ma and in Northland, New Zealand, around 24-21 Ma. A fundamental problem with these models is that they do not account for the fact that NE dipping subduction had already been established offshore Papua New Guinea by at least 65-60 Ma which resulted in the emplacement of the Papuan Ultramafic Belt (PUB) ophiolite at 59-58 Ma. A second issue is that the reconstructions are based largely upon unfounded assumptions as to the age and nature of the basement beneath the Loyalty arc and Three Kings Ridge. Finally, reconstructions of the Northland region are based upon the erroneous assumption that the age of the majority of the igneous component comprising the Northland allochthon is Late Cretaceous-Paleocene, when in fact it is Oligocene. A new model is presented whereby the PUB, New Caledonia, and Northland ophiolites formed and were emplaced in a cyclical fashion above an extensive NE dipping Cenozoic intraoceanic arc system which diachronously propagated (N-S) along the entire eastern margin of the Australian Plate. These "infant arc" ophiolites represent fragments of suprasubduction zone lithosphere (SSZL) generated in the earliest stages of magmatic arc formation that were emplaced shortly after (<20 m.y.) as a result of forearc-Australian Plate collision. Subduction inception was the result of subsidence of older MORB-like lithosphere generated within an extensive "back arc basin" to the east of the Norfolk Ridge during the earliest stages of SLB formation above a southwest dipping Pacific Plate. During emplacement of each ophiolite, a crustal fragment of the older lithosphere was scraped off the NE dipping slab and subsequently back-thrust beneath each ophiolite during its emplacement.

AB - Various reconstructions of the SW Pacific for the Late Cretaceous and Cenozoic suggest that northeast dipping subduction began in the South Loyalty Basin (SLB) at 55-50 Ma and that subsequent closure of the SLB resulted in the diachronous emplacement of Cretaceous-Paleocene ophiolitic nappes onto the Norfolk Ridge in New Caledonia at 40-34 Ma and in Northland, New Zealand, around 24-21 Ma. A fundamental problem with these models is that they do not account for the fact that NE dipping subduction had already been established offshore Papua New Guinea by at least 65-60 Ma which resulted in the emplacement of the Papuan Ultramafic Belt (PUB) ophiolite at 59-58 Ma. A second issue is that the reconstructions are based largely upon unfounded assumptions as to the age and nature of the basement beneath the Loyalty arc and Three Kings Ridge. Finally, reconstructions of the Northland region are based upon the erroneous assumption that the age of the majority of the igneous component comprising the Northland allochthon is Late Cretaceous-Paleocene, when in fact it is Oligocene. A new model is presented whereby the PUB, New Caledonia, and Northland ophiolites formed and were emplaced in a cyclical fashion above an extensive NE dipping Cenozoic intraoceanic arc system which diachronously propagated (N-S) along the entire eastern margin of the Australian Plate. These "infant arc" ophiolites represent fragments of suprasubduction zone lithosphere (SSZL) generated in the earliest stages of magmatic arc formation that were emplaced shortly after (<20 m.y.) as a result of forearc-Australian Plate collision. Subduction inception was the result of subsidence of older MORB-like lithosphere generated within an extensive "back arc basin" to the east of the Norfolk Ridge during the earliest stages of SLB formation above a southwest dipping Pacific Plate. During emplacement of each ophiolite, a crustal fragment of the older lithosphere was scraped off the NE dipping slab and subsequently back-thrust beneath each ophiolite during its emplacement.

KW - Cenozoic

KW - New Caledonia ophiolite

KW - Northland ophiolite

KW - Papuan Ultramafic Belt (PUB) ophiolite

KW - Suprasubduction zone lithosphere (SSZL)

KW - SW Pacific

UR - http://www.scopus.com/inward/record.url?scp=59149104470&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=59149104470&partnerID=8YFLogxK

U2 - 10.1029/2007GC001710

DO - 10.1029/2007GC001710

M3 - Article

VL - 9

JO - Geochemistry, Geophysics, Geosystems

JF - Geochemistry, Geophysics, Geosystems

SN - 1525-2027

IS - 3

M1 - Q03021

ER -