STRUCTURE OF ISLAND ARCS BOUNDING THE AUSTRALIAN CONTINENTAL PLATE

1972 ◽  
Vol 12 (2) ◽  
pp. 74
Author(s):  
P.G. Temple
Keyword(s):  
Subduction Zone ◽  
Oceanic Crust ◽  
New Caledonia ◽  
Island Arc ◽  
Island Arcs ◽  
North East ◽  
Continental Plate ◽  
Sequence Of Events ◽  
Australian Plate ◽  
Northern Edge

The New Global Tectonic theory is proving exceedingly valuable to understanding the geological history of large parts of the world's surface. However, in island arc areas, such as those bounding the Australian Continental Plate, the theory is meeting with certain difficulties. These might be due to (a) the theory itself not being valid here, or (b) it needs modification.Certain spectacular aspects of the geology of Timor, New Guinea, New Caledonia and Northland New Zealand suggest that a good case could be made for modification. Large areas of each of these islands are covered by thick chaotic masses of layered ultrabasic igneous rock, radiolarian chert, shale and other sediments of a pelagic nature normally associated with oceanic regimes. Moreover, this sequence of rocks appears to have been tectonically emplaced from an oceanward direction on to sediments of a continental shelf environment. Emplacement seems to have occurred at approximately the same time and to have involved rocks of approximately the same age in all areas.A logical way to account for the observations above in terms of the New Global Tectonic theory is as follows:In Late Cretaceous to Early Tertiary time the northern and eastern edge of the Australian continental plate was dragged down and began to underthrust the oceanic mantle along a north to north-east dipping subduction zone (the Tethian subduction zone, which is still active along the western edge of the Indonesian Arc).From Early to Middle Tertiary time, light continental crust could no longer be subducted under heavier mantle and subduction ceased. Isostatic re-adjustment occurred, raising the northern edge of the Australian plate which still carried large remnants of oceanic crust that had been emplaced above it.At about the same time, and continuing to the present, a new pattern of south to east dipping subduction formed. Edges of the Australian plate were torn away and migrated eastward, leaving areas of new oceanic crust behind.If the sequence of events above is essentially a true picture, it leads not only to some interesting modifications of the New Global Tectonic theory, but also to certain implications as to mineral and petroleum prospects within island arc areas.

Specifics of the Caledonian Collision in the Ol’khon Region (Lake Baikal, Russia)

2021 ◽  
Vol 62 (4) ◽  
pp. 389-400
Author(s):  
V.A. Makrygina
Keyword(s):  
Subduction Zone ◽  
Oceanic Crust ◽  
Lake Baikal ◽  
Siberian Craton ◽  
Island Arc ◽  
Geophysical Data ◽  
Igneous Rocks ◽  
Fold Belt ◽  
Adjacent Part

Abstract —Analysis of geochemical, geochronological, and new geophysical data on metasedimentary and igneous rocks of the Ol’khon region has made it possible to substantiate: (1) the absence of products of the Caledonian suprasubduction magmatism from the adjacent part of the Siberian craton and (2) the presence of a product of this magmatism in the Anga–Talanchan island arc, namely, the Krestovsky massif with gabbro-diorite to granite phases. This suggests subduction of the Paleoasian oceanic crust under the island arc before the collision. The geophysical data showed a steep sinking of the Siberian craton margin. This sinking and the supposed contrary movement and rotation of the Siberian craton prevented the appearance of a subduction zone beneath the craton during the collision but caused the wide development of fault plates in the fold belt at the late collision stage. The residue of oceanic crust slab was pressed out along the fault planes near the surface and formed a row of gabbro-pyroxenite massifs of the Birkhin Complex in the fold belt, where syncollisional granitic melts (Sharanur Complex) formed at the same time. The interaction of two contrasting melts gave rise to the Tazheran and Budun alkaline syenite massifs and alkaline metasomatites of the Birkhin and Ulanganta gabbroid massifs.

Subduction-related magmatic imprint of most Philippine ophiolites: implications on the early geodynamic evolution of the Philippine archipelago

2004 ◽  
Vol 175 (5) ◽  
pp. 443-460 ◽  
Author(s):  
Rodolfo A. Tamayo* ◽  
René C. Maury* ◽  
Graciano P. Yumul ◽  
Mireille Polvé ◽  
Joseph Cotten ◽  
...  
Keyword(s):  
Partial Melting ◽  
Subduction Zone ◽  
Volcanic Rocks ◽  
The Philippines ◽  
Island Arc ◽  
Island Arcs ◽  
Geodynamic Evolution ◽  
Wide Range ◽  
Opening And Closing ◽  
Back Arc

Abstract The basement complexes of the Philippine archipelago include at least 20 ophiolites and ophiolitic complexes. These complexes are characterised by volcanic sequences displaying geochemical compositions similar to those observed in MORB, transitional MORB-island arc tholeiites and arc volcanic rocks originating from modern Pacific-type oceans, back-arc basins and island arcs. Ocean island basalt-like rocks are rarely encountered in the volcanic sequences. The gabbros from the ophiolites contain clinopyroxenes and plagioclases showing a wide range of XMg and An values, respectively. Some of these gabbros exhibit mineral chemistries suggesting their derivation from basaltic liquids formed from mantle sources that underwent either high degrees of partial melting or several partial melting episodes. Moreover, some of the gabbros display a crystallization sequence where orthopyroxene and clinopyroxene appeared before plagioclase. The major element compositions of coexisting orthopyroxenes and olivines from the mantle peridotites are consistent with low to high degrees of partial melting. Accessory spinels in these peridotites display a wide range of XCr values as well with some of them above the empirical upper limit of 0.6 often observed in most modern mid-oceanic ridge (MOR) mantle rocks. Co-existing olivines and spinels from the peridotites also exhibit compositions suggesting that they lastly equilibrated under oxidizing mantle conditions. The juxtaposition of volcanic rocks showing affinities with modern MOR and island arc environments suggests that most of the volcanic sequences in Philippine ophiolites formed in subduction-related geodynamic settings. Similarly, their associated gabbros and peridotites display mineralogical characteristics and mineral chemistries consistent with their derivation from modern supra-subduction zone-like environments. Alternatively, these rocks could have, in part, evolved in a supra-subduction zone even though they originated from a MOR-like setting. A simplified scenario regarding the early geodynamic evolution of the Philippines is proposed on the basis of the geochemical signatures of the ophiolites, their ages of formation and the ages and origins of the oceanic basins actually bounding the archipelago, including basins presumed to be now totally consumed. This scenario envisages the early development of the archipelago to be largely dominated by the opening and closing of oceanic basins. Fragments of these basins provided the substratum on top of which the Cretaceous to Recent volcanic arcs of the Philippines were emplaced.

Trace elements and tectonic relationships of basaltic rocks in the Ballantrae igneous complex, Ayrshire

1974 ◽  
Vol 111 (1) ◽  
pp. 35-41 ◽  
Author(s):  
J. M. Wilkinson ◽  
J. R. Cann
Keyword(s):  
Trace Elements ◽  
Subduction Zone ◽  
Oceanic Crust ◽  
Hot Spot ◽  
Island Arc ◽  
Igneous Complex ◽  
Basaltic Rocks ◽  
Genetic Groups ◽  
Tectonic Environment ◽  
Low Potassium

SummaryIn order to obtain further evidence for the tectonic environment of generation of the basaltic rocks of the Ballantrae igneous complex, specimens of pillow lavas, dolerites, glaucophane schists and amphibolites were analysed for Ti, Zr, Y and Nb. Using Ti–Zr–Y, Ti–Zr and Y/Nb diagrams, three different genetic groups have been distinguished – (i) hot-spot basalts round Downan Point, round Bennane Head as far N as Balcreuchan Port, and also within serpentinite around Lendalfoot, (ii) island arc low-potassium tholeiites between Balcreuchan Port and Gamesloup, and (iii) possible ocean floor basalts at Knockormal and Knocklaugh. The interrelationships of these groups are in doubt. The hot-spot basalts may have been erupted through oceanic crust, but they could have formed prior to, or subsequent to, the island arc activity. More likely, the hot-spot basalts formed (possibly on oceanic crust) at a considerable distance from the island arc, and the two were later brought together tectonically, probably at the subduction zone associated with the arc.

Geochemistry of the upper Snooks Arm Group basalts, Burlington Peninsula, Newfoundland: evidence against formation in an island arc

1980 ◽  
Vol 17 (7) ◽  
pp. 888-900 ◽  
Author(s):  
G. A. Jenner ◽  
B. J. Fryer
Keyword(s):  
Subduction Zone ◽  
Oceanic Crust ◽  
Sedimentary Rocks ◽  
Oceanic Islands ◽  
Oceanic Island ◽  
Island Arc ◽  
Geochemical Data ◽  
Basaltic Rocks ◽  
Arc Setting ◽  
Back Arc

The Snooks Arm Group of the Newfoundland Appalachians, which includes the Betts Cove ophiolite at its base, has been interpreted as oceanic crust overlain by island arc volcanic and sedimentary rocks. The limited geochemical data available on the upper Snooks Arm Group basalts have been used as evidence for and against their formation in an island arc environment.Reinvestigation of the chemistry of the basaltic rocks of the upper Snooks Arm Group establishes them as large ion lithophile enriched tholeiites. Similar basalts have been found in oceanic islands, on aseismic ridges, and possibly in back-arc basins. Chemically analogous rocks are notably lacking from island arc settings.The geochemistry and geology of the upper Snooks Arm Group suggest that these rocks may have formed in either an oceanic island setting or, as recently suggested by Upadhyay and Neale, as part of a marginal basin. It is not possible to distinguish between these alternate models, although the most similar basaltic rocks occur in the former environment. It is most unlikely that these rocks formed in an early island arc setting and indeed there may be no need for them to be associated with a major subduction zone.

ID-TIMS U-PB GEOCHRONOLOGY OF LOWER CRUSTAL CUMULATE COMPLEXES IN THE KOHISTAN TERRANE, NORTH-EAST PAKISTAN: IMPLICATIONS FOR ISLAND ARC FORMATION

2016 ◽  
Author(s):  
Jack Edward Stirling ◽  
◽  
Steven W. Denyszyn ◽  
Marco L. Fiorentini ◽  
Robert R. Loucks
Keyword(s):  
Island Arc ◽  
North East ◽  
Lower Crustal

Redescription of Pseudogilquinia pillersi (Southwell, 1929) (Cestoda, Trypanorhyncha) from serranid and lethrinid fishes from New Caledonia and Australia

2007 ◽  
Vol 52 (3) ◽  
Author(s):  
Ian Beveridge ◽  
Claude Chauvet ◽  
Jean-Lou Justine
Keyword(s):  
Sri Lanka ◽  
Host Range ◽  
East Coast ◽  
New Caledonia ◽  
Epinephelus Coioides ◽  
North East ◽  
The North ◽  
Specific Variation ◽  
Epinephelus Malabaricus

AbstractPseudogilquinia pillersi (Southwell, 1929), a poorly known species of trypanorhynch, is redescribed from plerocerci collected from Epinephelus coioides (Hamilton, 1922), Epinephelus malabaricus (Bloch et Schneider, 1801) (Serranidae) and Plectropomus laevis (Lacépède, 1801) (Serranidae) off New Caledonia. These were compared with specimens from Lethrinus atkinsoni Seale, 1910 and Lethrinus miniatus (Forster, 1801) (Lethrinidae) off the north-east coast of Australia as well as syntypes from Protonibea diacantha (Lacépède, 1802) from Sri Lanka. Although size differences were found in parts of the scolex as well as in the sizes of the tentacular hooks, the hook arrangements were identical in all specimens. The differences observed were attributed provisionally to intra-specific variation across a wide geographic and host range.

scholarly journals Tectonic reconstruction of Uda-Murgal arc and the Late Jurassic and Early Cretaceous convergent margin of Northeast Asia–Northwest Pacific

2009 ◽  
Vol 4 ◽  
pp. 273-288 ◽  
Author(s):  
S. D. Sokolov ◽  
G. Ye. Bondarenko ◽  
A. K. Khudoley ◽  
O. L. Morozov ◽  
M. V. Luchitskaya ◽  
...  
Keyword(s):  
Northeast Asia ◽  
Upper Jurassic ◽  
Island Arc ◽  
Passive Margin ◽  
Northwest Pacific ◽  
Island Arcs ◽  
The South ◽  
Convergent Margin ◽  
Tectonic Zone ◽  
The North

Abstract. A long tectonic zone composed of Upper Jurassic to Lower Cretaceous volcanic and sedimentary rocks is recognized along the Asian continent margin from the Mongol-Okhotsk fold and thrust belt on the south to the Chukotka Peninsula on the north. This belt represents the Uda-Murgal arc, which was developed along the convergent margin between Northeast Asia and Northwest Meso-Pacific. Several segments are identified in this arc based upon the volcanic and sedimentary rock assemblages, their respective compositions and basement structures. The southern and central parts of the Uda-Murgal arc were a continental margin belt with heterogeneous basement represented by metamorphic rocks of the Siberian craton, the Verkhoyansk terrigenous complex of Siberian passive margin and the Koni-Taigonos Late Paleozoic to Early Mesozoic island arc with accreted oceanic terranes. At the present day latitude of the Pekulney and Chukotka segments there was an ensimatic island arc with relicts of the South Anyui oceanic basin in a backarc basin. Accretionary prisms of the Uda-Murgal arc and accreted terranes contain fragments of Permian, Triassic to Jurassic and Jurassic to Cretaceous (Tithonian–Valanginian) oceanic crust and Jurassic ensimatic island arcs. Paleomagnetic and faunal data show significant displacement of these oceanic complexes and the terranes of the Taigonos Peninsula were originally parts of the Izanagi oceanic plate.

scholarly journals The Imbert Formation of northern Hispaniola: a tectono-sedimentary record of arc-continent collision and ophiolite emplacement in the northern Caribbean subduction-accretionary prism

2015 ◽  
Vol 7 (2) ◽  
pp. 1827-1876 ◽  
Author(s):  
J. Escuder-Viruete ◽  
A. Suárez-Rodríguez ◽  
J. Gabites ◽  
A. Pérez-Estaún
Keyword(s):  
Subduction Zone ◽  
Continental Margin ◽  
Middle Eocene ◽  
Accretionary Prism ◽  
Island Arc ◽  
Caribbean Island ◽  
Stratigraphic Sequence ◽  
Oblique Collision ◽  
The Caribbean ◽  
Ophiolitic Complex

Abstract. In northern Hispaniola, the Imbert Formation (Fm) has been interpreted as an orogenic "mélange" originally deposited as trench-fill sediments, an accretionary (subduction) complex formed above a SW-dipping subduction zone, or the sedimentary result of the early oblique collision of the Caribbean plate with the Bahama Platform in the middle Eocene. However, new stratigraphical, structural, geochemical and geochronological data from northern Hispaniola indicate that the Imbert Fm constitutes a coarsening-upward stratigraphic sequence that records the transition of the sedimentation from a pre-collisional forearc to a syn-collisional piggy-back basin. This piggy-back basin was transported on top of the Puerto Plata ophiolitic complex slab and structurally underlying accreted units of the Rio San Juan complex, as it was emplaced onto the North America continental margin units. The Imbert Fm unconformably overlies different structural levels of the Caribbean subduction-accretionary prism, including a supra-subduction zone ophiolite, and consists of three laterally discontinuous units that record the exhumation of the underlying basement. The distal turbiditic lower unit includes the latest volcanic activity of the Caribbean island arc; the more proximal turbiditic intermediate unit is moderately affected by syn-sedimentary faulting; and the upper unit is a (caotic) olistostromic unit, composed of serpentinite-rich polymictic breccias, conglomerates and sandstones, strongly deformed by syn-sedimentary faulting, slumping and sliding processes. The Imbert Fm is followed by subsidence and turbiditic deposition of the overlying El Mamey Group. The 40Ar / 39Ar plagioclase plateau ages obtained in gabbroic rocks from the Puerto Plata ophiolitic complex indicate its exhumation at ∼ 45–40 Ma (lower-to-middle Eocene), contemporaneously to the sedimentation of the overlying Imbert Fm. These cooling ages imply the uplift to the surface and submarine erosion of the complex to be the source of the ophiolitic fragments in the Imbert Fm, during of shortly after the emplacement of the intra-oceanic Caribbean island-arc onto the continental margin.

Takhtajan's floristic regions and foliicolous lichen biogeography: a compatibility analysis

2003 ◽  
Vol 35 (1) ◽  
pp. 33-53 ◽  
Author(s):  
Robert Lücking
Keyword(s):  
Large Scale ◽  
New Caledonia ◽  
Vascular Plant ◽  
Distribution Patterns ◽  
Plant Distribution ◽  
Sufficient Information ◽  
East African ◽  
Foliicolous Lichens ◽  
North East ◽  
Compatibility Analysis

AbstractTakhtajan's floristic regions of the world, based on vascular plant distribution, were used for a comparative analysis of foliicolous lichen biogeography. Of the 35 regions distinguished by that author, 23 feature foliicolous lichens. The South-East African, Fijian, Polynesian and Hawaiian regions lack sufficient information and were excluded from further analysis. Using multi-dimensional scaling and cluster and cladistic analyses, the remaining 19 regions were grouped into six lichenogeographical regions: (1) Neotropics, (2) African Paleotropics (including Madagascar, Réunion and Seychelles), (3) Eastern Paleotropics (including North-East Australia and New Caledonia), (4) Valdivian region (temperate rainforest in southern South America), (5) Tethyan region (subtropical areas of Macaronesia, Mediterranean, and Western Irano-Turanian) and (6) Neozealandic-Tasmanian region (temperate rainforests of New Zealand and Tasmania). Affinities between these six large scale regions, with 57–77% shared species, are still stronger than those between the 35 smaller scale regions denned by Takhtajan [(20−)40–60(−75)% shared species]. Based on presence/absence within each of the six regions, 22 potential distribution patterns were defined for foliicolous lichens. Many species are widely distributed; 21% are cosmopolitan or pantropical, while 19% are disjunct on at least two continents, and only 60% are restricted to one of the three major tropical areas (nearly 100% in vascular plants). Most of the latter are found in the Neotropics, while the African Paleotropics are poor in endemics. Most genera deviate significantly from overall distribution patterns; for example, Strigula and Calopadia have higher proportions of widely distributed species, while Porina displays a concentration of Eastern Paleotropical endemics. Species diversity and composition of the six regions indicate that the three extra-tropical foliicolous lichen biotas (Valdivian, Tethyan, Neozealandic-Tasmanian) are the result of partly separate evolutionary histories. On the other hand, there is a strong affinity between the Neotropics and the African Paleotropics, suggesting a shared Western Gondwanan element in the foliicolous lichen biotas of these two regions.

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