scholarly journals Passive obduction and gravity-driven emplacement of large ophiolitic sheets: The New Caledonia ophiolite (SW Pacific) as a case study?

2013 ◽  
Vol 184 (6) ◽  
pp. 545-556 ◽  
Author(s):  
Yves Lagabrielle ◽  
Alain Chauvet ◽  
Marc Ulrich ◽  
Stéphane Guillot
Keyword(s):  
New Caledonia ◽  
Oceanic Lithosphere ◽  
Accretionary Wedge ◽  
Plate Convergence ◽  
Tectonic Force ◽  
Sw Pacific ◽  
Tropical Conditions ◽  
Significant Extension ◽  
Gravity Driven ◽  
Basaltic Layer

Abstract The 300 km long allochthonous sheet of oceanic mantle forming the New Caledonia ophiolite displays three specific characters: 1) the ophiolite pile lacks concordant sheeted dykes and pillow basalt layers; 2) the ophiolite, refered to as the Peridotite nappe, is thrusted over the basaltic formations of the Poya terrane which are classicaly thought to originate from a different oceanic environment; 3) The basal contact of the ultramafic sheet is remarkably flat all along New-Caledonia and the Peridotite nappe has not been thickened during obduction, rather it experienced significant extension. This suggests that the peridotites have not been emplaced by a tectonic force applied to the rear. New petrological and geochemical results obtained from mantle rocks finally show that the Poya terrane may originate from the same oceanic basin as the peridotites. In this article, we consider such possible cogenetic links and we propose a simple model for the obduction of the New Caledonia ophiolite in which the Poya basalts represent the original cover of the Peridotite nappe. We infer that continuous uplift of the subducted units buried beneath the oceanic lithosphere in the northern part of New Caledonia drove passive uplift of the ophiolite and led to erosion and to initiation of sliding of the basaltic layer. During the Priabonian (latest Eocene), products of the erosion of the basaltic layer were deposited together with sediments derived from the Norfolk passive oceanic margin. These sediments are involved as tectonic slices into an accretionary wedge formed in response to plate convergence. The volcaniclastic sedimentation ends up with the emplacement of large slided blocks of basalts and rafted mafic units that progressively filled up the basin. Obduction process ended with the gravity sliding of the oceanic mantle sheet, previously scalped from its mafic cover. This process is contemporaneous with the exhumation of the HP-LT units of Pouebo and Diahot. Gravity sliding was facilitated by the occurrence of a continuous serpentine sole resulting from metasomatic hydratation of mantle rocks, which developed during the uplift of the Norfolk basement and overlying Diahot and Pouébo units. Progressive emersion of the obducted lithosphere allowed subsequent weathering under subaerial, tropical conditions.

scholarly journals New seismological data from the Calabrian arc reveal arc-orthogonal extension across the subduction zone

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tiziana Sgroi ◽  
Alina Polonia ◽  
Graziella Barberi ◽  
Andrea Billi ◽  
Luca Gasperini
Keyword(s):  
Lateral Displacement ◽  
Tectonic Setting ◽  
Plate Boundary ◽  
Velocity Model ◽  
Tectonic Deformation ◽  
Accretionary Wedge ◽  
Tectonic Structures ◽  
Plate Convergence ◽  
Seismogenic Layer ◽  
Regional Tectonic

AbstractThe Calabrian Arc subduction-rollback system along the convergent Africa/Eurasia plate boundary is among the most active geological structures in the Mediterranean Sea. However, its seismogenic behaviour is largely unknown, mostly due to the lack of seismological observations. We studied low-to-moderate magnitude earthquakes recorded by the seismic network onshore, integrated by data from a seafloor observatory (NEMO-SN1), to compute a lithospheric velocity model for the western Ionian Sea, and relocate seismic events along major tectonic structures. Spatial changes in the depth distribution of earthquakes highlight a major lithospheric boundary constituted by the Ionian Fault, which separates two sectors where thickness of the seismogenic layer varies over 40 km. This regional tectonic boundary represents the eastern limit of a domain characterized by thinner lithosphere, arc-orthogonal extension, and transtensional tectonic deformation. Occurrence of a few thrust-type earthquakes in the accretionary wedge may suggest a locked subduction interface in a complex tectonic setting, which involves the interplay between arc-orthogonal extension and plate convergence. We finally note that distribution of earthquakes and associated extensional deformation in the Messina Straits region could be explained by right-lateral displacement along the Ionian Fault. This observation could shed new light on proposed mechanisms for the 1908 Messina earthquake.

scholarly journals IODP Expedition 330: Drilling the Louisville Seamount Trail in the SW Pacific

2013 ◽  
Vol 15 ◽  
pp. 11-22 ◽  
Author(s):  
A. A. P. Koppers ◽  
T. Yamazaki ◽  
J. Geldmacher ◽  
Keyword(s):  
Mantle Plume ◽  
Mantle Source ◽  
Isotope Geochemistry ◽  
Oceanic Lithosphere ◽  
Similar Amount ◽  
Mantle Plumes ◽  
Large Variability ◽  
Sw Pacific ◽  
Integrated Ocean Drilling Program ◽  
The Pacific

Deep-Earth convection can be understood by studying hotspot volcanoes that form where mantle plumes rise up and intersect the lithosphere, the Earth's rigid outer layer. Hotspots characteristically leave age-progressive trails of volcanoes and seamounts on top of oceanic lithosphere, which in turn allow us to decipher the motion of these plates relative to "fixed" deep-mantle plumes, and their (isotope) geochemistry provides insights into the long-term evolution of mantle source regions. However, it is strongly suggested that the Hawaiian mantle plume moved ~15° south between 80 and 50 million years ago. This raises a fundamental question about other hotspot systems in the Pacific, whether or not their mantle plumes experienced a similar amount and direction of motion. Integrated Ocean Drilling Program (IODP) Expedition 330 to the Louisville Seamounts showed that the Louisville hotspot in the South Pacific behaved in a different manner, as its mantle plume remained more or less fixed around 48°S latitude during that same time period. Our findings demonstrate that the Pacific hotspots move independently and that their trajectories may be controlled by differences in subduction zone geometry. Additionally, shipboard geochemistry data shows that, in contrast to Hawaiian volcanoes, the construction of the Louisville Seamounts doesn’t involve a shield-building phase dominated by tholeiitic lavas, and trace elements confirm the rather homogenous nature of the Louisville mantle source. Both observations set Louisville apart from the Hawaiian-Emperor seamount trail, whereby the latter has been erupting abundant tholeiites (characteristically up to 95% in volume) and which exhibit a large variability in (isotope) geochemistry and their mantle source components. <br><br> doi:<a href="http://dx.doi.org/10.2204/iodp.sd.15.02.2013" target="_blank">10.2204/iodp.sd.15.02.2013</a>

NEW TAXA IN PAPHIA AND DIMORPHANTHERA (ERICACEAE) IN PAPUASIA AND THE PROBLEM OF GENERIC LIMITS IN VACCINIEAE

2003 ◽  
Vol 60 (3) ◽  
pp. 267-298 ◽  
Author(s):  
P. F. STEVENS
Keyword(s):  
New Species ◽  
Papua New Guinea ◽  
New Caledonia ◽  
Current Knowledge ◽  
New Guinea ◽  
Morphological Data ◽  
Sw Pacific ◽  
The Status ◽  
Three New Species ◽  
Made In

New species of Ericaceae recently collected in Papua New Guinea necessitate a re-evaluation of the status of Agapetes subgenus Paphia section Paphia. The combination of molecular and morphological data confirms that Agapetes, currently a genus of about 100 species from Fiji, New Caledonia and Queensland to mainland SE Asia, and most diverse in the latter area, cannot be maintained in its current circumscription. Various taxonomic solutions that do justice to our current knowledge of the morphology and relationships of the two main parts of the genus are discussed. The reinstatement of Paphia does least violence nomenclaturally. All 23 taxa recognized in Paphia are listed, 14 new combinations of Agapetes from the New Guinea–SW Pacific area are made in Paphia, three new species are described (P. megaphylla, P. vulcanicola and P. woodsii), and an incompletely known taxon is characterized. A key to all taxa is presented. In Dimorphanthera, five new species are described (D. angiliensis, D. anomala, D. antennifera, D. cratericola and D. inopinata), three reduced to synonymy, one reduced to a variety and one variety recognized as a species (D. continua). A key to the 87 taxa currently recognized in the genus is presented.

scholarly journals Micro-caddisfly faunas of Australia and the southwest Pacific (Trichoptera, Hydroptilidae)

Zoosymposia ◽  
2016 ◽  
Vol 10 (1) ◽  
pp. 439-450
Author(s):  
ALICE WELLS ◽  
KJELL ARNE JOHANSON
Keyword(s):  
New Zealand ◽  
Pacific Islands ◽  
New Caledonia ◽  
New Guinea ◽  
Faunal Composition ◽  
Southwest Pacific ◽  
Sw Pacific ◽  
Chance Events ◽  
Corroborative Evidence

Today's distributions of faunal groups reflect historic events—geological and evolutionary, as well as dispersals, extinctions and chance events. The extent to which each of these contributed to the hydroptilid faunas of mainland Australia, Tasmania, New Guinea, New Zealand, New Caledonia, Fiji and Vanuatu is explored by comparison of the faunal composition, geology and geography of Australia and these SW Pacific islands. Corroborative evidence is sought from other groups, flora as well as fauna.

Petrotectonic implications of metabasites of the Eastern Andean Metamorphic Complex at Lago O´Higgins-San Martin, southern Patagonia

2021 ◽  
Author(s):  
Diego Rojo ◽  
Mauricio Calderón ◽  
Matias Ghiglione ◽  
Rodrigo Javier Suárez ◽  
Paulo Quezada ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Crustal Contamination ◽  
Oceanic Lithosphere ◽  
Passive Margin ◽  
Low Grade ◽  
Accretionary Wedge ◽  
Metamorphic Complex ◽  
Marginal Basin ◽  
Southern Patagonia ◽  
San Martín

&lt;p&gt;The Eastern Andean Metamorphic Complex (EAMC) in southwestern Patagonia (4&amp;#176;-52&amp;#176;S) is a 450 km long belt mainly composed by low-grade metasedimentary rocks of Upper Devonian-lower Carboniferous, and Permian-lower Triassic ages. Previous works have suggested a passive margin environment for the deposition of the protolith. &amp;#160;The EAMC comprise scarce interleaved tectonic slices of marbles, metabasites, and exceptional serpentinite bodies. At Lago O&amp;#180;Higgins-San Martin (48&amp;#176;30&amp;#8217;S-49&amp;#176;00&amp;#8217;S) the metasedimentary sucessions are tectonically juxtaposed with lenses of pillowed metabasalts and greenschists having OIB, N-MORB, BABB and IAT geochemical affinities. The Nd-isotopic composition of metabasalts is characterized by &amp;#949;Nd&lt;sub&gt;(t=350 Ma)&lt;/sub&gt; of +6 and +7. The metabasalts show no signal of crustal contamination, instead, the mantle source was probably modified by subduction components. New and already published provenance data based on mineralogy, geochemistry and zircon geochronology indicate that the quartz-rich protolith of metasandstones were deposited during late Devonian-early Carboniferous times (youngest single zircon ages around of latest Devonian-earliest Carboniferous times) sourced from igneous and/or sedimentary rocks located in the interior of Gondwana, as the Deseado Massif, for instance. Noticeable, the detrital age patterns of all samples reveal a prominent population of late Neoproterozoic zircons, probably directly derived from igneous and/or metaigneous rocks of the Brasiliano/Pan-African orogen or from reworked material from variably metamorphosed sedimentary units that crops out at the same latitudes in the extra-Andean region of Patagonia. We propose that the protolith of metabasites formed part of the upper part of an oceanic-like lithosphere generated in a marginal basin above a supra-subduction zone, where plume-related oceanic island volcanoes were generated. The closure of the marginal basin, probably in mid-Carboniferous times, or soon after. The oceanic lithosphere was likely underthrusted within an east-to-northeast-dipping subduction zone, where ophiolitic rocks and metasedimentary sequences were tectonically interleaved at the base of an accretionary wedge.&lt;/p&gt;

Sign in / Sign up

Export Citation Format

Share Document