Back-arc extension in the southern Andes: a review and critical reappraisal

1981 ◽  
Vol 300 (1454) ◽  
pp. 319-335 ◽  
Keyword(s):  
Gulf Of California ◽  
Pillow Lava ◽  
Andaman Sea ◽  
Southern Andes ◽  
The North ◽  
Field Evidence ◽  
Basin Floor ◽  
Arc Setting ◽  
Back Arc ◽  
Ocean Ridge

The interpretation that the mafic ‘rocas verdes’ (green rocks) complex of the southern Andes represents part of the uplifted floor of a Late Jurassic to Early Cretaceous back-arc basin has proved particularly useful in understanding the geological evolution of the southern Andes, the north Scotia Ridge and the Antarctic Peninsula. Clear field evidence of the back-arc setting of the 'rocas verdes’ gabbro-sheeted dyke - pillow lava ophiolitic assemblages has encouraged fruitful petrological and geochemical comparison with mid-ocean ridge and marginal basin basalts, other onshore ophiolite complexes, and Archaean greenstone belts. Uncertainty still surrounds estimates of the original width and depth of the basin, as well as the proportion of new mafic crust, compared with relict sialic crust, in the basin floor. These questions are unresolved, owing mainly to the considerable Lower Cretaceous turbiditic basin infill and the effects of mid-Cretaceous compressional deformation. While the field relations clearly indicate that the ‘rocas verdes’ basin is not an older piece of ocean floor ‘trapped’ behind a volcanic arc, it is not yet clear whether the basin is directly subduction-related or falls in the category of back-arc ‘leaky transforms’ like the proto-Gulf of California or apparent ‘rip-off’ features like the Andaman Sea.

Tholeiitic volcanic rocks of the late Archean Blake River Group, southern Abitibi greenstone belt: origin and geodynamic implications

1992 ◽  
Vol 29 (7) ◽  
pp. 1448-1458 ◽  
Author(s):  
M. R. Laflèche ◽  
C. Dupuy ◽  
J. Dostal
Keyword(s):  
Greenstone Belt ◽  
Volcanic Rocks ◽  
Incompatible Trace Element ◽  
Progressive Change ◽  
Abitibi Greenstone Belt ◽  
Mid Ocean Ridge ◽  
Compositional Variations ◽  
Arc Setting ◽  
Back Arc ◽  
Ocean Ridge

The late Archean Blake River Group volcanic sequence forms the uppermost part of the southern Abitibi greenstone belt in Quebec. The group is mainly composed of mid-ocean-ridge basalt (MORB)-like tholeiites that show a progressive change of several incompatible trace element ratios (e.g., Nb/Th, Nb/Ta, La/Yb, and Zr/Y) during differentiation. The compositional variations are inferred to be the result of fractional crystallization coupled with mixing–contamination of tholeiites by calc-alkaline magma which produced the mafic–intermediate lavas intercalated with the tholeiites in the uppermost part of the sequence. The MORB-like tholeiites were probably emplaced in a back-arc setting.

Are Wilson Cycles preserved in Archean cratons? A comparison of the North China and Slave cratons

2014 ◽  
Vol 51 (3) ◽  
pp. 297-311 ◽  
Author(s):  
Timothy M. Kusky ◽  
Xiaoyong Li ◽  
Zhensheng Wang ◽  
Jianmin Fu ◽  
Luo Ze ◽  
...  
Keyword(s):  
North China Craton ◽  
Plate Tectonics ◽  
North China ◽  
Passive Margin ◽  
The North ◽  
Tectonic History ◽  
History Of ◽  
Pacific Slab ◽  
Arc Setting ◽  
Back Arc

A review and comparison of the tectonic history of the North China and Slave cratons reveal that the two cratons have many similarities and some significant differences. The similarities rest in the conclusion that both cratons have a history of a Wilson Cycle, having experienced rifting of an old continent in the late Archean, development of a rift to passive margin sequence, collision of this passive margin with arcs within 100–200 Ma of the formation of the passive margin, reversal of subduction polarity, then eventual climactic collision with another arc terrane, microcontinental fragment, or continent. This cycle demonstrates the operation of Paleozoic-style plate tectonics in the late Archean. The main differences lie in the later tectonic evolution. The Slave’s post-cratonization history is dominated by subduction dipping away from the interior of the craton, and later incorporation into the interior of a larger continent, whereas the North China Craton has had a long history of subduction beneath the craton, including presently being located above the flat-lying Pacific slab resting in the mantle transition zone, placing it in a broad back-arc setting, with multiple mantle hydration events and collisions along its borders. The hydration enhances melting in the overlying mantle, and leads to melts migrating upwards to thermochemically erode the lithospheric root. This major difference may explain why the relatively small Slave craton preserves its thick Archean lithospheric root, whereas the eastern North China Craton has lost it.

Meta-igneous rocks of the West-Carpathian basement, Slovakia: indicators of Early Paleozoic extension and shortening events

2009 ◽  
Vol 180 (6) ◽  
pp. 461-471 ◽  
Author(s):  
Marián Putiš ◽  
Peter Ivan ◽  
Milan Kohút ◽  
Ján Spišiak ◽  
Pavol Siman ◽  
...  
Keyword(s):  
Early Paleozoic ◽  
The South ◽  
Ophiolite Complex ◽  
The North ◽  
Late Cambrian ◽  
Collision Zone ◽  
Gondwana Margin ◽  
Group A ◽  
Arc Setting ◽  
Back Arc

Abstract The paper reviews the main West-Carpathian Early Paleozoic metamorphosed originally sedimentary-magmatic complexes, dated by SHRIMP on zircons, as indicators of crustal extension and shortening events. Igneous precursors of a Layered Amphibolite Complex (LAC) – fractionated upper mantle gabbros to diorites, dated at 503 ± 4 and 492 ± 4 Ma from the North-Veporic, or 480 ± 5 and 450 ± 6 Ma from the Tatric basement are contemporaneous with subaluminous to metaluminous I-type (507 ± 4 Ma, the South-Veporic basement), peraluminous S-type (497 ± 4 Ma, the South-Veporic basement; 516 ± 7, 485 ± 6 and 462 ± 6 Ma, the North-Veporic basement; 497 ± 6, 472 ± 6 and 450 ± 6 Ma, the Tatric basement), alkaline A-type (511 ± 6 Ma, South-Veporic basement) granitic orthogneisses and calcalkaline rhyolitic (482 ± 6 Ma) and dacitic (476 ± 7 Ma) metavolcanics (Gemeric basement), indicating a magmatic immature back arc setting. The ages point to Middle/Late Cambrian, Early and Late Ordovician magmatic phases, coeval with the extension in the northern Gondwana margin. Separation of an inferred Avalonian and/or Galatian terranes distal continental ribbon corresponds with the opening of a Medio-European Basin. A 430-390 Ma dated MP/HP metamorphic event, recorded in the LAC and associated orthogneisses, occurred in the area of thinned immature back arc basin crust due to closure of the Medio-European Basin. Thus a distal Gondwana continental ribbon north of this basin could be an eastward lateral pendant of Armorica, derived from Galatian terrane. Metaophiolites of the Pernek Group (a metagabbrodolerite dated at 371 ± 4 Ma) in the Tatric basement, analogous to island-arc tholeiites and back-arc basin basalts, indicate a back-arc basin setting north of a 430-390 Ma old northward dipping subduction/collision zone, dividing the northward drifting western Galatian terrane microplate from the Gondwana margin. Some metabasites of the Gemeric basement might indicate Late Devonian to Mississippian opening of a peri-Gondwanan Paleotethyan oceanic basin: a 383 ± 3 Ma old remelted metagabbro (482 ± 9 Ma) from the Klátov gneiss-amphibolite complex, ca. 385 Ma old porphyritic metabasite of the Zlatník ophiolite complex, as well as a 350 ± 5 Ma old HP metabasite as tectonic fragment within the Rakovec Group. The closure of Devonian-Mississippian basins, accompanied by medium-pressure (the Pernek Group) to high-pressure (blueschist to eclogitic tectonic fragments in greenschist facies rocks of the Rakovec Group) metamorphism, occurred in late Carboniferous to early Permian, when Paleotethyan realm complexes accreted to a Galatian terrane microplate, the latter represented by the older and the higher-grade Tatric and Veporic basement complexes.

Unexplored deepwater basins of North Andaman Sea

2020 ◽  
Vol 39 (8) ◽  
pp. 551-557
Author(s):  
Rajesh Kalra ◽  
Roberto Fainstein ◽  
Srinivas Chandrashekar
Keyword(s):  
Seismic Velocity ◽  
State Of The Art ◽  
Far East ◽  
Seismic Inversion ◽  
Andaman Sea ◽  
Seismic Exploration ◽  
Carbonate Platforms ◽  
The North ◽  
Northern Edge ◽  
Back Arc

Deepwater basins of the North Andaman Sea in the northern edge of the Far East Archipelago were assessed recently by state-of-the-art seismic technology. The North Andaman Sea embraces several Tertiary basins consisting of a forearc basin, a volcanic arc, and a back-arc basin. Their massive but largely unknown stratigraphy consists of deeper Neogene lacustrine and deltaic sediments that infill basal synrift half-grabens, blanketed by massive sequences of the Late Oligocene, Miocene, and recent strata. In the extensional forearc, the deeper seismic marker horizons were structurally mapped and identified by acoustic impedance contrasts as carbonates, mass-transport complexes, synrift, and basement. The shallower Pliocene and Pleistocene sequences are dominated by low-seismic-velocity hemipelagic clays that were investigated using seismic attributes and seismic inversion. In the back arc, the relatively larger graben features were affected by tectonic inversion contemporaneous with the foundering of the basin into deep water in the Late Miocene. In the forearc and back arc, main hydrocarbon plays are the rimmed Early Miocene carbonate platforms, the paralic and deltaic sediments beneath the platform, and the deepwater clastics of hemipelagic clays and sands that form the dominant strata of the Mio-Pliocene. This modern seismic exploration involved acquisition, processing, and interpretation to assess the hydrocarbon prospectivity of undrilled deepwater regions in the forearc and back arc.

scholarly journals Evolution of Subduction Dynamics beneath West Avalonia in Middle to Late Ordovician Times

Lithosphere ◽  
2020 ◽  
Vol 2020 (1) ◽  
pp. 1-22
Author(s):  
Pierre Jutras ◽  
J. Brendan Murphy ◽  
Dennis Quick ◽  
Jaroslav Dostal
Keyword(s):  
Trace Element ◽  
Partial Melting ◽  
Volcanic Rocks ◽  
Upper Ordovician ◽  
The North ◽  
Trace Element Contents ◽  
Element Contents ◽  
Arc Setting ◽  
Back Arc ◽  
High Degree

Abstract Middle to Upper Ordovician volcanic rocks in the Arisaig area of Nova Scotia, Canada, constitute the only known record of volcanism in West Avalonia during that interval. Hence, they have been extensively studied to test paleocontinental reconstructions that consistently show Avalonia as a drifting microcontinent during that period. Identification of volcanic rocks with an intermediate composition (the new Seaspray Cove Formation) between upper Darriwilian bimodal volcanic rocks of the Dunn Point Formation and Sandbian felsic pyroclastic rocks of the McGillivray Brook Formation has led to a reevaluation of magmatic relationships in the Ordovician volcanic suite at Arisaig. Although part of the same volcanic construction, the three formations are separated by significant time-gaps and are shown to belong to three distinct magmatic subsystems. The tectonostratigraphic context and trace element contents of the Dunn Point Formation basalts suggest that they were produced by the high-degree partial melting of an E-MORB type source in a back-arc extensional setting, whereas trace element contents in intermediate rocks of the Seaspray Cove Formation suggest that they were produced by the low-degree partial melting of a subduction-enriched source in an arc setting. The two formations are separated by a long interval of volcanic quiescence and deep weathering, during which time the back-arc region evolved from extension to shortening and was eventually onlapped by arc volcanic rocks. Based on limited field constraints, paleomagnetic and paleontological data, this progradation of arc onto back-arc volcanic rocks occurred from the north, where an increasingly young Iapetan oceanic plate was being subducted at an increasingly shallow angle. Partial subduction of the Iapetan oceanic ridge is thought to have subsequently generated slab window magmatism, thus marking the last pulse of subduction-related volcanism in both East and West Avalonia.

scholarly journals TECTONIC EVOLUTION OF THE BETIC CORDILLERA: AN OVERVIEW

2004 ◽  
Vol 36 (4) ◽  
pp. 1598 ◽  
Author(s):  
F. Alonso-Chaves ◽  
J. I. Soto ◽  
M. Orozco ◽  
A. A. Kilias ◽  
M. D. Tranos
Keyword(s):  
Tectonic Evolution ◽  
Aegean Sea ◽  
Normal Faults ◽  
The South ◽  
Mountain Ranges ◽  
The North ◽  
Arc Setting ◽  
The One ◽  
Continental Basin ◽  
Back Arc

The Betic (Southern Spain) and the Rif (Morocco) mountain chains, connected through the Gibraltar Strait, shapes a W-E elongated and arcuate Alpine orogenic belt. The Alborân Sea, in continuity to the east with the South Balearic Basin, is located in the inner part of this alpine belt. The Iberian and African continental forelands bound the region as a whole to the north and south, respectively, and to the east it is connected to the oceanic Sardine-Balearic Basin. The peculiarities of these westernmost Mediterranean chains result from: (1) its position between two large convergent plates -Africa and Europe- that have had variable directions of relative motion since the late Cretaceous; and (2) the Neogene westward migration of the orogenic hinterland and its simultaneous "back-arc"-like extension, generating the Alborén Sea basin. The complexes and large paleogeographic terrains traditionally recognized in the Betic and Rif chains belong to four pre-Neogene crustal domains: the South-Iberian and Maghrebian passive continental paleomargins (External Zones of the orogen), the Flysch Units, and the Alborân Crustal Domain composed mainly of a pre- Miocene metamorphosed thrust-stack (Nevado-Filabride, Alpujârride, and Malaguide complexes, from bottom to top). The boundaries between the main metamorphic complexes of the Alborân Domain are extensional detachments, which finally developed under brittle conditions and are commonly sealed by middle-to-late Miocene marine-to-continental sediments. They, nonetheless, are not the most recent structures in the Alborân Domain, because upright, E-W open folds warp the extensional detachments, and finally, high-angle normal faults and strike-slip faults, many of which are still active, offset folds and extensional detachments. The tectonic evolution of the Betic  Alborân orogenic system shows close similarities with the one depicted in other arcuate-shaped, Alpine mountain ranges in the Mediterranean, such as the Hellenic Arc and the Aegean Sea. Like in the westernmost Mediterranean, a thickened (pre Miocene) crust is bounding there a thinned, continental (?) basin. Extension is also formed here in a "back-arc" setting, being developed simultaneously with the N-S convergence between the African and European plates.

Stratigraphy, structure and geochemistry of Archaean supracrustal rocks from Oqaatsut and Naajaat Qaqqaat, north-east Disko Bugt, West Greenland

1999 ◽  
pp. 65-78
Author(s):  
Henrik Rasmussen ◽  
Lars Frimodt Pedersen
Keyword(s):  
Tectonic Setting ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
West Greenland ◽  
North West ◽  
North East ◽  
Metavolcanic Rocks ◽  
Arc Setting ◽  
Area North ◽  
Back Arc

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Rasmussen, H., & Frimodt Pedersen, L. (1999). Stratigraphy, structure and geochemistry of Archaean supracrustal rocks from Oqaatsut and Naajaat Qaqqaat, north-east Disko Bugt, West Greenland. Geology of Greenland Survey Bulletin, 181, 65-78. https://doi.org/10.34194/ggub.v181.5114 _______________ Two Archaean supracrustal sequences in the area north-east of Disko Bugt, c. 1950 and c. 800 m in thickness, are dominated by pelitic and semipelitic mica schists, interlayered with basic metavolcanic rocks. A polymict conglomerate occurs locally at the base of one of the sequences. One of the supracrustal sequences has undergone four phases of deformation; the other three phases. In both sequences an early phase, now represented by isoclinal folds, was followed by north-west-directed thrusting. A penetrative deformation represented by upright to steeply inclined folds is only recognised in one of the sequences. Steep, brittle N–S and NW–SE striking faults transect all rock units including late stage dolerites and lamprophyres. Investigation of major- and trace-element geochemistry based on discrimination diagrams for tectonic setting suggests that both metasediments and metavolcanic rocks were deposited in an environment similar to a modern back-arc setting.

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