The late Paleozoic paired metamorphic belt of southern Central Chile: Consequence of a near-trench thermal anomaly?

Mapping Intimacies ◽

10.31223/x58s4b ◽

2021 ◽

Author(s):

Guido Gianni

Keyword(s):

Thermal Anomaly ◽

Accretionary Prism ◽

Late Paleozoic ◽

Metamorphic Belt ◽

Central Chile ◽

Geodynamic Process ◽

Mid Ocean Ridge ◽

Southern Central ◽

Geological Units ◽

Ocean Ridge

The hypothesis of a subduction-related Miyashiro-type paired metamorphic belt for the origin of the late Paleozoic igneous and metamorphic complex in the Andean Coastal Cordillera has remained unquestioned since its proposal in the early seventies. A synthesis of the advances in the study of these metamorphic rocks between 33°S and 42°S, revising field relations among geological units, and geochemical and geochronological data from the contemporaneous granitoids of the Coastal Batholith, highlights inconsistencies in this model. The record of short-lived forearc magmatism in the late Paleozoic intruding the partially synchronous accretionary prism, and geochemical and isotopic data from the igneous rocks indicating sources from the accretionary prism sediments and the back-top lithosphere, suggest a departure from typical subduction settings. I conclude that the anomalous configuration of the paired metamorphic belt and the associated Coastal Batholith resulted from a complex geodynamic process involving a near-trench thermal anomaly caused by the subduction of a trench parallel mid-ocean ridge.

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Upper Triassic Karmutsen Formation of Western Canada and Alaska: A Plume-Generated Oceanic Plateau Formed Along a Mid-Ocean Ridge Nucleated on a Late Paleozoic Active Margin

Topics in Igneous Petrology ◽

10.1007/978-90-481-9600-5_1 ◽

2010 ◽

pp. 3-27 ◽

Cited By ~ 1

Author(s):

Jaroslav Dostal ◽

J. Duncan Keppie ◽

J. Brendan Murphy ◽

Nicholas W. D. Massey

Keyword(s):

Upper Triassic ◽

Late Paleozoic ◽

Western Canada ◽

Active Margin ◽

Oceanic Plateau ◽

Mid Ocean Ridge ◽

Ocean Ridge

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Superimposed Quesnel (late PaleozoicJurassic) and YukonTanana (DevonianMississippian) arc assemblages, Cassiar Mountains, northern British Columbia: field, UPb, and igneous petrochemical evidence

Canadian Journal of Earth Sciences ◽

10.1139/e04-028 ◽

2004 ◽

Vol 41 (10) ◽

pp. 1201-1235 ◽

Cited By ~ 19

Author(s):

JoAnne Nelson ◽

Richard Friedman

Keyword(s):

British Columbia ◽

Early Jurassic ◽

Late Paleozoic ◽

Time Interval ◽

Magmatic Arc ◽

The North ◽

Mid Ocean Ridge ◽

Plutonic Belt ◽

Intrusive Suite ◽

Ocean Ridge

Allochthons in the Cassiar Mountains of northern British Columbia contain assemblages belonging to two distinct Canadian Cordilleran terranes, YukonTanana (YTT) and Quesnellia. These assemblages, of pre-Late Devonian, DevonianMississippian, PennsylvanianPermian, and Early Jurassic age, occur in intrusive and depositional, as well as structural, contact with each other. The allochthons are gently dipping thrust panels, interrupted by the mid-Cretaceous Cassiar Batholith. A key element for correlation across the batholith is the Mississippian and older pericratonic Dorsey Complex. New DevonianMississippian UPb ages for deformed plutons within it document an igneous suite like those in type YukonTanana exposures farther north. Other characteristics of the Dorsey Complex that ally it with YTT are orthoquartzites and grits, and amphibolite bodies with transitional mid-ocean ridge basalt (MORB) to ocean-island basalt (OIB) petrochemical signatures. Unconformities, deformed clasts in the late Paleozoic sequences, and a shared mid-Permian intrusive suite show that later arcs onlapped the mid-Paleozoic and older YTT assemblage. The Early Jurassic intrusive suite cuts all major contacts and fabrics except the terrane-bounding fault between the Slide Mountain and combined YTTQuesnel terranes. It represents a northern continuation of a plutonic belt that extends the length of the Mesozoic Quesnel magmatic arc. These relationships carry important implications for Cordilleran terrane history and the tectonic evolution of the North American margin. At least some of the major terranes were not unrelated entities prior to their accretion to the continent, but a system of superimposed and interconnected arcs that developed over a protracted time interval, with complex and evolving paleogeographic configurations much like the modern western Pacific province.

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Is Cr-Spinel Geochemistry Enough for Solving the Provenance Dilemma? Case Study from the Palaeogene Sandstones of the Western Carpathians (Eastern Slovakia)

Minerals ◽

10.3390/min8120543 ◽

2018 ◽

Vol 8 (12) ◽

pp. 543 ◽

Cited By ~ 2

Author(s):

Katarína Bónová ◽

Tomáš Mikuš ◽

Ján Bóna

Keyword(s):

Geodynamic Setting ◽

Chemical Compositions ◽

Volcanic Origin ◽

Mid Ocean Ridge ◽

Back Arc ◽

Geological Units ◽

Ocean Ridge ◽

The Relationship ◽

Island Basalt

The provenance of the Proč and Strihovce sandstones is crucial for understanding the relationship between the Pieniny Klippen (PKB) and Flysch (FB) belts in the easternmost part of the Western Carpathian realm. Detrital Cr-spinels in these tectonic units were assertively interpreted as sourced from the southern sources representing the Meliata mélange. In this study, we use the geochemistry of detrital chromian spinels to identify the mafic and ultramafic source of the sediments and to compare them each other. Simultaneously, we compare their chemical compositions with those from the different Western Carpathian geological units, which could feed the Proč and Krynica basins during the Paleogene, where the Proč and Strihovce formations (fms), respectively, were deposited. Chromian spinels from the Proč and Strihovce fms exhibit similar geochemical characteristics (Cr# = 0.44–0.88 and 0.29–0.89, Mg# = 0.17–0.68 and 0.2–0.72, TiO2 = 0.0–3.67 and 0.01–2.08 wt.%, respectively). The spinels show both supra-subduction zone (SSZ) peridotite signatures and volcanic origin. Whereas volcanic spinels from the Proč Formation (Fm.) were formed under an ocean island basalt (OIB) and back-arc basin basalt (BABB) geodynamic setting, those from the Strihovce Fm. suggest a predominantly mid-ocean ridge basalt (MORB) origin. To avoid mistakes in the provenance interpretations, the data from garnet geochemistry of both formations is supplied. The analysed Cr-spinels do not absolutely overlap with spinels reported from the Meliata Unit, and their composition indicates at least two independent sources.

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Geochemical, 40Ar/39Ar age, and isotopic data for crustal rocks of the Neyriz ophiolite, Iran

Canadian Journal of Earth Sciences ◽

10.1139/e05-111 ◽

2006 ◽

Vol 43 (1) ◽

pp. 57-70 ◽

Cited By ~ 55

Author(s):

Hassan A Babaie ◽

Abbed Babaei ◽

A Mohamad Ghazi ◽

Mohsen Arvin

Keyword(s):

Trace Element ◽

Accretionary Prism ◽

Tholeiitic Basalt ◽

Isotopic Data ◽

Crustal Rocks ◽

Mid Ocean Ridge ◽

Subduction Erosion ◽

Southwest Iran ◽

Ocean Ridge ◽

Low K

Trace-element data (including the rare-earth elements) in the crustal sequence of the Neotethyan Neyriz ophiolite in southwest Iran indicate normal mid-ocean ridge basalt (N-MORB) or island-arc tholeiite chemistry for the Tang-e Hana basalt. The data suggest that the Tang-e Hana rhyodacite, basalt, plagiogranite, and gabbro derived from a low-K tholeiitic parent magma. Trace-element distributions in amphibolite clasts, in the sole detachment of the ophiolite south of Lake Neyriz, correlate well with distributions in basalt clasts in the mélange and in the Tang-e Hana basalt. These trace elements suggest that the amphibolite originated from metamorphism and deformation of a tholeiitic basalt protolith. New 40Ar/39Ar incremental heating plateau ages from two hornblende plagiogranite specimens, in the crustal sequence in Tang-e Hana, are 92.07 ± 1.69 and 93.19 ± 2.48 Ma. Isotopic data for five Tang-e Hana basalts yield εNd values of +7.8 and +7.9, and 87Sr/86Sr values of 0.70368 to 0.70476. The isotopic compositions, ophiolite tectonostratigraphy, and correlation of the 40Ar/39Ar cooling (plagiogranite) and deformation (amphibolite) ages suggest emplacement of the Neyriz ophiolite either into an accretionary prism, through offscraping and subduction erosion, and (or) formation in a supra-subduction zone environment, around 8296 Ma. Progressive accretion probably led to the development of a fore-arc basin and deposition of Upper Cretaceous Eocene fore-arc and arc-derived sediments on the ophiolite.

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