Geochemical and Nd isotopic constraints for the origin of eclogite protoliths, northern Cordillera: implications for the Paleozoic tectonic evolution of the Yukon-Tanana terrane

1999 ◽  
Vol 36 (10) ◽  
pp. 1697-1709 ◽  
Author(s):  
Robert A Creaser ◽  
Jo-Anne S Goodwin-Bell ◽  
Philippe Erdmer
Keyword(s):  
High Pressure ◽  
Subduction Zone ◽  
Convergent Margins ◽  
Metasedimentary Rocks ◽  
High Pressure Metamorphism ◽  
Distal Edge ◽  
History Of ◽  
Convergent Plate Margin ◽  
Ocean Ridge ◽  
Subduction Zone Magmatism

On the basis of trace-element data, basaltic protoliths for Paleozoic eclogites from the Yukon-Tanana terrane (YTT) have diverse origins. Eclogites from Stewart Lake and the Simpson Range have characteristics of basaltic protoliths generated by subduction-zone magmatism, are hosted by serpentinitic-gabbroic rocks, and record Mississippian high-pressure metamorphism and cooling. In contrast, eclogites from Faro, Ross River, and Last Peak show either within-plate geochemistry or mid-ocean ridge protolith geochemistry with a small subduction component, are hosted by continental metasedimentary rocks of the Nisutlin assemblage, and record Permian high-pressure metamorphism and cooling. We interpret these results to derive from the following tectonic events in the Paleozoic history of the YTT: (1) activity at a Devonian-Mississippian convergent plate margin at the distal edge of North America, with near-contemporaneous subduction-zone magmatism and high-pressure metamorphism; (2) Mississippian rifting of that margin to form the outboard YTT, the Slide Mountain marginal basin, and the Faro, Ross River, and Last Peak eclogite protoliths; and (3) west-dipping subduction of the Slide Mountain Ocean under the outboard YTT in Permian time, to produce the Faro, Ross River, and Last Peak eclogites and Permian arc magmatism throughout the YTT. The basaltic protoliths of the Paleozoic YTT eclogites bear close similarity to those produced in rifted convergent margins, such as the Miocene Japanese arc - back-arc system.

40Ar-39Ar and Rb-Sr geochronology of high-pressure metamorphism and exhumation history of the Tavsanli Zone, NW Turkey

1999 ◽  
Vol 137 (1-2) ◽  
pp. 46-58 ◽  
Author(s):  
Sarah Sherlock ◽  
Simon Kelley ◽  
Simon Inger ◽  
Nigel Harris ◽  
Aral Okay
Keyword(s):  
High Pressure ◽  
High Pressure Metamorphism ◽  
Nw Turkey ◽  
History Of ◽  
Exhumation History

Neotethys closure history of Anatolia: insights from 40 Ar-39 Ar geochronology and P-T estimation in high-pressure metasedimentary rocks

2013 ◽  
Vol 31 (6) ◽  
pp. 585-606 ◽  
Author(s):  
A. Pourteau ◽  
M. Sudo ◽  
O. Candan ◽  
P. Lanari ◽  
O. Vidal ◽  
...  
Keyword(s):  
High Pressure ◽  
Metasedimentary Rocks ◽  
History Of ◽  
Ar Geochronology

P–T history of garnet-websterites in the Sharyzhalgai complex, southwestern margin of Siberian craton: evidence for Paleoproterozoic high-pressure metamorphism

2004 ◽  
Vol 132 (4) ◽  
pp. 327-348 ◽  
Author(s):  
Tsutomu Ota ◽  
Dmitry P. Gladkochub ◽  
Eugene V. Sklyarov ◽  
Anatoly M. Mazukabzov ◽  
Teruo Watanabe
Keyword(s):  
High Pressure ◽  
Siberian Craton ◽  
High Pressure Metamorphism ◽  
History Of ◽  
Southwestern Margin

scholarly journals The dynamothermal aureole of the Donqiao ophiolite (northern Tibet)

1997 ◽  
Vol 34 (1) ◽  
pp. 59-65 ◽  
Author(s):  
Mei-Fu Zhou ◽  
John Malpas ◽  
Paul T. Robinson ◽  
Peter H. Reynolds
Keyword(s):  
High Pressure ◽  
Subduction Zone ◽  
Greenschist Facies ◽  
Metamorphic Rocks ◽  
High Grade ◽  
Mineral Paragenesis ◽  
Metasedimentary Rocks ◽  
Northern Tibet ◽  
Suprasubduction Zone ◽  
Ar Geochronology

Metamorphic rocks found at the base of the Jurassic Donqiao ophiolite of northern Tibet are interpreted as a basal dynamothermal aureole produced during obduction of the massif. The rocks form a sequence some 8 m thick, varying from high-grade amphibolites at the contact with overlying harzburgites to greenschist facies metasedimentary rocks lower down. The mineral paragenesis is similar to other such aureoles, and indicates that temperatures in excess of 750 °C may have been reached during metamorphism. The lack of high-pressure minerals suggests that the rocks were produced by subcretion in a relatively shallow dipping subduction zone. Ar–Ar geochronology on amphibole separates provides dates of 175–180 Ma for the displacement of the ophiolite, significantly older than the age of emplacement estimated from stratigraphie relationships. The ophiolite was clearly obducted very soon after its formation in a suprasubduction zone environment.

scholarly journals Mantle wedge oxidation due to sediment-infiltrated deserpentinisation

2021 ◽  
Author(s):  
José Alberto Padrón-navarta ◽  
Vicente López Sánchez-Vizcaíno ◽  
Manuel Menzel ◽  
María Teresa Gómez-Pugnaire ◽  
Carlos Garrido
Keyword(s):  
High Pressure ◽  
Subduction Zones ◽  
Redox State ◽  
Mantle Wedge ◽  
Graphite Furnace ◽  
Convergent Margins ◽  
Tectonic Plates ◽  
Metasedimentary Rocks ◽  
Oxygen Breathing ◽  
Oxidation Reduction

Abstract The Earth's mantle is oxygen-breathing through the ¬sink of oxidised tectonic plates at convergent margins. Ocean floor serpentinisation increases the bulk oxidation state of iron relative to dry oceanic mantle and results in a variable intake of other redox-sensitive elements such as sulphur. The reversibility of seafloor oxidation in subduction zones during high-pressure dehydration of serpentinite (“deserpentinisation”) at subarc depths and the capacity of the resulting fluids to oxidise the mantle source of arc basalts are highly contested. Thermodynamic modelling, experiments, and metaperidotite study in exhumed high-pressure terrains result in differing estimates of the redox state of deserpentinisation fluids, ranging from low to highly oxidant. Here we show that although intrinsic deserpentinisation fluids are highly oxidant, the infiltration of small fractions of external fluids equilibrated with metasedimentary rocks strongly modulates their redox state and oxidation-reduction capacity explaining the observed discrepancies in their redox state. Infiltration of fluids equilibrated with graphite-bearing sediments reduces the oxidant, intrinsic deserpentinisation fluids to oxygen fugacities similar to those observed in most graphite-furnace experiments and natural metaperidotites. However, infiltration of CO2-bearing fluids equilibrated with modern GLOSS generates sulphate-rich, highly oxidising deserpentinisation fluids. We show that such GLOSS-infiltrated deserpentinisation fluids can effectively oxidise the mantle wedge of cold to hot subduction zones potentially accounting for the presumed oxidised nature of the source of arc basalts.

Metasedimentary rocks, intrusions and deformation history in the south-east part of the c. 1800 Ma Ketilidian orogen, South Greenland: Project SUPRASYD 1996

1997 ◽  
pp. 60-65
Author(s):  
Adam A. Garde ◽  
Brian Chadwick ◽  
John Grocott ◽  
Cees Swager
Keyword(s):  
Field Work ◽  
Deformation History ◽  
The South ◽  
Present Contribution ◽  
East Part ◽  
Metasedimentary Rocks ◽  
Deformational History ◽  
Base Camp ◽  
History Of ◽  
Geological Map

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Garde, A. A., Chadwick, B., Grocott, J., & Swager, C. (1997). Metasedimentary rocks, intrusions and deformation history in the south-east part of the c. 1800 Ma Ketilidian orogen, South Greenland: Project SUPRASYD 1996. Geology of Greenland Survey Bulletin, 176, 60-65. https://doi.org/10.34194/ggub.v176.5063 _______________ The south-east part of the c. 1800 Ma Ketilidian orogen in South Greenland (Allaart, 1976) is dominated by strongly deformed and variably migmatised metasedimentary rocks known as the ‘Psammite and Pelite Zones’ (Chadwick & Garde, 1996); the sediments were mainly derived from the evolving Julianehåb batholith which dominates the central part of the orogen. The main purpose of the present contribution is to outline the deformational history of the Psammite Zone in the region between Lindenow Fjord and Kangerluluk (Fig. 2), investigated in 1994 and 1996 as part of the SUPRASYD project (Garde & Schønwandt, 1995 and references therein; Chadwick et al., in press). The Lindenow Fjord region has high alpine relief and extensive ice and glacier cover, and the fjords are regularly blocked by sea ice. Early studies of this part of the orogen were by boat reconnaissance (Andrews et al., 1971, 1973); extensive helicopter support in the summers of 1992 and 1994 made access to the inner fjord regions and nunataks possible for the first time.A preliminary geological map covering part of the area between Lindenow Fjord and Kangerluluk was published by Swager et al. (1995). Hamilton et al. (1996) have addressed the timing of sedimentation and deformation in the Psammite Zone by means of precise zircon U-Pb geochronology. However, major problems regarding the correlation of individual deformational events and their relationship with the evolution of the Julianehåb batholith were not resolved until the field work in 1996. The SUPRASYD field party in 1996 (Fig. 1) was based at the telestation of Prins Christian Sund some 50 km south of the working area (Fig. 2). In addition to base camp personnel, helicopter crew and the four authors, the party consisted of five geologists and M.Sc. students studying mafic igneous rocks and their mineralisation in selected areas (Stendal et al., 1997), and a geologist investigating rust zones and areas with known gold anomalies.

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