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

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.

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Contribution of magnetite (U-Th-Sm)/He thermometer to quantify the final exhumation of high-pressure ultramafic rocks : example of the Rocher Blanc ophiolite (western Alps)

10.5194/egusphere-egu2020-4505 ◽

2020 ◽

Author(s):

Stéphane Schwartz ◽

Cécile Gautheron ◽

Richard A Ketcham ◽

Fabrice Brunet ◽

Arnaud Agranier ◽

...

Keyword(s):

High Pressure ◽

Thermal History ◽

Thermal Sensitivity ◽

Western Alps ◽

The Past ◽

Zircon Fission Track ◽

Geological Information ◽

History Of ◽

Dating Method ◽

Exhumation History

<p>This contribution investigates the use of the (U-Th-Sm)/He dating method to unravel the exhumation history of ultramafic ophiolite rocks. Magnetite-bearing rocks are widely distributed on the Earth's surface and are associated with a large range of geological and geodynamic settings. However, little is known of the crystallization and exhumation history of in case of oceanic accretion to orogenic zones, due to a lack of datable minerals. In the past few years, the (U-Th-Sm)/He method applied on magnetite or spinel appears to be very relevant and promising. However, the applicability of this method to access the thermal history has never been quantitatively investigated, limiting the age interpretation. To highlight the applicability and to access geological information using magnetite (U-Th-Sm)/He method (MgHe), we applied it on a well-known high-pressure low-temperature alpine ophiolite (Rocher Blanc ophiolite, Western Alps) where the P-T-t exhumation history is well constrained. A study of magnetite petrology, mineralogy and geochemistry has allowed us to characterize that magnetite crystallize at T>250&#176;C. MgHe ages that range between apatite and zircon fission track (AFT and ZFT) ages of surrounding rocks in agreement with the known thermal sensitivity of those methods. MgHe data were co-inverted with AFT and ZFT data to determine the most robust thermal history associated with the ophiolite cooling. This first MgHe age inversion is consistent with experimental He diffusion data, opening the use of MgHe as a thermochronometer. This result allows us to refine the thermal history and to precise the geodynamical context associated to the final exhumation of this alpine ophiolite.</p>

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Metamorphic and Ar/Ar geochronology constraints on the Alakeçi shear zone: Implications for the extensional exhumation history of the northern Kazdağ Massif, NW Turkey

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1307/2/1/012012 ◽

2008 ◽

Vol 2 ◽

pp. 012012

Author(s):

N Bonev ◽

L Beccaletto ◽

M Robyr ◽

P Monié

Keyword(s):

Shear Zone ◽

Nw Turkey ◽

History Of ◽

Ar Geochronology ◽

Exhumation History

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The subduction and exhumation history of the Voltri Ophiolite, Italy: Evaluating exhumation mechanisms for high-pressure metamorphic massifs

Lithos ◽

10.1016/j.lithos.2020.105767 ◽

2020 ◽

Vol 376-377 ◽

pp. 105767

Author(s):

Paul G. Starr ◽

Kirkland S. Broadwell ◽

Besim Dragovic ◽

Marco Scambelluri ◽

Anne A. Haws ◽

...

Keyword(s):

High Pressure ◽

History Of ◽

Exhumation History

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Unraveling the exhumation history of high-pressure ophiolites using magnetite (U-Th-Sm)/He thermochronometry

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2020.116359 ◽

2020 ◽

Vol 543 ◽

pp. 116359

Author(s):

Stéphane Schwartz ◽

Cécile Gautheron ◽

Richard A. Ketcham ◽

Fabrice Brunet ◽

Marianna Corre ◽

...

Keyword(s):

High Pressure ◽

History Of ◽

Exhumation History

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Along-strike variations in the Hellenide Anatolide orogen: A tale of different lithospheres and consequences

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.11096 ◽

2017 ◽

Vol 47 (2) ◽

pp. 625 ◽

Cited By ~ 1

Author(s):

U. Ring ◽

K. Gessner ◽

S. Thomson ◽

V. Markwitz

Keyword(s):

High Pressure ◽

Large Scale ◽

Aegean Sea ◽

Fold Belt ◽

Lithosphere Structure ◽

Continental Extension ◽

Lithospheric Thinning ◽

Anatolian Peninsula ◽

History Of ◽

Exhumation History

Structure and exhumation history of the Hellenide-Anatolide Orogen in the Aegean Sea region and the adjacent Anatolian peninsula is controlled by along-strike variations of pre-Alpine palaeogeography. In the Hellenides, Mesozoic extension created ribbon-like continental fragments of thinned and dense lithosphere that pinch out eastwards. In the east, the relatively large Anatolide microcontinent mostly escaped Mesozoic extension and lithospheric thinning, presumably because it had a distinctly different, thicker and more depleted lithosphere. In the Aegean transect these alongstrike differences in lithosphere structure ultimately resulted in sustained highpressure metamorphism followed by progressive slab retreat since about 60 Ma. Further east, collision of the Anatolide microcontinent at about 42 Ma formed a south verging greenschist-facies thrust-and-fold belt. Pronounced slab retreat in the Aegean forced differential extension resulting in a broad sinistral wrench corridor that started to from at 24-23 Ma. Since then, extension in both regions mainly controlled denudation. This review highlights how differences in pre-orogenic architecture control lithospheric thickening and the subsequent exhumation of high-pressure rocks, and how large-scale continental extension evolves

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