Preserved Zr-temperatures and U–Pb ages in high-grade metamorphic titanite: Evidence for a static hot channel in the Himalayan orogen

Kohn, Matthew J.; Corrie, Stacey L.

doi:10.1016/j.epsl.2011.09.008

Cited by 131 publications

(93 citation statements)

References 40 publications

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“…1.75 Ga and HP metamorphism at ca. 400 Ma followed (Zhang and Scharer 1996;Gao et al 2012;Kohn and Corrie 2011;Spencer et al 2013). Caledonian metamorphic tectonites preserve evidence for deformation during HP metamorphism in eclogite and retrograde amphibolite-facies deformation in host gneiss during exhumation between 390 and 370 Ma.…”

Section: Discussionmentioning

confidence: 99%

The Timing of Strike-Slip Deformation Along the Storstrømmen Shear Zone, Greenland Caledonides: U–Pb Zircon and Titanite Geochronology

Hallett¹,

McClelland²,

Gilotti³

2014

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The Storstrømmen shear zone (SSZ) in the Greenland Caledonides is widely interpreted to have formed in a transpressional regime during sinistral, oblique collision between Baltica and Laurentia in the Silurian to Devonian. New mapping of the SSZ at Sanddal documents a 100 m thick, greenschistfacies mylonite zone cutting the eclogite to amphibolite-facies gneiss complex. We present U–Pb ion probe geochronology on zircon and titanite from a variety of lithologies that shows the SSZ was active from late Devonian to the Carboniferous (at least until 350 Ma). The age of thrusting in the foreland is not well known, but must be younger than the age of eclogite-facies metamorphism at ~400 Ma. It is, therefore, possible that contraction is the same age as strike-slip motion, and that transpression is a viable model. The timing of the SSZ is synchronous with dextral strike-slip displacement on the Germania Land deformation zone. Simultaneous displacement on sinistral and dextral, conjugate shear zones suggests that the SSZ is part of a strikeslip fault system that led to lateral escape of material northward (present day coordinates) during the waning stages of plate convergence between Laurentia and Baltica.SOMMAIRELa zone de cisaillement de Storstrømmen (SSZ) dans les Calédonides du Groenland est généralement comprise comme ayant été formée durant un régime de transpression sénestre lors de la collision oblique entre Baltica et Laurentie, du Silurien au Dévonien. Une nouvelle cartographie de la SSZ à Sanddal décrit une zone de 100 m d’épaisseur de mylonite au faciès des schistes verts qui recoupe un complexe de gneiss au faciès éclogite à amphibolite. Notre analyse géochronologique par sonde ionique U-Pb sur zircon et titanite sur diverses lithologies, montre que la SSZ a été active de la fin du Dévonien jusqu’au Carbonifère (au moins jusqu’à 350 Ma). L’âge du chevauchement dans l’avant-pays n’est pas bien connue, mais il doit être plus jeune que le métamorphisme au faciès d’éclogite à ~400 Ma. Il est donc possible que la contraction soit du même âge que le mouvement de coulissage, et que la transpression soit un modèle viable. La chronologie de la SSZ est synchrone au mouvement de coulissage dextre de la zone de déformation de Germania Land. Les déplacements simultanés, sénestre et dextre, sur des zones de cisaillement conjuguées permettent de penser que la SSZ fait partie d’un système de décrochement qui a engendré une éjection latérale de matériau vers le nord (selon les coordonnées actuelles) durant les stades de convergence des plaques Laurentie et Baltica.

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Section: Discussionmentioning

confidence: 99%

The Timing of Strike-Slip Deformation Along the Storstrømmen Shear Zone, Greenland Caledonides: U–Pb Zircon and Titanite Geochronology

Hallett¹,

McClelland²,

Gilotti³

2014

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“…Thus, U-Pb titanite dates are often interpreted as metamorphic ages, recording the time of pulsed magmatic heating, fluid infiltration, or deformation (e.g., Verts et al, 1996;Storey et al, 2007;Shang et al, 2010;Gao et al, 2011). Pb diffusion is also a well-documented phenomenon in titanite, and many titanite dates are interpreted to indicate the time of cooling of the host rock below a certain temperature (e.g., Mezger et al, 1991a;Flowers et al, 2006;Warren et al, 2012) -cited as being anywhere between~500-800°C for typical geologic cooling rates (Mezger et al, 1991a;Cherniak, 1993;Scott and St-Onge, 1995;Verts et al, 1996;Kohn and Corrie, 2011;Spencer et al, 2013). In many cases, however, it remains unclear to what extent the U-Pb systematics of titanite are affected by diffusive Pb loss, and therefore the extent to which initial U-Pb titanite ages are disturbed (partially or wholly reset).…”

Section: Introductionmentioning

confidence: 99%

“…Titanite, CaTi[SiO 4 ](O,OH,F), is a common accessory mineral in alkaline igneous and many types of metamorphic rocks, and is a widely used U-Pb geochronometer (e.g., Tilton and Grunenfelder, 1968;Mezger et al, 1991a;Verts et al, 1996;Frost et al, 2000;Kohn and Corrie, 2011;Spencer et al, 2013). The geologic problems to which titanite U-Pb geochronology can be applied depend on the amount and retention of radiogenic Pb within individual titanite grains.…”

Section: Introductionmentioning

confidence: 99%

Combined oxygen-isotope and U-Pb zoning studies of titanite: New criteria for age preservation

et al. 2015

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Titanite is an important U-Pb chronometer for dating geologic events, but its high-temperature applicability depends upon its retention of radiogenic lead (Pb). Experimental data predict similar rates of diffusion for lead (Pb) and oxygen (O) in titanite at granulite-facies metamorphic conditions (T = 650-800°C). This study therefore investigates the utility of O-isotope zoning as an indicator for U-Pb zoning in natural titanite samples from the Carthage-Colton Mylonite Zone of the Adirondack Mountains, New York. Based on previous field, textural, and microanalytical work, there are four generations (types) of titanite in the study area, at least two of which preserve diffusion-related δ 18 O zoning. U-Th-Pb was analyzed by SIMS along traverses across three grains of type-2 titanite, which show well-developed diffusional δ 18 O zoning, and one representative grain from each of the other titanite generations. Type-2 and type-4 titanites show broadly core-to-rim decreasing 206 Pb/ 238 U zoning, consistent with Pb diffusion at higher temperatures, and uniform or even slightly increasing 206 Pb/ 238 U near grain rims, indicating subsequent recrystallization and/or new growth below the Pb blocking temperature. Type-2 and type-4 grain cores preserve ca. 1160 Ma ages that correlate with the anorthositemangerite-charnockite-granite magmatic phase of the Grenville orogeny, whereas grain rims give ca. 1050 Ma 206 Pb/ 238 U ages that coincide with the culminating Ottawan phase. The type-3 titanite grain was sampled from a vein and yields 206 Pb/ 238 U dates older than the syenite into which the vein was emplaced; accordingly, its 206 Pb/ 238 U dates are interpreted as indicating excess uncorrected common Pb. Type-2 grains with recrystallized or shear-eroded margins show truncated or reversed 206 Pb/ 238 U zoning but retain symmetrically decreasing δ 18 O zoning, consistent with grain margin modification following arrest of Pb diffusion but before arrest of O diffusion. It is concluded that O diffusion was slightly faster than Pb diffusion in Adirondack titanites at the conditions of (local) peak Ottawan metamorphism, making δ 18 O zoning a useful discriminator of closed-system age domains that did not suffer Pb loss. In addition, the small offset in the O and Pb partial retention zones constrains the timing and temperature of oblique-slip deformation along the Carthage-Colton Mylonite Zone: the details of porphyroclast microstructure and zoning data show that the oblique-slip shear zones were active at ca. 1050 Ma, with deformation initiating near the peak of Ottawan metamorphism at~700°C and continuing through the O blocking temperature at~550°C.Published by Elsevier B.V.

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“…Its role as geochronometer is limited by low U and thus radiogenic Pb contents and high proportion of initial Pb (Romer 2001). As for rutile, titanite in mafic rocks is particularly difficult to date, and best results have been obtained for titanite in metasediments (Kohn and Corrie 2011), including metacarbonates (Rubatto and Hermann 2001).…”

Section: Methodsmentioning

confidence: 96%

Uranium-Lead, Metamorphic Rocks

Rubatto

2013

Encyclopedia of Scientific Dating Methods

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Definition: The word metamorphism derives from the Greek word "metamorphosis," meaning change of form. Metamorphism is the process by which the mineralogy of rocks is changed as the result of pressure and temperature according to their composition and with the aid of fluid and deformation. Metamorphism is mainly concerned with the changes that take place when rocks are in the solid state, even though melt can be one of the phases present.

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Preserved Zr-temperatures and U–Pb ages in high-grade metamorphic titanite: Evidence for a static hot channel in the Himalayan orogen

Cited by 131 publications

References 40 publications

The Timing of Strike-Slip Deformation Along the Storstrømmen Shear Zone, Greenland Caledonides: U–Pb Zircon and Titanite Geochronology

The Timing of Strike-Slip Deformation Along the Storstrømmen Shear Zone, Greenland Caledonides: U–Pb Zircon and Titanite Geochronology

Combined oxygen-isotope and U-Pb zoning studies of titanite: New criteria for age preservation

Uranium-Lead, Metamorphic Rocks

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