High resolution Sm–Nd garnet geochronology reveals the uneven pace of tectonometamorphic processes

Pollington, Anthony D.; Baxter, Ethan F.

doi:10.1016/j.epsl.2010.02.019

Cited by 104 publications

(66 citation statements)

References 35 publications

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“…In the case of the southwestern Tauern Window (Selverstone et al 1984, Selverstone 1985) the pressure maximum of 1.0-1.1 GPa predated the attainment of peak temperature conditions of 550°C, at 0.7 GPa around 30 Ma ago (Christensen et al 1994). Garnet growth under decreasing pressures (Selverstone 1993;Christensen et al 1994) was pulse-like during the interval of 30-20 Ma (Pollington and Baxter 2010). The Eclogite Zone (21) of the Central Tauern Window was thrust onto the Venediger Duplex after the end of a first phase of decompression ending at about 32 Ma, and then was re-heated at around 30 Ma (Kurz et al 2008;their Fig.…”

Section: Major Tectonic Units Of the Tauern Window Derived From The Dmentioning

confidence: 99%

The Tauern Window (Eastern Alps, Austria): a new tectonic map, with cross-sections and a tectonometamorphic synthesis

et al. 2013

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We present a tectonic map of the Tauern Window and surrounding units (Eastern Alps, Austria), combined with a series of crustal-scale cross-sections parallel and perpendicular to the Alpine orogen. This compilation, largely based on literature data and completed by own investigations, reveals that the present-day structure of the Tauern Window is primarily characterized by a crustal-scale duplex, the Venediger Duplex (Venediger Nappe system), formed during the Oligocene, and overprinted by doming and lateral extrusion during the Miocene. This severe Miocene overprint was most probably triggered by the indentation of the Southalpine Units east of the Giudicarie Belt, initiating at 23-21 Ma and linked to a lithosphere-scale reorganization of the geometry of mantle slabs. A kinematic reconstruction shows that accretion of European lithosphere and oceanic domains to the Adriatic (Austroalpine) upper plate, accompanied by highpressure overprint of some of the units of the Tauern Window, has a long history, starting in Turonian time (around 90 Ma) and culminating in Lutetian to Bartonian time (45-37 Ma).

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Section: Major Tectonic Units Of the Tauern Window Derived From The Dmentioning

confidence: 99%

The Tauern Window (Eastern Alps, Austria): a new tectonic map, with cross-sections and a tectonometamorphic synthesis

et al. 2013

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“…Recent studies show that metamorphic processes such as exhumation, fluid flow, and/or heating can occur in pulses separated by long periods with little or no metamorphic activity [Ague and Baxter, 2007;Pollington and Baxter, 2010;Dragovic et al, 2012;Viete et al, 2013]. If this was the case for our study, time-averaged reaction rates could be faster during metamorphic pulses and almost zero at other times.…”

Section: Limitations Of the Present Studymentioning

confidence: 83%

“…Field-based parameterization of metamorphic fluid flow has been achieved by modeling the propagation of reaction fronts using the well-known governing equation for one-dimensional transport (advection and diffusion) and fluid-mineral reaction in a homogeneous porous media [e.g., Ogata, 1964;Baumgartner and Ferry, 1991;Bickle, 1992;Skelton et al, 1997;Ague, 2003]. This equation, written for mass conservation of a fluid species (e.g., CO 2 ) in the metamorphic fluid, can be expressed as follows:…”

Section: Methodsmentioning

confidence: 99%

An assessment of the role of nonlinear reaction kinetics in parameterization of metamorphic fluid flow

Zhao

Skelton

2014

JGR Solid Earth

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Based on inverse modeling of reaction progress data using a numerical framework that considers coupled advection and diffusion, linear and nonlinear reaction kinetics, and with effective diffusivity given by Archie's law, we show that (1) choice of reaction order has little effect (<0.3 orders of magnitude) on estimates of time-integrated and time-averaged metamorphic fluid fluxes and metamorphic fluid flow durations based on reaction progress data, (2) reaction order must be known for robust determination of time-averaged net reaction rates based on reaction progress data and that underestimation of this term by more than 3 orders of magnitude can arise from assuming linear reaction kinetics, (3) differing reaction orders between laboratory experiments and natural metamorphic systems and/or a nonlinear dependence of effective diffusivity on porosity can explain order-of-magnitude discrepancies between field-based and laboratory-based estimates of time-averaged net reaction rates, and (4) parameterization of metamorphic fluid flow is limited to time-averaged values which fail to account for the possibility that metamorphism occurs in short-lived pulses during longer time periods of metamorphic quiescence.

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“…These are: (1) Sm-Nd or Lu-Hf thermal ionization mass spectrometry (TIMS) performed on single growth sectors of metamorphic garnet (e.g. Baxter et al 2002;Ducea et al 2003;Lancaster et al 2008;Pollington & Baxter 2010;Dragovic et al 2012Dragovic et al , 2015, (2) the 'asymptotes and limits' approach to identifying the effects of brief heating and/or limited recrystallization on 40 Ar/ 39 Ar step-heating spectra (e.g. Forster & Lister 2004, 2005Lister & Forster 2016), and (3) petrologically controlled U-Pb depth profiling approaches, including single-shot laser ablation split stream (SS-LASS) inductively coupled plasma mass spectrometry (ICP-MS) petrochronology, capable of deciphering distinct, fine-scale episodes of accessory mineral growth (e.g.…”

Section: Development Of New Very High-precision Petrologically Contrmentioning

confidence: 99%

“…Moreover, examples of temporal non-uniformity in rates of metamorphism have been related to extremely short-duration thermal instabilities (tectonometamorphic episodicity) within collisional orogens and subduction zones (e.g. Wijbrans & McDougall 1986, 1988Keay et al 2001;Kohn 2004;Camacho et al 2005;Ague & Baxter 2007;Pollington & Baxter 2010;Viete et al 2011bViete et al , 2015Dragovic et al 2012Dragovic et al , 2015.…”

mentioning

confidence: 99%

On the significance of short-duration regional metamorphism

Viete

Lister

2016

JGS

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Short-duration regional metamorphism is a recently observed and poorly understood phenomenon in metamorphic geology. In this review, it is defined as metamorphism on time scales that limit length scales (of the associated thermal anomaly) to significantly less than the thickness of the orogenic crust (<10 myr) or subducted oceanic lithosphere (<5 myr). Without appealing to exceptional heat sources, thermal models have been unable to account for peak metamorphic temperature during collisional orogenesis and subduction. This observation, combined with restricted time scales for regional metamorphism, suggests that metamorphic facies series can record atypical and transient thermal conditions (related to punctuated and localized heat advection and/or production), rather than normal, ambient conditions for the tectonic setting to which they are allied. Highprecision geochronology can resolve short-duration metamorphic estimates of 1 -10 myr. However, diffusion geospeedometry typically yields extremely short metamorphic durations (<1 myr); tools in metamorphic geology may have matured to the point that the discipline is beginning to recognize episodicity and criticality in deep processes. New, very high-precision petrochronology techniques offer great potential to probe the veracity of extremely short metamorphic durations being obtained from diffusion geospeedometry. Benchmarking of these new very high-precision petrochronology techniques must become a priority for metamorphic geology.Received 26 May 2016; revised 2 October 2016; accepted 27 October 2016Early interpretations of the geological record leant heavily on catastrophism. As geology matured as a science, uniformitarianism came to supersede catastrophism. Uniformitarianism offers a more sophisticated, logical framework for interpretation of the rock record within the context of current and observable processes. However, the grand success of the uniformitarian philosophy has also resulted in a propensity toward interpretation of deep (and thus unobservable) geological phenomena in terms of slowly evolving or steady-state processes. A notable example of this preference for gradualism in deep processes has been ideas for the origins of regional metamorphism and metamorphic facies series, and implications for the nature of tectonism. Barrow (1893Barrow ( , 1912 was the first to map regional metamorphism on the basis of diagnostic mineral assemblages. His Barrovian metamorphic sequence, exposed in NE Scotland, comprises a series of 'isograds' marking the first appearance of chlorite, biotite, garnet, staurolite, kyanite and sillimanite in pelitic lithologies, in the direction of increasing metamorphic grade. Regional metamorphism recorded by Barrovian-type isograds defines intermediate pressure/temperature (P/T ) conditions (575 -1250°C GPa Barrow (1893) originally proposed that his Barrovian metamorphism resulted from magmatic advection of heat from depth. Following development of the theory of plate tectonics, numerous models were proposed for the ori...

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High resolution Sm–Nd garnet geochronology reveals the uneven pace of tectonometamorphic processes

Cited by 104 publications

References 35 publications

The Tauern Window (Eastern Alps, Austria): a new tectonic map, with cross-sections and a tectonometamorphic synthesis

The Tauern Window (Eastern Alps, Austria): a new tectonic map, with cross-sections and a tectonometamorphic synthesis

An assessment of the role of nonlinear reaction kinetics in parameterization of metamorphic fluid flow

On the significance of short-duration regional metamorphism

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