Pulsed dehydration and garnet growth during subduction revealed by zoned garnet geochronology and thermodynamic modeling, Sifnos, Greece

Dragovic, Besim; Baxter, Ethan F.; Caddick, Mark J.

doi:10.1016/j.epsl.2014.12.024

Cited by 106 publications

(122 citation statements)

References 55 publications

(96 reference statements)

Supporting

Mentioning

104

Contrasting

Unclassified

Order By: Relevance

“…System free energy is lowered by ~0.5 kJ/mol of oxygen in garnet if ~1 vol% garnet is grown at these P-T conditions. sample suggest that primary growth compositions are preserved without significant diffusive modification, and repeatability of the observation in different Sifnos lithologies, including samples that underwent 3D tomographic analysis prior to thin sectioning (e.g., Dragovic et al 2015), limits the chances of systematically failing to expose the true garnet core. It remains most likely that initiation of garnet growth was delayed and that the total duration of crystal growth was then brief (<1 Myr).…”

Section: Incongruities Between Calculated and Observed Phase Equilibriamentioning

confidence: 96%

Beyond the equilibrium paradigm: How consideration of kinetics enhances metamorphic interpretation

Carlson

Pattison

Caddick

2015

American Mineralogist

Self Cite

View full text Add to dashboard Cite

The equilibrium model of prograde metamorphism, in which rocks are regarded as departing only negligibly from equilibrium states as they recrystallize, has generated a wealth of petrologic insights. But mounting evidence from diverse approaches and observations over a range of scales has revealed that kinetic impediments to reaction may prevent metamorphic rocks from attaining rock-wide chemical equilibrium along their prograde crystallization paths. To illustrate the resulting potential for inaccurate interpretation if kinetic factors are disregarded, we briefly review several case studies, including: out-of-sequence, metastable, and displaced isograds in contact aureoles; paragenetic sequences documenting overstepped, disequilibrium reaction paths; patterns of compositional zoning in garnet demonstrating partial chemical equilibrium; petrologic incongruities between observation and thermodynamic prediction; and inhibited reaction progress revealed by petrologically constrained numerical simulations of garnet crystallization. While the equilibrium model provides an indispensable framework for the study of metamorphic systems, these examples emphasize that all reactions require departures from rock-wide equilibrium, so all rocks must traverse kinetically sensitive reaction paths during recrystallization. Mindfulness of the potential significance of kinetic influences opens new avenues for petrologic investigation, thereby enhancing both analysis and interpretation.

show abstract

Section: Incongruities Between Calculated and Observed Phase Equilibriamentioning

confidence: 96%

Beyond the equilibrium paradigm: How consideration of kinetics enhances metamorphic interpretation

Carlson

Pattison

Caddick

2015

American Mineralogist

Self Cite

View full text Add to dashboard Cite

show abstract

“…Such diffusion features are Dragovic et al (2012Dragovic et al ( , 2015 and Gatewood et al (2015); (c) asymptotes and limits 40 Ar/ 39 Ar white mica step-heating approach of Forster & Lister (2004). Results summarized in (a)-(c) are from Viete et al (2015), Dragovic et al (2015) and Lister & Forster (2016), respectively, and have been reproduced from the original files, with permission from the authors. Image of microdrilled garnets in (b) is from Dragovic et al (2015, fig.…”

Section: Self Affinity In Metamorphic Time Scales?mentioning

confidence: 99%

“…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%

“…England et al 1992;Treloar 1997;Stüwe 1998;Burg & Gerya 2005) heat production, or fluid (e.g. Camacho et al 2005;Dragovic et al 2012Dragovic et al , 2015, magmatic (e.g. Baxter et al 2002;Brouwer et al 2004;Reverdatto & Polyansky 2004;Viete et al 2013) or tectonic (e.g.…”

mentioning

confidence: 99%

See 2 more Smart Citations

On the significance of short-duration regional metamorphism

Viete

Lister

2016

JGS

View full text Add to dashboard Cite

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...

show abstract

Stepwise exhumation of the Triassic Lanling high‐pressure metamorphic belt in Central Qiangtang, Tibet: Insights from a coupled study of metamorphism, deformation, and geochronology

et al. 2017

View full text Add to dashboard Cite

The E‐W trending Central Qiangtang metamorphic belt (CQMB) is correlated to the Triassic orogeny of the Paleo‐Tethys Ocean prior to Cenozoic growth of the Tibetan Plateau. The well‐exposed Lanling high‐pressure, low‐temperature (HP‐LT) metamorphic complex was chosen to decipher the process by which it was exhumed, which thereby provides insights into the origin of the CQMB and Qiangtang terrane. After a detailed petrological and structural mapping, three distinct N‐S‐trending metamorphic domains were distinguished. Microscopic observations show that core domain garnet (Grt)‐bearing blueschist was exhumed in a heating plus depressurization trajectory after peak eclogitic conditions, which is more evident in syntectonic vein form porphyroblastic garnets with zoning typical of a prograde path. Grt‐free blueschist of the mantle domain probably underwent an exhumation path of temperature increasing and dehydration, as evidenced by pervasive epidote veins. The compilation of radiometric results of high‐pressure mineral separates in Lanling and Central Qiantang, and reassessments on the published phengite data sets of Lanling using Arrhenius plots allow a two‐step exhumation model to be formulated. It is suggested that core domain eclogitic rocks were brought onto mantle domain blueschist facies level starting at 244–230 Ma, with exhumation continuing to 227–223.4 Ma, and subsequently were exhumed together starting at 223–220 Ma, reaching lower greenschist facies conditions generally after 222–217 Ma. These new observations indicate that the CQMB formed as a Triassic autochthonous accretionary complex resulting from the northward subdcution of the Paleo‐Tethys Ocean and that HP‐LT rocks therein were very probably exhumed in an extensional regime.

show abstract

Pulsed dehydration and garnet growth during subduction revealed by zoned garnet geochronology and thermodynamic modeling, Sifnos, Greece

Cited by 106 publications

References 55 publications

Beyond the equilibrium paradigm: How consideration of kinetics enhances metamorphic interpretation

Beyond the equilibrium paradigm: How consideration of kinetics enhances metamorphic interpretation

On the significance of short-duration regional metamorphism

Stepwise exhumation of the Triassic Lanling high‐pressure metamorphic belt in Central Qiangtang, Tibet: Insights from a coupled study of metamorphism, deformation, and geochronology

Contact Info

Product

Resources

About