Abstract
Continental crust buried during collisional orogeny typically records pressures of 3 GPa or lower; however, pressures much higher than this are recorded locally, which would suggest burial to mantle depths. Deep continental subduction is not observed in active orogens and should be hindered by the positive buoyancy of sialic crust relative to the mantle. Non-lithostatic pressure caused by mechanical contrasts between rock types provides an alternative explanation for extreme pressures recorded in buried continental crust; however, its occurrence and significance in natural systems is debated. Mechanical pressure heterogeneities were proposed specifically to explain extreme pressures of c. 5.5 GPa obtained in enstatite eclogite veins in the archetypal subducted continental terrane, the Western Gneiss Complex (WGC) in Norway. In this study, we use Lu–Hf garnet geochronology to test when, and thus, in what part of the burial cycle of the WGC the enstatite eclogite assemblages actually equilibrated. The results show that equilibration occurred at c. 393 Ma, which is much later than the typical ages obtained from ‘normal’ eclogites in the WGC and represents a time when the terrane was already at crustal depths (< 2.5 GPa). Finite element modeling of mechanical pressure distribution demonstrates that late extreme pressure excursions are feasible for the given rock system and could explain the seemingly spurious conditions recorded in these unusual rocks. The recognition of non-lithostatic ultrahigh-pressure in deeply buried continental crust allows crucial simplification of models for continental subduction and validates the importance of rock thermo-mechanics in interpreting observations from collision zones.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Ague JJ, Baxter EF (2007) Brief thermal pulses during mountain building recorded by Sr diffusion in apatite and multicomponent diffusion in garnet. Earth Planet Sci Lett 261:500–516. https://doi.org/10.1016/j.epsl.2007.07.017
Andersen TB, Corfu F, Labrousse L, Osmundsen P-T (2012) Evidence for hyperextension along the pre-Caledonian margin of Baltica. J Geol Soc 169:601–612. https://doi.org/10.1144/0016-76492012-011
Austrheim H, Corfu F, Bryhni I, Andersen TB (2003) The Proterozoic Hustad igneous complex: a low strain enclave with a key to the history of the Western Gneiss Region of Norway. Precambr Res 120:149–175. https://doi.org/10.1016/S0301-9268(02)00167-5
Baxter EF, Scherer EE (2013) Garnet geochronology: timekeeper of tectonometamorphic processes. Elements 9:433–438
Bizzarro M, Baker JA (2003) A new digestion and chemical separation technique for rapid and highly reproducible determination of Lu/Hf and Hf isotope ratios in geological materials by MC-ICP-MS. Geostand Geoanal Res 27:133–145
Blichert-Toft J, Chauvel C, Albarède F (1997) Separation of Hf and Lu for high-precision isotope analysis of rock samples by magnetic sector-multiple collector ICP-MS. Contrib Mineral Petrol 127:248–260. https://doi.org/10.1007/s004100050278
Blichert-Toft J, Boyet M, Télouk P, Albarède F (2002) Sm–Nd and Lu–Hf in eucrites and the differentiation of the HED parent body. Earth Planet Sci Lett 204:167–181
Bloch E, Ganguly J (2015) 176Lu–176Hf geochronology of garnet II: numerical simulations of the development of garnet–whole-rock 176Lu–176Hf isochrons and a new method for constraining the thermal history of metamorphic rocks. Contrib Mineral Petrol 169:147. https://doi.org/10.1007/s00410-015-1115-x
Bloch E, Ganguly J, Hervig R, Cheng W (2015) 176Lu–176Hf geochronology of garnet I: experimental determination of the diffusion kinetics of Lu3+ and Hf4+ in garnet, closure temperatures and geochronological implications. Contrib Mineral Petrol 169:12. https://doi.org/10.1007/s00410-015-1109-8
Brey GP, Köhler T (1990) Geothermobarometry in four-phase Lherzolites II. New thermobarometers, and practical assessment of existing thermobarometers. J Petrol 31:1353–1378
Butler JP, Jamieson RA, Dunning GR et al (2018) Timing of metamorphism and exhumation in the Nordøyane ultra-high-pressure domain, Western Gneiss Region, Norway: new constraints from complementary CA-ID-TIMS and LA-MC-ICP-MS geochronology. Lithos 310–311:153–170. https://doi.org/10.1016/j.lithos.2018.04.006
Carswell DA, Tucker RD, O’Brien PJ, Krogh TE (2003) Coesite micro-inclusions and the U/Pb age of zircons from the Hareidland Eclogite in the Western Gneiss Region of Norway. Lithos 67:181–190. https://doi.org/10.1016/S0024-4937(03)00014-8
Carswell DA, van Roermund HLM, de Vries DFW (2006) Scandian ultrahigh-pressure metamorphism of proterozoic basement rocks on Fjørtoft and Otrøy, Western Gneiss Region, Norway. Int Geol Rev 48:957–977. https://doi.org/10.2747/0020-6814.48.11.957
Chen K, Kunz M, Tamura N, Wenk HR (2015) Residual stress preserved in quartz from the San Andreas Fault Observatory at Depth. Geology 43:219–222. https://doi.org/10.1130/G36443.1
Chu X, Ague JJ, Podladchikov YY, Tian M (2017) Ultrafast eclogite formation via melting-induced overpressure. Earth Planet Sci Lett 479:1–17. https://doi.org/10.1016/j.epsl.2017.09.007
Cutts JA, Smit MA (2018) Rates of deep continental burial from Lu-Hf garnet chronology and Zr-in-rutile thermometry on (Ultra)high-Pressure rocks. Tectonics 37:71–88. https://doi.org/10.1002/2017TC004723
Cutts JA, Smit MA, Kooijman E, Schmitt M (2019) Two-stage cooling and exhumation of deeply subducted continents. Tectonics. https://doi.org/10.1029/2018TC005292
Dabrowski M, Powell R, Podladchikov YY (2015) Viscous relaxation of grain-scale pressure variations. J Metamorph Geol 33:859–868. https://doi.org/10.1111/jmg.12142
DesOrmeau JW, Gordon SM, Kylander-Clark ARC et al (2015) Insights into (U)HP metamorphism of the Western Gneiss Region, Norway: a high-spatial resolution and high-precision zircon study. Chem Geol 414:138–155. https://doi.org/10.1016/j.chemgeo.2015.08.004
England P (1981) Metamorphic pressure estimates and sediment volumes for the Alpine orogeny: an independent control on geobarometers? Earth Planet Sci Lett 56:387–397
Gerya TV (2015) Tectonic overpressure and underpressure in lithospheric tectonics and metamorphism. J Metamorph Geol 33:785–800. https://doi.org/10.1111/jmg.12144
Griffin WL, Brueckner HK (1980) Caledonian Sm–Nd ages and a crustal origin for Norwegian eclogites. Nature 285:319–321
Hacker BR, Andersen TB, Johnston SM et al (2010) High-temperature deformation during continental-margin subduction and exhumation: the ultrahigh-pressure Western Gneiss Region of Norway. Tectonophysics 480:149–171. https://doi.org/10.1016/j.tecto.2009.08.012
Hacker BR, Kylander-Clark ARC, Holder R et al (2015) Monazite response to ultrahigh-pressure subduction from U–Pb dating by laser ablation split stream. Chem Geol 409:28–41
Ibanez-Mejia M, Bloch EM, Vervoort JD (2018) Timescales of collisional metamorphism from Sm-Nd, Lu-Hf and U-Pb thermochronology: a case from the Proterozoic Putumayo Orogen of Amazonia. Geochim Cosmochim Acta 235:103–126. https://doi.org/10.1016/j.gca.2018.05.017
Jackson SE, Pearson NJ, Griffin WL, Belousova E (2004) The application of laser ablation-inductively coupled plasma-mass spectrometry to in situ U/Pb zircon geochronology. Chem Geol 211:47–69
Kelly ED, Carlson RW, Connelly JN (2011) Implications of garnet resorption for the Lu–Hf garnet geochronometer: an example from the contact aureole of the Makhavinekh Lake Pluton, Labrador. J Metamorph Geol 29:901–916
Kohn MJ (2009) Models of garnet differential geochronology. Geochim Cosmochim Acta 73(1):170–182. https://doi.org/10.1016/j.gca.2008.10.004
Kooijman E, Smit MA, Kylander-Clark ARC (2017) A novel approach to in situ rutile petrochronology. European Geosciences Union General Assembly, Vol. 19, 7442
Krogh TE, Kamo SL, Robinson P et al (2011) U-Pb zircon geochronology of eclogites from the Scandian Orogen, northern Western Gneiss Region, Norway: 14–20 million years between eclogite crystallization and return to amphibolite-facies conditions. Can J Earth Sci 48:441–472. https://doi.org/10.1139/e10-076
Krogh-Ravna EJ (2000) The garnet–clinopyroxene Fe2 + –Mg geothermometer: an updated calibration. J Metamorph Geol 18:211–219
Kylander-Clark ARC, Hacker BR (2014) Age and significance of felsic dikes from the UHP western gneiss region. Tectonics 33:2342–2360. https://doi.org/10.1002/2014TC003582
Kylander-Clark ARC, Hacker BR, Johnson CM et al (2009) Slow subduction of a thick ultrahigh-pressure terrane. Tectonics. https://doi.org/10.1029/2007tc002251
Lagos M, Scherer EE, Tomaschek F et al (2007) High precision Lu–Hf geochronology of Eocene eclogite-facies rocks from Syros, Cyclades, Greece. Chem Geol 243:16–35
Marques FO, Ranalli G, Mandal N (2018) Tectonic overpressure at shallow depth in the lithosphere. The effects of boundary conditions. Tectonophysics. https://doi.org/10.1016/j.tecto.2018.03.022
Moulas E, Podladchikov YY, Aranovich LY, Kostopoulos D (2013) The problem of depth in geology: when pressure does not translate into depth. Petrology 21:527–538. https://doi.org/10.1134/S0869591113060052
Moulas E, Burg J-P, Podladchikov YY (2014) Stress field associated with elliptical inclusions in a deforming matrix: mathematical model and implications for tectonic overpressure in the lithosphere. Tectonophysics 631:37–49. https://doi.org/10.1016/j.tecto.2014.05.004
Nábělek J, Hetényi G, Vergne J et al (2009) Underplating in the Himalay-Tibet collision zone revealed by the Hi-CLIMB experiment. Science 325:1371–1374. https://doi.org/10.1126/science.1176112
Nickel KG, Green DH (1985) Empirical geothermobarometry for garnet peridotites and implications for the nature of the lithosphere, kimberlites and diamonds. Earth Planet Sci Lett 73:158–170
Nimis P, Grütter H (2010) Internally consistent geothermometers for garnet peridotites and pyroxenites. Contrib Mineral Petrol 159:411–427. https://doi.org/10.1007/s00410-009-0455-9
Nimis P, Taylor WR (2000) Single-clinopyroxene thermobarometry for garnet peridotites. Part I. Calibration and testing of a Cr-in-Cpx barometer and an enstatite-in-Cpx thermometer. Contrib Mineral Petrol 139:541–554
Paces JB, Miller DJ (1993) Precise U-Pb ages of Duluth Complex and related mafic intrusions, northeastern Minnesota; geochronological insights to physical, petrogenetic, paleomagnetic, and tectonomagnetic processes associated with the 1.1 Ga midcontinent rift system. J Geophys Res 98:997–14013
Pleuger J, Podladchikov YY (2014) A purely structural restoration of the NFP20-East cross section and potential tectonic overpressure in the Adula Nappe (central Alps). Tectonics 33:656–685. https://doi.org/10.1002/(ISSN)1944-9194
Reuber G, Kaus BJP, Schmalholz SM, White RW (2016) Nonlithostatic pressure during subduction and collision and the formation of (ultra)high-pressure rocks. Geology 44:343–346. https://doi.org/10.1130/G37595.1
Root DB, Hacker BR, Gans PB et al (2005) Discrete ultrahigh-pressure domains in the Western Gneiss Region, Norway: implications for formation and exhumation. J Metamorph Geol 23:45–61. https://doi.org/10.1111/j.1525-1314.2005.00561.x
Schenker FL, Schmalholz SM, Moulas E et al (2015) Current challenges for explaining (ultra)high-pressure tectonism in the Pennine domain of the Central and Western Alps. J Metamorph Geol 33:869–886. https://doi.org/10.1111/jmg.12143
Scherer EE (2003) The Lu decay constant discrepancy; terrestrial samples versus meteorites. 66th Annual Meteoritical Society meeting 38
Scherer EE, Cameron KL, Blichert-Toft J (2000) Lu–Hf garnet geochronology: closure temperature relative to the Sm–Nd system and the effect of trace mineral inclusions. Geochim Cosmochim Ac 64:3413–3432
Scherer EE, Münker C, Mezger K (2001) Calibration of the Lutetium-Hafnium Clock. Science 293:683–687. https://doi.org/10.1126/science.1061372
Schmalholz SM, Podladchikov YY (2013) Tectonic overpressure in weak crustal-scale shear zones and implications for the exhumation of high-pressure rocks. Geophys Res Lett 40:1984–1988. https://doi.org/10.1002/grl.50417
Schmalholz SM, Medvedev S, Lechmann SM, Podladchikov YY (2014) Relationship between tectonic overpressure, deviatoric stress, driving force, isostasy and gravitational potential energy. Geophys J Int 197:680–696. https://doi.org/10.1093/gji/ggu040
Schmidt K, Tajčmanová L, Vrijmoed J et al (2019) Mechanically-controlled chemical zoning and its preservation in high-temperature minerals from the Western Gneiss Region. European Geosciences Union General Assembly, Norway
Smit MA, Scherer EE, Bröcker M, van Roermund HLM (2010) Timing of eclogite facies metamorphism in the southernmost Scandinavian Caledonides by Lu–Hf and Sm–Nd geochronology. Contrib Mineral Petrol 159:521–539. https://doi.org/10.1007/s00410-009-0440-3
Smit MA, Scherer EE, Mezger K (2013) Lu–Hf and Sm–Nd garnet geochronology: chronometric closure and implications for dating petrological processes. Earth Planet Sci Lett 381:222–233. https://doi.org/10.1016/j.epsl.2013.08.046
Söderlund U, Patchett PJ, Vervoort JD, Isachsen CE (2004) The 176Lu decay constant determined by Lu–Hf and U–Pb isotope systematics of Precambrian mafic intrusions. Earth Planet Sci Lett 219:311–324. https://doi.org/10.1016/S0012-821X(04)00012-3
Tajčmanová L, Podladchikov YY, Powell R et al (2014) Grain-scale pressure variations and chemical equilibrium in high-grade metamorphic rocks. J Metamorph Geol 32:195–207. https://doi.org/10.1111/jmg.12066
Tajčmanová L, Vrijmoed J, Moulas E (2015) Grain-scale pressure variations in metamorphic rocks: implications for the interpretation of petrographic observations. Lithos 216–217:338–351. https://doi.org/10.1016/j.lithos.2015.01.006
Taylor WR (1998) An experimental test of some geothermometer and geobarometer formulations for upper mantle peridotites with application to the thermobarometry of fertile lherzolite and garnet websterite. J Mineral Geochem 172:381–408
Terry MP, Robinson P, Krogh-Ravna EJ (2000) Kyanite eclogite thermobarometry and evidence for thrusting of UHP over HP metamorphic rocks, Nordoyane, Western Gneiss Region, Norway. Am Mineral 85:1637–1650
Vervoort JD, Blichert-Toft J (1999) Evolution of the depleted mantle: Hf isotope evidence from juvenile rocks through time. Geochim Cosmochim Acta 63(3–4):533–556. https://doi.org/10.1016/S0016-7037(98)00274-9
Vrijmoed J, van Roermund HLM, Davies GR (2006) Evidence for diamond-grade ultra-high pressure metamorphism and fluid interaction in the Svartberget Fe–Ti garnet peridotite–websterite body, Western Gneiss Region, Norway. Mineral Petrol 88:381–405. https://doi.org/10.1007/s00710-006-0160-6
Vrijmoed J, Podladchikov YY, Andersen TB, Hartz EH (2009) An alternative model for ultra-high pressure in the Svartberget Fe–Ti garnet-peridotite, Western Gneiss Region, Norway. Eur J Mineral 21:1119–1133. https://doi.org/10.1127/0935-1221/2009/0021-1985
Walsh EO, Hacker BR, Gans PB et al (2013) Crustal exhumation of the Western Gneiss Region UHP terrane, Norway: 40Ar/39Ar thermochronology and fault-slip analysis. Tectonophysics 608:1159–1179. https://doi.org/10.1016/j.tecto.2013.06.030
Young DJ, Hacker BR, Andersen TB, Gans PB (2011) Structure and 40Ar/39Ar thermochronology of an ultrahigh-pressure transition in western Norway. J Geol Soc 168:887–898. https://doi.org/10.1144/0016-76492010-075
Zhang RY, Liou JG, Ernst WG (2009) The Dabie-Sulu continental collision zone: a comprehensive review. Gondwana Res 16:1–26. https://doi.org/10.1016/j.gr.2009.03.008
Acknowledgements
We thank K. Gordon, V. Lai, and E. Czech for their assistance with MC-ICPMS, LA-ICPMS, and EPMA analyses, respectively, E. Kooijman, D. Spengler, and H.L.M. Van Roermund for many fruitful discussions in the field, and J. Scoates and D. Weis for their comments and suggestions. Constructive criticisms and suggestions by J. Ganguly and two anonymous reviewers helped improve this manuscript and we gratefully acknowledge editor O. Müntener for his careful and considerate editorial handling. Financial support is provided by the Multi-disciplinary Applied Geochemistry Network travel fund, a Natural Sciences and Engineering Research Council of Canada (NSERC)—Alexander Graham Bell Canada Graduate Scholarship (CGSD3-475186-2015) to J.A.C., an NSERC Discovery Grant (RGPIN-2015-04080) and a Canadian Foundation for Innovation and British Columbia Knowledge Development Fund infrastructure grant (joint project 229814) to M.A.S. All data needed to evaluate the conclusions of this paper are present in the paper or in the Supplementary materials.
Author information
Authors and Affiliations
Corresponding author
Additional information
Communicated by Othmar Müntener.
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Electronic supplementary material
Below is the link to the electronic supplementary material.
Rights and permissions
About this article
Cite this article
Cutts, J.A., Smit, M.A. & Vrijmoed, J.C. Evidence for non-lithostatic pressure in subducted continental crust. Contrib Mineral Petrol 175, 3 (2020). https://doi.org/10.1007/s00410-019-1633-z
Received:
Accepted:
Published:
DOI: https://doi.org/10.1007/s00410-019-1633-z