Refining the P–T records of UHT crustal metamorphism

Journal of Metamorphic Geology - Tập 26 Số 2 - Trang 125-154 - 2008
Simon L. Harley1
1Grant Institute of Earth Science, School of GeoSciences, University of Edinburgh, Kings Buildings, West Mains Road, Edinburgh EH9 3JW, UK ([email protected])

Tóm tắt

AbstractUltra‐high‐temperature (UHT) metamorphism occurs when the continental crust is subjected to temperatures of greater than 900 °C at depths of 20–40 km. UHT metamorphism provides evidence that major tectonic processes may operate under thermal conditions more extreme than those generally produced in numerical models of orogenesis. Evidence for UHT metamorphism is recorded in mineral assemblages formed in magnesian pelites, supported by high‐temperature indicators including mesoperthitic feldspar, aluminous orthopyroxene and high Zr contents in rutile. Recent theoretical, experimental and thermodynamic data set constraints on metamorphic phase equilibria in FMAS, KFMASH and more complex chemical systems have greatly improved quantification of the P–T conditions and paths of UHT metamorphic belts. However, despite these advances key issues that remain to be addressed include improving experimental constraints on the thermodynamic properties of sapphirine, quantifying the effects of oxidation state on sapphirine, orthopyroxene and spinel stabilities and quantifying the effects of H2O–CO2 in cordierite on phase equilibria and reaction texture analysis. These areas of uncertainty mean that UHT mineral assemblages must still be examined using theoretical and semi‐quantitative approaches, such as P(–T)–μ sections, and conventional thermobarometry in concert with calculated phase equilibrium methods. In the cases of UHT terranes that preserve microtextural and mineral assemblage evidence for steep or ‘near‐isothermal’ decompression P–T paths, the presence of H2O and CO2 in cordierite is critical to estimates of the P–T path slopes, the pressures at which reaction textures have formed and the impact of fluid infiltration. Many UHT terranes have evolved from peak P–T conditions of 8–11 kbar and 900–1030 °C to lower pressure conditions of 8 to 6 kbar whilst still at temperature in the range of 950 to 800 °C. These decompressional P–T paths, with characteristic dP/dT gradients of ∼25 ± 10 bar °C−1, are similar in broad shape to those generated in deep‐crustal channel flow models for the later stages of orogenic collapse, but lie at significantly higher temperatures for any specified pressure. This thermal gap presents a key challenge in the tectonic modelling of UHT metamorphism, with implications for the evolution of the crust, sub‐crustal lithosphere and asthenospheric mantle during the development of hot orogens.

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Tài liệu tham khảo

10.1111/j.1525-1314.1987.tb00388.x

10.1007/BF00636519

10.2138/am-1997-3-413

Aranovich L. Ya., 1989, Evolution of Metamorphic Belts, 45

10.1130/0091-7613(1986)14<844:SPFTNG>2.0.CO;2

10.1111/j.1525-1314.1995.tb00223.x

10.1007/s004100050522

10.1093/petrology/44.2.329

10.1111/j.1525-1314.2005.00591.x

10.1130/G23285A.1

10.1130/0091-7613(1997)025<0215:OASRCI>2.3.CO;2

10.1180/minmag.1979.043.327.09

10.1038/414738a

10.1144/GSL.SP.2006.268.01.05

10.1007/BF00307326

10.1111/j.1525-1314.1991.tb00518.x

10.1093/petrology/44.6.1121

10.1130/G22853A.1

10.2747/0020-6814.49.3.193

10.1111/j.1525-1314.2005.00563.x

10.2475/ajs.278.9.1334

10.1007/BF00377479

10.1127/ejm/7/4/0949

10.1007/BF00306508

10.1111/j.1525-1314.1995.tb00246.x

10.1130/0091-7613(1996)024<0647:CAAMOF>2.3.CO;2

10.1007/BF00372834

10.1007/BF00199554

10.1111/j.1525-1314.1988.tb00443.x

10.1038/219476a0

10.2138/am-2001-11-1211

10.1093/petrology/44.6.1055

10.1093/petrology/36.2.435

10.1111/j.1525-1314.1997.00017.x

Degeling H. S. 2003.Zr Equilibria in Metamorphic Rocks.Unpublished PhD Thesis Australian National University Canberra Australia 231 pp.

10.1111/j.1525-1314.1989.tb00604.x

10.1007/BF01132005

10.1130/0091-7613(1987)15<167:OAEOGI>2.0.CO;2

10.1007/BF00399473

10.1007/s00410-007-0201-0

10.1093/petrology/37.2.395

10.1093/petrology/35.2.543

10.1111/j.1525-1314.2006.00630.x

10.1046/j.1525-1314.2000.00270.x

10.1086/629321

10.1007/s004100050240

10.2113/gselements.3.1.43

Grew E. S., 1980, Sapphirine + quartz association from Archaean rocks in Enderby Land, Antarctica, American Mineralogist, 65, 821

Grew E. S., 1982, Osumilite in the sapphirine‐quartz terrane of Enderby Land, Antarctica: implications for osumilite petrogenesis in the granulite facies, American Mineralogist, 67, 762

10.1093/petrology/egi098

10.1111/j.1525-1314.1996.00046.x

10.1127/ejm/8/6/1375

10.1093/petrology/25.3.665

10.1093/petrology/26.4.819

10.1007/BF00376338

10.1111/j.1525-1314.1987.tb00389.x

10.1017/S0016756800022330

Harley S. L., 1998, What Controls Metamorphism and Metamorphic Reactions, 75

Harley S. L., 1998, Origin and Evolution of Continents, 49

10.1111/j.1525-1314.1998.00155.x

10.2465/jmps.99.140

10.1093/petrology/42.9.1595

10.1111/j.1525-1314.1991.tb00519.x

10.1038/300697a0

10.1007/s004100050564

10.1017/S0263593304000100

10.1111/j.1525-1314.1990.tb00490.x

10.1046/j.0263-4929.2001.00344.x

10.2113/gselements.3.1.25

10.2138/am-2002-0406

10.1007/BF00374063

10.1007/BF00572165

10.1111/j.1525-1314.1987.tb00383.x

Hensen B. J., 1988, Chemical potential diagrams and chemographic projections: application to sapphirine‐granulites from Kiranur and Ganguvarpatti, Tamil Nadu. Evidence for rapid uplift in part of the South Indian Shield, Neues Jahrbuch für Mineralogie Abhandlungen, 158, 193

10.1007/BF00373879

10.1007/978-94-015-3929-6_2

Herd R. K., 1986, The Grenville Province, 241

10.2138/am-2001-0718

10.1007/s00410-003-0550-2

10.1111/j.1525-1314.1998.00140.x

10.1007/s004100050198

10.1007/s00410-002-0412-3

10.1016/0024-4937(94)90027-2

10.1016/j.gr.2005.11.019

10.1029/2003JB002811

10.1007/978-3-642-61049-3

10.1093/petrology/egh023

10.1007/s00410-004-0635-6

10.1016/j.gr.2007.06.001

10.1046/j.1525-1314.2003.00456.x

10.1046/j.1525-1314.2003.00476.x

10.1111/j.1525-1314.2004.00533.x

10.1111/j.1525-1314.2005.00573.x

10.1016/j.epsl.2006.07.048

10.1144/0016-76492006-013

10.1093/petrology/40.8.1211

10.1093/petrology/28.6.1139

10.1016/j.tecto.2006.05.022

10.1046/j.1525-1314.2003.00417.x

10.1046/j.0263-4929.2000.00296.x

10.1016/j.lithos.2007.05.005

Mohan A., 1986, Reaction textures and P–T–X trajectory in the sapphirine‐spinel bearing granulites from Ganguvarpatti, Southern India, Neues Jahrbuch Mineralogie Abhandlungen, 154, 1

10.1093/petrology/43.9.1673

10.1016/0012-821X(71)90037-9

Motoyoshi Y., 1997, The Antarctic Region: Geological Evolution and Processes, 65

Motoyoshi Y., 1994, Reaction textures in granulites from Forefinger Point, Enderby Land, East Antarctica: an alternative interpretation on the metamorphic evolution of the Rayner Complex, Proceedings National Institute of Polar Research Symposium on Antarctic Geosciences, 7, 101

10.1180/0026461036750140

10.2465/jmps.99.159

10.1086/317947

Newton R. C., 1972, An experimental determination of the high‐pressure stability limits of magnesian cordierite under wet and dry conditions, Journal of Geophysical Research, 80, 398

10.1007/BF01164524

10.1046/j.1525-1314.2003.00420.x

10.2465/jmps.99.225

10.1111/j.1525-1314.1996.00049.x

10.1093/petrology/44.3.517

10.1111/j.1525-1314.1994.tb00031.x

10.1093/petrology/44.5.867

10.1029/98TC02204

Podlesskii K. K., 2006, Geothermobarometry of Orthopyroxene‐bearing Aluminous Granulites based on Internally Consistent Thermodynamic Datasets

10.1111/j.1525-1314.1988.tb00415.x

10.1007/BF00371910

10.1111/j.1525-1314.1997.00027.x

Sandiford M., 1986, Pyroxene exsolution in granulites from Fyfe Hills, Enderby Land, Antarctica: evidence for 1000°C metamorphic temperatures in Archaean continental crust, American Mineralogist, 71, 946

10.1007/BF00381271

10.1046/j.0263-4929.2000.00312.x

10.1086/627958

10.1093/petrology/31.5.971

10.1016/j.epsl.2005.11.042

10.1111/j.1525-1314.2005.00600.x

10.1007/s004100100276

10.1111/j.1525-1314.2007.00724.x

10.1127/ejm/3/2/0367

10.1007/s00410-006-0068-5

10.1046/j.0263-4929.2000.00303.x

10.1111/j.1525-1314.2005.00597.x

10.1111/j.1525-1314.2007.00711.x

10.1007/s00410-004-0617-8

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Journal of Metamorphic Geology

Tập 26 Số 2

125-154

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