Raman spectra of carbonaceous material in metasediments: a new geothermometer

Journal of Metamorphic Geology - Tập 20 Số 9 - Trang 859-871 - 2002
Olivier Beyssac1, Bruno Goffé1, Christian Chopin1, Jean‐Noël Rouzaud2
1Laboratoire de Géologie, CNRS – UMR 8538, Ecole Normale Supérieure, 24 rue Lhomond, 75231 Paris Cedex 5, France ( [email protected] )
2Centre de Recherche sur la Matière Divisée, CNRS-Université d’Orléans, UMR 6619, 1B rue de la Férollerie, 45071 Orléans Cedex 2, France

Tóm tắt

Abstract

Metasedimentary rocks generally contain carbonaceous material (CM) deriving from the evolution of organic matter originally present in the host sedimentary rock. During metamorphic processes, this organic matter is progressively transformed into graphite s.s. and the degree of organisation of CM is known as a reliable indicator of metamorphic grade. In this study, the degree of organisation of CM was systematically characterised by Raman microspectroscopy across several Mesozoic and Cenozoic reference metamorphic belts. This degree of organisation, including within‐sample heterogeneity, was quantified by the relative area of the defect band (R2 ratio). The results from the Schistes Lustrés (Western Alps) and Sanbagawa (Japan) cross‐sections show that (1) even through simple visual inspection, changes in the CM Raman spectrum appear sensitive to variations of metamorphic grade, (2) there is an excellent agreement between the R2 values calculated for the two sections when considering samples with an equivalent metamorphic grade, and (3) the evolution of the R2 ratio with metamorphic grade is controlled by temperature (T). Along the Tinos cross‐section (Greece), which is characterised by a strong gradient of greenschist facies overprint on eclogite facies rocks, the R2 ratio is nearly constant. Consequently, the degree of organisation of CM is not affected by the retrogression and records peak metamorphic conditions. More generally, analysis of 54 samples representative of high‐temperature, low‐pressure to high‐pressure, low‐temperature metamorphic gradients shows that there is a linear correlation between the R2 ratio and the peak temperature [T(°C) = −445 R2 + 641], whatever the metamorphic gradient and, probably, the organic precursor. The Raman spectrum of CM can therefore be used as a geothermometer of the maximum temperature conditions reached during regional metamorphism. Temperature can be estimated to ± 50 °C in the range 330–650 °C. A few technical indications are given for optimal application.

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Tài liệu tham khảo

10.2113/172.5.617

10.1046/j.0263-4929.2001.00322.x

Azanon J. M. 1994.Metamorfismo de alta presion/baja temperatura baja presion/alta temperatura y tectonica del complejo Alpujarride (Cordilleras Betico‐Rifenas).PhD Thesis University of Granada . Granada .

10.1016/0024-4937(86)90015-0

Bény‐Bassez C., 1985, Scanning Electron Microscopy,, 119

Beyssac O., 2000, Pressure effects on graphitization: experimental constraints, Journal of Conference Abstracts, 5, 13

10.1007/s00410-001-0324-7

10.1016/0166-5162(82)90018-0

Borghi A., 1985, Metamorphism in the northern part of the Dora Maira massif (Cottian Alps), Bollettino Del Museo Regionale Di Scienze Naturali, Torino, 3, 369

Borghi A., 1986, Composite P‐T paths in the. Internal Penninic Massifs of the Western Alps: Petrological constraints to their thermo‐mechanical evolution, Eclogae Geologicae Helvetiae, 89, 345

Bouybaouene M., 1998, High‐Pressure granulites on top of the Beni Bousera peridotites, Morocco: a record of an ancient thickened crust in the Alboran domain, Bulletin de la Société Géologique de France, 169, 153

10.1016/0016-7037(85)90059-6

10.1007/s004100050496

10.1127/ejm/3/2/0263

10.1016/S0008-6223(97)00141-3

10.1017/CBO9780511573088.008

10.1016/0166-5162(87)90074-7

10.1007/BF00375447

10.1016/S0166-5162(00)00012-4

10.1111/j.1525-1314.1992.tb00100.x

10.1111/j.1525-1314.1983.tb00269.x

10.1007/BF00310699

10.1016/0008-6223(91)90064-P

Faure M., 1985, Microtectonic evidence for eastward ductile shear in the Jurassic orogen of SW Japan, Journal of Metamorphic Geology, 7, 175

Frey M., 1980, Alpine metamorphism along the GeoTraverse Basel‐Chiasso‐a review, Eclogae Geologicae Helvetiae, 73, 527

10.1086/627936

10.1016/0024-4937(81)90043-8

10.1016/0146-6380(92)90132-H

10.1016/0146-6380(90)90123-H

10.1029/2000TC900021

10.1016/0016-7037(94)90104-X

10.1016/S0008-6223(00)00120-2

10.1111/j.1525-1314.1994.tb00038.x

10.1007/BF00373366

10.1007/BF00310693

10.1016/0008-6223(84)90009-5

10.2475/ajs.298.6.471

10.1016/S0016-7037(99)00409-3

10.1103/PhysRevB.20.392

10.2138/am-2000-11-1206

10.1111/j.1525-1314.1987.tb00375.x

10.1016/S0024-4937(02)00115-9

10.1366/0003702894202878

Pasteris J. D., 1991, Raman spectra of graphite as indicators of degree of metamorphism, Canadian Mineralogist, 29, 1

Patriat M., 1998, Post‐orogenic extension and shallow‐dipping shear zones, study of a brecciated decollement horizon in Tinos (Cyclades, Greece), Comptes Rendus de l'Académie Des Sciences, Paris, 326, 355

10.1007/BF00320978

10.1038/315733a0

Saliot P., 1973, Les principales zones de métamorphisme dans les Alpes françaises. répartition et signification. Comptes rendus de l'Académie des Sciences, Paris, 276, 3081

10.1111/j.1525-1314.1997.00038.x

Trotet F. 2000.Exhumation des roches de Haute Pression – Basse Temperature le long d'un transect des Cyclades au Péloponnèse (Grèce): implications géodynamiques.PhD Thesis Université Paris 11 Paris.

10.1016/0038-1098(78)90382-4

10.1063/1.1674108

10.2475/ajs.301.6.557

10.1007/BF00306643

10.1016/0008-6223(89)90125-5

Wopenka B., 1993, Structural characterization of kerogens to granulite‐facies graphite: Applicability of Raman microprobe spectroscopy, American Mineralogist, 78, 533

10.1046/j.1525-1314.1996.05792.x

10.1111/j.1945-5100.1995.tb01115.x

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Journal of Metamorphic Geology

Tập 20 Số 9

859-871

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