The Zermatt‐Saas ophiolite: the largest (60‐km wide) and deepest (c. 70–80 km) continuous slice of oceanic lithosphere detached from a subduction zone?

Terra Nova - Tập 21 Số 3 - Trang 171-180 - 2009
Samuel Angiboust1, P. Agard1, Laëtitia Le Pourhiet1, Olivier Beyssac2
1Laboratoire de Tectonique, UMR CNRS 7072, Université Pierre et Marie Curie, Tour 46-00, 2èmeétage, Case 129, 4 Place Jussieu, 75252 Paris, France
2Laboratoire de Géologie, UMR CNRS 8538, Ecole Normale Supérieure, 24 rue Lhomond, 75005, Paris, France

Tóm tắt

AbstractThe Western Alps are a classic subduction‐related collisional orogen with well‐preserved, deeply subducted ophiolitic remnants of oceanic lithosphere. Some (e.g. Monviso, Voltri) were recognized as a palaeo‐subduction channel, with tectonic blocks showing a wide range of pressure–temperature conditions. We herein evaluate for the first time the metamorphic homogeneity of the extensive Zermatt‐Saas ophiolite. Zermatt‐Saas peak eclogitic assemblages are represented by omphacite–garnet ± phengite ± epidote ± lawsonite ± glaucophane in MORB‐derived metabasalts and garnet–chloritoid–talc ± lawsonite ± phengite in hydrothermalized metabasalts. Thermobarometric estimates with thermocalc and Raman Spectroscopy of carbonaceous material reveal homogeneous peak burial conditions at around 540 ± 20 °C and 23 ± 1 kbar. P–T paths indicate that the whole of the ophiolite, at least 60 km across, strikingly underwent similar burial and exhumation patterns and detached from the slab at depths around 80 km. The Zermatt‐Saas ophiolite thus appears to be the world’s largest oceanic lithosphere fragment exhumed from such depths, which provides important constraints on interplate coupling mechanisms.

Từ khóa


Tài liệu tham khảo

10.1046/j.1525-1314.2002.00391.x

10.1029/2005JB004103

10.1016/j.earscirev.2008.11.002

10.1016/S0012-821X(99)00161-2

10.1016/j.epsl.2005.11.058

10.1111/j.1365-3121.1991.tb00148.x

10.1144/gsjgs.143.4.0607

Bearth P., 1953, Elauterungen zu Blatt 535 Zermatt, Geol. Altas Schweiz 1:25 000, 29

Bearth P., 1967, Die Ophiolithe der Zone von Zermatt‐Saas Fee. Matériaux pour la Carte Géologique de la Suisse, Neue Folge, 132, 130

Bearth P., 1973, Gesteins‐ und Mineralparagenesen aus den Ophiolithen von Zermatt, Schweiz. Mineral. Petrogr. Mitt., 44, 15

Bearth P., 1981, The post‐Triassic sediments of the ophiolite zone Zermatt‐Saas Fee and the associated manganese mineralizations, Eclo. Geol. Helve., 74, 198

10.1046/j.1525-1314.2002.00408.x

10.1016/j.epsl.2004.05.023

10.1029/JB087iB08p07073

10.1111/j.1525-1314.1994.tb00013.x

Bucher K., 2008, The eclogite‐facies Allalin gabbro of the Zermatt‐Saas ophiolite, Western Alps, a record of subduction zone hydration, International Geological Congress abstract, Oslo

10.2138/am.2005.1718

10.1016/0012-821X(96)00123-9

10.1007/BF00381838

10.1016/S0012-821X(03)00261-9

10.1007/BF00381295

10.1127/0935-1221/2007/0019-1719

Dal Piaz G.V., 1979, Calc‐alkaline to ultrapotassic postcollisional volcanic activity in the internal northwestern Alps, Mem. Sci. Geol. Padova, 32, 16

Dercourt J., 1993, Atlas Tethys Palaeoenvironmental Maps

Elter G., 1987, Carte géologique de la vallée d’Aoste au 1:100 000

10.1016/0012-821X(79)90177-8

10.1029/JB075i005p00886

Ernst W.G., 1978, Mineral parageneses of eclogitic rocks and related mafic schists of piemonte ophiolite nappe, Breuil‐St‐Jacques Area, Italian Western Alps, Am. Mineral., 63, 621

Ernst W.G., 2000, Overview of UHP metamorphism and tectonics in well‐studied collisional orogens, final report of the Task Group III‐6 (1994–1998) of the International Lithosphere Project, Geol. Soc. Am., 293, 3

10.1016/0024-4937(90)90003-J

10.1016/j.lithos.2003.12.001

10.1130/G23190A.1

10.1029/2002TC001406

10.1029/2007GL031059

10.1016/S0012-821X(01)00490-3

Guillot S., 2004, The Monviso ophiolitic Massif (Western Alps), a section through a serpentinite subduction channel. Evolution of the western Alps: insights from metamorphism, structural geology, tectonics and geochronology, Virtual Explor., 16, 3

Guillot S., 2009, Exhumation processes in oceanic and continental subduction contexts: a review, Front. Earth Sci., 10.1007/978-3-540-87974-9_10

Hacker B.R., 1996, The Tectonics of Asia, 345

10.1029/2000JB900039

Hacker B.R., 2003, Subduction factory – 2. Are intermediate‐depth earthquakes in subducting slabs linked to metamorphic dehydration reactions?, J. Geophys. Res. Solid Earth, 108, B1, 10.1029/2001JB001129

Holland T.J.B., 1980, The reaction albite = jadeite + quartz determined experimentally in the range 600‐1200 degrees C, Am. Mineral., 65, 129

10.1111/j.1525-1314.1998.00140.x

10.2475/ajs.303.5.353

10.1016/j.epsl.2005.06.047

Kretz R., 1983, Symbols for rock‐forming mineral, Am. Mineral., 68, 277

10.1016/0264-8172(86)90044-9

10.1111/j.1525-1314.2004.00503.x

10.1038/364520a0

Martin S., 1989, Polyphase HP metamorphism in the ophiolitic glaucophanites of the lower St. Marcel valley (Aosta, Italy), Ofioliti, 14, 135

Martin S., 2008, An eclogitized oceanic palaeo‐hydrothermal field from the St Marcel valley (Italian Western Alps), Ofioliti, 33, 49

10.1127/ejm/7/5/1149

10.1046/j.1525-1314.1999.00198.x

Meyer J., 1983, The development of the high pressure metamorphism in the Allalin metagabbro (Switzerland), Terra Cognita, 3, 187

Oberhansli R., 1980, PT Bestimmungen anhand von Mineralanalysen in Eklogiten und Glaukophaniten der Ophiolite von Zermatt, Schweiz, Mineral. Petro. Mitt., 60, 215

Oberhansli R., 2004, Explanatory notes to the map: metamorphic structure of the Alps: introduction, Mitt. Osterr. Mineral. Gesellsch., 149, 175

10.1029/1999GL900558

10.1016/0012-821X(94)90042-6

10.1111/j.1365-3121.1993.tb00237.x

10.1016/j.epsl.2008.07.037

10.1127/ejm/3/1/0007

10.1016/S0024-4937(97)00041-8

10.1007/s004100050421

10.1016/S0985-3111(00)00112-1

10.1016/S0040-1951(01)00162-7

10.1016/j.epsl.2004.12.027

10.1029/JB091iB10p10229

10.1038/ngeo336

10.1016/S0024-4937(97)82006-3

10.1029/2006JB004441

Thông tin
Thông tin xuất bản

Terra Nova

Tập 21 Số 3

171-180

Thông tin tác giả