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?

被引：178

作者：

Angiboust, S. ^{[1
]}

Agard, P. ^{[1
]}

Jolivet, L. ^{[1
]}

Beyssac, O. ^{[2
]}

机构：

[1] Univ Paris 06, CNRS, UMR 7072, Lab Tecton, F-75252 Paris, France

[2] Ecole Normale Super, CNRS, UMR 8538, Geol Lab, F-75005 Paris, France

来源：

TERRA NOVA | 2009年 / 21卷 / 03期

关键词：

HIGH-PRESSURE METAMORPHISM; LAGO DI CIGNANA; WESTERN ALPS; CONTINENTAL-CRUST; ECLOGITIC ROCKS; MANTLE WEDGE; SM-ND; EXHUMATION; COMPLEX; MELANGE;

D O I：

10.1111/j.1365-3121.2009.00870.x

中图分类号：

P [天文学、地球科学];

学科分类号：

07 ;

摘要：

The 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 degrees 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.

引用

页码：171 / 180

页数：10

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