Eclogitic metasediments from the Tso Morari area (Ladakh, Himalaya): evidence for continental subduction during India-Asia convergence

Guillot, Stéphane; Sigoyer, Julia de; Lardeaux, Jean‐Marc; Mascle, Georges

doi:10.1007/s004100050303

Cited by 164 publications

(127 citation statements)

References 63 publications

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“…Shaded area refers to the garnet-blueschist facies. (b) PT paths of studied metasediments in a petrogenetic grid for the system NFMASH (redrawn and modified after Guillot et al [23]). Si isopleths of phengite from Massonne & Schreyer [2]; glaucophane stability field from Maresch [25].…”

Section: Pressure -Temperature -Deformation Evolutionmentioning

confidence: 99%

“…7b shows the PT trajectories inferred for the metasedimentary blocks. The PT grid is built considering a NFMASH system with excess SiO 2 and H 2 O, originally proposed by Guiraud et al [26] and modified by Guillot et al, [23] for Fe-rich metapelites. This diagram does not consider phengite, but we can neglect it since it is stable throughout the metamorphic evolution and is not involved in the most important reactions observed in our samples.…”

Section: Pressure -Temperature -Deformation Evolutionmentioning

confidence: 99%

“…C27: eclogitic metabasite showing rare coarse-grained relics of Na-clinopyroxene 1 replacing older Na-amphibole. Garnet is characterized by a prograde core-to-rim zonation from Alm Prp (0,5) Grs (25)(26)(27) Sps (3)(4)(5)(6)(7)(8) to Alm Prp (2)(3) Grs (22)(23) Sps (8)(9) and sometimes contains 10 micronswide inclusions of Fe-glaucophane. Na-clinopyroxene 2 ranging in composition from omphacite to aegirinaugite (Fig.…”

Section: Sample Descriptionmentioning

confidence: 99%

“…C9: blueschist metabasalt with an assemblage of Na-amphibole 1 + almandine-rich garnet (Alm (51-63) Prp (0,-0,8) Grs (22)(23)(24)(25) Sps (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23) ) + phengite 1 + sphene, followed by the blastesis of synkinematic finer-grained Na-amphibole 2 + phengite 2 (Si + = 3,5-3,6 p.f.u.) + epidote + sphene.…”

Section: Sample Descriptionmentioning

confidence: 99%

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Different PT paths recorded in a tectonic mélange (Voltri Massif, NW Italy): implications for the exhumation of HP rocks

et al. 2007

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The Cascine Parasi Mélange (CPM) of the high-pressure, meta-ophiolitic Voltri Massif (Ligurian Western Alps), consists of a foliated chlorite-actinolite greenschist matrix enclosing lenses of metabasites and metasediments. The surrounding units consist of serpentinites not enclosing these metamorphic rocks. The matrix records three sets of folds: (i) Dm1/Dm2 (blueschist to greenschist-facies conditions), which can be correlated to folds in the metasedimentary blocks; (ii) Dm3, which are the most obvious in the field and which partially re-orient the previous structures. The metabasite lenses preserve internal High-Pressure (HP) schistosities unrelated to the matrix foliation. The lenses equilibrated at different peak metamorphic conditions (ranging from eclogite-to blueschist-facies) and some recorded the prograde transition from lawsonite-bearing assemblages to garnet blueschists. Individual lenses display different segments of typical subduction PT paths which apparently converge in the blueschist facies. A late stage greenschist-facies re-equilibration is particularly widespread at the rims of the HP lenses. These structural and metamorphic features suggest that the mélange was active during early phases of the structural evolution of the area, at least through the exhumation and emplacement of the HP blocks into shallower crustal levels at conditions transitional from blueschist-to greenschist-facies; the older history is only preserved inside the blocks.

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Section: Pressure -Temperature -Deformation Evolutionmentioning

confidence: 99%

Section: Pressure -Temperature -Deformation Evolutionmentioning

confidence: 99%

Section: Sample Descriptionmentioning

confidence: 99%

Section: Sample Descriptionmentioning

confidence: 99%

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Different PT paths recorded in a tectonic mélange (Voltri Massif, NW Italy): implications for the exhumation of HP rocks

et al. 2007

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“…Meanwhile, detailed geological investigations conducted in the Indus Suture Zone and Molasse (Fuchs & Linner 1996) and new petrographic and thermobarometric data from the Tso Morari eclogites (discovered by Berthelsen 1953) were published (Fig. 2;De Sigoyer et al 1997;Guillot et al 1997). Geochronological data for the Tso Morari metamorphism, published by , were used to constrain the time of continental subduction and collision; Lu-Hf and Sm-Nd methods were used to date metamorphism related to subduction and gave an age of c. 55 Ma, whereas timing of retrogression to amphibolite facies, related to collision, was estimated at c. 47 Ma by Sm-Nd, RbSr and 40 Ar/ 39 Ar methods.…”

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confidence: 99%

Exhumation history of eastern Ladakh revealed by ⁴⁰ Ar/ ³⁹ Ar and fission-track ages: the Indus River–Tso Morari transect, NW Himalaya

Schlup

Carter

Cosca

et al. 2003

JGS

118

103

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Fission-track and 40 Ar/ 39 Ar ages place time constraints on the exhumation of the North Himalayan nappe stack, the Indus Suture Zone and Molasse, and the Transhimalayan Batholith in eastern Ladakh (NW India). Results from this and previous studies on a north-south transect passing near Tso Morari Lake suggest that the SW-directed North Himalayan nappe stack (comprising the Mata, Tetraogal and Tso Morari nappes) was emplaced and metamorphosed by c. 50-45 Ma, and exhumed to moderately shallow depths (c. 10 km) by c. 45-40 Ma. From the mid-Eocene to the present, exhumation continued at a steady and slow rate except for the root zone of the Tso Morari nappe, which cooled faster than the rest of the nappe stack. Rapid cooling occurred at c. 20 Ma and is linked to brittle deformation along the normal Ribil-Zildat Fault concomitant with extrusion of the Crystalline nappe in the south. Data from the Indus Molasse suggest that sediments were still being deposited during the Miocene.

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Tectonic Stacking of HP/LT Metamorphic Rocks in Accretionary Wedges and the Role of Shallowing Slab‐Mantle Decoupling

Aygül

Oberhänsli

2017

Tectonics

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High‐pressure/low‐temperature (HP/LT) chloritoid‐bearing micaschists crop out widely in the central part of northern Turkey and represent deep‐seated subduction‐accretionary complexes. Three peak metamorphic assemblages are identified in the area studied: (1) garnet‐chloritoid‐glaucophane with pseudomorphs after lawsonite; (2) chloritoid with pseudomorphs after glaucophane; and (3) chloritoid with pseudomorphs after jadeite in addition to phengite, paragonite, quartz, chlorite, rutile, and apatite. The latter is interpreted as transformation of a chloritoid + glaucophane assemblage to chloritoid + jadeite with increasing pressure; PT modeling indicates ~17 and 22–25 kbars for the two peak parageneses. The diversity of peak metamorphic assemblages and the PT estimates suggest that basal accretion occurred at different depths within the wedge. The depth of the basal accretion is possibly controlled by the slab‐mantle decoupling depth. Stretching and thinning of the lithospheric fore arc induced by the slab rollback possibly caused shallowing of the slab‐mantle decoupling depth which limited depth of the basal accretion from 70–80 km to ~55 km within the subduction channel. A slab‐mantle coupling depth‐controlled basal accretion may also explain the scarcity of eclogite and high‐grade blueschist facies metamorphic rocks in active intraoceanic subduction zones. Because the overriding plate is young and hot in intraoceanic subductions, the slab and mantle are coupled at a relatively shallow depth before eclogitization of the oceanic crust. This prevents accretion and exhumation of eclogite along the subduction channel.

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Eclogitic metasediments from the Tso Morari area (Ladakh, Himalaya): evidence for continental subduction during India-Asia convergence

Cited by 164 publications

References 63 publications

Different PT paths recorded in a tectonic mélange (Voltri Massif, NW Italy): implications for the exhumation of HP rocks

Different PT paths recorded in a tectonic mélange (Voltri Massif, NW Italy): implications for the exhumation of HP rocks

Exhumation history of eastern Ladakh revealed by ⁴⁰ Ar/ ³⁹ Ar and fission-track ages: the Indus River–Tso Morari transect, NW Himalaya

Tectonic Stacking of HP/LT Metamorphic Rocks in Accretionary Wedges and the Role of Shallowing Slab‐Mantle Decoupling

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Eclogitic metasediments from the Tso Morari area (Ladakh, Himalaya): evidence for continental subduction during India-Asia convergence

Cited by 164 publications

References 63 publications

Different PT paths recorded in a tectonic mélange (Voltri Massif, NW Italy): implications for the exhumation of HP rocks

Different PT paths recorded in a tectonic mélange (Voltri Massif, NW Italy): implications for the exhumation of HP rocks

Exhumation history of eastern Ladakh revealed by 40 Ar/ 39 Ar and fission-track ages: the Indus River–Tso Morari transect, NW Himalaya

Tectonic Stacking of HP/LT Metamorphic Rocks in Accretionary Wedges and the Role of Shallowing Slab‐Mantle Decoupling

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Exhumation history of eastern Ladakh revealed by ⁴⁰ Ar/ ³⁹ Ar and fission-track ages: the Indus River–Tso Morari transect, NW Himalaya