Relicts of an intra-oceanic arc in the Sapi-Shergol mélange zone (Ladakh, NW Himalaya, India): implications for the closure of the Neo-Tethys Ocean

Mahéo, Gweltaz; Fayoux, Xavier; Guillot, Stéphane; Garzanti, Eduardo; Capiez, Paul; Mascle, Georges

doi:10.1016/j.jseaes.2005.01.004

Cited by 68 publications

(13 citation statements)

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“…The prograde P – T conditions of metamorphism of the Naga Hills eclogites and Sapi‐Shergol blueschists of the Indus‐Tsangpo suture zone in northern Himalayas, both of ocean floor, tholeiitic affinity, and emplaced as tectonic slices within ophiolite in the Burma and Ladakh forearc regions, respectively, may be used to constrain the P – T conditions of the subducting leading edge of the Indian plate prior to the India–Eurasia collision. The peak pressure of eclogite metamorphism at Naga Hills is higher than the peak pressures obtained from the Sapi‐Shergol blueschists (0.9–1.0 GPa at 350–420 °C; Mahéo et al. , 2006) (Fig.…”

Section: Discussionmentioning

confidence: 72%

Metamorphic evolution of the Naga Hills eclogite and blueschist, Northeast India: implications for early subduction of the Indian plate under the Burma microplate

Chatterjee

Ghose

2010

Journal Metamorphic Geology

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Tectonic slices and lenses of eclogite within mafic and ultramafic rocks of the Early Cretaceous–Eocene Naga Hills ophiolite were studied to constrain the physical conditions of eastward subduction of the Indian plate under the Burma microplate and convergence rate prior to the India–Eurasia collision. Some of the lenses are composed of eclogite, garnet‐blueschist, glaucophanite and greenschist from core to margin, representing a retrograde hydrothermal alteration sequence. Barroisite, garnet, omphacite and epidote with minor chlorite, phengite, rutile and quartz constitute the peak metamorphic assemblage. In eclogite and garnet‐blueschist, garnet shows an increase in Mg and Fe and decrease in Mn from core to rim. In chlorite in eclogite, Mg increases from core to rim. Inclusions of epidote, glaucophane, omphacite and quartz in garnet represent the pre‐peak assemblage. Glaucophane also occurs profusely at the rims of barroisite. The matrix glaucophane and epidote represent the post‐peak assemblage. The Fe3+ content of garnet‐hosted omphacite is higher than that of matrix omphacite, and Fe3+ increases from core to rim in matrix glaucophane. Albite occurs in late stage veins. P–T pseudosection analysis indicates that the Naga Hills eclogites followed a clockwise P–T path with prograde metamorphism beginning at ∼1.3 GPa/525 °C and peaking at 1.7–2.0 GPa/580–610 °C, and subsequent retrogression to ∼1.1 GPa/540 °C. A comparison of these P–T conditions with numerical thermal models of plate subduction indicates that the Naga Hills eclogites probably formed near the top of the subducting crust with convergence rates of ∼ 55–100 km Myr−1, consistent with high pre‐collision convergence rates between India and Eurasia.

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Section: Discussionmentioning

confidence: 72%

Metamorphic evolution of the Naga Hills eclogite and blueschist, Northeast India: implications for early subduction of the Indian plate under the Burma microplate

Chatterjee

Ghose

2010

Journal Metamorphic Geology

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“…The Karakoram and Lhasa Terranes are considered to have existed previously as a single tectonic unit, now separated by the Karakoram Fault [e.g., Searle et al , 1988]. To the south of the Karakoram‐Lhasa block lies the Kohistan Ladakh Island Arc (KLIA), considered to have collided with the southern margin of Eurasia during mid to late Cretaceous times [e.g., Clift et al , 2000; Maheo et al , 2006; Robertson and Degnan , 1994; Rolland et al , 2000, 2002b; Schärer et al , 1984b; Searle et al , 1988; Sutre , 1990; Treloar et al , 1996], creating the Shyok Suture Zone (SSZ) [ Robertson and Collins , 2002].…”

Section: Geology Of the Himalayamentioning

confidence: 99%

“…However, much uncertainty still exists with regards to the order and nature of tectonic events which governed the early phases of India‐Eurasia collision. One of these issues concerns the collisional history of Kohistan‐Ladakh Island Arc with most authors suggesting that it collided with Eurasia before India in the mid‐late Cretaceous [e.g., Clift et al , 2000; Gaetani et al , 1993; Maheo et al , 2006; Robertson and Collins , 2002; Rolland et al , 2000; Searle et al , 1988; Treloar , 1997; Treloar et al , 2003], and others suggesting an India‐arc collision at 61 Ma, predating India‐Eurasia collision at 50 Ma [e.g., Andrews‐Speed and Brookfield , 1982; Khan et al , 2009]. Although that problem is beyond the scope of this paper, detrital zircon data from the Jurutze Formation (see section 8) suggests Lhasa Block contributing sediment within the ITSZ by 53.4 (±1.4) Ma, favoring docking of the Kohistan‐Ladakh Island Arc and Eurasia earlier than a 50 Ma India‐Eurasia collision.…”

Section: Summary: Paleogeographic Reconstructionmentioning

confidence: 99%

Geology of the Cenozoic Indus Basin sedimentary rocks: Paleoenvironmental interpretation of sedimentation from the western Himalaya during the early phases of India-Eurasia collision

Henderson

Najman

Parrish³

et al. 2010

Tectonics

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103

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This study reassesses the stratigraphy, sedimentology, and provenance of the Indus Basin sedimentary rocks, deposited within the Indus Tsangpo Suture Zone (ITSZ) during the early phases of India‐Eurasia collision. Using field observations, biostratigraphy, and petrographic and isotopic analyses we create a paleodepositional reconstruction within the paleotectonic setting of the early phases of India‐Eurasia collision. We then re‐examine existing constraints to the timing of India‐Eurasia collision previously interpreted from the earliest occurrence of mixed Indian‐ and Eurasian‐derived detritus in the succession. From mid‐Cretaceous to early Paleocene times the Jurutze and Sumda Formations were deposited within an arc‐bounded marine basin between the Dras and Kohistan‐Ladakh Island arcs. The <51 Ma aged deltaic Chogdo Formation then filled the basin until deposition of the 50.8–49.4 Ma aged Nummulitic Limestone during a marine incursion, before continental facies developed in an evolving intermountain basin with the deposition of the Paleogene Indus Group. Within these systems, sediment was sourced from the Eurasian margin to the north and was transported southward into the suture zone. In this section, we see no unequivocal evidence of Indian Plate input to the sedimentary succession (and thus no evidence of mixed Indian‐Eurasian‐derived detritus indicative of India‐Asia collision) until the upper stratigraphic horizons of the Indus Group, when facies are representative of an axial, northwesterly flowing river system. We suggest that the paleo‐Indus River was initiated within the ITSZ during late Oligocene‐early Miocene times. Sedimentation of the Indus Group continued until the late Miocene.

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“…Identification of these high‐ P lithologies may be a challenge in cases where they are affected by strong retrogression during exhumation. Descriptions of serpentinite mélanges are common in Mesozoic and Cenozoic orogens, especially those located in the circum‐Pacific and Caribbean regions (García‐Casco et al ., , , ; Kato & Saka, ; Mahéo et al ., ; Guilmette et al ., ; Hirauchi et al ., ; Lázaro et al ., ; Blanco‐Quintero et al ., ,b; Escuder‐Viruete et al ., ; Escuder‐Viruete & Baumgartner, ). These units are more unusual in Palaeozoic orogens, with recent reports from the Caledonian orogen of southern Scotland (Kawai et al ., ), and are almost absent in Precambrian orogens, although some significant reports, as in the Anti‐Atlas mountains of Morocco, have been provided (Hefferan et al ., ).…”

Section: Introductionmentioning

confidence: 99%

The metahyaloclastitic matrix of a unique metavolcanic block reveals subduction in the Somozas Mélange (Cabo Ortegal Complex, NW Iberia): tectonic implications for the assembly of Pangea

Novo‐Fernández

Garcia‐Casco

Arenas

et al. 2016

Journal Metamorphic Geology

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The allochthonous Cabo Ortegal Complex (NW Iberian Massif) contains a ~500 m thick serpentinite‐matrix mélange located in the lowest structural position, the Somozas Mélange. The mélange occurs at the leading edge of a thick nappe pile constituted by a variety of terranes transported to the East (present‐day coordinates; NW Iberian allochthonous complexes), with continental and oceanic affinities, and represents a Variscan suture. Among other types of metaigneous (calcalkaline suite dated at 527–499 Ma) and metasedimentary blocks, it contains close‐packed pillow‐lavas and broken pillow‐breccias with a metahyaloclastitic matrix formed by muscovite–paragonite–margarite–garnet–chlorite–kyanite–hematite–epidote–quartz–rutile. Pseudosection modelling in the MnCNTKFMASHO system indicates metamorphic peak conditions of ~17.5–18 kbar and ~550 °C followed by near‐isothermal decompression. This P–T evolution indicates subduction/accretion of an arc‐derived section of peri‐Gondwanan transitional crust. Subduction below the Variscan orogenic wedge evolved to continental collision with important dextral component. Closure of the remaining oceanic peri‐Gondwanan domain and associated release of fluid led to hydration of the overlying mantle wedge and the formation of a low‐viscosity subduction channel, where return flow formed the mélange. The submarine metavolcanic rocks were deformed and detached from the subducting transitional crust and eventually incorporated into the subduction channel, where they experienced fast exhumation. Due to the cryptic nature of the high‐P metamorphism preserved in its tectonic blocks, the significance of the Somozas Mélange had remained elusive, but it is made clear here for the first time as an important tectonic boundary within the Variscan Orogen formed during the late stages of the continental convergence leading to the assembly of Pangea.

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Relicts of an intra-oceanic arc in the Sapi-Shergol mélange zone (Ladakh, NW Himalaya, India): implications for the closure of the Neo-Tethys Ocean

Cited by 68 publications

References 51 publications

Metamorphic evolution of the Naga Hills eclogite and blueschist, Northeast India: implications for early subduction of the Indian plate under the Burma microplate

Metamorphic evolution of the Naga Hills eclogite and blueschist, Northeast India: implications for early subduction of the Indian plate under the Burma microplate

Geology of the Cenozoic Indus Basin sedimentary rocks: Paleoenvironmental interpretation of sedimentation from the western Himalaya during the early phases of India-Eurasia collision

The metahyaloclastitic matrix of a unique metavolcanic block reveals subduction in the Somozas Mélange (Cabo Ortegal Complex, NW Iberia): tectonic implications for the assembly of Pangea

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