Multistage evolution of the Jijal ultramafic–mafic complex (Kohistan, N Pakistan): Implications for building the roots of island arcs

Dhuime, Bruno; Bosch, Delphine; Bodinier, Jean-Louis; Garrido, Carlos J.; Bruguier, Olivier; Hussain, Shahid; Dawood, Hamid

doi:10.1016/j.epsl.2007.06.026

Cited by 127 publications

(39 citation statements)

References 68 publications

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“…Second, the material mainly returned from depths around 30–40 km in the subduction zone, either as coherent, kilometer‐scale bodies (Ashin, Iran; Stepanavan, Armenia) or as blocks in a melange (Segina, Iran; Cetmi, Turkey). Third, it coincides with a regional‐scale geodynamic reorganization, marked by (1) obduction processes to the south of the Neotethys, encompassing the very same region (Figure 1a) [ Nicolas , 1989; Hacker et al , 1996; Parlak and Delaloye , 1999]; (2) kinematic changes and acceleration of convergence [ Dercourt et al , 1986; Agard et al , 2007]; (3) the formation of voluminous magmatic arcs (e.g., Kohistan arc [ Rolland et al , 2002; Dhuime et al , 2007]); and (4) the development of en echelon, marginal back‐arc basins in the upper plate [ Arvin and Robinson , 1994; Shojaat et al , 2003; Mahéo et al , 2004; Bagheri and Stampfli , 2008].…”

Section: Exhumation Of Slab Materials Along the Neotethyan Subduction mentioning

confidence: 89%

Coeval blueschist exhumation along thousands of kilometers: Implications for subduction channel processes

Monié

Agard

2009

Geochem Geophys Geosyst

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[1] We herein focus on understanding what controls the detachment and migration of oceanic crustal slices along subduction zones. We provide evidence for the coeval Middle to Late Cretaceous exhumation of oceanic blueschists in the same Neotethyan subduction zone, across more than 3000 km, from depths around 30-40 km, over a short time interval (25 Ma) compared to the duration of subduction (>100 Ma). We stress the importance of such a geodynamic process and suggest that this exhumation was promoted by a regional-scale change in the long-term interplate mechanical coupling. On the basis of geological and geophysical evidence, we propose that the upward migration of oceanic fragments in subduction zones is normally inhibited and only occurs discontinuously, as the subduction channel opens up in response to a major change in plate geodynamics, slab geometry and dynamics, mantle wedge and slab hydration, or a combination of these.Components: 6917 words, 2 figures, 1 table.

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Section: Exhumation Of Slab Materials Along the Neotethyan Subduction mentioning

confidence: 89%

Coeval blueschist exhumation along thousands of kilometers: Implications for subduction channel processes

Monié

Agard

2009

Geochem Geophys Geosyst

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“…14b) (Pearce et al 1981;Browning 1982;Pearce et al 1984;Lippard et al 1986;Beurrier et al 1989;Stern 2004;Dhuime et al 2007). Rock types within the Oman ophiolite that crosscut the primary ophiolitic pile include ultramafic cumulates (dunite, wehrlite) and mafic cumulates (melagabbro, gabbronorite), as well as diorite, tonalite, amphibole-trondhjemite, and doleritic dykes.…”

Section: Interpretation Of Ree Patternsmentioning

confidence: 95%

An early Palaeozoic supra-subduction lithosphere in the Variscides: new evidence from the Maures massif

Bellot¹,

Laverne

Bronner

2009

Int J Earth Sci (Geol Rundsch)

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Petrographic and geochemical studies of peridotites and melagabbros from the Maures massif (SE France) provide new constraints on the Early Palaeozoic evolution of the continental lithosphere in Western Europe. Peridotites occur as lenses along a unit rooted in the main Variscan suture zone. They are dominantly spinel peridotites and minor garnet-spinel peridotites. Spinel peridotites represent both residual mantle and ultramafic cumulates. Mantle-related dunites and harzburgites display high temperature textures, with olivine (Mg# 0.90 ), orthopyroxene (Mg# 0.90 ) and spinel (TiO 2 \ 0.2%; Cr# 0.64-0.83 ) compositions typical of fore-arc upper mantle. Ultramafic cumulates are dunite adcumulates, harzburgite heteradcumulates and mesocumulates, melagabbro heteradcumulates and amphibole peridotites, with olivine (Mg# 0.85-0.89 ), orthopyroxene (Mg# 0.86-0.89 ) and Cr-spinel (TiO 2 = 0.5-3.3%; Cr# 0.7-0.98 ) compositions typical of ultramafic cumulates. Cr-spinel compositions of both spinel peridotite types suggest their genesis in a supra-subduction zone lithosphere. Core to rim zoning in spinel is related to the incomplete influence of regional metamorphism and serpentinisation. The covariation of major and minor elements with Al 2 O 3 for cumulates is consistent with igneous processes involving crystal accumulation. Both mantle and cumulate dunites and harzburgites have U-shaped REE patterns and extremely low trace element contents, similar to peridotites from modern fore-arc peridotites (South Atlantic) and from ophiolites related to supra-subduction zones (Semail, Cyclops, Pindos, Troodos). Melagabbros also have U-shaped REE patterns similar to xenoliths from the Philippine island arc, but also similar to intrusive ultramafic cumulates from the Semail nappe of Oman related to a proto-subduction setting. A wehrlite has a REE pattern similar to that of amphibole peridotites reflecting metasomatism of clinopyroxene-bearing peridotites due to subduction-related fluids. The Maures spinel peridotites and melagabbros are therefore interpreted as the lowermost parts of a crustal sequence and minor residual mantle of lithosphere generated in a supra-subduction zone during Early Palaeozoic time. Garnet-spinel peridotites are chemically close to melagabbros, but have recorded high pressure metamorphism before their retrogression similar to spinel peridotites into amphibolites to greenschists facies metamorphism. They indicate burial to mantle depths of the margin of the supra-subduction lithosphere during the Early Palaeozoic continental subduction. Both peridotite types were exhumed during the Upper Palaeozoic continental collision. Comparable observations from other Variscanrelated peridotites, in particular of the Speik complex of the Autroalpine basement, and a common age for the subduction stage allow extension of these regional conclusions to a broad area sharing the Cambrian suture zone, extending from the Ossa-Morena to the Bohemian massif.

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“…The discrepancy with previous interpretations is further supported by the precise intrusion age of a 49.80 ± 0.15 Ma metagabbro, which presents an intense fabric, hence all visual characteristics of a stage 1 intrusion (Heuberger et al 2007). The assumptions Windley 1985, 1986;Treloar et al 1996) Garrido et al 2006;Dhuime et al 2007), and deep crustal xenoliths from Sierra Nevada (Lee et al 2006). Natural data is compared to the trend of calculated cumulate compositions from mineral composition and modal abundance of hydrous high pressure fractional crystallization experiments (Alonso-Perez et al 2009), and to the trend of the melt and calculated restite composition of partial melting experiments (Wolf and Wyllie 1991).…”

Section: Regional Implication Of the Geochronological Datamentioning

confidence: 99%

Construction of the granitoid crust of an island arc part I: geochronological and geochemical constraints from the plutonic Kohistan (NW Pakistan)

Jagoutz

Burg

Hussain

et al. 2009

Contrib Mineral Petrol

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170

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We present major and trace element analyses and U-Pb zircon intrusion ages from I-type granitoids sampled along a crustal transect in the vicinity of the Chilas gabbronorite of the Kohistan paleo-arc. The aim is to investigate the roles of fractional crystallization of mantlederived melts and partial melting of lower crustal amphibolites to produce the magmatic upper crust of an island arc. The analyzed samples span a wide calc-alkaline compositional range (diorite-tonalite-granodiorite-granite) and have typical subduction-related trace element signatures. Their intrusion ages (75.1 ± 4.5-42.1 ± 4.4 Ma) are younger than the Chilas Complex (*85 Ma). The new results indicate, in conjunction with literature data, that granitoid formation in the Kohistan arc was a continuous rather than punctuated process. Field observations and the presence of inherited zircons indicate the importance of assimilation processes. Field relations, petrographic observations and major and trace element compositions of the granitoid indicate the importance of amphibole fractionation for their origin. It is concluded that granitoids in the Kohistan arc are derivative products of mantle derived melts that evolved through amphibole-dominated fractionation and intra crustal assimilation.

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Multistage evolution of the Jijal ultramafic–mafic complex (Kohistan, N Pakistan): Implications for building the roots of island arcs

Cited by 127 publications

References 68 publications

Coeval blueschist exhumation along thousands of kilometers: Implications for subduction channel processes

Coeval blueschist exhumation along thousands of kilometers: Implications for subduction channel processes

An early Palaeozoic supra-subduction lithosphere in the Variscides: new evidence from the Maures massif

Construction of the granitoid crust of an island arc part I: geochronological and geochemical constraints from the plutonic Kohistan (NW Pakistan)

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