Metamorphic evolution,
            <sup>40</sup>
            Ar-
            <sup>39</sup>
            Ar chronology and tectonic model for the Neelum valley, Azad Kashmir, NE Pakistan

Fontan, Dario; Schouppe, Michel; Hunziker, C. J.; Martinotti, Giovanni; Verkaeren, Jean

doi:10.1144/gsl.sp.2000.170.01.23

Cited by 16 publications

(26 citation statements)

References 40 publications

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“…Major rivers and their tributaries in the Kaghan Valley (River Kunhar) and in the Neelum Valley (River Neelum) and two major lakes (Lake Lulusar and Lake Saif‐ul‐Muluk) are also shown. Modified after Wadia (), Chaudhry and Ghazanfar (), Greco et al (), Greco and Spencer (1993), Fontan, Schouppe, Hunziker, Martinpotti, and Verkaeren (), Kaneko et al (), O'Brien, Zotov, Law, Khan, and Jan (), Rehman et al () and references therein…”

Section: Geological Backgroundmentioning

confidence: 99%

Varieties of the Himalayan eclogites: A pictorial review of textural and petrological features

et al. 2017

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A pictorial review and brief description of metabasites (mainly eclogites) exposed in the western part of Himalaya, north Pakistan are presented. The metabasites occur in the Kaghan and Neelum valleys in the form of thick sheets, dikes, lenses, and zoned bodies. On the basis of petrography and mineral paragenesis, they can be distinguished into greenschist, amphibolites, garnet‐amphibolites, eclogites, amphibolitized eclogites, and garnetites. In this review, first a brief history of the term eclogite and its origin for understanding the process of eclogite formation is presented. Then, a description on the occurrence of various metabasites/eclogites outcrops in the western Himalaya is given. Later, detailed petrological and textural features observed in hand specimen and under the microscope are discussed for individual rock types. Finally, an overview of the Himalayan metabasites tracing back from their magmatic basaltic source to their transformation into amphibolites and eclogites via multi‐stage metamorphism is provided. The field features, with the aid of petrological and geochemical evidence of these metabasites, help to constrain the tectono‐metamorphic evolution of the continent–continent collision type orogenic belts such as the India–Asia collision‐related Himalayan metamorphic belt.

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Section: Geological Backgroundmentioning

confidence: 99%

Varieties of the Himalayan eclogites: A pictorial review of textural and petrological features

et al. 2017

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“…Tertiary-aged UHP eclogites have been described from North Pakistan (Pognante & Spencer 1991;Fontan et al 2000;O'Brien et al 2001) and northern India (Guillot et al 1997). In the NW Himalaya, collision between continental India and the Kohistan island arc (the last exotic block to be accreted to continental Asia) is interpreted as having occurred at between 50 and 55 Ma (see discussions by Rowley (1996) and Treloar (1997)).…”

Section: Geological Settingmentioning

confidence: 99%

“…Cooling through 500 8C after this early Tertiary metamorphism was complete by c. 40 Ma (Treloar & Rex 1990;Chamberlain et al 1991;Tonarini et al 1993). The eclogite-facies rocks described from the Kaghan and Neelum valleys in Pakistan (Pognante & Spencer 1991;Fontan et al 2000;O'Brien et al 2001) lie in the most northerly exposed parts of the Indian Plate on the immediate footwall of the Main Mantle Thrust, which separates the Indian Plate rocks from the overriding Kohistan arc. Treloar (1997) suggested that, during early stages of their exhumation, the UHP rocks were thrust upon the amphibolitefacies rocks of the Indian Plate.…”

Section: Geological Settingmentioning

confidence: 99%

Exhumation of early Tertiary, coesite-bearing eclogites from the Pakistan Himalaya

Treloar

O’Brien

Parrish³

et al. 2003

JGS

103

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Early Tertiary, coesite-bearing eclogites crop out in the internal zones of the Indian Plate in the Kaghan Valley of North Pakistan. Field and geochronological data suggest that UHP metamorphism, at c. 46 Ma, accompanied subduction of the leading edge of continental India beneath Kohistan. A new U-Pb rutile age of 44.1 AE 1.1 Ma can be interpreted as either a growth or a cooling age, given the uncertainty of the closure temperature of rutile for Pb, but clearly documents a very short-lived metamorphic peak, with cooling occurring between 44 and 40 Ma. Eclogitic assemblages are preserved in Permo-Triassic mafic rocks in both cover and basement sequences, with the best-preserved eclogites hosted in the anhydrous basement. The eclogite-facies rocks lie on the hanging wall of a major south-directed ductile thrust zone, which placed basement rocks that contain coesite eclogites southward onto lower-pressure cover metasediments. Shear criteria show that those sequences that contain eclogite-facies rocks are flanked above by a zone of pervasive north-directed extensional shearing. Mineral assemblages contained within both the thrust and extensional shear zones are consistent with them both having operated synchronously during the amphibolite-to greenschist-facies transition. Amphibole Ar-Ar cooling history data suggest that this was at c. 40-42 Ma. As in the Alps this implies exhumation from the metamorphic peak to greenschist-facies conditions within a few million years. This short time scale has important implications, as it is likely that both the thrust and extensional shear zones represent the late stage of a deformation continuum that commenced at UHP and brought the UHP rocks back to 'mid'-crustal levels. This late Eocene extensional shearing, and associated exhumation of HP or UHP rocks, has not previously been recorded in the Pakistan Himalaya. The thrusts and shears were later folded by major east-trending folds, themselves cut by Miocene-aged, north-vergent extensional faults that currently separate the Indian Plate from the structurally overlying Kohistan island arc.

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“…1), were found at the end of the 1980s in the Kaghan Valley, NE Pakistan (Spencer et al. , 1990; Pognante & Spencer, 1991) and of the adjoining Neelum Valley (Fontan et al. , 2000) (Fig.…”

Section: Introductionmentioning

confidence: 96%

“…Eclogites, in particular, first discovered by Berthelsen (1953) as boudinaged dykes in the granitic orthogneiss of the Tso Morari dome, eastern Ladakh (Fig. 1), were found at the end of the 1980s in the Kaghan Valley, NE Pakistan (Spencer et al, 1990;Pognante & Spencer, 1991) and of the adjoining Neelum Valley (Fontan et al, 2000) (Fig. 1), whereas granulitized and amphibolitized eclogites were discovered in the Eastern Himalaya Parkinson & Kohn, 2002).…”

Section: Introductionmentioning

confidence: 99%

Clockwise exhumation path of granulitized eclogites from the Ama Drime range (Eastern Himalayas)

Groppo

Lombardo

Rolfo

et al. 2006

Journal Metamorphic Geology

164

168

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The metamorphic evolution of a granulitized eclogite from the Phung Chu Valley (Eastern Himalaya) was reconstructed combining microstructural observations, conventional thermobarometry and quantitative pseudosection analysis. The granulitized eclogite consists of clinopyroxene, plagioclase, garnet, brown amphibole, and minor orthopyroxene, biotite, ilmenite and quartz. On the basis of microstructural observations and mineral relationships, four metamorphic stages and related mineral assemblages have been recognized: (i) M1 eclogite-facies assemblage, consisting of garnet, omphacite (now replaced by a clinopyroxene + plagioclase symplectite) and phengite (replaced by biotite + plagioclase symplectite); (ii) M2 granulite-facies assemblage, represented by clinopyroxene, orthopyroxene, garnet, plagioclase and accessory ilmenite; (iii) M3 plagioclase + orthopyroxene corona developed around garnet, and (iv) M4 brown amphibole + plagioclase assemblage in the rock matrix. Because of the nearly complete lack of eclogitic mineral relics, M1 conditions can be only loosely constrained at >1.5 GPa and >580°C. In contrast, assemblage M2 tightly constrains the peak granulitic stage at 0.8-1.0 GPa and >750°C. The second granulitic assemblage M3, represented by the plagioclase + orthopyroxene corona, formed at lower pressures (0.4 GPa and 750°C). During the subsequent exhumation, the granulitized eclogite experienced significant cooling to nearly 700°C, marked by the appearance of brown amphibole and plagioclase (M4) in the rock matrix. U-Pb SHRIMP analyses on low-U rims of zircon from an eclogite of the same locality suggest an age of 13-14 Ma for the M3 stage. The resulting decompressional clockwise P-T path of the Ama Drime eclogite is characterized by nearly isothermal decompression from >1.5 GPa to 0.4 GPa, followed by nearly isobaric cooling from 775°C to 710°C. Modelling of phase equilibria by a calculated petrogenetic grid and conventional thermobarometry on a biotite-garnet-sillimanite metapelite hosted in the country rock granitic orthogneiss extends the inferred P-T trajectory down to 630°C and 0.3 GPa.

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Metamorphic evolution, ⁴⁰ Ar- ³⁹ Ar chronology and tectonic model for the Neelum valley, Azad Kashmir, NE Pakistan

Cited by 16 publications

References 40 publications

Varieties of the Himalayan eclogites: A pictorial review of textural and petrological features

Varieties of the Himalayan eclogites: A pictorial review of textural and petrological features

Exhumation of early Tertiary, coesite-bearing eclogites from the Pakistan Himalaya

Clockwise exhumation path of granulitized eclogites from the Ama Drime range (Eastern Himalayas)

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Metamorphic evolution, 40 Ar- 39 Ar chronology and tectonic model for the Neelum valley, Azad Kashmir, NE Pakistan

Cited by 16 publications

References 40 publications

Varieties of the Himalayan eclogites: A pictorial review of textural and petrological features

Varieties of the Himalayan eclogites: A pictorial review of textural and petrological features

Exhumation of early Tertiary, coesite-bearing eclogites from the Pakistan Himalaya

Clockwise exhumation path of granulitized eclogites from the Ama Drime range (Eastern Himalayas)

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Metamorphic evolution, ⁴⁰ Ar- ³⁹ Ar chronology and tectonic model for the Neelum valley, Azad Kashmir, NE Pakistan