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Metadata Files

Data Publication

Kaghan Valley, Pakistan: metamorphic rocks, their chemistry and age

Wilke, Franziska

GFZ Data Services

(2022)

Descriptions

This data set is the source of my doctoral thesis and of three resulting publications. Through whole rock geochemistry of selected samples and microprobe and geochronological analyses of key minerals, formerly selected by extensive microscopical studies, standard geothermobarometry and modelling was applied. It has been shown that metamorphic rocks, in particular, the eclogites of the northern Kaghan Valley, Pakistan, were buried to depths of 140-100 km (36-30 kbar) at 790-640°C. Subsequently, cooling during decompression (exhumation) towards 40-35 km (17-10 kbar) and 630-580°C has been superseded by a phase of reheating to about 720-650°C at roughly the same depth before final exhumation has taken place. In the southern-most part of the Kaghan Valley, amphibolite facies assemblages with formation conditions similar to the deduced reheating phase indicate a juxtaposition of both areas after the eclogite facies stage and thus a stacking of Indian Plate units. Radiometric dating of zircon, titanite and rutile by U-Pb and amphibole and micas by Ar-Ar reveal peak pressure conditions at 47-48 Ma. With a maximum exhumation rate of 14 cm/a these rocks reached the crust-mantle boundary at 40-35 km within 1 Ma. Subsequent exhumation (46-41 Ma, 40-35 km) decelerated to ca. 1 mm/a at the base of the continental crust but rose again to about 2 mm/a in the period of 41-31 Ma, equivalent to 35-20 km. Apatite fission track (AFT) and (U-Th)/He ages from eclogites, amphibolites, micaschists and gneisses yielded moderate Oligocene to Miocene cooling rates of about 10°C/Ma in the high altitude northern parts of the Kaghan Valley using the mineral-pair method. AFT ages are of 24.5±3.8 to 15.6±2.1 Ma whereas apatite (U-Th)/He analyses yielded ages between 21.0±0.6 and 5.3±0.2 Ma. The southern-most part of the Valley is dominated by younger late Miocene to Pliocene apatite fission track ages of 7.6±2.1 and 4.0±0.5 Ma that support earlier tectonically and petrologically findings of a juxtaposition and stack of Indian Plate units. As this nappe is tectonically lowermost, a later distinct exhumation and uplift driven by thrusting along the Main Boundary Thrust is inferred. Out of this geochemical, petrological, isotope-geochemical and low temperature thermochronology investigations it was concluded that the exhumation was buoyancy driven and caused an initial rapid exhumation: exhumation as fast as recent normal plate movements (ca. 10 cm/a). As the exhuming units reached the crust-mantle boundary the process slowed down due to changes in buoyancy. Most likely, this exhumation pause has initiated the reheating event that is petrologically evident (e.g. glaucophane rimmed by hornblende, ilmenite overgrowth of rutile). Late stage processes involved widespread thrusting and folding with accompanied regional greenschist facies metamorphism, whereby contemporaneous thrusting on the Batal Thrust (seen sometimes equivalent to the MCT) and back sliding of the Kohistan Arc along the inverse reactivated Main Mantle Thrust caused final exposure of these rocks. Similar circumstances have been seen at Tso Morari, Ladakh, India, 200 km further east where comparable rock assemblages occur. In conclusion, as exhumation was already done well before the initiation of the monsoonal system, climate dependent effects (erosion) appear negligible in comparison to far-field tectonic effects. Thus, the channel flow model is not applicable for this part of the Himalayas.

Keywords


Originally assigned keywords
whole rock geochemistry
microprobe
U-Pb geochronology
Ar/Ar geochronology
apatite fission track
U-Th/He thermochronology
metamorphic rocks
eclogite
Himalayas
Pakistan
Kaghan Valley
EARTH SCIENCE > SOLID EARTH > GEOCHEMISTRY > GEOCHEMICAL PROCESSES
EARTH SCIENCE > SOLID EARTH > GEOCHEMISTRY > GEOCHEMICAL PROPERTIES
EARTH SCIENCE > SOLID EARTH > GEOCHEMISTRY > GEOCHEMICAL PROPERTIES > ISOTOPIC AGE
In Situ/Laboratory Instruments > Spectrometers/Radiometers > LA-ICP-MS
In Situ/Laboratory Instruments > Spectrometers/Radiometers > XRF

Corresponding MSL vocabulary keywords
electron probe micro-analyzer
electron probe micro analyser
metamorphic rock
eclogite

MSL enriched keywords
equipment
electron probe micro-analyzer
Apparatus
microchemical analysis
electron probe micro analyser
metamorphic rock
eclogite
amphibolite
schist
greenschist
minerals
oxide mineral
ilmenite
rutile
carbonate minerals
apatite
silicate minerals
nesosilicates
titanite
zircon
inosilicates
amphibole
glaucophane
hornblende
Phanerozoic
Cenozoic
Neogene
Pliocene
Miocene
Paleogene
Oligocene
tectonic plate boundary
convergent tectonic plate boundary
continental collision
rock exhumation
Earth's structure
Earth crust
continental crust
analysis
geochronology
uranium dating
uranium-lead dating
measured property
age of sample
uranium age
uranium-lead age
Analyzed feature
deformation microstructure
pressure solution microstructure
overgrowths
Models
field system model
flow model

MSL enriched sub domains i

geochemistry
microscopy and tomography
geo-energy test beds

Source

https://dataservices.gfz-potsdam.de/panmetaworks/showshort.php?id=ca6cb5aa-9ecb-11ec-a8b4-7d2338b1cdf0

Source publisher

GFZ Data Services


DOI

10.5880/gfz.3.1.2022.001


Creators

Wilke, Franziska

GFZ German Research Centre for Geosciences, Potsdam, Germany

ORCID:

https://orcid.org/0000-0002-3463-6176


Contributors

Microprobe Lab (GFZ German Research Centre For Geosciences, Germany)

HostingInstitution

GFZ German Research Centre for Geosciences, Potsdam, Germany

Ar/Ar Geochronology Laboratory (University Of Potsdam, Germany)

HostingInstitution

University of Potsdam, Potsdam, Germany

X-Ray Fluorescence Spectroscopy (XRF) (GFZ German Research Centre For Geosciences, Germany)

HostingInstitution

GFZ German Research Centre for Geosciences, Potsdam, Germany

Fission Track Laboratory (University Of Potsdam, Germany)

HostingInstitution

University of Potsdam, Potsdam, Germany

Isotope, FIERCE-Frankfurt

HostingInstitution

Goethe Universität Frankfurt, Frankfurt, Frankfurt, Germany

Geesthacht Neutron Facility (GeNF) (Helmholtz Centre Hereon, Germany)

HostingInstitution

Helmholtz Centre hereon GmbH, Geesthacht, Germany

ElMiE Elements And Minerals Of The Earth Laboratory (GFZ German Research Centre For Geosciences, Germany)

HostingInstitution

GFZ German Research Centre for Geosciences, Potsdam, Germany

Wilke, Franziska

ContactPerson

GFZ German Research Centre for Geosciences, Potsdam, Germany


References

10.25932/publishup-4119

10.1016/s0009-2541(00)00291-6

10.1127/0935-1221/2010/0022-2051

10.1016/j.lithos.2009.07.015

10.1016/j.jseaes.2012.06.014

10.1007/bf00470631


Citation

Wilke, F. (2022). Kaghan Valley, Pakistan: metamorphic rocks, their chemistry and age [Data set]. GFZ Data Services. https://doi.org/10.5880/GFZ.3.1.2022.001


Dates

Issued:

2022


Rights

Creative Commons Attribution 4.0 International


Geo location(s)

Kaghan Valley, Pakistan: study area


Spatial coordinates