Unravelling the geochemical and geochronological diversities of the pre-collisional magmatism: Implications for the subduction dynamics in the Kohistan island arc and Karakorum block, Pakistan

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985831%3A_____%2F25%3A00617690" target="_blank" >RIV/67985831:_____/25:00617690 - isvavai.cz</a>

Result on the web

<a href="https://www.sciencedirect.com/science/article/pii/S1674987125000039?via%3Dihub" target="_blank" >https://www.sciencedirect.com/science/article/pii/S1674987125000039?via%3Dihub</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.gsf.2025.102003" target="_blank" >10.1016/j.gsf.2025.102003</a>

Result language

angličtina

Original language name

Unravelling the geochemical and geochronological diversities of the pre-collisional magmatism: Implications for the subduction dynamics in the Kohistan island arc and Karakorum block, Pakistan

Original language description

The magmatic arcs in the north-west region of Pakistan comprises of numerous volcanic and plutonic bodies of different ages and compositions evolved during the subduction of the Neo- Tethys Ocean under the Eurasian supercontinent. This study focusses on the examination of the granitoids of the Kohistan batholith (a part of Kohistan-Ladakh Island Arc, KLIA) and the Khunjerab pluton, concentrating on their petrological traits, mineral chemistry, in-situ zircon U-Pb geochronology, and whole-rock major and trace element geochemistry. According to zircon U-Pb dating, the Kohistan batholith granitoid was emplaced around 91.7 ± 0.3 Ma, while zircons of the Khunjerab pluton yield ages of 106.4 ± 0.4 Ma and 106.4 ± 1.0 Ma. All the samples from both magmatic units have calcic to calc-alkaline (Na2O + K2O: 3.6–10.6 wt.% and SiO2: 60–73 wt.%), metaluminous to peraluminous properties (Aluminum Saturation Index (ASI): 0.9–1.2). Notably, Nb, Ta, and Ti show depletion, while large ion lithophile elements like Cs, Rb, and K have been enriched. Additionally, we find that SiO2 and P2O5 have a negative correlation while Rb and Th have a positive correlation, which confirm an I-type arc magmatism. Together with the published literature, TEM analysis, and thermal modelling, our zircon U-Pb results point to a period of continuous magmatic activity from the Late Jurassic to the Late Cretaceous (between 150 Ma and 91 Ma) in the Kohistan Island arc region while the Khunjerab pluton (part of Karakorum block/Eurasian plate) experienced widespread magmatism around 120 Ma to 106 Ma. With SiO2 concentrations ranging from 67.5–73.3 wt.% and 60–71.4 wt.% and relatively low alkali (Na2O + K2O) contents between 3.6–10.6 wt.% and 5.1–7.4 wt.% in the Kohistan batholith and Khunjerab pluton respectively, showing clear signs of acidity. The whole rock as well as the mineral geochemical analysis and the elevated water contents (8–10 wt.% and 3.1–3.5 wt.%) inferred from amphibole and biotite chemistry respectively, indicates that the Kohistan batholith was most likely formed through partial melting of a (hydrous) magma originating from a more or less altered metasomatized mantle wedge. Likewise, the Khunjerab pluton whole rock geochemistry also indicates its origin through partial melting of magma originating from an altered metasomatized mantle wedge. This study also shows that both units are not only different in terms of the nature of magmatism but also in terms of their ages i.e., continental arc magmatism occurred in the Khunjerab (Karakoram) block in the middle Cretaceous (106 Ma) while island arc magmatism occurred on the Kohistan side in the late Cretaceous (91 Ma). Further, this study also investigate why multi-grain U-Pb zircon dating is necessary for studying magmatic rocks by using transmission electron microscopy.

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

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OECD FORD branch

10505 - Geology

Project

—

Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2025

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Geoscience Frontiers

ISSN

1674-9871

e-ISSN

1674-9871

Volume of the periodical

16

Issue of the periodical within the volume

2

Country of publishing house

CN - CHINA

Number of pages

27

Pages from-to

102003

UT code for WoS article

001422792500001

EID of the result in the Scopus database

2-s2.0-85216763232