&lt;i&gt;In situ&lt;/i&gt; U-Pb Zircon Micro-Geochronology of MCT Zone Rocks in the Lesser Himalaya Using LA–MC–ICPMS Technique

Mukherjee, Pinaki; Singhal, Saurabh; Adlakha, Vikas; Santosh, K.; Dutt, Som; Kharya, Aditya; Gupta, Anil K.

doi:10.18520/cs/v112/i04/802-810

Cited by 23 publications

(12 citation statements)

References 26 publications

(38 reference statements)

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“…However, we used Plesovice (TIMS reference age 337.13 ± 0.37 Ma) (Sláma et al 2008) as a secondary standard for U-Pb geochronology. The complete methodology adopted in this paper is similar to that described by Mukherjee et al (2017). Off-line processing of the data obtained from the mass spectrometer was done using Iolite version 2.5 (Paton et al 2011).…”

Section: Methodsmentioning

confidence: 99%

Closure of India–Asia collision margin along the Shyok Suture Zone in the eastern Karakoram: new geochemical and zircon U–Pb geochronological observations

et al. 2020

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New whole-rock geochemical analyses along with laser ablation multi-collector inductively coupled plasma mass spectrometry U–Pb zircon ages of the granite–rhyolite from the Karakoram Batholith, exposed along the Shyok Valley, NW India, have been performed to understand the timing and geochemical evolution of these magmatic bodies and their implications for the geodynamic evolution of the Karakoram Batholith. New geochronological data on granites and rhyolites along with previously published geochronological data indicate that the Karakoram Batholith evolved during Albian time (~110–100 Ma) owing to the subduction of Tethys oceanic lithosphere along the Shyok Suture Zone. This region witnessed a period of no magmatism during ~99–85 Ma. Following this, the Kohistan–Ladakh arc and Karakoram Batholith evolved as a single entity in Late Cretaceous and early Palaeogene times. Late Cretaceous (~85 Ma) rhyolite intrusions within the Karakoram Batholith show calc-alkaline subduction-related signatures with a highly peraluminous nature (molar A/CNK = 1.42–1.81). These intrusions may have resulted from c. ~13.8 % to ~34.5 % assimilation of pre-existing granites accompanied by fractional crystallization during the ascent of the magma. The contamination of mantle wedge-derived melts with crust of the active continental margin of the Karakoram most likely enhanced the high peraluminous nature of the rhyolite magma, as has been constrained by assimilation fractional crystallization modelling. Two granite samples from the contact of the Shyok Metamorphic Complex and Karakoram Batholith indicate that the post-collisional Miocene magmatism was not only confined along the Karakoram Fault zone but also extends ~30 km beyond the Shyok–Muglib strand.

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Section: Methodsmentioning

confidence: 99%

Closure of India–Asia collision margin along the Shyok Suture Zone in the eastern Karakoram: new geochemical and zircon U–Pb geochronological observations

et al. 2020

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“…The analyses were carried out with a spot diameter of 20 µm (the spots were positioned relative to the CL images), a repetition rate of 5 Hz, an energy density of 4 J/cm 2 and 75% laser intensity. Instrumental conditions, analysis methods and data acquisition were similar to those described by Mukherjee et al [2017]. For fractionation correction and calculation of results, we used the Z 91500 zircon standard (Thermal Ionization Mass Spectrometry [TIMS] normalization data 206 Pb/ 238 U = 1062.32 ± 2.22 [2 sigma]; Wiedenbeck et al [1995]) and the accuracy was later checked using the Plesovice zircon standard (Isotope Dilution [ID] TIMS 206 Pb/ 238 U age = 337.13 ± 0.37 Ma; Slama et al [2008]) as the external standard.…”

Section: La-mc-icpms -Zircon U-pb Geochronologymentioning

confidence: 99%

Continental extension of northern Gondwana margin in the Eastern Himalaya: Constraints from geochemistry and U–Pb zircon ages of mafic intrusives in the Siang window, Arunachal Himalaya, India

Oinam¹,

Singh²,

Joshi³

et al. 2020

Comptes Rendus. Géoscience

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We report new U-Pb zircon age and whole-rock geochemical data from the Pangin mafic intrusive rocks of the Siang window, eastern Himalayas. These mafic rocks are medium to coarse-grained gabbros, consisting mainly of plagioclase and clinopyroxene with accessory phases (hornblende + Fe-Ti oxides) that retain granular and interlocking texture. Geochemically, they display enriched-mid oceanic ridge basalt (E-MORB) affinity characterized by moderate to slightly fractionated REE patterns marked by (La/Yb) N = 2.65 − 3.99. Their geochemical characteristics suggest that the parental magmas of these rocks were formed by medium to higher degrees (∼12-28%) of partial melting similar to that of the asthenospheric mantle in the garnet-spinel transition zone. Magmatic zircons from two gabbros yield U-Pb ages of 521.50 ± 2.53 Ma and 568 ± 2 Ma. This new age reveals two pulses of Late Neoproterozoic and Early Cambrian mafic magmatism that are inconsistent with the temporal distribution of Paleozoic magmatism in the Siang window of the Eastern Himalayas. However, based on the results of this study and the correlation of continental extensional mafic magmatism in the Northwest Himalaya, we suggest that investigated mafic intrusive rocks might have been generated in an extensional tectonic environment during the long-lasting Pan-African orogenic cycle of the late Neoproterozoic to early Cambrian which ended with the formation of the Gondwana supercontinent.

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“…A laboratory dedicated to in situ zircon geochronology and Hf-isotope analysis has been set up at the Wadia Institute of Himalayan Geology (WIHG) during the last few years comprising LA-MC-ICPMS-Q-ICPMS. Basic analytical protocols and performance information is available in Mukherjee et al (2017). A mixed collector configuration of MC-ICPMS is used for zircon geochronology.…”

Section: Wadia Institute Of Himalayan Geology (Wihg)mentioning

confidence: 99%

New initiatives to bolster analytical facilities in India for in situ U-Th-Pb Geochronology, Hf and O isotope systematics in zircon: a focus on laboratories at the IUAC, WIHG and CSIR-NGRI

Rao¹,

Chopra²,

Kumar³

et al. 2020

PINSA

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<i>In situ</i> U-Pb Zircon Micro-Geochronology of MCT Zone Rocks in the Lesser Himalaya Using LA–MC–ICPMS Technique

Cited by 23 publications

References 26 publications

Closure of India–Asia collision margin along the Shyok Suture Zone in the eastern Karakoram: new geochemical and zircon U–Pb geochronological observations

Closure of India–Asia collision margin along the Shyok Suture Zone in the eastern Karakoram: new geochemical and zircon U–Pb geochronological observations

Continental extension of northern Gondwana margin in the Eastern Himalaya: Constraints from geochemistry and U–Pb zircon ages of mafic intrusives in the Siang window, Arunachal Himalaya, India

New initiatives to bolster analytical facilities in India for in situ U-Th-Pb Geochronology, Hf and O isotope systematics in zircon: a focus on laboratories at the IUAC, WIHG and CSIR-NGRI

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