Petrogenesis of Middle–Late Triassic volcanic rocks from the Gangdese belt, southern Lhasa terrane

Implications for early subduction of Neo-Tethyan oceanic lithosphere

Chao Wang, Lin Ding, Li Yun Zhang, Paul A Kapp, Alex Pullen, Ya Hui Yue

Research output: Contribution to journalArticle

64 Citations (Scopus)

Abstract

The Gangdese belt is dominantly composed of igneous rocks that formed during the northward subduction of Neo-Tethyan oceanic lithosphere beneath the Lhasa terrane and has played a crucial role in understanding the pre-collisional evolution of southern Tibet. This paper presents new geochronological and geochemical (whole-rock major and trace element and Sr–Nd and zircon Hf isotope) data for recently identified volcanic rocks exposed in Changguo area, southernmost part of the Lhasa terrane. Zircon U–Pb dating from six samples yields consistent ages of 237.1 ± 1.1 Ma to 211.7 ± 1.5 Ma for magma emplacement through volcanic eruption, showing the Middle–Late Triassic magmatic activity in the southernmost Gangdese Belt. The Changguo volcanic rocks are mainly composed of basaltic and andesitic rocks and exhibit LILE enrichment and HFSE depletion. They also exhibit relatively uniform Nd–Hf isotopic compositions (εNd(t) = + 5.20 to + 7.74 and εHf(t)zircon = + 10.2 to + 15.9). The basaltic magmas were likely sourced from partial melting of sub-arc mantle wedge that was metasomatized by not only the aqueous fluid derived from subducting altered oceanic crust but also hydrous melt derived from subducting seafloor sediments, and subsequently experienced fractional crystallization and juvenile crustal contamination during ascent. The andesitic magmas were generated by partial melting of mafic–ultramafic metasomes through melt/fluid–peridotite reaction at slab–mantle interface. Taking into account the temporal and spatial distribution of the Early Mesozoic magmatic rocks and regional detrital zircon data, we further propose that the northward subduction of Neo-Tethyan oceanic lithosphere beneath the Lhasa terrane commenced by Middle Triassic.

Original languageEnglish (US)
Pages (from-to)320-333
Number of pages14
JournalLithos
Volume262
DOIs
StatePublished - Oct 1 2016

Fingerprint

Volcanic rocks
oceanic lithosphere
petrogenesis
terrane
volcanic rock
zircon
Triassic
subduction
Rocks
partial melting
Melting
Volcanic Eruptions
melt
rock
Igneous rocks
crustal contamination
Trace Elements
Crystallization
fractional crystallization
Isotopes

Keywords

  • Gangdese
  • Lhasa terrane
  • Middle–Late Triassic magmatic activity
  • Subduction of Neo-Tethyan oceanic lithosphere
  • Tibet

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

Petrogenesis of Middle–Late Triassic volcanic rocks from the Gangdese belt, southern Lhasa terrane : Implications for early subduction of Neo-Tethyan oceanic lithosphere. / Wang, Chao; Ding, Lin; Zhang, Li Yun; Kapp, Paul A; Pullen, Alex; Yue, Ya Hui.

In: Lithos, Vol. 262, 01.10.2016, p. 320-333.

Research output: Contribution to journalArticle

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abstract = "The Gangdese belt is dominantly composed of igneous rocks that formed during the northward subduction of Neo-Tethyan oceanic lithosphere beneath the Lhasa terrane and has played a crucial role in understanding the pre-collisional evolution of southern Tibet. This paper presents new geochronological and geochemical (whole-rock major and trace element and Sr–Nd and zircon Hf isotope) data for recently identified volcanic rocks exposed in Changguo area, southernmost part of the Lhasa terrane. Zircon U–Pb dating from six samples yields consistent ages of 237.1 ± 1.1 Ma to 211.7 ± 1.5 Ma for magma emplacement through volcanic eruption, showing the Middle–Late Triassic magmatic activity in the southernmost Gangdese Belt. The Changguo volcanic rocks are mainly composed of basaltic and andesitic rocks and exhibit LILE enrichment and HFSE depletion. They also exhibit relatively uniform Nd–Hf isotopic compositions (εNd(t) = + 5.20 to + 7.74 and εHf(t)zircon = + 10.2 to + 15.9). The basaltic magmas were likely sourced from partial melting of sub-arc mantle wedge that was metasomatized by not only the aqueous fluid derived from subducting altered oceanic crust but also hydrous melt derived from subducting seafloor sediments, and subsequently experienced fractional crystallization and juvenile crustal contamination during ascent. The andesitic magmas were generated by partial melting of mafic–ultramafic metasomes through melt/fluid–peridotite reaction at slab–mantle interface. Taking into account the temporal and spatial distribution of the Early Mesozoic magmatic rocks and regional detrital zircon data, we further propose that the northward subduction of Neo-Tethyan oceanic lithosphere beneath the Lhasa terrane commenced by Middle Triassic.",
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