Postcollisional calc-alkaline lavas and xenoliths from the southern Qiangtang terrane, central Tibet

Lin Ding, Paul A Kapp, Yahui Yue, Qingzhou Lai

Research output: Contribution to journalArticle

137 Citations (Scopus)

Abstract

A newly recognized east-west trending province of 43 to 28 Ma volcanic rocks occurs in the southern Qiangtang terrane of central Tibet. The lavas are Na-rich calc-alkaline in composition, relatively primitive, and locally host ultramafic and mafic xenoliths. Foliated mafic granulite xenoliths from ∼ 28 Ma lavas equilibrated at temperatures in the range of 980 to 1260 °C, indicating that the southern Qiangtang terrane lower crust was deformed and heated to very high temperatures during or before the Oligocene. In the northern Qiangtang terrane is a parallel suite of volcanic rocks of coeval age. However, here, the volcanic rocks are (ultra)potassic in composition and underlain by a hot (T > 800 °C) metasedimentary-bearing lower crust. We suggest that both suites of Qiangtang lavas were derived from a primitive mantle source and that the enriched nature of the northern Qiangtang lavas reflects contamination by partial melts of metasedimentary lower crust. This contrasts with the conventional interpretation that Tibetan potassic lavas were solely derived from an ancient, enriched mantle lithospheric source. While removal of lithospheric mantle seems to be required to produce the high temperature melts, Eocene-Oligocene volcanism was coeval with thrust reactivation along bounding suture zones, implying that mantle dynamics were linked to intracontinental subduction.

Original languageEnglish (US)
Pages (from-to)28-38
Number of pages11
JournalEarth and Planetary Science Letters
Volume254
Issue number1-2
DOIs
StatePublished - Feb 15 2007

Fingerprint

Volcanic rocks
Tibet
lower crust
terrane
volcanic rock
Earth mantle
mantle
volcanology
crusts
Oligocene
Bearings (structural)
rocks
melt
suture zone
granulite
Chemical analysis
reactivation
mantle source
Temperature
volcanism

Keywords

  • Intracontinental subduction
  • Postcollisional volcanism
  • Tibetan plateau
  • Xenoliths

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)

Cite this

Postcollisional calc-alkaline lavas and xenoliths from the southern Qiangtang terrane, central Tibet. / Ding, Lin; Kapp, Paul A; Yue, Yahui; Lai, Qingzhou.

In: Earth and Planetary Science Letters, Vol. 254, No. 1-2, 15.02.2007, p. 28-38.

Research output: Contribution to journalArticle

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AB - A newly recognized east-west trending province of 43 to 28 Ma volcanic rocks occurs in the southern Qiangtang terrane of central Tibet. The lavas are Na-rich calc-alkaline in composition, relatively primitive, and locally host ultramafic and mafic xenoliths. Foliated mafic granulite xenoliths from ∼ 28 Ma lavas equilibrated at temperatures in the range of 980 to 1260 °C, indicating that the southern Qiangtang terrane lower crust was deformed and heated to very high temperatures during or before the Oligocene. In the northern Qiangtang terrane is a parallel suite of volcanic rocks of coeval age. However, here, the volcanic rocks are (ultra)potassic in composition and underlain by a hot (T > 800 °C) metasedimentary-bearing lower crust. We suggest that both suites of Qiangtang lavas were derived from a primitive mantle source and that the enriched nature of the northern Qiangtang lavas reflects contamination by partial melts of metasedimentary lower crust. This contrasts with the conventional interpretation that Tibetan potassic lavas were solely derived from an ancient, enriched mantle lithospheric source. While removal of lithospheric mantle seems to be required to produce the high temperature melts, Eocene-Oligocene volcanism was coeval with thrust reactivation along bounding suture zones, implying that mantle dynamics were linked to intracontinental subduction.

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