Potassic volcanic rocks in NE China

Geochemical constraints on mantle source and magma genesis

Ming Zhang*, Paul Suddaby, Robert N. Thompson, Matthew F. Thirlwall, Martin A. Menzies

*Corresponding author for this work

Research output: Contribution to journalArticle

138 Citations (Scopus)

Abstract

Potassic volcanic rocks from the Wudalianchi, Erkeshan and Keluo (WEK) fields in NE China are located between the Mesozoic Songliao Basin and the Palaeozoic Xing'am Mountains fold belt. These rocks erupted during three main eruptive episodes-Miocene (9{dot operator}6-7{dot operator}0 Ma), Pleistocene (0{dot operator}56-0{dot operator}13 Ma) and Recent (AD 1719-1721)-and are subdivided into three types-olivine leucitite, leucite basanite and trachybasalt-on the basis of modal composition. In comparison with Cenozoic alkaline basalts from East China that are similar to oceanic island basalts (OIBs), WEK volcanic rocks are lower in Al2O3, CaO, Fe2O3 and Sc, but higher in K2O (3{dot operator}5-7{dot operator}1 wt %), K2O/Na2O (>1) and incompatible elements. High 87Sr/86Sr (0{dot operator}7050-0{dot operator}7056), low 143Nd/144Nd (0{dot operator}51238-0{dot operator}51250) and 206Pb/204Pb (17{dot operator}06-16{dot operator}61) ratios also distinguish them from oceanic and Chinese basalts. Trace element and isotope data indicate that a post-Archaean subcontinental lithospheric mantle source similar to the postulated EM1 component (enriched mantle with low l43Nd/144Nd and moderate high 87Sr/86Sr) must have played a significant role in magma generation. The source rock is considered to be refractory phlogopite-bearing garnet peridotite heterogeneously enriched in both large ion lithophile elements and light rare earth elements by ancient metasomatism during Proterozoic times. This source may have mixed recently with OIB-like melts, but has not been modified by subduction of the Kula-Pacific plate. Primitive WEK potassic magma was generated by a low degree of partial melting, initiated by an extensional phase beginning in the late Tertiary, at pressures of 20-45 kbar and in the presence of mixed volatile components of H2O, CO2 and halogens.

Original languageEnglish
Pages (from-to)1275-1303
Number of pages29
JournalJournal of Petrology
Volume36
Issue number5
DOIs
Publication statusPublished - Oct 1995
Externally publishedYes

Keywords

  • Geochemistry
  • Montle sourc
  • NE China
  • Potassic volcanic rocks

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