Petrogenesis of the ultrapotassic Fanshan intrusion in the North China Craton: Implications for lithospheric mantle metasomatism and the origin of apatite ores

Tong Hou, Zhaochong Zhang, Jakob K. Keiding, Ilya V. Veksler

Research output: Contribution to journalArticleResearchpeer-review

26 Citations (Scopus)

Abstract

The Fanshan intrusion in the North China Craton (NCC) is concentrically zoned with syenite in the core (Unit 1), surrounded by ultramafic rocks (clinopyroxenite and biotite clinopyroxenite; Unit 2), and an outer rim of garnet-rich clinopyroxenite and orthoclase clinopyroxenite and syenite (Unit 3). The intrusive rocks are composed of variable amounts of Ca-rich augite, biotite, orthoclase, melanite, garnet, magnetite and apatite, with minor primary calcite. Monomineralic apatite rocks, nelsonite and glimmerite exclusively occur in Unit 2. Geochemically, the Fanshan rocks are highly enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE), moderately depleted in high field strength elements (HFSE), and have a limited range of Sr-Nd-O isotopic compositions. The similar mineralogy, mineral compositions, and trace element characteristics of the three units suggest that all the rocks are co-magmatic. The parental magma is ultrapotassic and is akin to kamafugite. Very low-degree partial melting of metasomatized lithospheric mantle best explains the geochemistry and petrogenesis of the parental magmas of the Fanshan intrusion. We propose that the mantle source may have been metasomatized by a hydrous carbonate-bearing melt, which has imprinted the enriched Sr-Nd isotopic signature and incompatible element enrichment with conspicuous negative Nb-Ta-Zr-Hf-Ti anomalies and LREE enrichments. The mantle source enrichment may be correlated with oceanic sediment recycling during southward subduction of the Paleo-Asian oceanic plate during the Carboniferous and Permian. We propose that crystal settling and mechanical sorting combined with repeated primitive magma replenishment and mixing with previously fractionated magma is the predominant process responsible for the formation of the apatite ores.

Original languageEnglish
Pages (from-to)893-918
Number of pages26
JournalJournal of Petrology
Volume56
Issue number5
DOIs
Publication statusPublished - May 2015

Keywords

  • Apatite
  • Fanshan intrusion
  • Mantle metasomatism
  • North China Craton
  • Ultrapotassic

Programme Area

  • Programme Area 4: Mineral Resources

Fingerprint

Dive into the research topics of 'Petrogenesis of the ultrapotassic Fanshan intrusion in the North China Craton: Implications for lithospheric mantle metasomatism and the origin of apatite ores'. Together they form a unique fingerprint.

Cite this