Geochronological, geochemical and Sr-Nd-Hf isotopic constraints on petrogenesis of Late Mesozoic gabbro-granite complexes on the southeast coast of Fujian, South China

Insights into a depleted mantle source region and crust-mantle interactions

Zhen Li, Jian Sheng Qiu*, Xi Sheng Xu

*Corresponding author for this work

Research output: Contribution to journalArticle

39 Citations (Scopus)

Abstract

The Quanzhou (QZ) and Huacuo (HC) gabbro-granite complexes on the southeast coast of Fujian, South China, are important components of a Late Mesozoic calc-alkaline volcanic-plutonic belt in the region. The complexes provide an excellent opportunity to investigate the genetic relationships between acid and basic magmas, and their interactions within the intrusive environment. The complexes are composed mainly of monzogranite and biotite granodiorite in the QZ complex, and biotite granite in the HC complex, with lesser amounts of hornblende gabbro. Zircon U-Pb dating provides consistent crystallization ages of 109 ± 1 Ma and 108 ± 1 Ma for the QZ gabbros and monzogranites, and an age of 111 ± 1 Ma for the HC gabbro, which is contemporaneous with the spatially associated HC granites. Both the mafic and felsic intrusions in these complexes are enriched in light rare earth elements (LREEs) and large-ion lithophile elements (LILEs), and are depleted in high-field-strength elements (HFSEs; e.g. Nb and Ta). They show similarly homogeneous Sr-Nd isotopic compositions. All these factors indicate a close genetic relationship between the gabbroic and granitic rocks in the QZ and HC complexes. Although the enriched Sr-Nd isotopic signatures of the QZ and HC gabbros seemingly point to an enriched mantle source (EM-1), they have highly variable zircon Hf isotopic compositions, with ε Hf(t) values ranging from negative to positive (specifically -4.6 to +6.1 for the QZ gabbros and -4.8 to +11.6 for the HC gabbros). We interpret the parental basic magmas of these gabbros to have received contributions from a depleted mantle source and crustal components. Contributions from such a depleted mantle source resulted in the growth of juvenile basaltic lower crust, the partial melting of which generated the parental felsic magmas of the QZ and HC complexes. Furthermore, based on a synthesis of petrography, geochronology, elemental and isotopic geochemistry and tectonics, we propose that break-off and rollback of the Late Mesozoic subducted Palaeo-Pacific Plate triggered the upwelling of asthenospheric mantle below the coastal area of the South China Block, which induced extension of the overlying continental lithosphere, and finally initiated the large-scale Late Yanshanian magmatism in the study area.

Original languageEnglish
Pages (from-to)459-482
Number of pages24
JournalGeological Magazine
Volume149
Issue number3
DOIs
Publication statusPublished - May 2012
Externally publishedYes

Keywords

  • asthenospheric mantle upwelling
  • crust-mantle interaction
  • gabbro-granite complexes
  • geochemistry
  • petrogenesis
  • South China
  • southeast coast Fujian

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