Geochemistry of Paleoproterozoic (similar to 1770 Ma) mafic dikes from the Trans-North China Orogen and tectonic implications

Yuejun Wang, Guochun Zhao, Peter Anthony Cawood, Weiming Fan, Touping Peng, Linhua Sun

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59 Citations (Scopus)

Abstract

Paleoproterozoic (similar to 1770 Ma) mafic dikes occur throughout the Trans-North China Orogen. These dikes can be divided into three geochemically distinct groups. Group 1 with FeOt of 12.73-18.06%, (Nb/La)(N) 0.18-0.39, (Th/La)(N) of, 0.60-1.24, epsilon(Nd)(t) of -5.1 to -2.4, and an enrichment in LILE's and a depletion in HFSE's. Group 2 has flat REEs and incompatible elements patterns, and possesses (Nb/La)(N) = 0.64-0.87, (Th/La)(N) = 0.61-1.20 and epsilon(Nd)(t) = - 1.7 to 1.1. Group 3 has low FeOt contents (8.19-11.57%) and (Th/La)(N) ratios (0.29-0.72), but similar (Nb/La)N ratios and epsilon(Nd)(t) values to those of Group 1. Petrological and geochemical data suggest that these dikes may have originated from different sources. Group I could be derived from a "re-fertilized" lithospheric source incorporating a continental basaltic component trapped from a earlier phase of subduction. Group 2 was likely a product of a subduction-modified lithospheric mantle hybridized by recycled gabbroic lower crust. By contrast, Group 3 originated from a mixture of subduction-modified lithospheric mantle with a MORB component. In combination with the available data, we propose that the sources of the mafic dikes were initially modified by the similar to 1.85 Ga subduction/collision event that assembled the North China Craton, and partially melted under subsequent rifting in response to the upwelling convective mantle. (C) 2007 Elsevier Ltd. All rights reserved.

Original languageEnglish
Pages (from-to)61-77
Number of pages17
JournalJournal of Asian Earth Sciences
Volume33
Issue number1-2
DOIs
Publication statusPublished - 20 Jun 2008

Keywords

  • geochemistry
  • mafic dikes
  • subduction-related lithospheric mantle
  • Paleoproterozoic
  • Trans-North China Orogen
  • INCOMPATIBLE TRACE-ELEMENTS
  • EXPERIMENTAL CONSTRAINTS
  • ISOTOPIC CONSTRAINTS
  • CONTINENTAL-CRUST
  • OCEANIC-CRUST
  • MANTLE PLUMES
  • ZIRCON GEOCHRONOLOGY
  • MELTING EXPERIMENTS
  • GARNET PYROXENITE
  • FLOOD BASALTS

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