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

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

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Abstract

Paleoproterozoic (∼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, εNd(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 εNd(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 εNd(t) values to those of Group 1. Petrological and geochemical data suggest that these dikes may have originated from different sources. Group 1 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 ∼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.

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
Externally publishedYes

Keywords

  • Geochemistry
  • Mafic dikes
  • Paleoproterozoic
  • Subduction-related lithospheric mantle
  • Trans-North China Orogen

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