| As one of the major ancient cratonic nuclei in eastern Eurasia,the North China Craton(NCC)preserves a complex history of crustal evolution,cratonization and stabilization.The Trans-North China Orogen(TNCO)is considered as the collisional suture between the Western and Eastern Blocks of the NCC.The Fuping Complex incorporates important basement units in the central segment of the TNCO,and is dominantly composed of TTG gneiss,gneissic granite,meta-sedimentary rock(paragneiss,schist,marble and calc-silicate rock),hornblendite,pyroxene hornblendite,mafic granulite,amphibolite and garnet amphibolite.This thesis presents the results from an integrated study including field investigation,petrology,mineral chemistry,whole rock geochemistry,P-T pseudosection modelling,zircon U-Pb geochronology,zircon Hf-O isotopes and C-O isotopes,in conjunction with previous data,to gain further insights into the Late Neoarchean-Paleoproterozoic tectonic evolution of the Fuping Complex and the TNCO.The late Neoarchean arc magmatism recorded by the Yangmuqiao mafic-ultramafic intrusion and the Fuping TTG gneiss is probably related to the subduction-collision process of the Ordos and the Qianhuai microblocks along the zone of ocean closure represented by the Wutai greenstone belt.The geochemical data suggest that the 2.1-2.0 Ga granitic rocks and amphibolites from the Fuping Complex formed in subduction-related arc setting.Based on the widespread 2.1-2.0 Ga magmatism as recorded in different rock types within the TNCO,we propose a tectonic model where we envisage simultaneous subduction and continental rifting process between several micro-blocks(or complexes).During 2.1-2.0 Ga,the Wutai Complex and the Fuping Complex were separated by the Longquanguan ocean.The double-sided subduction of the Longquanguan oceanic lithosphere resulted in distinct arc magmatism.Continental rift setting developed in the Hengshan,Huai'an and Zanhuang Complexes coevally.The salient lithological,geochemical and isotopic features imply that the protoliths of the meta-carbonates from the Wanzi Group(Fuping Complex)and Central Zanhuang Domain(Zanhuang Complex)were formed in a proximal and shallow marine environment.The Wanzi Group was deposited in a forearc basin during 1.95-1.93 Ga and the Central Zanhuang Domain was formed in a back-arc basin during 2.03-1.90 Ga.The geochemical imprints and biospheres of the oceanic basin in the Fuping area were possibly affected by the Lomagundi or Jatulian Event,resulting in the positive excursion of ?13C values in the dolomite-calcite marbles.However,the back-arc basin in the Zanhuang area was formed after the 2.1-2.0 Ga rifting event,thus it was generated after the Jatulian Event,thus preserving normal ?13C values of marine carbonates.Mafic granulites are exposed as boudins within TTG gneisses,and record peak metamorphic P–T conditions of 8.2–9.2 kbar,870–882 ?(15FP-02),9.6–11.3 kbar,855–870 ?(15FP-03)and 9.7–10.5 kbar,880–900 ?(15FP-06),respectively.Data from LA-ICP-MS zircon U–Pb dating show that the mafic dyke protoliths of the granulite were emplaced at ~2327 Ma.The metamorphic zircons show two groups of ages at 1.90–1.96 Ga(peak at 1.92–1.93 Ga)and 1.80–1.89 Ga(peak at 1.83–1.86 Ga),consistent with the two metamorphic events widely reported from different segments of the Trans-North China Orogen.The 1.93–1.92 Ga ages are considered to date the peak granulite-facies metamorphism,whereas the 1.83–1.86 Ga ages are correlated with the retrograde event.Thus,the collisional assembly of the major crustal blocks in the North China Craton might have occurred during 1.93 to 1.90 Ga,marking the final cratonization of the North China Craton. |
PDF Full Text Request