Journal
LITHOS
Volume 198, Issue -, Pages 298-315Publisher
ELSEVIER
DOI: 10.1016/j.lithos.2014.04.003
Keywords
Trans-North China Orogen; Luliang Complex; Back-arc basin; Metabasic rocks; Paleoproterozoic
Categories
Funding
- NSFC [41372195, 41190075]
- China Geological Survey Program [12120114061901]
- Hong Kong RGC GRF [7069/12P, 7063/13P]
- Basic Outlay of Scientific Research Work from the Ministry of Science and Technology [J1218]
- Austrian Science Fund (FWF) [J1218] Funding Source: Austrian Science Fund (FWF)
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The Luliang Complex is located at the western margin of the middle segment of the Trans-North China Orogen, along which the Western and Eastern Blocks amalgamated to form the basement of the North China Craton. The complex consists of the late Neoarchean to Paleoproterozoic granitic plutons and meta-supracrustal rocks, of which the latter are subdivided into the Jiehekou, Luliang,Yejishan, and Heichashan/Lanhe Groups. The Luliang Group is composed mainly of siliciclastic rocks in the lower part and volcanic rocks in the upper part, all of which have been metamorphosed from greenschist- to amphibolite-facies. U-Pb ages of detrital zircons from meta-sedimentary rocks in the Luliang Group yield four populations of 3061-2920 Ma, 2790-2600 Ma, 2599-2280 Ma and 2211-2202 Ma, suggesting that their provenances were derived mainly from the Luliang and Taihua Complexes in the Trans-North China Orogen. The meta-volcanic rocks give igneous zircon U-Pb ages of 2209-2178 Ma and epsilon(Hf)(t) values of -0.8 to +3.6. Geochemically, they are subalkaline basalts and andesites that can be classified into two groups, of which one group has flat LREEs, weak enrichment in LREEs relative to HREEs and flat HREEs and displays E-MORB-like spider diagrams with the exception of insignificantly negative Nb-Ta, Zr-Hf and Ti anomalies. In contrast, the other group displays stronger LREE fractionation, stronger enrichment in LREEs relative to HREEs and mildly fractionated HREEs and is characterized by spiky spider diagrams similar to arc volcanic rocks. The first group is interpreted to have originated from a Neoarchean E-MORB source, whereas the second group shows inputs of newly subduction-derived fluids in the mantle source. These geochronological and geochemical signatures indicate the existence of an 22-2.1 Ga continental back-arc system in the Luliang Complex of the Trans-North China Orogen, which is consistent with the model that the collision between the Eastern and Western Blocks to form the coherent basement of the North China Craton in the Paleoproterozoic, not at the end of Neoarchean. (C) 2014 Elsevier B.V. All rights reserved.
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