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The Putative¨Radiolarian Cherts¨from Ophiolitic and MetamorphicComplexes in Northeast Jiangxi:A Re-examination

WANG Yujing1, YANG Qun1, YIN Lei-ming1, SHU Liang-shu2, LOU Fa-sheng3, WANG Bo2   

  1. 1. Nanjing Institute of Geology & Palaeontology, CAS, Nanjing 210008, China ; 2. Department of Earth Sciences, Nanjing University, Nanjing 210093, Chian ; 3. Geological Survey of Jiangxi Province, Nanchang 330201, China
  • Received:2006-03-20 Revised:2006-03-20 Online:2006-03-20 Published:2006-03-20

Abstract: The age assignment of the putative radiolarian cherts from the ophiolitic/metamorphic complexes in northeast Jiangxi is widely regarded as one of the crucial issues in the tectonic interpretation of South China. Traditionally,these ophiolitic/lightly metamorphic complexes have been regarded as part of the Proterozoic"Banxi (=Penhsi)Group"of the Jiangnan Uplift.However,recent reports of late Palaeozoic radiolarians from the rock complexes have caused some researchers to question the traditional interpretation of the tectonic and palaeogeographic framework in the region,though other workers are suspicious about these findings. In order to test the reality of the putative radiolarians,we,an interdisciplinary study group including micropalaeontologists,tectonic specialists and regional geologists,conducted field investigations and multiple resamplings of the localities where the reported lossils were collected.We also reanalyzed the published materials of the above mentioned new findings.Our study shows that the putative radiolarian-bearing chert of the ophiolitic complex and the low-grade metamorphic strata do not yield any identifiable radiolarian fossils,although Mesoproterozoic and Neoproterozoic aeritarehs are diseovered from them.Geochemical characteristics such as the element composition, Ce anomaly,La/Ce ratio and trace e1ements indicate that the chert sedimentation is closely related with a terrestrial provenance. a setting far away from the deep oceanic settings.Because our investigation has not verified the Palaeozoic radiolarian findings,five probable causes for the radiolarian reports are discussed.