On the Age of the Ophiolitic Complexes in Northeastern Jiangxi:A Micropaleontological Analysis

• 作 者: YANG Qun Wang Yujing Yin Leimi
• 机 构: Nanjing Institute of Geology and Palaeontology,Department of Earth Sciences,Geological Survey of Jia
• 出 处: 地质学报（英文版）
• 发表日期: 2004年期
• 关键词: radiolarians chert Banxi Group northeastern Jiangxi
• 基金项目: This study received financial support from the National Natural Science Foundation of China;中国科学院资助项目

The age assignment of cherts from ophiolitic/metamorphic complexes in northeastern Jiangxi is widely regarded as one of the crucial issues in the tectonic interpretation of South China. The ophiolitic and metamorphic complexes in northeastern Jiangxi have been traditionally regarded as part of the Proterozoic "Banxi (=Penhsi) Group" of the Jiangnan Uplift. However, recent reports of Late Paleozoic radiolarians from the rock complexes have caused some researchers to question the traditional interpretation of the tectonic and paleogeographic framework in the region; but other workers are suspicious about these findings. In order to test the validity of the putative radiolarians, we, an interdisciplinary study group including micropaleontologists, tectonic specialists and regional geologists, conducted field investigations and multiple re-samplings of the localities where the reported fossils were collected. Our comprehensive study shows that the chert of the ophiolitic complex and the associated low-grade metamorphic slate yield Mesoproterozoic and Neoproterozoic acritarchs, confirming the traditional view of their age assignment (Proterozoic); on the other hand, no recognizable radiolarian fossils have been discovered therein, thus raising questions about the recently published result of Paleozoic radiolarian findings. Probable causes for the putative radiolarian findings are thus discussed herein. Geochemical characteristics indicate that the chert sedimentation most probably occurred under a continental margin setting.