Geochemistry of the Late Paleozoic radiolarian cherts within the NE Jiangxi ophiolite melange and its tectonic significance

摘要

Major and trace elements are presented for the late Paleozoic radiolarian cherts, which were spatially associated with the NE Jiangxi ophiolite melange. These chert samples show relatively low SiO2 (78.40%-89.28%) and high AI2O3 (3.42%-11.02%). Low Si/AI ratios (6.3-23) and tight negative correlation between Si/Al and AI2O3 of the samples indicate that they are muddy cherts containing high and variable contents of pelitic detritus. Geochemically, they are characterized by AI2O3/(AI2O3+Fe2O3) = 0.51-0.90, shale-normalized Lan/Cen = 0.76-1.11, Ce/Ce’ = 0.91-1.22, V20 μg/g, V/Y2.6 and Ti/V40, resembling those of cherts formed in the continental margin regimes. It is therefore concluded that these late Paleozoic radiolarian muddy cherts were most likely formed in a continental margin regime, and not genetically related to the ophiolite suite in NE Jiangxi. It is also unlikely that an oceanic basin existed between the Yangtze and Cathaysia blocks during the late Paleozoic.