Geochemistry and sedimentary environments of the siliceous rocks from the Sinian-Lower Cambrian Laobao Formation in Tiechang, Yinjiang, Guizhou: An approach

The sedimentary environments of the siliceous rocks from the Sinian-Lower Cambrian Laobao Formation in Tiechang, Yinjiang, Guizhou are classified, according to lithological associations and geochemical signatures, into the platform-margin to the platform basin sedimentary environments. The siliceous deposits are primarily derived from the terrigenous clastic deposits rather than the hydrothermal deposits. Geochemically, the V/(V + Ni) ratios suggest the euxinic environment for the formation of the siliceous rocks from the Laobao Formation. The Al/(Al + Fe + Mn) ratios and Al-Fe-Mn triangular diagram indicate that the terrigenous clastics have play an important part in the formation of the siliceous rocks. The Al₂O₃/(Al₂O₃ + Fe₂O₃) ratios and Al₂O₃/(Al₂O₃ + Fe₂O₃) versus Fe₂O₃/TiO₂ diagrams indicate the continental marginal environment for the tectonic setting of the siliceous rocks from the Laobao Formation. The δCe values and (La/Ce)_N values also show that the siliceous rocks from the Laobao Formation were formed in the sedimentary environments intermediate between the open basin and continental marginal environments.