SHRIMP zircon age for a K-bentonite in the top of the Laobao Formation at the Pingyin section, Guizhou, South China

Prominent Lower Cambrian K-Bentonites In South China: Distribution, Mineralogy, and Geochemistry

“…11). Such a regional correlation result is consistent with the conclusion made by Zhou et al (2013) through studies on REE geochemistry and geochronology (Fig. 4).…”

“…A similar mineralogical result was acquired by Pasava et al (2010) from the study of the K-bentonite in the Lower Cambrian Zhujiaqing Formation at the Meishucun section in Yunnan Province. During U-Pb zircon dating of the Lower Cambrian K-bentonites from the two stratigraphic levels at various sections in South China, the cathodoluminescence (CL) images indicated that the euhedral to sub-euhedral zircons in the K-bentonites have obvious oscillatory zoning, suggesting their volcanic origin Zhu et al 2009;Chen et al 2009;Wang et al 2012;Zhou et al 2013). In the present study, we analyzed the clay fraction of the Kbentonite in the base of the Niutitang Formation at the Songlin section in Guizhou Province using X-ray diffraction (see Fig.…”

“…Thus, we believe that the viewpoint considering the polymetallic Ni-Mo layer as the PC/C boundary is inappropriate. Previous geochronology studies indicated that the age of the K-bentonite in the middle Zhujiaqing Formation (bed 5) in eastern Yunnan Province and its equivalent in deepwater realm has been constrained between 535.2 6 1.7 Ma and 539.4 6 2.9 Ma by U-Pb zircon ages (Compston et al 2008;Sawaki et al 2008;Zhu et al 2009;Chen et al 2009;Zhou et al 2013). Therefore, either in the shallow-water platform or in the deep-water realm, the PC/C boundary in South China should be placed within the strata underlying the older one of the two significant Lower Cambrian K-bentonite beds.…”

Discussion on the PGE anomalies and source materials of K-bentonite (Bed 5) in the Lower Cambrian Meishucun section, Yunnan

“…7 Ce/Ce* versus Pr/Pr* diagram for this study and the data cited for comparison (modified after Bau and Dulski 1996). Filled diamond represent samples from the K-bentonite layer (Bed 5) in the Meishucun section for this study; filled circle represents sample MSC9; filled triangle represents a sample from the K-bentonite layer (Bed 5) in the Meishucun section reported by Pašava et al (2010); filled square represents a sample from the deeper water facies of the Pingyin sectionin Jiangkou County, Guizhou Province, equivalent to Bed 5 of the Meishucun section ); symbols open diamond and open circle represent samples from the K-bentonite layer (Bed 5 and the bottom of Bed 9, respectively) in the Meishucun section reported by Zhang et al (1997) water facies in Guizhou, the equivalent K-bentonite layer of Bed 5 of the Meishucun section has total PGE concentrations of 2.95 9 10 -9 , Pt concentrations of 0.76 9 10 -9 , and Pd concentrations of 1.92 9 10 -9 (PY-13, Zhou et al 2013Zhou et al , 2014. These are slightly higher than Bed 5 samples of this study, but well lower than Pašava et al (2010), showing obvious PGE enrichment.…”

“…Zhou et al (2011) suggested that the K-bentonite layers (equivalent to Bed 9 bottom bentonite of the Meishucun section) discovered in the Lower Cambrian section in Zunyi, Guizhou Province can provide new clues for the material sources of the Lower Cambrian polymetallic Ni-Mo-PGE layer in South China. Typically, Bed 5 of the Meishucun section and its equivalent layers lie up to several meters to tens meters below the polymetallic Ni-Mo-PGE layer (Chen et al 2009;Zhu et al 2009;Zhou et al 2013). Detailed geochemical research of this layer, especially PGE studies, have important significance in determining the material sources of the polymetallic Ni-Mo-PGE layer.…”