A silicalite bed was found in the hanging wall and foot wall of the sulfide-rich bed ofthe Lower Cambrian black rock series in South China. Its origin was not described before. Onthe oxide （SiO2-Al2O3, SiO-2-MgO, SiO2-K2O+ Na2O） diagrams for discriminating silicalitesof chemical, biological and volcanic origins （Liu Xiufeng, 1991）, most of the data points of silicalites fall within the areas representing silicaIites of chemical and volcanic origins. On the AlFe-Mn diagram for discriminating silicalites of hydrothermal and biological origins （Yamamoto,1987）, the data points fall within the areas representing silicalites of hydrothermal and hydrothermal-biological origins. On the SiO2-Al2O3 diagram for discriminating silicalites of hydrothermal and hydrogenous origins （Bonatti, 1975 ）, the data points mostly fall within thehydrothermal area. The ratios of SiO2Al2O3, SiO2/（K2O+Na2O）, SiO2/MgO, and K2O/Na2O in the silicalites stand between those of volcanic sediments and of sea floor hydrothermalsediments. The total amount of rareuearth elements in the silicalites is low; the North American Shale-normalized REE patterns decline leftward with obvious negative Ce anomaly. Thetrace elements Mo, Zn, As, Sb, Se, U, and Ba are higher than those in non-hydrothermalsediments and U/Th≥1. The present authors think that the silicalites are derived fromseafloor hot brines which had attracted elements from igneous rocks.
