Geochemical characteristics and depositional environment of siliceous rocks in the Hongshan iron deposit, Beishan area, Gansu Province

Geochemical characteristics and depositional environment of siliceous rocks in the Hongshan iron deposit were studied based on the field investigation and analysis of major elements, trace elements and rare earth elements. A suite of siliceous rocks closely related to Fe mineralization is widespread in the Hongshan iron deposit. The massive chert is gray and purple in color and has low SiO2 content, whereas SiO2 is negatively correlated with Al2O3. In SiO2-Al2O3 discrimination diagrams, chert samples fall into the hydrothermal region. The North American shale normalized REE patterns of siliceous rocks are flat with obvious positive Eu anomaly. These characteristics are similar to those of East Pacific hot springs and Red Sea hot brine，indicating their hydrothermal origin. Trace elements such as V, Ni, Ba and Cu have hydrothermal characteristics of continental-margin cherts.