ZHANG Yan-ni1,2, LI Rong-xi1,2, DUAN Li-zhi1,2, ZHANG Shao-ni1,2, ZHU Rui-jing1,2, CHEN Bao-yun1,2
1. School of Geosciences and Resources, Chang'an University, Xi'an 710054, China;
2. Ministry of Education Key Laboratory of West Mineral Resources and Geological Engineering, Chang'an University, Xi'an 710064, China
Abstract: The genesis of the Sinian Dengying siliceous rocks in the Dabashan and the Beiba dome tectonic belts, north Verge of the Upper Yangtze block, was investigated by studying their silicon and oxygen isotopes. The δ30Si values of the siliceous rocks and the quartz veins in the study area were in the range of 0.6‰-1.6‰. These values are all positive high values and are very close to those of sedimentary originated siliceous rocks, other studies had showed that the study region was in a neritic platform environment with great effect from terrigenous clastics, all of these suggested that the siliceous rocks are sedimentary originated. The δ18O of siliceous rocks and quartz veins in the study area are in the range of 20.3‰-21.6‰, consisting with the δ18O values of sedimentary rocks. The geological thermometer calculation of the siliceous rocks using oxygen isotope showed that the formation temperature of silicalites in this area was significantly higher than that of the ancient sea, indicating effects of submarine hot water. In summary, we concluded that the siliceous rock series in the study area were sedimentary originated and were affected by submarine hot water during deposition.
Keywords: the causes of silicalite rocks Dabashan tectonic belt silicon isotopes oxygen isotopes
