Acknowledgments
This research was financially supported by the National Key Research and
Development Program of China (2019YFC1804803-2), and the research fund
of Ningxia Geological Exploration (Grant No. HZ20170040-I). The authors
are thankful to Mr. Zhipeng Zhao, Mr. Yuxue Ma and Mr. Liang Gong from
Ningxia Geological Survey Institute for helping with the field work.