Synthesis of jadarite in the Li.sub.2O-Na.sub.2O-B.sub.2O.sub.3-SiO.sub.2-NaCl-H.sub.2O system: FTIR, Raman, and Li and B K-edge XANES characterizations and theoretical calculations

The occurrence of jadarite (LiNaSiB.sub.3 O.sub.7 OH) as a major ore mineral in the world-class lithium-boron deposit of the Miocene Jadar lacustrine basin (western Serbia) raises interesting questions about its formation conditions and potential associations for lithium mineralization in other sedimentary basins. This contribution reports on the first successful synthesis of jadarite in the Li.sub.2 O-Na.sub.2 O-B.sub.2 O.sub.3 -SiO.sub.2 -NaCl-H.sub.2 O system at temperatures from 180 to 230 .sup." C and pH values from 6 to 12. Synthetic jadarite has been characterized by powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) spectroscopy, laser Raman spectroscopy, and synchrotron Li and B K-edge X-ray absorption near-edge structure (XANES). First-principles theoretical calculations reproduce the measured FTIR and Raman spectra and allow definitive assignments of vibration modes. Similarly, the measured Li and B K-edge XANES spectra are reasonably reproduced by first-principles theoretical calculations. Our synthesis results, together with its association with searlesite in the Jadar basin, suggest jadarite forms in deep sediments derived from Li-rich alkaline brines under high-temperature diagenetic conditions.