• journal_title：American Mineralogist
• Contributor：Bing Zhou ; Erfeng Ren ; Barbara L. Sherriff ; Yefeng Yao
• Publisher：Mineralogical Society of America
• Date：2013-05-01
• Format：text/html
• Language：en
• Identifier：10.2138/am.2013.4273
• journal_abbrev：American Mineralogist
• issn：0003-004X
• volume：98
• issue：5-6
• firstpage：907
• section：Articles

The large scale Targejia hot spring type Cs deposit in Tibet is unique and still active today with the distribution of hot springs being controlled by tectonic movements of the Tibetan Plateau. The ore bodies of the Targejia Cs deposit are mainly composed of geyserite, a Cs-containing opal. In this study, a combination of X-ray diffraction, infrared spectroscopy, and ²⁹Si, ¹H, ¹³³Cs magic angle spinning nuclear magnetic resonance (MAS NMR) were used to study the location and mobilization of Cs in geyserites. ²⁹Si NMR spectra indicate that the relative amounts of Q², Q³, and Q⁴ species vary in geyserite samples of different mineralization stages. Based on the ¹³³Cs chemical shift as well as the change in ²⁹Si chemical shift ranges (especially for Q²), cesium is inferred to associate with Q³ and Q² silanol groups, where it is coordinated by O²⁻, OH⁻, and H₂O as a network modifying cation. As Cs-bearing geyserite ages and dehydrates, Q² and Q³ polymerize giving an increase in Q⁴. This is accompanied with a decrease in Cs content indicating that Cs may be leached out from the opals as it loses its original coordination environment in the silicate framework.