Geothermal waters from the Taupo Volcanic Zone , New Zealand : Li , 1 B and Sr isotopes characterization

11 12 13 In this study, we report chemical and isotope data for 23 geothermal water samples collected in New Zealand 14 within the Taupo Volcanic Zone (TVZ). We analyzed major and trace elements including Li, B and Sr and their 15 isotopic compositions ( 7 Li,  11 B, 87 Sr/ 86 Sr) in high temperature geothermal waters collected from deep boreholes 16 in different geothermal fields (Ohaaki, Wairakei, Mokai, Kawerau and Rotokawa geothermal systems). Lithium 17 concentrations are high (from 4.5 to 19.9 mg/L) and lithium isotopic compositions ( 7 Li) are very homogeneous, 18 being comprised between-0.5 and +1.4‰. In particular, it is noteworthy that, except the samples from the 19 Kawerau geothermal field having slightly higher  7 Li values (+1.4%), the other geothermal waters have a very 20 constant  7 Li signature around a mean value of 0‰ ± 0.6 (2, n=21). Boron concentrations are also high and 21 relatively homogeneous for the geothermal samples, falling between 17.5 and 82.1 mg/L. Boron isotopic 22 compositions ( 11 B) are all negative, and display a range between-6.7 and-1.9‰. These B isotope compositions 23 are in agreement with those of the Ngawha geothermal field in New Zealand. Li and B isotope signatures are in a 24 good agreement with a fluid signature mainly derived from water/rock interactions involving magmatic rocks with 25 no evidence of seawater input. On the other hand, strontium concentrations are lower and more heterogeneous 26 and fall between 2 and 165 µg/L. 87 Sr/ 86 Sr ratios range from 0.70549 to 0.70961. These Sr isotope compositions 27 overlap those of the Rotorua geothermal field in New Zealand, also confirming that some geothermal waters (with 28 more radiogenic strontium) have interacted with bedrocks from the metasedimentary basement. Each of these 29 isotope systems on their own reveals important information about particular aspects of either water source or 30 water/rock interaction processes, but, considered together, provide a more integrated understanding of the 31 geothermal systems from the TVZ in New Zealand. 34 isotopes 35 5 102 words (without references and captions)