Boron isotopic composition of tourmaline from massive sulfide deposits and tourmalinites |
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| Authors: | Martin R Palmer John F Slack |
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| Institution: | (1) Department of Earth, Atmospheric and Planetary Sciences, E34-201, Massachusetts Institute of Technology, 02139 Cambridge, MA, USA;(2) US Geological Survey, National Center, MS 954, 22092 Reston, VA, USA;(3) Present address: Department of Geology, University of Bristol, Queen's Rd., BS8 1RJ Bristol, UK |
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| Abstract: | Boron isotope ratios (11B/10B) have been measured on 60 tourmaline separates from over 40 massive sulfide deposits and tourmalinites from a variety of geologic and tectonic settings. The coverage of these localities is global (5 continents) and includes the giant ore bodies at Kidd Creek and Sullivan (Canada), Broken Hill (Australia), and Ducktown (USA). Overall, the tourmalines display a wide range in
11B values from –22.8 to +18.3 Possible controls over the boron isotopic composition of the tourmalines include: 1) composition of the boron source, 2) regional metamorphism, 3) water/rock ratios, 4) seawater entrainment, 5) temperature of formation, and 6) secular variations in seawater
11B. The most significant control appears to be the composition of the boron source, particularly the nature of footwall lithologies; variations in water/ rock ratios and seawater entrainment are of secondary importance. The boron isotope values seem especially sensitive to the presence of evaporites (marine and non-marine) and carbonates in source rocks to the massive sulfide deposits and tourmalinites. |
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