Boron isotope systematics of hydrothermal fluids and tourmalines: A synthesis

Abstract

Boron isotope and concentration data are presented for hydrothermal fluids from different tectonic settings that reflect derivation of boron from marine evaporites (Red Sea brines), non-marine evaporites (Salton Sea), elastic sediments (Escanaba Trough and Guaymas Basin), back-arc basalts (Mariana Trough) and mid-ocean ridge basalts (21° and 11–13°N East Pacific Rise; Juan de Fuca Ridge; and 23° and 26°N, Mid-Atlantic Ridge). Boron isotope systematics of these fluids are used to constrain the S″B-values of tourmalines found in ancient massive sulfide deposits and tourmalinites that formed under conditions analogous to those of modern hydrothermal systems. The data also provide insights into the physical conditions required for the formation of tourmaline in certain geologic environments.