Water in Hydrothermal Feldspar

Abstract

Feldspar is the most common mineral in the Earth's crust, and although water is present in only trace amounts (~ hundreds of ppm), this quantity is sufficient to make crustal feldspar one of, if not the, largest reservoir for water on our planet. Here we report on measurements of water contained in feldspar grown in hydrothermal veins of the Swiss Alps. Gemmy specimens of adularia (K-feldspar), albite (Na-feldspar), and quartz have been analyzed using infrared spectroscopy at high spatial resolution (100-um spot sizes). We note the presence of distinctive absorption bands associated with each type of mineral. We characterize the 3-dimensional variation within single crystals and compare and contrast their variations with other minerals that grew contemporaneously in the same host vein. Our results show potential for discerning variations in fluid conditions present during and subsequent to crystal growth.