Constraining the hydrology at Minas da Panasqueira W Sn Cu deposit Portugal This dissertation combines field and geochemical observations and analyses with numerical modeling to understand the formation of vein hosted Sn W ore in the Panasqueira deposit of Portugal which is among the ten largest worldwide. The deposit is located above a granite body that is altered by magmatic hydrothermal fluids in its upper part (greisen). These fluids are thought to be the source of metals but that was still under debate. The goal of this study is to determine the composition and temperature of hydrothermal fluids at Panasqueira and with that information to construct a numerical model of the hydrothermal system. The focus is on analysis of the minerals tourmaline and white mica which formed during mineralization and are widespread throughout the deposit. Tourmaline occurs mainly in alteration zones around mineralized veins and is less abundant in the vein margins. White mica is more widespread. It is abundant in vein margins as well as alteration zones and also occurs in the granite greisen. The laboratory work ...