Major and trace elements in scales in pipes from well 9, Reykjanes, Iceland

摘要

Scale has been deposited from geothermal brine from boiling level in well 9, Reykjanes, Iceland, to the separation station. The amount of deposit increases drastically downstream of a pressure drop orifice near the wellhead but diminishes further away. Scale in surface pipes is mostly an uncrystallized mass of silica, and iron-silicates (up to 85%), and metal sulfides, mainly sphalerite, chalcopyrite, galena, and/or mixtures of these minerals. Upstream of the orifice, in surface pipelines hardly any silica precipitates but right after the orifice (downstream) the silica proportion of the deposit increases to 47 wt%, and to 82 wt% 30 m from the orifice, and exceeds 93 wt% 70 m downstream of the orifice. Precious metals like gold, silver, copper, lead, and zinc are present in considerable amounts, or up to 140 ppm, 0,2%, 20%, 3,3%, and 21%, respectively.