Zinc-bearing actinolite from the Kakkonda geothermal system， Iwate Prefecture， northeastern Japan

Abstract

Zinc-bearing actinolite was found in a hydrothermal vein of a drill core retrieved at 1，223 m in depth of the deep research well， WD-1， which had been drilled in the Kakkonda geothermal area， northeastern Japan. Zinc-bearing actinolite is fibrous and occurs with sphalerite，chalcopyrite， pyrite， quartz， anhydrite， epidote and clay minerals in the vein. The ZnO content of actinolite ranges in 0.4-1.5 wt.%， relatively high compared with zinc-bearing calcic amphiboles in previous reports. The actinolite was possibly formed from zinc-rich hydrothermal fluid at early stage of geothermal activity in Kakkonda.