Nickel-Cobalt Vein Deposits

Nickel - Cobalt are vein deposits that are formed in open fractures. They can be in any number of host rocks, although they are most common in crystalline metamorphic rocks, granitic intrusions and sediments. Such deposits are rare in volcanic rocks. They contain nickel and cobalt arsenides and may contain native silver, argentite, pitch-blende, pyrite, chalcopyrite, sphalerite and galena: the gangue is any or all of quartz, calcite and dolomite. Examples include the cobalt district of Ontario, Freiberg in eastern Germany and Jachymov in the Czech Republic.

Without previous structural disturbance to cause the fracturing, the deposits would have nowhere to form. However, the deposits themselves are almost always un-deformed. This suggests that they are emplaced very late in a region’s geological history.

Most geologists who have studied these deposits recognize that veins are hydrothermal, but no single genetic model is accepted widely.