Biogeochemical study of chromite bearing zones in Forumad area, Sabzevar ophiolite, Northeastern Iran

• The relationship between soil and plant was used in chromite prospecting.
• Ni was used as pathfinder in biogeochemical exploration in Sabzevar ophiolite.
• Salsola orientalis was defined as Ni indicator plant at reconnaissance survey.

Chromite ores in Forumad area from Sabzevar ophiolite belt, northeastern Iran are surrounded by magmatic dunite that is rich in nickel as compared with other ultramafics. Chromium is intensively bonded within chromite and is not an essential element for plant's life cycle, whereas Ni is more bioavailable and is an essential constituent of plant enzymes. Determined bio-concentration factor (BCF) for Ni in Salsola orientalis S.G. Gmel., the predominant plant species on the soils developed on dunite zones from 20 locations (average 0.81) indicated that Ni can be successfully used as a pathfinder for tracing the chromite ore bodies hosting dunites in the studied area. In soils developed on serpentinized ultramafics, maximum total concentrations of 719, 1150, 181, 617, 4481, 2314, and 20,790 μg g− l were determined for Ni, Cr, Co, Mn, Fe, Mg, and Ca, respectively by using Atomic Absorption Spectroscopy (AAS). Dry climate, low rainfall and high temperature of the area lead to grow a specific flora including annual and perennial herbaceous plants. The chemical data showed excellent correlation coefficient between Cr and Ni (0.91) in soils developed on dunite zones. Investigation on 107 species from 30 families, growing on the studied soils indicated that S. orientalis could consider as promising plant for prospecting of chromite ores in Sabzevar ophiolite belt in reconnaissance survey.