By definition, only small amounts of micronutrients are required by plants.
Most micronutrients come from soil parent materials.
Cl - has atmospheric sources, and is rarely limiting. All micronutrients are found in varying quantities in igneous rocks. All micronutrients but Mo are more soluble and available for plant uptake in acid soils. Fritted Trace Elements - Zinc along with other micronutrients is currently being produced in the form of a frit. Frits containing Zn alone are not currently available.