Petrography and mineral chemistry of a newly discovered ag and cd ore minerals in the zn-pb-barite occurrence in al-Anish area, Zakho, northern Iraq

Abstract EN

The alanish locality, situated along the northern passive margin of the arabian plate, is one of several zn-pb-barite occurrences widespread in northern iraq (north of zakho city).

the mineralization was emplaced in the late permian dolostone of the chia zairi formation and can be seen at the superficial exposures.

a scanning electron microprobe coupled with an x-ray energy-dispersive spectrometer (sem-edx) was used for the identification of mineral phases.

acanthite (ag2s) and greenockite (cds) are reported here as their first occurrence in iraq within a strata-bound polymetallic sulfide ores of zn, pb, fe, cu, ag, and cd.

it is a mississippi valley type (mvt) deposit formed at 120 °c as inferred from cd fractionation in sphalerite and galena.

the metals and sulfur sources are derived from the brines originated from the sedimentary basin rich in evaporate.

the average composition of acanthite is 83.9 wt.% ag and 12.5 wt.% s equivalent to 96.4% acanthite as tiny inclusions of lenticular shape inside galena and smithsonite grains.

the remobilization of cd from the sphalerite lattice resulted in the formation of greenockite with an average composition of 68.9 wt.% cd and 21.2 wt.% s.

the mineralization is dominated by sphalerite and galena with minor amounts of chalcopyrite, pyrite, marcasite, and fewer amounts of acanthite and greenockite associated with dolomite, calcite, barite, and siderite as gangue minerals.

the common features of the mineralization are replacement, veins, veinlets, and cavity filling of small paleo-karsts.

the fault plane and the secondary permeability formed pathways for the movement of metals-bearing solution into dolostone in which the ore body was accommodated.