GSINET | Geological Survey of Iran , North - East Territory

Writers : Momeni, Gholam Reza; supervisor: M. Razmara, Kh. Ebrahimi; advisor: M. H. Karimpour
Refference : M.Sc.Thesis _ Ferdowsi university, Mashhad
Publishing Year : 1382

Abstract :

The Chah Yabou mines arc situated in the centeral part of a larger ophiolite belt Which extents from northeastern Sabzevar to north Abbass abad (Shahroud) along a major suture zone. Detailed filed study showed that the complex consist of four distinct stratigraphic units. The uppermost�unit is comprised of deep water limestone and radiolarian chert. This is underlain by pillow basalt cross cut by diabase dikes which in turn overlays gabbro. These units rest on a base of peridotite and dunit which contains most of the minable chromitite. Detailed petrographic analysis of mafic and ultramafic rocks in the area has revealed an assemblage typical ophiolitic rock types as well. these include partly serpentinized harzburgite , dunite. serpeiltinite, pediform clironiitite, Lherzolitc and cumulate rocks. The orebodies of Al-poor chromite containing up to 56.6 wt.%Cr2O3occur in depleted mantle rocks hariburgite )، and are characteristically enveloped by dunite halos of variabk(thickness. At least two large and numerous smaller chromite? are recognized within the area. The chromitites are commonly lens shaped and are . concordant with the foliation of the enclosing partly serpentinized harzburgite Based on reinote sensing studies two main trends of kiults and joints(SE-NW and NE_SW) wereidentified in the area. The minerahzation in the Chah Yabou area is associated with SE -NW set of fault. In addition, faulting is ubiquitous.high rich peridotite massifs angle faults are common with the ore zones sometimes appearing to be squceezed or plastered along fault zones. in other cases faults offset orezones. The chromitc occurs in a series of discontinuous hands.
The study demonstrated that the Chah Yabou chromile has several industrial end uses, priniari ly based on its Cr:Fe content. high chromium ores can be used for metallurgical applications such as stainless steel and special uses (special steels plating) Higher iron chromitites can be used for the production of low quality ferro chromum, foundry sands, clirontiuni salts and refractory purposes as well. The nitneralogical properties, of Chah Yabou chromites pose a major limitation in utilising a wide variety of chemical grade chromitite in the soda-ash roasting process. The physical and chemical properties of the chromite ores were investigated using the atomic absorption spectroscopy (AAS), X-ray fluorescence spectroscopy (XRF) an X -ray diffraction analysis (XRD) techniques. The XRD experiments showed that the substitution of�Al in the structure of chromitc affected the structure. The cell parameters and cell valume show smooth deereases with increasing Al content. This0.615 meters is to be expected as Cr is larger than Al (ionic radii A and 0.535 A for Cr and Al respectively). In this study some of the compositional trend of cell par data from Chah Yabou chromite were used as petrogcnctic indicator and geochemical exploration pathfinder. It seems that in the area of the study, Cr-rich pods are located near the harzhurgite-lherzolite transition zone and harzburgites which are part of the depleted upper sequence.

Subject List : Chromite

Thesises

Geochemical studies of Chromite ore deposits and mineral potential of Ophiolitic and post Ophiolitic rocks from Chahyabou area