(Sahlabad Sheet 1:100000)
Sahlabad is located in southeastern Birjand, South Khorasan. It is at longitude 59° 30' - 60° E and latitude 32°- 32° 30' N.
The study area belongs to Flysch and Colored Mélange Belt in eastern Iran. The general trend of rock units in Sahlabad is NW-SE. Exposed igneous, metamorphic and sedimentary rock units (Late Cretaceous- Neogene) are found in the area. Ultrabasics, serpentinites and listvenites, exposed in Atashkuh, are among the oldest rocks, but their exact age is still unknown. Other rock units include flysch facies and metamorphic rocks like listvenites, amphibolites, serpentinite ultrabasic rocks, metadiabases, etc.
In the study area Upper Cretaceous clastics, limestones, diabases, gabbros and radiolarites, Paleogene acidic-intermediate volcanic rocks, tuffs, clastics and limestones, Neogene clastics, limestones, tuffs and basic-intermediate volcanic rocks underlie Quaternary travertines, alluvium, mud flats and salt flats.
712 geochemical samples were collected and analyzed for Co, Cr, Ni, Ti, Mn, Sr, Ba, Au, Fe, As, Sb, Bi, Hg, W, Cu, Pb, Mo, Sn, Ag, Zn. Furthermore, 111 heavy mineral samples were collected. Accuracy of analysis was examined by Thompson Diagram and calculation of relative error.
Statistical parameters of raw data were calculated and homogenous groups were separated. Then, each group was normalized to its median value and enrichment indices of elements were determined. Next, enrichment indices were normalized. Data analysis was performed, using mono- and multivariate statistical methods like correlation coefficient, cluster analysis and factor analysis. Monovariate maps were drawn using network estimation method for enrichment indices. Finally, 10 anomalous areas, covered about 168 km2, were identified with the help of factor analysis method for geochemical samples (33 sheets were prepared), and network estimation method for heavy mineral samples. Anomalies were modeled regarding their compatibility with typical ores.
The 10 anomalous areas are
Anomaly 1- Pb, Ag, Sn, Zn, Sb, Ni, Fe, Co anomalies in northeastern Sahlabad;
Co and Ni are associated with serpentenite ultrabasic rocks and Zn, Ag, Pb with limestones and calcareous shales. Magnetite, hematite and limonite in heavy mineral samples indicate the presence of Fe anomaly.
Anomaly 2- Cu, Fe, Ni, Cr, Au, Co, Mn anomalies in Atashkadeh;
Cr, Co and Ni are associated with ultrabasic rocks, Cu with acidic rocks and Au with both ultrabasic and acidic rocks. Fe anomaly is due to the presence of magnetite, listvenite and hematite, and Mn anomaly is due to the presence of garnet.