Report on geochemical exploration in 1:100000 sheet of Arak
The 1:100000 sheet of Arak is located in the Markazi province between 49?30' to 50? eastern longitudes and 34? to 34?30' northern latitudes. According to the structural divisions of Iran, the study area belongs to the Sanandaj-Sirjan (south and west) and Central Iran zones.
Oldest rock units of area are Jurassic shale and sandstone that are covered by clay limestone of Cretaceous, Qom and Upper Red formations, Oligo-Miocene andesite, basalt and volcanic rocks and Pliocene volcanic conglomerate. There are three small intrusive bodies in the area, granodiorite-diorite in composition. Regional metamorphism of Sanandaj-Sirjan is evident in metadolomites and schists of the area. The Main structural trend is NW-SE including Talkhab and Tabrateh faults.
In this survey 448 stream sediment samples were taken and analyzed for 44 elements. Data processing includes separation of rock classes, determination of background, threshold and anomaly values, processing censored data and cluster analysis, network estimation and calculation of enrichment index etc. As the result these anomalies were identified: three Co anomalies, sic Pb anomalies, six Zn anomalies, seven Ti anomalies, 10 V anomalies, three Ag (3.5 Km away from east of Moradabad, 1 Km away from north of Jahak mountain and 1.5 Km away from northeast of Anjirak), two Bi anomalies, two Au anomalies (south of Dayen village and 2 Km away from east of Mehrabad village) and 6 Hg anomalies. Also there are other anomalies for Be, S, Sb, Sn, Sr, Te, Th, Tl, V, W, La, Mo, Co, Ce, Cd, Ba and As.
In the project these maps were prepared: geochemical map of factor score distribution, occurrences probability cross total number of samples, and enrichment index map. In addition 55 heavy mineral and 24 mineralized samples were taken from the area that contain rutile, pyroxene, pyrite, limonite, barite, pyrolusite, ilmenite, hematite, oligist and zircon. Mineralized samples show evidence of tourmaline, gold, tungsten, copper and tin. Based on above data, these variables were defined:
1- First group: assemblage of barite, zircon, rutile, hematite, ilmenite, pyroxene and oligist
2- Second group: include limonite and pyrolusite
Following processing of data, of six anomalous zones, four one were modeled.