جستجوی مقالات مرتبط با کلیدواژه "golcheshmeh" در نشریات گروه "زمین شناسی"

The Golcheshmeh copper deposit is located in the north-easth of Iran (south of Neyshabour) at the margin of Sabzevar Structural Zone. Based on geological and labratory studies, the outcroped rocks consist of Eocene volcanic rocks such as andesite, basaltic- andesite and basalt, that associated with the sedimentary and volcanosedimentry rocks including limestone, tuff and breccia. The alteration is hosted andesitic layers that includes carbonatization, propylitic and less argilic and sericitic. The carbonatization zone is the most important alteration zone in this area. Mineralization mainly occurs in Eocene or younger volcanic rocks as vein- veinlets, amygdaloidal fillings and some replacement and disseminated styles. According to the minerallographic studies, the main ores containing copper are divided into oxide and sulfide types. Mineralization mainly consists of oxide phases and can be seen as contamination of surface fractures and pores or voids filling in host rocks. The main oxide minerals are malachite, azurite and chrysocolla and sulfide minerals are chalcocite, covellite, with minor chalcopyrite, bornite, digenit and also native copper. Chalcocite is the most abundant sulfide ore in this area. There are probably two generations: The first generation is a primary ore that was formed directly in joints, cracks, and fractures from the ore-containing solution and currently is replaced covellites, and the second generation is chalcocite that was probably formed from the conversion of bornite and chalcopyrite through substitution and under supergene conditions. In most cases, the observed intergrowth between copper ores suggests the multi-stage mineralization in this region. Geochemical studies based on minor and trace elements obtained from this research indicate that the igneous rocks in this region were characterized by the calc-alkaline basalt characteristics and in terms of tectonic setting, could be attributed to subduction zone-related continental arc magmatism. In addition, based on the results of the analyses of trace and rare earth elements, the high amount of Nb (more than 16 ppm), Rb-rich, (Zr / Nb)N (less than 2 and between 0.7 to 0.46), could be an indication of contamination of magma with continental crust. The absence of Eu anomaly suggests a broadly defined melting conditions at oxidation state. On the basis of this study and with respect to some evidences such as tectonic setting, host rock types, structure and texture of ore body, mineral paragenesis, shape of the ore body and associated elements, this area is comparabale to a Manto type deposit located in Chile regardless of some differences. Thus, it is suggested that the Golcheshmeh copper mine classified a Cu- Manto type deposit.

The study area is located at 220 km southwest of Mashhad and 80 km south of Neyshabur and is situated between 58° 40' 30" to 58° 43' 30" E longitudes and 35° 47' 30" to 35° 52' 00" N latitudes. The study area is part of Sabzevar zone. The lithology of the area consists mainly of volcanic rocks with trachyte, trachy andesite, and basaltic trachy andesite composition and in some parts has been subjected to argillic, carbonate and propylitic alteratins. The dominent phenocrysts in these rocks are plagioclase, alkali feldespar, opacitized hornblende and pyroxene. The main texture in these rocks is porphyritic with fine and medium grain matrix. These rocks have calc-alkaline nature and show enrichment in LILE (except for Ba) and depletion of HFSE. The enrichment of LREEs relative to HREEs indicates that the parental magma formed in a subduction zone, which is well manifested by the volcanic rocks of Golcheshmeh area. Tectonic setting diagrams and geochemical properties of volcanic rocks of the study area suggest an active continental margin setting. The low ratios of (La/Yb)N (5.3 to 9.3) and (Ce/Yb)N (4.2 to 7) point to low degree partial melting at shallow depths and low garnet in the source magma. The source magma formed by 2 to 5% partial melting of a spinel-garnet lherzolite source (low garnet) accompanied by crustal contamination.

The study area is located about 220 km southwest of Mashhad and 80 km south of Neyshabur, at 54° 42' 15" to 54° 43' 40" longitude. Initially, remote sensing is carried out based on the SAM method and it denotes propylitic, carbonitization, silicification and argillic alterations. This area comprises of outcrops of Paleocen-Eocene volcanics. Golcheshmeh area also shows copper mineralization at surface such as malachite, chrysocolla and chalcocite. The copper minerals are seen as filling voids and thin veinlets in association with volcanic rocks in the study area. In some parts of the district, the movement of copper solutions is controlled by linear structures and fault zones, and the amount of solutions’ penetration-which differs from a few centimeters to several meters - in the host rocks is dependent on the wall rock composition, texture and the volume of the solutions. Based on the analysis, 80% of the samples show more than 1% copper.