Journal of Economic Geology

97-110

Authors: Farid Moore; Saleh Deymar; Batoul Taghipour

Most skarn deposits are directly related to magmatic activity, and there is a systematic correlation between composition of causative plutons and the metal contents of the related skarns. Darreh Zerreshk deposit is located in southwest of Yazd. Petrological and geochemical studies show that Darreh Zerreshk granitoid ranges in composition from granite through quartz monzodiorite and has subalkaline, calc-alkaline and metaluminous to prealuminous characteristics like most worldwide skarn granitoids. This study shows that geochemical characteristics of the Darreh Zerreshk granotoid rocks are similar to granitoids of Millstream Cu-Fe skarn deposit in Canada, Fe skarns in British Columbia and Au-Cu skarns in the RioNarcea gold belt in Spain. The similarity between REE patterns in Darreh Zerreshk intrusion and skarns also confirms the strong petrogenetic relationship between magmatic and skarnization processes.

127-145

Authors: Mehrab Moradi; Mohammad Hasan Karimpour; J Eleng Farmer; Charlz Stern

The study area is located south of Ghonabad in Eastern Iran. This area is situated between two major faults, Darouneh to the north and Dashtbyaz to the south. The movements of these faults cased major dislocation of this block. Najmabad granodiorite to granite batholith is elongated trending east-west 2×8 Km2. Mineralization is associated with granite and monzonite. Alteration zones are: propylitic, sericitic, argillic and silicification. Chemically, granite-granodiorite is met-aluminous,, spider diagram normalized to lower continental crust show enrichment of LILE such as Rb, Cs, K and LREE (La, Ce) , depletion of Ti, Sr, Ta, Nb, Ba, Cs. Based on low values of magnetic susceptibility [(5 to 11) × 10-5 SI], therefore it is classified as belonging to the ilmenite-series (reduced type).The result of U-Pb zircon age dating of granodiorite is 161.85 Ma (Middle Jurassic, Callovian time). Based on Initial εNd isotope values for granodiorite is -6.51, initial 87Sr/86Sr and 143Nd/144Nd ratios for granodiorite is (0.70913 and 0.512095), the magma for granite and granodiorite originated from the continental crust. During Middle Jurassic (Callovian) due to continental collision, Upper Triassic to Lower Jurassic rocks is regionally metamorphosed. During the continental collision, Middle Jurassic (164-162Ma) reduced type granitoid magma (Ilmenite series, continental crust melting) formed and intruded these regional metamorphosed rock in Najmabad, Shah Kuh and Sorkh Kuh area.

165-181

Authors: Ali Abedini; Rahim Masumi; Ali Asghar Calagari

Kajal kaolin deposit is located ~20 km northwest of Hashtjin, Ardebil province. Field evidence and laboratory investigations show that the deposit is an alteration product of ignimbrites, tuffs, and trachy-andesites of Eocene age. According to mineralogical data, the major rock-forming minerals include kaolinite, montmorillonite, polygorskite, orthoclase, zeolite (stilbite), quartz, and chalcedony. Mass change calculations of elements, with assumption of Ti as immobile monitor element, indicate that leaching and fixation are two prominent regulators for concentration of major, minor, trace, and rare earth elements in the deposit. The distribution pattern of REEs, normalized to ignimbrite, in kaolin samples illustrates a weak fractionation of LREEs from HREEs coupled with strong negative Eu anomaly during the evolution of the deposit. Calculations of correlation coefficients among elements show that there is a high intrinsic correlation between HREEs in the studied samples. According to geochemical indices, it can be inferred that the hypogene alterations are superimposed by supergene ones in the course of evolution of the deposit. In accordance with the mode of distribution of elements in the deposit, it appears that the behavior of elements during kaolinization of ignimbrites was affected by the function of factors such as pH, redox potential, temperature variations, high fluid to rock ratio, preferential adsorption by clays and iron oxides, discrepancies in the stability rate of minerals, abundance of complex-forming ions (CO32-, F־, Cl־, PO43-, and SO42-), and isomorphic substitution. The obtained results indicate that epithermal acid-sulfate solutions along with acidic supergene solutions originated from oxidation of hypogene pyrites played an important role in development of the deposit. Further geochemical considerations show that clay minerals along with secondary phosphates like monazite, rabdophane, and xenotime are the potential hosts for REEs in the deposit.

193-216

Authors: Mohammad Hasan Karimpour; Azade Malekzadeh Shafaroudi; Akbar Esfandiarpour; Hasan Mohammad Nejad

Neyshabour turquoise mine is located in northwest of Neyshabour, southern Quchan volcanic belt. Eocene andesite and dacite forming as lava and pyroclastic rocks cover most of the area. Subvolcanic diorite to syenite porphyry (granitoids of magnetite series) intruded the volcanic rocks. Both volcanic and subvolcanic rocks are highly altered. Four types of alteration are recognized including: silicification, argillic, calcification and propylitic. Silicification is dominant followed by argillic alteration. Mineralization is present as stockwork, disseminated and hydrothermal breccia. Hypogene minerals are pyrite, magnetite, specularite, chalcopyrite, and bornite. Secondary minerals are turquoise, chalcocite, covellite, and iron oxides. A broad zone of gossan has developed in the area. Oxidized zone has a thickness of about 80 m. Mineralized samples show high anomalies of Cu, Au, Zn, As, Mo, Co, U, LREE, Nb, and Th. Both aeromagnetic and radiometric (U and Th) maps show very strong anomalies (10 × 5km) within the mineralized area. Based on geology, alteration, mineralization, geochemistry, and geophysics, Neyshabour turquoise mine is a large Iron oxide Cu-Au-U-LREE (IOCG) mineralized system. In comparison with other IOCG deposits, it has some similarities with Olympic Dam (Australia) and Candelaria (Chile). In comparison with Qaleh Zari and Kuh Zar mines, Neyshabour turquoise mine is the first Iron oxide Cu-Au-U-LREE (IOCG) mineralized system discovered in Iran.

231-249

Authors: Vahideh Alipour; Ali Abedini

The Zonouz kaolin deposit is located ~15 km northeast of Marand, East-Azarbaidjan province. Based on physical features in field investigations, such as color, five distinct kaolin types including (1) white, (2) lemon, (3) gray, (4) brown, and (5) yellow are distinguished in the deposit. Field evidence and petrographic studies indicate that the deposit is genetically close to trachy-andesite rocks. According to mineralogical data, the deposit contains quartz, kaolinite, montmorillonite, calcite, pyrophyllite, chlorite, muscovite-illite, dolomite, hematite, and anatase minerals. Geochemical data indicate that function of alteration processes on trachy-andesite rocks during development of Zonouz ore deposit was accompanied by leaching of elements such as Al, Na, K, Rb, Ba, V, Hf, Cu, Zr, Tm, Yb, and Lu, enrichment of elements such as U, Nb, and Ta, and leaching-fixation of elements such as Si, Fe, Ca, Mg, Ti, Mn, P, Cs, Sr, Th, Co, Cr, Ni, Y, Ga, LREE, Tb, Dy, Ho, and Er. Incorporation of obtained results from mineralogical and geochemical studies show that physico-chemical conditions of alteration environment, the relative stability of primary minerals, surface adsorption, preferential sorption by metallic oxides, existing of organic matters, scavenging and concentration processes, and fixation in neomorphic mineralogical phases played important role in distribution of elements in the deposit. Geochemical studies show that development of the deposit is relative to two types of processes, (1) hypogene and (2) supergene. The distribution pattern of REEs indicates that differentiation degree of LREEs from HREEs in supergene kaolins is more than hypogene kaolins. Geochemical studies indicate that minerals such as Mn-oxides, zircon, anatase, hematite, cerianite, and secondary phosphates (monazite, rhabdophane, churchite, and zenotime) are the potential hosts for rare earth elements in this deposit.