Economic Geology
Robabeh Masoomi; Yousef Rahimsouri; Hemayat Jamali; Ali Abedini
Abstract
The aim of this research is the geochemical study of the major and trace elements of the alteration systems in the Kamar-Gov district (south of Hashtjin, Ardabil province). The rock units of the studied area include volcanic rocks with the composition of basaltic-trachy andesite to rhyolite and ...
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The aim of this research is the geochemical study of the major and trace elements of the alteration systems in the Kamar-Gov district (south of Hashtjin, Ardabil province). The rock units of the studied area include volcanic rocks with the composition of basaltic-trachy andesite to rhyolite and crystal vitric-tuff with Eocene and Oligocene age. These rocks have calk alkaline and shoshonitic affinity and belong to post-collisional arc tectonic setting. In the Kamar-Gov district, the alteration zones include silicic, sericitic (quartz + muscovite + pyrite ± illite ± rutile), sericite-argillic (quartz + sericite + kaolinite + dolomite), intermediate argillic (quartz + kaolinite + illite), advanced argillic (quartz + kaolinite + alunite + diaspore ± anatase ± muscovite), and chloritic (quartz + chlorite + illite). The distribution pattern of the normalized-BSE major and trace elements and the mass change calculations (volume factor method) show that the silicic and advanced argillic alteration zones have more elemental depletion and different distribution patterns from the parent rock. However, chloritic, intermediate argillic, and sericite-argillic alterations have relatively little mass change and almost similar distribution patterns to the primary parent rock. The major elements like Ca, Mg, Al, Na, and Fe have frequently depleted. Ti shows slight depletion. K has frequently enriched. Trace elements such as Zr, Nb, Sc, and Th have mass reduction. Co, Cr, Ni, and Rb have experienced depletion and enrichment processes. Sr and V show relatively high depletion. Sb, S, and As (chiefly) have enriched. LREEs have depleted more than HREEs. Elements like Pb, Zn, and Cu only in the siliceous and sericite-argillic zone show enrichment. This research shows that factors like pH of hydrothermal fluid and primary rock-forming and secondary minerals resulting from alteration have caused differences in the behavior and concentration of elements in different alteration zones in the Kamar-Gov district.
Economic Geology
Robabe masoomi; Yoseph Rahimsouri; Hemayat Jamali; Ali Abedini
Abstract
The action of alteration processes on the Eocene tuffs has led to the formation of a spread argillic alteration zone in the Kamar district (south of Ardebil, Tarom-Hashtjin Zone). The aim of this study is to determine the factors controlling argillic alteration, using mineralogical studies and chemical ...
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The action of alteration processes on the Eocene tuffs has led to the formation of a spread argillic alteration zone in the Kamar district (south of Ardebil, Tarom-Hashtjin Zone). The aim of this study is to determine the factors controlling argillic alteration, using mineralogical studies and chemical alteration indices. Quartz, kaolinite, muscovite (sericite), rutile, anatase, illite, diaspore, alunite, albite, clinochlore, jarosite, gypsum, pyrite, orthoclase and dolomite are the mineral assemblage of this alteration zone. The mineralization of sulfides includes pyrite (predominantly), chalcopyrite, borneite, chalcocite, galena, and sphalerite. The chemical index of alteration (CIA) values are between 51.55 to 74.3 %, and the mineralogical index of alteration (MI) values vary from 8.22 to 48.3%. The mafic index of alteration (MIA(O)) ranges from 55.88% to 87.48%, Depletion of a large number of elements, including some immobile elements (Zr, Y, V, Al and LREEs), the presence of minerals indicating acidic pH, such as jarosite and alunite, and high-temperature minerals such as rutile and anatase, the presence of the vuggy quartz in some altered regions, and concomitant enrichment of As, Sb and Mo, in the Kamar argillic zone, bear similarities to the hot fluid alterations of high-sulfidation epithermal deposits.
M Norouzi; M. Lotfi; M. H. Emami; H. Jamali; A. Abedini
Abstract
Mesgarabad area is located in ~10 km southeast of Tehran, the Central- Alborz structural zone (CASZ) of Iran. The rock units exposed in the area consist of Eocene volcanics, volcano-sedimentary and sedimentary rocks intruded by post upper Eocene granodiorite to quartz monzo-diorite. These subvolcanic ...
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Mesgarabad area is located in ~10 km southeast of Tehran, the Central- Alborz structural zone (CASZ) of Iran. The rock units exposed in the area consist of Eocene volcanics, volcano-sedimentary and sedimentary rocks intruded by post upper Eocene granodiorite to quartz monzo-diorite. These subvolcanic intrusive bodies show porphyroid to microgranular textures and have calc-alkaline magmatic nature. These bodies produced hydrothermal fluids causing extensive alteration zones developed along the Se-Darreh-e-Bozorg strike-slip fault. The effects of hydrothermal fluids on the entire Eocene rock units and subvolcanic intrusive bodies are remarkable. The main alterations are silicification, sericitization, chloritization, epidotizaton, actinolitization, argillization, carbonatization, and alunitization-jarositization, which provided suitable physico-chemical conditions for ore-mineralization. The penetration of subvolcanic intrusive bodies into the Eocene volcanics, volcano-sedimentary and sedimentary rocks brought about skarn mineralization and epithermal barite veins. Microscopic studies and advanced analysis showed that the principal mineral phases in the epithermal zones are magnetite, pyrite, chalcopyrite, bornite, chalcocite, barite, Cu+Sn+Fe alloy, hematite, psilomelane, jacobsite, martite, geothite, and lepidochrosite. The skarnification processes occurred at two distinct stages, (1) progressive and (2) retrogressive. The pyrometasomatic anhydrous minerals such as andradite-grossularite formed during progressive stage and the hydrous minerals like epidote, chlorite, tremolite- actinolite, calcite, quartz, pyrite, chalcopyrite and chalcocite were developed during retrogressive stage. Fluid inclusion studies on primary aqueous inclusions trapped in barite crystals revealed fluid that mixing of two fluids having different physico-chemical conditions played an important role for ore deposition.
H. Jamali; A. Yaghubpur; B. Mehrabi
Abstract
Miveh – Rud area is located 50 km north of Tabriz and 65 km west of Ahar at 36ْْ 33′ 02″to 38ْ, 34′ 52″ N and 46 ْْ 12′ 20″ to 46 ْْ 14′ 35″ E. The oldest rock unit in the area includes a thick sequence of Paleocene sedimentary rocks comprising ...
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Miveh – Rud area is located 50 km north of Tabriz and 65 km west of Ahar at 36ْْ 33′ 02″to 38ْ, 34′ 52″ N and 46 ْْ 12′ 20″ to 46 ْْ 14′ 35″ E. The oldest rock unit in the area includes a thick sequence of Paleocene sedimentary rocks comprising of sandstone, shale, siltstone, marl and marly limestone that have been intruded by a porphyritic intrusive body and dykes of granodioritic to diabasic composition (probably Oligocene in age). The intrusive rocks resulted in the formation of hornfels, skarn and alteration in Paleocene rocks. All of the mentioned rock units are unconformably covered by Pliocene age trachyte, trachyandesite. Alteration of potassic, sericitic, argillic, propylithic and silicification types occurred in the subvolcanic and sedimentary rocks, while there is no observed alteration in the volcanic cover. Anomalies of Au, Ag, Sb, Cu, Bi, W and Mo detected by geochemical investigations are confirmed by field evidences.
The anomalies of Sb, Ag, Au and As are located in the northern part, while the Cu, Co, W and Mo anomalies are in the southern part of the area. The degree of the contact metamorphism decreases toward the north and the potassic alteration can be shown mostly in the southern part of the area. This may suggest uplift and erosion of the southern part compared to northern part of the studied area. Composite halos of As, Pb, Ag / Cu, W and Co confirm the results.The mineralization includes formation of skarn, epithermal and sheeted veins. The epithermal veins cut the skarn and other contact metamorphic rocks.
