Identifying areas of high economic-potential copper mineralization using aster data in the urumieh-dokhtar volcanic belt, Iran

Extraction of hydrothermal alterations from ASTER SWIR data from east Zanjan, northern Iran

This paper provides a review of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Advanced Land Imager (ALI), and Hyperion data and applications of the data as a tool for ore minerals exploration, lithological and structural mapping. Spectral information extraction from ASTER, ALI, and Hyperion data has great ability to assist geologists in all disciplines to map the distribution and detect the rock units exposed at the earth’s surface. The near coincidence of Earth Observing System (EOS)/Terra and Earth Observing One (EO-1) platforms allows acquiring ASTER, ALI, and Hyperion imagery of the same ground areas, resulting accurate information for geological mapping applications especially in the reconnaissance stages of hydrothermal copper and gold exploration, chromite, magnetite, massive sulfide and uranium ore deposits, mineral components of soils and structural interpretation at both regional and district scales. Shortwave length infrared and thermal infrared bands of ASTER have sufficient spectral resolution to map fundamental absorptions of hydroxyl mineral groups and silica and carbonate minerals for regional mapping purposes. Ferric-iron bearing minerals can be discriminated using six unique wavelength bands of ALI spanning the visible and near infrared. Hyperion visible and near infrared bands (0.4 to 1.0 μm) and shortwave infrared bands (0.9 to 2.5 μm) allowed to produce image maps of iron oxide minerals, hydroxyl-bearing minerals, sulfates and carbonates in association with hydrothermal alteration assemblages, respectively. The techniques and achievements reviewed in the present paper can further introduce the efficacy of ASTER, ALI, and Hyperion data for future mineral and lithological mapping and exploration of the porphyry copper, epithermal gold, chromite, magnetite, massive sulfide and uranium ore deposits especially in arid and semi-arid territory.

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ASTER, ALI and Hyperion sensors data for lithological mapping and ore minerals exploration

The Sanandaj-Sirjan Zone (SSZ) trends northwestward in western Iran on the Precambrian to Paleozoic basement and exposes abundant I-type granitoids and calc-alkaline volcanic rocks that were most active during the Late Jurassic to Upper Cretaceous. The petrogenesis of the granitoids and associated volcanic rocks has been widely related to Neotethyan subduction beneath the Iranian plate. We report a geochronological and geochemical study of the Suffi abad granite (SLG) body that crops outs southeast of Sanandaj within the SSZ and is mainly composed of K-feldspar + quartz + plagioclase ± hornblende. The SLG, which shows a high-K calc-alkaline affinity, has LA-ICPMS zircon U–Pb ages ranging between 149 ± 2 and 144 ± 3 Ma and initial 87 Sr/ 86 Sr of ∼0.7024–0.7069 and 143 Nd/ 144 Nd of ∼0.5125–0.5127. These value correspond to an ɛ Nd (145 Ma) of +1.5 and +4.9, suggesting that the SLG originated from the juvenile crust or depleted mantle with a young T DM (650–900 Ma) over the subduction zone beneath the SSZ. Zircon saturation temperatures suggest that crystallization of the zircons, or emplacement of the host magmas, occurred at 560–750 °C, consistent with an intergrowth texture of K-feldspar and quartz that implies crystallization around the K-feldspar-quartz eutectic at lower temperatures. Overall, geochemical data suggest that crystallization of the hornblende and plagioclase played a role in magma differentiation. These data allow us to conclude that the high-K SLG did not originate directly from the juvenile mantle source as do most I-type, calc-alkaline granitoids, but more likely was produced from the partial melting of pre-existing I-type granitoids in the upper continental crust under low pressure conditions.

Geochronological and geochemical constraints on the petrogenesis of high-K granite from the Suffi abad area, Sanandaj-Sirjan Zone, NW Iran

One of the most important characteristics of porphyry copper deposits (PCDs) is the type and distribution pattern of alteration zones which can be used for screening and recognizing these deposits Hydrothermal alteration minerals with diagnostic spectral absorption properties in the visible and near-infrared (VNIR) through the shortwave infrared (SWIR) regions can be identified by multispectral and hyperspectral remote sensing data Six Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) bands in SWIR have been shown to be effective in the mapping of Al-OH, Fe-OH, Mg-OH group minerals The five VNIR bands of Landsat-8 (L8) Operational Land Imager (OLI) are useful for discriminating ferric iron alteration minerals In the absence of complete hyperspectral coverage area, an opportunity, however, exists to integrate ASTER and L8-OLI (AO) to compensate each other’s shortcomings in covering area for mineral mapping This study examines the potential of AO data in mineral mapping in an arid area of the Duolong porphyry Cu-Au deposit(Tibetan Plateau in China) by using spectral analysis techniques Results show the following conclusions: (1) Combination of ASTER and L8-OLI data (AO) has more mineral information content than either alone; (2) The Duolong PCD alteration zones of phyllic, argillic and propylitic zones are mapped using ASTER SWIR bands and the iron-bearing mineral information is best mapped using AO VNIR bands; (3) The multispectral integration data of AO can provide a compensatory data of ASTER VNIR bands for iron-bearing mineral mapping in the arid and semi-arid areas

Integrating Data of ASTER and Landsat-8 OLI (AO) for Hydrothermal Alteration Mineral Mapping in Duolong Porphyry Cu-Au Deposit, Tibetan Plateau, China

Magnetite–apatite deposits in the Alborz volcano–plutonic belt, southeast Zanjan, in Iran, have blade, lenzoid, and vein forms, which extend in an E-W direction. There are many magnetite–apatite veins and veinlets in this region, and some of them are economically important, such as Zaker, Morvarid, Sorkheh–Dizaj, and Aliabad. The sizes of the vein orebodies vary between 2 and 16 m in width, 10–100 m in length, and 5–40 m in depth. Microscopic examination of thin sections and polishes indicate that they are composed of magnetite and apatite, with minor amounts of goethite, hematite, actinolite, quartz, muscovite–illite, talc, dolomite, and calcite. The geochemistry and mineralogy of the granitic host rock reveals that it is calc-alkaline and I-type. Field observations, mineral paragenesis, the composition of the orebodies, and the composition of the fluid inclusions in the apatite minerals with low salinity (less than 20 wt.% NaCl equivalent) indicate that these magnetite veins were hydrothermally generated at about 200–430°C and are not related to silica–iron oxide immiscibility, as are the major Precambrian magnetite deposits in central Iran.

Genesis of Tertiary Magnetite–Apatite Deposits, Southeast of Zanjan, Iran

The study area is northwest part of Sanandaj–Sirjan or Esfandegha–Marivan zone in the northwest of Iran. The oldest rocks which are limestone, sandstone, tuff, and lava belong to the Jurassic which have deformed during the Late Cimmerian orogeny. This complex is unconformably overlain by Cretaceous volcano sedimentary. The dominantly Cretaceous outcrops are limestone, shale, tuff, and basic to intermediate volcanic rocks. The Jurassic complex was locally metamorphosed by granitoid intrusions during the Cretaceous. Geochemical interpretations show some differences in magmatic activity in the Jurassic and Cretaceous periods. Furthermore, the chemical composition confirms the alkaline to calc alkaline trend for these two major groups. In petro-tectonic diagrams, they plot in the extensional and active margin tectonic regime. The existence of a few hundred meters of Jurassic lava with interbeded sediments, which have deformed in the Late Cimmerian orogeny infer the simultaneous existence of extension and subsidence during the Jurassic and so a compression regime in the late Jurassic (Late Cimmerian). Based on our findings, this area shows sporadically occurring extension and compression tectonic regimes over the subduction zone in the Jurassic and Cretaceous such as Cordilleran belt.

Afshin Akbarpour

Papers

Extraction of hydrothermal alterations from ASTER SWIR data from east Zanjan, northern Iran

Genesis of Tertiary Magnetite–Apatite Deposits, Southeast of Zanjan, Iran

Mesozoic magmatism in the northwestern Sanandaj–Sirjan zone as an evidence for active continental margin