حسین حاجی میرزاجان

IntroductionThe Dehzaman iron deposit is located in the Northeast of Kashmar- Kerman tectonic zone (KKTZ) (Ramezani and Tucker, 2003), southwest of Bardaskan in the Khorasan Razavi province. Mineralization are in two type: 1- Hematite ore (that is extracted for decades) 2- Magnetite ± Specularite and Magnetite - Specularite associated with apatite veins. Metarhyolite- Metarhyodacite units with low magnetic susceptibility are the most important host rocks in the study area. In the present paper, we provide an overview of the geological, alteration and mineralization characteristics, particularly the results of REE Geochemical data and Ground Magnetic data to explore the Magnetite ± Specularite veins. Identification of these characteristics can be used as a model for exploring this type of iron mineralization in the KKTZ specifically and elsewhere.
Materials and methodsDetailed field work was carried out in the Dehzaman study area. A total of 95 polished blocks and thin sections were prepared and studied from host rock, mineralization and altered zones, and geology, mineralogy and alteration maps were prepared by conventional petrographic and mineralogical methods at the Department of Geology of the Ferdowsi University of Mashhad. In addition, 9 samples from the ore zones (Magnetite ± Specularite and Magnetite – Specularite) were analyzed by ICP-MS for minor and trace elements and REE content at ACME lab, Canada. Also in order to determine the iron ore grade, 7 samples were analyzed by titration methods. Magnetic susceptibility of ore veins and host rocks was measured in order to determine the magnetic susceptibility contrast, and then ground magnetic survey was carried out with Geometrics G856. Total magnetic Intensity was measured at 2223 stations, processed and interpretation maps were prepared. Finally, magnetic anomalies in the eastern and central parts of the study area were interpreted.
ResultsIn the northeast of KKTZ, the outcrops of Precambrian to Neogene lithological units are observable. Metamorphosed volcano-sedimentary series of the Dehzaman mine area, all belong to the Upper Neoproterozoic- Lower Cambrian and are considered as low-grade regional metamorphism and deformation of high tectonic activity.
Outcrop Rock units in the Dehzaman area consist of slate-phylite, Recrystallized carbonate units (Dolomite and limestone), Sericite schist, metavolcanic units, Mylonitic granite, Seynogranite. Metavolcanic units consist of Metarhyolite to metarhyodacite with porphyritic textures which hosts iron ore. Mineralization in the Dehzaman area consists of Magnetite and Specularite associated with apatite and lower amounts of chalcopyrite and Malachite.
The structure of the area plays an important role in iron mineralization (Magnetite ± Specularite and Magnetite – Specularite) which occurs as vein and veinlet and multiple displacement of it are the result of this tectonic activity. Alteration is mainly limited to Magnetite ± Specularite and Magnetite – Specularite mineralized zone and is classified into chlorite, carbonate, silisification, biotite and tourmalinisation. Chip composite result from mineral veins show a high anomaly of REE (10.44 to 4827 ppm). Increase in rare earth elements is directly related to increasing microcrystals or inclusions of apatite in the Dehzaman iron ore. LREE is enriched into MREE and HREE in all samples. The amount of rare earth elements and their normalized pattern in the Dehzaman iron ore are similar with high rare earth elements in iron oxide ores that are usually known as Kiruna type which shows LREE enrichment relative to HREE (Frietsch and Perdahl, 1995).
The higher magnetic susceptibility of magnetite ± Specularite and apatite-bearing Magnetite- Specularite in the center and east part respectively relative to volcanic host rocks has resulted in direct responses of mineralization from magnetic data. Integration of this data with geology, outcrop mineralization and filed survey delineated the trend, distribution and depth of magnetite mineralization. High anomaly of REE (in apatite) can also help us explore it indirectly from magnetic data. There is a weak magnetic response in mineral veins especially in the east and central parts of the deposit due to an increase of specularite. The result of ground magnetic survey in the eastern part of the veins shows an east-west anomaly in RTP image particularly at places which have no comparable outcrop. The width of mineralization is more than 20 meters in the northern and south eastern parts. Upward continued maps show the depth extension of the anomaly sources, mineralization to a depth of over 50 meters in the north and south of the eastern part. Based on magnetic anomalies and slope of veins, dip toward the east, 4 drilling locations to a maximum depth of 120 meters and at a vertical angle of 80 degrees in the hanging wall of faults associated with north and south magnetic anomalies are proposed in the eastern part of the Dehzaman deposit. Magnetic anomalies in the central part of the Dehzaman deposit show better correlation with surface outcrops because of higher concentration of magnetite in the veins. Anomalies here have an East-West trend with maximum width of 25 m in the central part. Upward continued images indicate that the depth of anomaly sources, mineralization, extend to over 50 meters.
Anomaly discontinuities in the middle of the central part are due to two faults, located to the right and left of the center, which caused the displacement of mineral zone after mineralization.
Based on magnetic anomalies and dip of the veins, two drilling locations to a maximum depth of 100 meters and at 80 degree angle are suggested in the eastern and western parts of central Dehzaman deposit.
AcknowledgementsThis project is sponsored by the Ferdowsi University of Mashhad in connection with a research project dated 5.3.2015 No. 3/36972 that has been done. This research was made possible by the help of Opal Kany Pars Co.

Dehzaman iron deposit is located southwest of Bardaskan, Khorasan Razavi province, and northeast of Kashmar-Kerman Tectonic Zone. Geology of the study area consists of late-Neoprotrozoic-lower Cambrian metamorphsed volcano-sedimentary units, including slate- phyllite, sericite schist, recrystallized carbonate rocks, metarhyolite-metarhyodacite and granitic intrusions. Mineralization is hosted by metarhyolite-metarhyodacite as vein-veinlet, massive, brecciate, and dessiminated forms. Magnetite, specularite (low Ti and V), apatite micrograins associated with chlorite, calcite, and quartz are the most important minerals at deposit. Minor chalcopyrite is present. Hematite and malachite are the main secondary minerals. The main alterations of the area are chloritic, carbonate, silicification, potassic and tourmalinization. Tectonic setting, host rock, mineralogy, alteration, and structure and texture of this part of Dehzaman deposit have the most similarity with the Kiruna type iron deposits

The Roud Gaz area is located 25 km southeast of Gonabad city، Khorasan Razavi province. During Middle Jurassic، shale and sandstone was regionally metamorphosed to slate، schist and quartzite. The Tertiary subvolcanic rocks are mainly monzodiorite to monzonite. These rocks are mostly altered to: argillic، carbonisation، sericitic and silicification- tourmalinisation. Mineralization in the area is mostly as vein type and controlled by fault zones which are trending NW-SE and 85º to 90º dip. The primary minerals are quartz، tourmaline، chalcopyrite، pyrite and the secondary minerals are malachite، azurite and goethite. Lithogeochemical exploration (chip composite method) revealed Cu، Sn، Pb، As (up to 10000 ppm)، Zn (up to 5527 ppm) and Au (up to 325 ppb) anomalies. The least altered rocks are chemically meta-aluminous and medium-potassium. They were formed in a subduction magmatic arc and are strongly enriched in LREE and depleted in HREE and also LILE (K، Rb، Ba، Sr and Th) enriched rather than HFSE (Ti، Nb and Ta)، all features indicate that the magma formed in subduction zone. The positive Eu anomaly، high Sr (411 to 684 ppm) and high (La/Yb) N ratio (more than 21. 55) in all the samples can be attributed to the presence of residual garnet in mantle source. Based on high Sr/Y ratio (more than 67)، Y<8 ppm، Yb<0. 61 ppm and high (La/Yb) N ratio، the parent magma is adakitic type. The magma formed as the result of medium degree of partial melting (25%) from a garnet-amphibolite source. Apparently، these rocks have been only the veins host and have no effect on mineralization. The mineralization of the area is polymetal vein type and related to reduced intrusions in deeper zone.

Roudgaz prospect area is a Cu، Sn، Pb، Zn، and Au polymetal vein system located to the southeast of Gonabad and in the northeast of Lut block. Oxidan subvolcanic Tertiary rocks with monzonite to monzodiorite porphyry composition intruded the metamorphic rocks of middle Jurassic. The majority of intrusive bodies are affected by carbonation، argillic، sericitic، and silicification-tourmaline alteration. Mineralization in the area is controlled by fault and is present as vein with domination of NW-SE direction and 85-90º dip. Primary minerals are quartz، tourmaline، chalcopyrite، pyrite، and secondary minerals are malachite، azurite، and goethite. Geochemical sampling using chip composite method indicated high anomalies of Cu، Sn، Pb، and As (up to 10000 ppm)، Zn (up to 5527 ppm)، and Au (up to 325 ppb). Broad gossan zone is present in the area and is related to the oxidation of sulfide minerals. IP/RS survey was performed over the geochemical anomalies for identification of the location and extension of sulfide mineralization at depth. Generally، chargeability increases in gossan zones، veins، old workings and geochemical anomalies. Resistivity over the quartzite unit and also in locations where mineralized vein is associated with quartz has a high anomaly of up to 425 ohm-m. Due to high geochemical anomaly of Sn and its relation with reduced subvolcanic intrusives، ground magnetic survey was performed to identify the location of magnetite (oxidant) and ilmenite (reduced) series at depth. Variation of Total Magnetic Intensity (TMI) is 335. 1 Gamma in the TMI map. The highest magnetic anomalies in the RTP map are located to the north of the survey area which is related to magnetite series (hornblende biotite monzodiorite porphyry) and extend to the south at depth. The lowest magnetic anomaly is located to the center of the survey area and particularly to the east of the Roudgaz village correlating the highest chargeability and geochemical anomaly. Based on coincidence of geochemical and chargeability anomalies، two holes were drilled in the area and 24 samples were collected from the core drills for geochemical analyses. The highest anomalies are accompanied by silicification and chlorite alteration and locations of extension of secondary Fe oxides.