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Introduction The Garmab copper deposit is located northeast of Qaen (South Khorasan province) in the1:100,000 scale map of Abiz in the eastern tectonic zone of Iran. It is hosted by Late Paleocene-Eocene lava flows consisting mainly of andesite, trachy¬andesite, andesite-basalt and basalt lavas, as well as pyroclastic rocks, including tuffs and ignimbrites. The Lut Block has undergone intense magmatic activitywith a variety of geochemical characteristics due to changing tectonic conditions (e.g., compression during subduction followed by tensional conditions; Karimpour et al., 2012; Zarrinkoub et al., 2012). The Lut Block has a great potential for the discovery of new mineral deposits, like the Mahrabad and Khonik porphyry copper-gold deposits (Malekzadeh shafarodi, 2009), the Dehsalam porphyry copper deposit (Arjmandzadeh, 2011), high sulfidation epithermal gold deposits such as Chah Shalghami (Karimpour, 2005) and IOCG deposits such as Kuh-E-Zar and Qaleh Zari (Mazlomi et al., 2008). Materials and methods After field studies of the Garmab area, 32 thin sections and 21 polished sections were prepared for petrological and mineralogical studies.In addition, 10 least-altered and fractured samples of volcanic rocks were selected for geochemical studies. Major oxides were determined using XRF analyses at the Zarazma laboratory. Induced polarization and resistivity geophysical data were collected and correlated with geological and alteration maps. The geophysical datawere collectedfrom 420 individual points, using a dipole-dipole arrangement along five profiles separated 60m apart.This covered the study area entirely. After a change in the mineralization trend was observed,additional profileswere designed, twoon bearings of 25º and three on 75º. Results The Garmab volcanic rocks exhibit typical geochemical characteristics of subduction zone magmas including strong enrichment in LILE and depletion in HFSE. Based on the discrimination plot of Irvine and Baragar (1971), all samples belong to the calc-alkaline series, and based on the TAS diagram of Cox et al., 1979, the volcanic ore host rocks of Garmab range from andesite to basaltic andesite to trachyandesite. Hydrothermal alteration, associated with deposition of copper sulfide mineralization, occursmostly along the fault zones. .Mineralization also occurs disseminated and as veinlets, restricted to uppermost parts of the volcanic sequences. The deposit has the form of a layer of supergene enrichment characterized principally by chalcocite as the main ore mineral accompanied by digenite, covellite, bornite and chalcopyrite. The locationof the anomalies has been determined from their medium chargeability and low to medium resistivity values. This can be attributed to the presence of sulfide minerals in the mineralized zones. The average sulfide mineral grain size was determined using the results of time constant parameter. Since the results of raw data do not indicate accurate information about the depth and geometry of mineralization, smooth inverse modeling was applied to determine probable zones and vertical and horizontal extension of mineralization.Geophysical studies show that zones of mineralization are small and scattered. Acknowledgements This research was made possible by the help of the Zarnab exploration consultant engineers and Kani Kavan Samangan. References Arjmandzadeh, R., 2011. Studies of mineralization, geochemistry and tectonic setting in the Dehsalam and Chahshlghmy mining indexes, Lut Block, East Iran. Ph.D. Thesis, Ferdowsi University of Mashhad, Mashhad, Iran, 369 pp (in Persian with English abstract). Cox, K.G., Bell, J.D. and Pankhurst, R.G., 1979.The interpretation of igneous rocks. George, Allen and Unwin, London, 449 pp. Irvine, T.N. and Baragar, W.R.A., 1971. A guide to the classification of the common volcanic rocks. Journal of Earth Sciences, 8 (2): 235-458. Karimpour, M.H., 2005. Quartz-alunite and quartz pitted alteration zones (high sulfidation) of the upper zone of porphyry copper systems in Chah Shalghami area, South Khorasan. 13th Congress of Crystallography and Mineralogy, Bahonar University of Kerman, Kerman, Iran. Karimpour, M.H., Malekzadeh shafarodi, A., Farmer, L. and Stern, S., 2012. petrogenesis of granitoids, age assessment method zircon U-Pb, Sr- Nd isotope geochemistry and mineralization Tertiary important event in the Lut Block, East Iran. Journal of Economic Geology, 1(4): 1-27 (in Persian with English abstract). Malekzadeh shafarodi, A., 2009. Geology, mineralization, alteration, geochemistry, interpretation of geophysical data, microthermometry, isotope studies and determination of the origin of the mineralization of Mahrabad and khonik, South Khorasan province. Ph.D. Thesis, Ferdowsi University of Mashhad, Mashhad, Iran, 600 pp. Mazlomi, A. R., Karimpour, M.H., Rassa, I., Rahimi, B. and Vosoughi Abedini, M., 2008. Kuh-E-Zar Gold Deposit in Torbat-e-Heydaryeh New Model of Gold Mineralization. Iranian Journal of Crystallography and Mineralogy, 3(16): 364-376 (in Persian with English abstract) Zarrinkoub, M.H., Pang, K.N., Chung, S.L., Khatib, M.M., Mohammadi, S.S., Chiu, H.Y. and Lee, H.Y., 2012. Zircon U–Pb age and geochemical constraints on the origin of the Birjand ophiolite, Sistan suture zone, eastern Iran. Lithos. 154(1): 392–405. |
