The study area is located in northwestern Iran in the central Iran zone, specifically the western Alborz sub-zone south of the Tarom-Hashtjin metallogenic zone. The exposed rock units in this area generally include Eocene volcanic rocks (lava flows and pyroclasts belonging to the Karaj formation) and Oligocene granitoid intrusive bodies. The intrusive bodies in the area have a petrographic composition of granite, syenite and monzonite and are mostly metaluminous. The dual characteristics of these intrusives (for example, the behavior of elements such as Rb, P, Ga/Al, Y/Nb, K/ Na, and FeO/Fe2O3, the Rb/Nb ratios, the A/CNK molar ratios and the ACF and A/CNK-Fe2O3+FeO diagrams), some of which are consistent with the I nature and others with the S and A natures, show that the rocks are among hybrid granitoids and, in terms of the tectonic setting, lie within the WPG range. According to the Rb/Sr, Zr/Hf, K/Rb ratios, the granite melts that form the aforementioned bodies are not extremely evolved and have not undergone post magmatic activity, which would lead to mineralization. The Sm/Eu and Rb/Ba ratios and the behavior of Rb, Ba and Sr within the aforementioned granitoids show that the rocks are similar to average granitoids unrelated to Li, Be, Sn, W and Ta deposits; they fall within the range of barren granitoids but are partially fertile in Cu. El área de este estudio está localizada en el noroeste de la zona central de Irán, específicamente en el oeste de la subzona de Alborz y al sur de la zona metalogénica de Tarom-Hashtjin. Las unidades de roca expuesta en esta área se clasifican generalmente como rocas volcánicas del Eoceno (flujos de lava y piroclastos pertenecientes a la formación Karaj) y como cuerpos granitoides intrusivos del Oligoceno. Los cuerpos intrusivos en el área tienen una composición petrográfica de granito, sienita y monzonita mayormente metaluminosa. Las características duales de estas intrusiones (por ejemplo, el comportamiento de de elementos como Rb, P, Ga/ Al, Y/Nb, K/Na, y Feo/Fe2O3, los índice de Rb/Nb, la proporción molar de los A/CNK y los diagramas ACF y A/CNK-Fe2O3+FeO), algunas de las cuales son consistentes con la índole I y otras con las índoles S y A, muestran que las rocas son granitoides híbridos y, en términos de orden tectónico, subyacen en la cadena WPG. De acuerdo con los índices Rb/Sr, Zr/Hf, K/Rb, los granitos fundieron la forma de los cuerpos sin desarrollarse completamente y sin registrar actividad magmática posterior, lo que llevó a la mineralización. Los índices Sm/ Eu y Rb/Ba y el comportamiento del Rb, Ba y Sr al interior de los granitoides mencionados muestran que las rocas son similares al promedio de los granitoides no relacionados con los depósitos de Li, Be, Sn, W y Ta; estos se incluyen en el rango de granitoides estériles, pero son parcialemente fértiles en Cu. EARTH SCIENCES RESEARCH JOURNAL Eart Sci. Res. J. Vol. 18, No. 2 (December, 2014): 123 - 129 ABSTRACT RESUMEN Key words: Intrusive, Valis, Tarom, Hybrid, Barren. Palabras clave: Intrusión, Valis, Tarom, híbrido, estéril. Record Manuscript received: 06/08/2014 Accepted for publication: 09/09/2014 Study of the mineralization potential of the intrusives around Valis (Tarom-Iran) Mojtaba Bahajroy1, Saeed Takiֿ ² email: Taki_Saeed 2002@yahoo.com 1&2: Department of Geology, Lahijan Branch, College of Basic Sciences, Islamic Azad University, Lahijan, Iran. ORE DEPOSITS ISSN 1794-6190 e-ISSN 2339-3459 http://dx.doi.org/10.15446/esrj.v18n2.44799 http://dx.doi.org/10.15446/esrj.v18n2.44799 124 Mojtaba Bahajroy, Saeed Taki Introduction The study area is located in northwestern Iran and is part of the Alborz mountain range. Alborz itself is affected by the Alp-Himalayan orogeny and generally trends northwest-southeast. This area is geographically located between the eastern longitudes of 48º 30ʹ to 48º 40ʹ and northern latitudes of 37º to 37º 5ʹ. In terms of Iran’s structural division, this area is located in the western Alborz subzone in central Iran (Alavi, 1996) (figure 1), and from metallogenic point of view, it belongs to the multimetallic belt of Tarom-Hashtjin (Ghorbani, 2013). The Tarom-Hashtjin belt covers an area between Qazvin (west of Taleghan) and north-northwest of Mianeh; it is limited by the Manjil depression and Talesh Mountains to the north and by the Alborz-Zanjan-Mianeh axis to the south. In fact, this belt is structurally confined to the north by the Sefidrood fault, to the south by the continuation of the Tabriz–Soltanieh and Soltanieh–Takestan faults, and to the west by the Astara–Marivan fault (Ghorbani, 2013) (figure 1). Almost the entire study area is composed of Cenozoic volcanic, intrusive, and sedimentary rocks. The rocks along the Tarom-Hashtjin axis, which are considered equivalent to the Karaj Formation, are different from those in central Alborz in terms of the lithology and chemical composition because the lava flows do not consist only of volcaniclastic rocks along this axis and their compositions are more basic. In fact, the rocks in the Karaj Formation in central Alborz are predominantly acidic tuffs, while their equivalents along the Tarom-Hashtjin axis are mostly andesites and basaltic andesites. The ancient rocks in the Tarom-Hashtjin belt are not exposed within the central parts (Ghorbani, 2013), and the basement is mostly composed of Tertiary magmatic rocks. The volcanic rocks in the Tarom area vary from rhyodacite and dacite to basalt. These rocks are observed in the form of lava flows, tuffs and sometimes tuffites. According to the conducted studies, the following volcanic rocks have been observed in this belt: basalt, basaltic andesite, andesite, trachyte, latite, trachyandesite, dacite and rhyodacite ignimbrite and acidic to intermediate tuffs. Among these rocks, andesites are the most voluminous. Moein-Vaziri (1985) believed that most volcanic rocks from the Tarom-Hashtjin are potassic-alkaline, while some are sodic-alkaline or calc-alkaline. Most of the andesites are shoshonitic. The emplacement of Oligocene age acidic to intermediate intrusive bodies within the Eocene volcanic rocks and the existence of the mining indices of Zehabad, Barikabad, Khalifehlou, Aliabad and Golouje in the Tarom region along with vast alteration zones have caused this area to be geologically considered as a prime geological district for the detection and identification of metallic and non-metallic deposits (Ghorbani, 2013). The studies conducted by different researchers (Peyrovan H., 1992; Torkamani E., 1997; Moayyed M., 2001) show that the granitoid bodies in this zone are of the I type. Haj Alilou (2000) believed that the intrusive bodies have been emplaced at a depth between 1400 to 3000 m and their formation temperature ranged from 700 to 880 degrees centigrade. Because of the high water content and sulfur fugacity, the bodies managed to create very extensive hydrothermal alterations together with vein, veinlet and scattered mineralizations in tuffites and Eocene volcanic rocks. The magmatic series of these intrusive bodies are shoshonite and high K calc-alkaline and are of the I type (Ghorbani, 2013). Shallower bodies are observed in the form of prophyrite with the general composition of monzonite porphyry and occurred along with major bodies with important roles in mineralization and hydrothermal alteration. The structural geology features similar anticline and syncline axes, and faults trending east-west and northwest-southeast had important roles in the emplacement of intrusive bodies and the development of hydrothermal alteration areas. Sericitic, argillic (advanced, intermediate and weak), silicic, chloritic, propyltic, zeolitic and alunite alteration zones have been recognized along this axis. The igneous bodies, which have economic concentrations of either genetic or paragenetic chemical elements, generally show specific geochemical patterns (Beus, 1968), the identification of which potentially distinguishes metalliferous geological units from barren types. When determining the mineralization potential of felsic intrusive bodies, it is important to recognize their nature, which generally accompanies special types of ore deposits. To achieve this purpose and determine the mineralization ability of the granitoid bodies around Valis, petrography, petrology, and geochemical ratios and the distribution of major and rare elements have been studied; in addition, this granitoid body was compared with the world’s most well-known fertile and barren granitoid bodies. Figure 1. Location of the study area (red square) on Iran’s structural divisions map (Alavi, 1996). This area is located in Alborz in the Tarom- Hashtjin metallogenic zone according to the structural zoning implemented by Ghorbani (2013). Geological Setting This area is separated from the Talesh Mountains by Manjil Basin and from the Soltanieh Mountains by the Zanjan-Abhar Plain. The rock units in the area mainly include Eocene volcanic rocks (lava flows and pyroclasts belonging to the Karaj formation) and Oligocene granitoid intrusive bodies (figure 2). The volcaniclastic succession lithology in Tarom, as in other areas in Alborz, consists of green tuffs and shaly and sometimes calcareous intercalations. The Eocene volcanic rocks in the area include volcaniclastic and extrusive rocks. The extrusive rocks in this area include andesite, basaltic andesite, quartz trachyandesite and basalt, though the bulk of these rocks are basaltic andesites and quartz trachyandesite. Many intrusive bodies have been injected into Eocene volcaniclastic assemblages, so these bodies are post-Eocene (most likely Oligocene) in age. One characteristic of the Oligocene intrusive bodies is the creation of alteration areoles in Eocene volcaniclastics, and their hydrothermal phases have been generally accompanied by the formation of elements such as epithermal gold, copper, lead, zinc and kaolin. The main body is exposed at the surface in the form of a prolate batholith trending northwest- southeast. Subvolcanic bodies are mostly observed in dyke form. Most faults in the area generally trend northwest-southeast, but some faults trend northeast- southwest. The aforementioned bodies were injected along the structures and longitudinal faults in the highs in Tarom. Most structures in this area follow the fault system so that a set of alteration zones occurs along the faults. Figure 2. Simplified geological map of the study area (Davis et al, 1972). 125Study of the mineralization potential of the intrusives around Valis (Tarom-Iran) Methodology The rock samples were collected from the intrusive bodies in the study area. Forty-five thin sections were prepared for petrological study. To study the chemical characteristics, 11 of the most representative rock samples taken from the intrusives were selected for whole rock major oxide, trace element, and REE analysis and sent to ACME Company in Canada and the Atomic Energy Organization of Iran. At the ACME Company, the samples were first dried and then crushed and pulverized to pass a 200 mesh sieve. A lithium borate fusion and dilute nitric acid digestion of a 0.2 g sample pulp followed by ICP emission spectrometry was used to carry out the whole rock analysis for 11 major oxides and some minor elements. The loss on ignition (LOI) was obtained by sintering at 1000°C. Two separate ICP-MS analyses were done to determine the trace elements. The rare earth and refractory elements were collected from a lithium borate decomposition (same as that used for the major elements) to determine the total abundances. The precious and base metals and their associated pathfinder elements were generated from an aqua regia digestion (table 1). At the Atomic Energy Organization of Iran, the pulverized samples were mixed with boric acid and then pressed and analyzed using the XRF method (table 2). The geochemical data were processed using the Minpet 2.02 software. Because iron has been reported in its unseparated form, Irvine and Baragar’s (1971) method was used in this study to calculate the bivalent and trivalent iron. Table 1. Representative whole rock major oxides (wt %), trace elements (ppm) and rare earth elements (ppm) for samples from the intrusives around Valis (ICP-AES and ICP-MS) (implemented by the Acme Laboratory). B8B7B3B2B1 Sample no. Analyte 67.3656.8366.0068.9961.08SiO2 14.6416.3314.5014.3415.30Al2O3 3.596.293.823.115.58Fe2O3 0.463.391.080.651.38MgO 1.527.452.011.631.78CaO 3.223.293.583.012.64Na2O 7.333.996.726.407.49K2O 0.580.940.560.460.75TiO2 0.100.350.120.090.18P2O5 0.080.230.140.140.61MnO 0.0190.0110.0060.0190.007Cr2O3 20<20<20<20<2020, magmatic hydrothermal alteration has not occurred. The Zr/Hf ratio in the study area’s intrusives is between 33.8 and 44.4; therefore, magmatic hydrothermal alteration has not occurred. The Sm/Eu and Rb/Ba ratios and amounts of Rb, Ba and Sr in the intrusives around Valis are higher than those of the S type granite source rocks of porphyry tin deposits around the world (Rongfupei and Dawei Hog, 1995; Lehmann et al, 1989) (table 5). Diagrams using the aforementioned parameters can show the fertility of the granitoids with respect to Sn (Karimpour, 1999); accordingly, the intrusives in the study area lack tin mineralization (figure 12a and b). To discriminate granitoids and recognize their economic potential for tin, molybdenum or porphyry copper, the Rb/Sr and Ce/Yb ratios and color index (obtained from [CI=(SiO2+K2O+Na2O)/ (MgO+CaO+FeO)]) can be used (Karimpour et al, 1983) (figure 13a and b). Tin, high grade and low-grade molybdenum and porphyry copper deposits have been completely discriminated in these diagrams. The chemical data imply that the intrusives in the study area are barren in Sn and Mo but somewhat fertile in Cu (especially sample B7). The geochemical behaviors of the copper and zinc in magnetic crystallization products are different. Unlike copper, which is found in the chalcopyrite phase, zinc replaces iron in iron and magnesium silicates. In intermediate rocks (with 52 to 60 wt% silica), the amount of zinc is fixed at approximately 85 ppm. In rocks with over 60% silica, the zinc amount decreases linearly with increasing SiO2. In rhyolite with 75% SiO2, the amount reaches 35 ppm (Wolf, 1975). Wolf believed that practically all rocks with total iron higher than 10% can be used in regional explorations of zinc. Considering prior research and using the SiO2 versus Fe and Zn diagrams by Wolf (1975), we recognize the barren nature of the study area’s intrusive bodies with respect to zinc (Figure 14). Table 3. Average of the rare and major elements in the intrusives around Valis. Zr/ HfRb/SrBa/ RbK/RbEu (ppm) Hf (ppm) Zr (ppm) Ba (ppm) Sr (ppm) Rb (ppm) K (%)Element 34.10.9621.99189.430.8910.82369517.752692594.9Average Table 4. K/Rb ratios of barren and fertile granites (Beus, 1968) compared to those in the intrusives around Valis. Type of Granitoid K/Rb Average of the granitoids Average of the granitoids unrelated to Li, Be, Sn, W and Ta deposits. Average of the granitoids related to Li, Be, Sn, W and Ta deposits. Average of the biotite granites related to Li, Be, Cs and Ta pegmatitic deposits. Average of the biotite granites related to Ta pegmatitic and apogranitic deposits. 170 170 130 160 126 Average of the granitoids in the study area. 189/43 Table 5. Amount and ratios of some rare elements in S type granites around the world that contain tin compared to the intrusives in the study area (Not Analyzed = NA). Rb/BaSm/EuRb(ppm)Ba(ppm)Sr(ppm)Mine’s Name 25-16251100-80065-3523-18China, Yanbei granites NA18NANANASouth of China, Yanyan granites 2165-204300-36003535Southeast of China, Gianlishan granites NA75NANANASoutheast of China, Yoaganixian granites NA45NANANASoutheast of China, Xihuashan granites 1535-20543-15003531-9Australia, Blue Tier batholith 100-20120-40700-50035-519-5Australia, Emuford Herberton region 115-3395-155100-6703220Brazil (northeast), Maderia granites 1770-503502520Southwest of Japan, Sanyo 55-30NA2570-110085-389-1Thailand, Thai-Barmese granites 75-30 NA1390-68085-2044-9South of Thailand, Phuket Island, Kato body 1.4-0.210.78- 4.12347-1311293- 236 492- 199The intrusives around Valis Figure 9. Plot of K/Rb versus SiO2 (Blevin, 2003). The study area’s intrusives are semi-evolved. Figure 10. Plot of the study area’s samples on Sr, Rb and Ba triangular diagram (El Bouseily and El Sokhary, 1975). 128 Mojtaba Bahajroy, Saeed Taki Figure 11. Diagram of Rb/Sr versus SiO2 (Blevin, 2003) and a plot of the study area’s samples. Figure 12. Plot of the study area’s intrusives on a) Sm/Eu versus Rb and b) Rb-Ba-Sr diagrams, which discriminate tin-bearing granites from barren ones (Karimpour et al, 1983). Figure 13. The discrimination source rock diagrams of Cu, Sn and Mo porphyry deposits using a color index and ratios of a) Rb/Sr and b) Ce/Yb (Karimpour, 1999), and a plot of the study area’s samples. Figure 14. The relationship between changes in a) Fe and b) Zn versus SiO2 in barren and fertile granites (Wolf, 1975), and a plot of the data related to the study area. Results Based on the information obtained from field studies and the petrography and analysis results of the intrusives around Valis, the following results are determined: 1 - These intrusives have granite, syenite and monzonite petrographic compositions (granitoid) and are mostly metaluminous. 2 - Contradictory features in the intrusives (such as the behavior of P, Rb, Ga/Al, Y/Nb, K/Na, and FeO/Fe2O3, the Rb/Nb ratios, the A/CNK molar ratios and the A/CNK-Fe2O3+FeO and ACF diagrams), some of which are consistent with the I nature and others with the S and A natures, show that the rocks are classified as hybrid granitoids. 3 - In terms of the tectonomagmatic setting, the rocks are classified as WPG granitoids. 4 - Based on the K/Rb ratio, these granitoids are not strongly differentiated and have not undergone post magmatic activity, which would lead to mineralization. The amount of K/Rb in the study area’s intrusives is similar to the average of granitoids unrelated to Li, Be, Sn, W and Ta deposits, classifying the intrusives as barren granites. 6 - The Sm/Eu and Rb/Ba ratios and the behavior of Rb, Ba and Sr in the intrusives around Valis are completely different compared to the S type granite source rocks of porphyry tin deposits around the world and are barren in terms of tin. 7 - The chemical data (Rb/Sr, Ce/Yb ratios and color index) imply that the intrusives in the study area are barren in terms of Sn and Mo but are somewhat fertile in Cu. 8 - The changes in Zn and Fe versus SiO2 show the barren nature of these intrusives. References Alavi, M. (1996) Tectonostratigraphy synthesis and structural style of the Alborz Mountain system in northern Iran. Geodynamics Journal, 21, 1–33. Bea, F., Montero, P. and Ortega, M. (2006) A LA-ICP-MS evaluation of Zr reservoirs in common crustal rocks: implications for Zr and Hf geochemistry, and zircon forming processes. The Canadian Mineralogist, 44, 693–714. Beus, A. A. (1968) Geochemical criteria in theoretical principles of exploration for mineral deposits, Moscow, PP. 127-145. Blevin, P. (2003) Metallogeny of granitic rocks, The Ishihara Symposium, Granites and Associated Metallogenesis, 14, 5–8. Blevin, P. L. and Chappell, B. W., (1992) The role of magma sources, oxidation states and fractionation in determining the granite metallogeny of eastern Australia, Transaction of the Royal Society of Edinburgh: Earth Sciences, 83, 305–316. Chappell, B. W. and White, A. J. R., (1974) Two contrasting granite types. Pacific Geology, 9: 173-174. Chappell B. W., White A. G. R. (1992) I and S type granites in the Lachlan fold belt, Transactions of the Royal Society of Edinburgh Sciences, 83, 1-26. Clarke, D. B. (1992) Granitoid Rocks: Chapman and Hall, pp. 238. Cox K. G., Bell J.D., Pankhurst R.J. (1979) The interpretation of igneous rocks, Allen and Unwin, London, 405 p. Davis, R. G., Jones, C. R., Hamzepour B. and Clark, G. C. (1972) The Geology of the Musuleh sheet (Northwest Iran): Geol. Survey of Iran, Report No. 24, 110 pp. Eby, G. N., (1992) Chemical subdivision of the A-type granitoids, petrogenetic and tectonic implications, Geology 20, 641-644. El Bouseily, A. M. and El Sokkary, A. A. (1975) The relation between Rb, Ba and Sr in granitic rocks, Chemical Geology, 16, 207–219. Haj Ailou, B. (2000) Metallogeny of tertiary in western Alborz-Azerbaijan (Miyaneh-Siyahroud) with specific view on Hashtjin area, PhD thesis, Shahid Beheshti University. Ghorbani, M. (2013) The economic Geology of Iran Mineral Deposits and Natural Resources, Springer, 569 pp. 129Study of the mineralization potential of the intrusives around Valis (Tarom-Iran) Irvine, T. N., Baragar, W. R. A. (1971) A guide to the chemical classification of the common volcanic rocks, Can. J. Earth Sc., 523-548. Ishihara, S. and Tani, K. (2004) Magma mingling/mixing v. magmatic fractionation: Genesis of the Shirakawa Mo-mineralized granitoids, Central Japan, Resource Geology, 54, 373–382. Jonasson, I. R. and Boyle R. W. (1972) Geochemistry of mercury and origins of natural contamination of the environment, Can. Inst. Min. Metall. Bull., 65 (717): 32-39. Karimpour, M.H. (1999) Application of Sm/Eu, Rb/Sr, Ce/Yb and F-Rb ratios to discriminate between tin mineralized and non-mineralized S-type granite, Journal of earth sciences, Iran. Karimpour, M.H, and Bowes, W.W. (1983) Application of trace elemnts and isotopes for discriminatig between porphyry molybdenum, copper, and tin systems and the implications for predicting the grade: Global Tectonics and Metallogeny, V. 2, No. 1, 2, pp. 29-36. Lehmann B. and Mahawat C. (1989) Metallogeny of tin in Central Thailand: A genetic Concept, Geology, P.D., and Piccoli, P.M, 1989, Tectonic discrimination of granitoids: Geol. Soc. of Am. Bull., V. 101, p. 635-6430. Maniar, P. D. and Piccoli P. M. (1989) Tectonic discrimination of granitoids, Geological society of America Bulletin, 101: 635-643. Moayyed, M., 2001, Petrologic study of Tertiary volcano-plutonic belt in western Alborz, Azerbaijan, Ph.D. Thesis, Shahid Beheshti University Pearce, J.A., Harris, N.B.W., Tindle, A.G., (1984) Trace element discrimination diagrams for the tectonic interpretation of granitic rocks, J. Petrol., 25, 956-983. Peyrovan, H., (1992) Petrographic, petrologic and geochemical studies of intrusive rocks north of Abhar and the association of plutonism in the area with mineralization, MSc thesis, Tarbiyat Moalem University. Rongfu Pei and Dawei Hog (1995) the granites of south China and their metallogeny: Episodes: Vol. 1&2, pp. 77-82. Rossi, J. N., Toselli, A. J., Basei, M. A., Sial, A. N. and Baez, M. (2011) Geochemical indicators of metalliferous fertility in the Carboniferous San Blas pluton, Sierra de Velasco, Argentina, in: Sial, A. N., Bettencourt, J. S., De Campos, C.P. & Ferreira, V. P. (eds) Granite-Related Ore Deposits, Geological Society, London, Special Publications, 350, 175–186. Rozendaal, A., and Bruwer, L. (1995) Tourmaline nodules: mineralization in the Cape Granite Suite, South Africa. Journal of African Earth Sciences, 21, 141–155. Torkamani, E., (1997) Petrologic study of intrusive rocks north of Abhar- Khoramdarreh. MSc thesis, Shahid Beheshti University Whalen, J. D., Currie, K. L., and Chappell, E. W. (1987) A-type granites: geochemical charactristics, discrimination and petrogenesis, cont. Min. Pet., 95, 407-419. Wolf, M. B., (1975) Estimation of parameters affecting rapid fluid transfers in the whole body, isotopic infusions, Ann. Biomed Eng., 3: 209-224.