Pressure-temperature condition and hydrothermal-magmatic fluid evolution of the Cu-Mo Senj deposit, Central Alborz: fluid inclusion evidence

زمین شناسی اقتصادی

Article 9, Volume 8, Issue 2 - Serial Number 15, February 2017, Pages 431-455   

Document Type: Research Article

DOI: 10.22067/econg.v8i2.36877

Authors

Ebrahim Tale Fazel^{* 1}; Behzad Mehrabi²; Hassan Zamanian³; Masoumeh Hayatalgheybi³

¹Bu-Ali Sina

²Kharazmi

³Lorestan

Abstract

Introduction
The Senj deposit has significant potential for different types of mineralization, particularly porphyry-like Cu deposits, associated with subduction-related Eocene–Oligocene calc-alkaline porphyritic volcano-plutonic rocks. The study of fluid inclusions in hydrothermal ore deposits aims to identify and characterize the pressure, temperature, volume and fluid composition, (PTX) conditions of fluids under which they were trapped (Heinrich et al., 1999; Ulrich and Heinrich, 2001; Redmond et al., 2004). Different characteristics of the deposit such as porphyrtic nature, alteration assemblage and the quartz-sulfide veins of the stockwork were poorly known. In this approach on the basis of alterations, vein cutting relationship and field distribution of fluid inclusions, the physical and chemical evolution of the hydrothermal system forming the porphyry Cu-Mo (±Au-Ag) deposit in Senj is reconstructed.

Materials and Methods
Over 1000 m of drill core was logged at a scale of 1:1000 by Pichab Kavosh Co. and samples containing various vein and alteration types from different depths were collected for laboratory analyses. A total of 14 samples collected from the altered and least altered igneous rocks in the Senj deposit were analyzed for their major oxide concentrations by X-ray fluorescence in the SGS Mineral Services (Toronto, Canada). The detection limit for major oxide analysis is 0.01%. Trace and rare earth elements (REE) were analyzed using inductively coupled plasma-mass spectrometery (ICP-MS), in the commercial laboratory of SGS Mineral Services. The analytical error for most elements is less than 2%. The detection limit for trace elements and REEs analysis is 0.01 to 0.1 ppm. Fluid inclusion microthermometry was conducted using a Linkam THMS600 heating–freezing stage (-190 °C to +600 °C) mounted on a ZEISS Axioplan2 microscope in the fluid inclusion laboratory of the Iranian Mineral Processing Research Center (Karaj, Iran).

Results
The Cu-Mo Senj deposit covering an area about 5 km2 is located in the central part of the Alborz Magmatic Arc (AMA). The Nb/Y versus Zr/TiO2 diagram (after Winchester and Floyd, 1977) illustrates a typical trend for the magmas in the Senj magmatic area–starting from basaltic and evolving to dacite/rhyodacitic compositions, with few data plotting in the alkali basalt field. Most of the igneous rocks plot within the medium- and high-K fields in the K2O versus SiO2 diagram. The igneous rocks from the Senj area define a typical high-K calc-alkaline on SiO2 versus K2O diagram (Le Maitre et al., 1989). All studied rocks show similar incompatible trace element patterns with an enrichment of large ion lithophile elements (LILE: K, Rb, Ba, Th) and depletion of high field strength elements (HFSE: Nb and Ti), which are typical features of magmas from convergent margin tectonic settings (Pearce and Can, 1973). At least three veining stages namely QBC, QM, and QP which are related to alteration and mineralization are distinguished at the Senj mineralized area. Three distinct alteration assemblages including K-feldspar-biotite-sericite-quartz, quartz-sericite-K-feldspar-pyrite, and K-feldspar-biotite-sericite-quartz, are distinguishable with these veins. About 80 % of the copper at Senj is associated with the early QBC-stage veins, with another 5 to 15 % in the QM-and QP-stage veins. About 70 % of the molybdenite occur in QM veins.

Discussion
Fluid inclusion distribution, fluid chemistry, and homogenization behavior document that S2-type fluids are samples of magma-derived aqueous-saline fluids characterized by high salinity and temperature, and high Cu content. Such parental fluids scavenged Cu and Mo from the melt below and transported them to the hydrothermal system above. The increased abundance of S- and LV-types inclusion coinciding with the highest grade Cu mineralization (early QBC-stage veins) at the Senj deposit suggests that brine-vapor unmixing and phase separation plays an important role in Cu-ore precipitation and alteration zonation. In addition to unmixing, cooling and water-rock interaction also played important roles in chalcopyrite precipitation at the Senj deposit.
Compositions, deposit-scale distribution, and trapping conditions of fluid inclusions can be explained by the continued influx of a parental high salinity magmatic hydrothermal fluid, with no significant change in the bulk composition of the input fluid over the integrated lifetime of ore metal precipitation and vein formation. Fluid inclusion evidence and vein-cutting relationships indicate that molybdenum mineralization (QM vein) occurred at moderate temperatures coinciding with phyllic alteration, rather than from later, lower temperature fluids. Furthermore, early fluids decompressed rapidly relative to cooling, forming quartz-stockwork veins with K-silicate alteration at depth and QP veins at shallower levels in the Senj deposit. Later, as the hydrothermal system waned, the rate of decompression relative to fluid cooling slowed, causing the fluid to remain above its solvus, forming barren quartz-dominated veins with quartz-kaolinite±illite alteration which overprint much of the deposit.

References
Heinrich, C.A., Günther, D., Audétat, A., Ulrich, T. and Frischknecht, R., 1999. Metal fractionation between magmatic brine and vapor, determined by micro-analysis of fluid inclusions. Geology, 27(7): 755–758.
Le Maitre, R.W., Bateman, P., Dudek, A., Keller, J., Lameyre, J., Le Bas, M.J., Sabine, P.A., Schmid, R., Sorensen, H., Streckeisen, A., Woolley, A.R. and Zanettin, B., 1989. A classification of igneous rocks and glossary of terms. Blackwell Scientific Publications, Oxford, 193 pp.
Pearce, J.A. and Can, J.R., 1973. Tectonic setting of basic volcanic rocks determined using trace elements analysis. Earth and planetary science letter, 19(2): 290-300.
Redmond, P.B., Einaudi, M.T., Inan, E.E., Landtwing, M.R. and Heinrich, C.A., 2004. Copper deposition by fluid cooling in intrusion-centered systems: New insights from the Bingham porphyry ore deposit, Utah. Geology, 32(3): 217–220.
Ulrich, T. and Heinrich, C.A., 2001. Geology and alteration geochemistry of the porphyry Cu– Au deposit at Bajo de la Alumbrera, Argentina. Economic Geology, 96(8): 1719–1742.
Winchester, J.A. and Floyd, P.A., 1977. Geochemical discrimination of different magma series and their differentiation products using immobile elements. Chemical Geology, 20(5): 325-343.

Keywords

Cu-Mo mineralization; fluid inclusions; ore-forming fluid evolution; Senj deposit; Central Alborz

References

Allan, M.M., Morrison, G.W. and Yardley, B.W.D., 2011. Physicochemical Evolution of a Porphyry-Breccia System: A Laser Ablation ICP-MS Study of Fluid Inclusions in the Mount Leyshon Au Deposit, Queensland, Australia. Economic Geology, 106(3): 413–436.

Amini, B., 1993. Geological map of Tehran scale 1:100,000. Geological survey of Iran.

Aude´tat, A., Gunther, D. and Heinrich, C.A., 2000. Causes for large-scale metal zonation around mineralized plutons: fluid inclusion LA–ICP–MS evidence from the Mole Granite, Australia. Economic Geology, 95(8): 1563–1581.

Bakker, R.J., 2003. Package FLUIDS 1. Computer programs for analysis of fluid inclusion data and for modeling bulk fluid properties. Chemical Geology, 194(1-3): 3–23.

Bakker, R.J., Baumgartner, M. and Doppler, G., 2012. Diffusion of water through quartz: a fluid inclusion study. Goldschmidt conference, Montreal Convection Center, Montreal, Canada.

Beane, R.E., 1983. The magmatic–meteoric transition. Geothermal Resources Council, California, Special Report 13, 381 pp.

Bodnar, R.J., 1994. Synthetic fluid inclusions: XII: the system H2O–NaCl. Experimental determination of the halite liquidus and isochores for a 40 wt.% NaCl solution. Geochimica et Cosmochimica Acta, 58(3): 1053–1063.

Bodnar, R.J., 1995. Revised equation and table for determining the freezing point depression of H2O-NaCl solutions. Geochimica et Cosmochimica Acta, 57(3): 683-684.

Bodnar, R.J. and Beane, R.E., 1980. Temporal and spatial variations in hydrothermal fluid characteristics during vein filling in pre-ore cover overlying deeply buried porphyry copper-type mineralization at Red Mountain, Arizona. Economic Geology, 75(6): 876–893.

Bodnar, R.J., Burnham, C.W. and Sterner, S.M., 1985. Synthetic fluid inclusions in natural quartz. III. Determination of phase equilibrium properties in the system H2O–NaCl to 1000ºC and 1500 bars. Geochimica et Cosmochimica Acta, 49(9): 1861–1873.

Bodnar, R.J., Sterner, S.M. and Hall, D.L., 1989. SALTY: a FORTRAN program to calculate compositions of fluid inclusions in the system NaCl–KCl–H2O. Computer Geoscience, 15(1): 19–41.

Brathwaite, R.L., Simpson, M.P., Faure, K. and Skinner, D.N.B., 2001. Telescoped porphyry Cu-Mo-Au mineralisation, advanced argillic alteration and quartz-sulfide-gold-anhydrite veins in the Thames District, New Zealand. Miner Deposita, 36(7): 623–640.

Brown, P.E., 1989. Flincor: a microcomputer program for the reduction and investigation of fluid inclusion data. American Mineralogist, 74(11-12): 1390–1393.

Cao, Y., Du, Y., Gao, F., Hu, L., Xin, F. and Pang, Z. 2012. Origin and evolution of hydrothermal fluids in the Taochong iron deposit, Middle–Lower Yangtze Valley, Eastern China: Evidence from microthermometric and stable isotope analyses of fluid inclusions. Ore Geology Reviews, 48(4): 225–238.

Cline, J. and Bodnar, R.J., 1994. Direct evolution of brine from a crystallizing silicic melt at the Questa, New Mexico, Molybdenum deposit. Economic Geology, 89(8): 1780–1802.

Cloke, P.L. and Kesler, S.E., 1979. The halite trend in hydrothermal solutions. Economic Geology, 74(8): 1823–1831.

Cox, D.P. and Singer, D.A., 1986. Mineral deposit models. United State Geological Survey, Bulltein 1693, 400 pp.

Dedual, E., 1967. Zur Geologie des mittleren und lnteren Karaj Tales zental Elburz (Iran). M.Sc. Thesis Mitt Geolical institute, Eidgen Technology Hochsch University, Zurrich, 125 pp.

Farahkhah, N., 2009. Petrology and geochemistry of igneous rocks in NE Baraghan with special view on molybdenum mineralization and application of GIS for geological unit enhancement. M.Sc. Thesis. Kharazmi university, Tehran, Iran, 173 pp.

Fournier, R.O., 1999. Hydrothermal processes related to movement of fluid from plastic into brittle rock in the magmatic–epithermal environment. Economic Geology, 94(8): 1193–1211.

Haas, J.L., 1971. The effect of salinity on the maximum thermal gradient of a hydrothermal system at hydrostatic pressure. Economic Geology, 66(6): 940-946.

Hall, D.L., Sternert, S.M. and Bodnar, R.J., 1988. Freezing point depression of NaCl-KCl-H2O. Economic Geology, 83(1): 197-202.

Harris, A.C., Golding, S.D. and White, N.C, 2005. Bajo de la Alumbrera copper-gold deposit: Stable isotope evidence for a porphyry-related hydrothermal system dominated by magmatic aqueous fluids. Economic Geology, 100(5): 63–86.

Hayatolgheibi, M., 2011. Mineralogy, geochemistry and fluid inclusion of Cu-Mo Senj deposit (north of Karaj). M.Sc. Thesis. Kharazmi university, Tehran, Iran, 170 pp.

Hedenquist, J.W., Arribas, A. and Reynolds, T.J., 1998. Evolution of an intrusion-centered hydrothermal system: Far Southeast Lepanto porphyry and epithermal Cu-Au deposits, Philippines. Economic Geology, 93(4): 374–404.

Hedenquist, J.W. and Lowenstern, J.B., 1994. The role of magmas in the formation of hydrothermal ore deposits. Nature, 370(6490): 519–527.

Heinrich, C.A., Günther, D., Audetat, A., Ulrich, T. and Frischknecht, R., 1999. Metal fractionation between magmatic brine and vapor, determined by micro-analysis of fluid inclusions. Geology, 27(7): 755–758.

Hezarkhani, A. and Williams-Jones, A., 1998. Controls of alteration and mineralization in the Sungun porphyry copper deposit, Iran: evidence from fluid inclusion and stable isotope. Economic Geology, 93(5): 651–670.

Iran Minerals Production and Supply Corporation (IMPASCO), 2009. Report on drilling operation in Senj polymetallic deposit (Tehran province). Ministry of Mines and Metals, Republic Islamic of Iran (unpublished), 440 pp (in Persian).

Le Maitre, R.W., Bateman, P., Dudek, A., Keller, J., Lameyre, J., Le Bas, M.J., Sabine, P.A., Schmid, R., Sorensen, H., Streckeisen, A., Woolley, A.R. and Zanettin, B., 1989. A classification of igneous rocks and glossary of terms. Blackwell Scientific Publications, Oxford, 193 pp.

Liu, W. and McPhail, D.C., 2005. Thermodynamic properties of copper chloride complexes and copper transport in magmatic-hydrothermal solutions. Chemical Geology, 221(1-2): 21–39.

Mahdizade, S., 1995. Geological map of Karaj scale 1:100,000. Geological survey of Iran.

Momenzade, M. and Rachidnejad-Omran, N., 1985. Brief report on Cu-Mo Senj abonden mine. Geological Survey of Iran, Tehran, Report 3, 55 pp.

Norollahi, Z., 2004. Petrology and geochemistry of igneous rocks of the Karaj basement. M.Sc. Thesis. Tehran university, Tehran, Iran, 180 pp.

Pearce, J.A. and Can, J.R., 1973. Tectonic setting of basic volcanic rocks determined using trace elements analysis. Earth and planetary science letter, 19(2): 290-300.

Pichab Kavosh, 2007. Detail exploration report of Senj Mo mine. Ministry of Mines and Metals, Republic Islamic of Iran (unpublished), 201 pp (in Persian).

Ramboz, C., Pichavant, M. and Weisbrod, A., 1982. Fluid immiscibility in natural processes: use and misuse of fluid inclusion data. II. Interpretation of fluid inclusion data in terms of immiscibility. Chemical Geology, 37(6): 29–48.

Redmond, P.B., Einaudi, M.T., Inan, E.E., Landtwing, M.R. and Heinrich, C.A., 2004. Copper deposition by fluid cooling in intrusion-centered systems: New insights from the Bingham porphyry ore deposit, Utah. Geology, 32(3): 217–220.

Richards, J.P., 2011. Magmatic to hydrothermal metal fluxes in convergent and collided margins. Ore Geology Reviews, 40(1): 1–26.

Roedder, E., 1984. Fluid inclusions. Review in Mineralogy, Mineralogical Society of America, United State of America, 646 pp.

Roedder, E. and Bodnar, R.J., 1980. Geological pressure determinations from fluid inclusion studies. Annual Review of Earth and Planetary Science, 8(1): 263–301.

Rusk, B., Reed, M.H. and Dilles, J.H., 2008. Fluid Inclusion Evidence for Magmatic-Hydrothermal Fluid Evolution in the Porphyry Copper-Molybdenum Deposit at Butte, Montana. Economic Geology, 103(2): 307–334.

Sillitoe, R.H., 2010. Porphyry copper systems. Economic Geology, 105(1): 3–41.

Sterner, S.M., Hall, D.L. and Bodnar, R.J., 1988. Synthetic fluid inclusions V: solubility relations in the system NaCl–KCl–H2O under vapor saturated conditions. Geochim Cosmochim Acta, 52(2): 989–1005.

Sun, S.S. and McDonough, W.F., 1989. Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. In: A.D. Saunders and M.J. Norrey (Editors), Magmatism in the Ocean Basins. Geological Society, London, pp. 313–345.

Ulrich, T., Günthur, D. and Heinrich, C.A., 2001. The evolution of a porphyry Cu–Au deposit, based on LA-ICP-MS analysis of fluid inclusions: Bajo de la Alumbrera, Argentina. Economic Geology, 96(3): 1743–1774.

Ulrich, T. and Heinrich, C.A., 2001. Geology and alteration geochemistry of the porphyry Cu– Au deposit at Bajo de la Alumbrera, Argentina. Economic Geology, 96(8): 1719–1742.

Valizade, M., 1987. Petrological study of igneous rocks of the Karaj dam basement. Basic science journal of Tehran university, 16(2): 5-28.

Valizade, M. and Abdollahi, H.R., Sadeghian, M., 2008. Geological investigation of main intrusions of the central Alborz. Journal of geoscience, 67(17): 182-197.

Van Den Kerkhof, A.M. and Hein, U.F., 2001. Fluid inclusion petrography. Lithos, 55(1-4): 27-47.

Williams, P.J., Kendrick, M.A. and Xavier, R.P., 2010. Sources of ore fluid components in IOCG deposits. In: T.M. Porter (Editor), Hydrothermal Iron Oxide Copper–Gold and Related Deposits: A Global Perspective. Porter GeoConsultancy Publishing, Adelaide, Australia, pp. 107–116.

Whitney, D.L. and Evans, B.W., 2010. Abbreviations for names of rock-forming minerals. American Mineralogist, 95: 185–187.

Winchester, J.A. and Floyd, P.A., 1977. Geochemical discrimination of different magma series and their differentiation products using immobile elements. Chemical Geology, 20(5): 325-343.