Study of REE behaviors, fluid inclusions, and O, S stable Isotopes in Zafar-abad iron skarn deposit, NW Divandarreh, Kordestan province

Document Type : Research Article

Authors

• Mehrdad Barati
• Maysam Gholipoor

Bu-Ali Sina

10.22067/econg.v6i2.20257

Abstract

Introduction
The Zafar-abad iron ore deposit, situated in the NW part of Divandarreh (lat. 36°01'14" and long. 46°58'22"). The ore body is located on the northern margin of the Sanandaj-Sirjan igneous metamorphic zone. The Zafar-abad Fe-skarn deposit is one of the important, medium- size mineral deposits in western Iran.
REE patterns of skarn magnetite were among others studied in Skarn deposit by (Taylor, 1979) Hydrothermal alteration and fluid-rock interaction significantly affect total contents of REE and their patterns in fluids. Moreover, fractionation of REE by chemical complication, adsorption effects and redox reactions are characteristic processes determining REE behavior during crystallization.
Stable isotope data for oxygen and sulfur have been widely used with great success to trace the origin and evolution history of paleo-hydrothermal fluids of meteoric, magmatic, and metamorphic.

Materials and methods
The present study investigates REE and stable Isotope geochemistry of magnetite and pyrite in Zafar-abad deposit and temperature of trapped fluid inclusions based on geothermometry analysis. In order to study the major, trace and REE compositions of Zafar-abad magnetite, twelve samples were collected from surface of ore exposures. The emphasis during sampling was on ores with primary textures.

Discussion
The Zafar-abad district is situated in Mesozoic and Cenozoic sedimentary, meta-sedimentary and meta-igneous rocks in Sanandaj-Sirjan igneous metamorphic zone. Sedimentary sequences dominantly composed of calcareous and conglomerate rocks. Various meta-sedimentary rocks are intercalated with the sedimentary rocks, and comprise biotite and muscovite-rich schist, calc-schist, calc-silicate rock. Several distinct ductile tectonic fabrics have been identified around the Zafar-abad deposit. The main ore body at Zafar-abad is in the form of a roughly horizontal, discordant, lens to tabular-shaped body plunging 10° NW, where it appears to interfinger with meta-sedimentary and fragmental wall-rock. The thickness of the ore body is 25 to 35 m with 40 m wide and around 130 m in elongate.
The chondrite normalized REE distribution pattern of Zafar-abad magnetite shows V shape. The analyzed samples display similar patterns. The average (La/Yb)cn ratio of 6.8 indicates a high degree of fractionation. The fractionation is more pronounced in HREE part of diagram, where the average (Gd/Yb)cn ratio is 1.07, whereas the average (La/Sm)cn ratio in the LREE part of the diagram is only 5.9. This indicates that the REE content in Zafar-abad magnetite is not affected by hydrothermal alteration. The ΣREE content varies between 2.09 and 15.02 ppm with an average of 8.4 ppm. These REE values are equal to those reported for the type of Skarn- type iron deposits (Bowman et al., 1985).
Other features include pronounced negative Eu and Ce and positive Pr and Gd anomalies.
Six purified magnetite samples used for Isotope Studies and δ18O values are measured in them. The units of results are permil (‰) relative to SMOW for oxygen. The δ18O values content varies between -5.93 and -0.28 ‰ with an average of -2.26 ‰. Considering that the magnetites formed at two stages (Meinert, 1995), the first one about 370 °C, and the second one about 240°C which is a reasonable guess bearing in mind that they are associated with intrusive and extrusive granitoids, then the fluid from which they formed, would yield δ18O values that range from 4.1 to 8.1 ‰ which will fall in the boundary of magmatic water box and hence provide further support for a mixed magmatic and meteoric origins of Zafar-abad magnetite deposit.
In the Zafar-abad deposit, sulfur isotope composition was studied on six pyrite samples. The δ34S values for this mineral in Zafar-abad vary from +1.2 to +1.9 ‰, with an average value of +1.61‰. Zafar-abad isotopic temperatures have been determined from the δ34S values in pyrite. This temperature range is from 204 to 350°C.
Fluid inclusion studies illustrate the presence of two different types of hydrothermal fluids at Zafar-abad iron deposit. The earliest hydrothermal fluid with high salinity (11 to 49 wt % NaCl equiv) and high temperature (> 320°C) had a magmatic origin. This magmatic fluid moved upward to shallower levels, and its temperature subsequently decreased.
The meteoric water circulated in the peripheral parts of magnetic lens and layers this water moved inside the earth and after interaction with magmatic water, the magmatic fluid gradient decreased and then produced a mixture of magmatic and meteoric fluid with salinity of 15 to 25 wt % NaCl equiv.

Results
Geochemistry and REE studies indicate that the iron has magmatic origin and the REE content in Zafar-abad magnetite is not affected by hydrothermal alteration. The ΣREE content indicate Skarn-type for this deposit.
The δ34S values of pyrite at Zafar-abad ranging from +1.2 to +1.9‰ that suggest a predominant magmatic origin for sulfur. The δ18O values of magnetite at Zafar-abad ranging from between -5.93 and -0.28 ‰ with an average of -2.26‰ that suggest the magnetites formed at two stages.
Fluid inclusion studies show the presence of two hydrothermal fluids at Zafar-abad deposit. The fluid 1, originated from high temperature and pressure magma. The fluid 2, is a mixture of magmatic fluid with meteoric water which has low temperature and salinity, these fluids were responsible for genesis of ore body.

References
Bowman, J.R., O,Neil, J.R. and Essene, E.J., 1985. Contact skarn formation at Elkhorn, Montana.1I Origin and evolution of C-O-H skarn fluids. American Journal of Science, 285(7): 621- 660.
Meinert, L.D., 1995.Coppositional variation of igneous rocks associated with skarn deposits- Chemical evidence for a genetic connection between petrogenesis and mineralization. In: J.F.H. Thompson (Editor), Magmas, fluids and ore deposits. Mineralogical Association of Canada, Canada, pp. 401- 418.
Taylor, H.P., 1979. Oxygen and hydrogen isotope relationships in hydrothermal mineral deposits. In: H.L. Barnes (Editor), Geochemistry of Hydrothermal Ore Deposits. Wiley, New York, pp. 229-302.

Keywords

• Zafar-abad ore body
• magnetite
• fluid inclusions
• stable isotopes
• magmatic and meteoric waters

20.1001.1.20087306.1393.6.2.3.0

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References

Appel, P.W.U., 1983. Rare earth element in the early Archaen Isua iron-formation, west Greenland. Precambrian Research, 20(2-4): 243- 258.

Bodnar, R.J., 1983. A method of calculating fluid inclusion volumes based on vapor bubble diameters and P-V-T-X properties on inclusions fluid. Economic Geology, 78(3): 535- 542.

Bodnar, R.J. and Vityk, M.O., 1994. Interpretation of micro thermometric data for H2o-NaCl fluid inclusions. In: B. De Vivo and M.L. Frezzotti (Editors), fluid inclusions in Minerals, Methods and Applications. Fluids Research Laboratory, Dept. of Geological Sciences, Virginia Tech, Virginia, pp. 117-130.

Bodnar, R.J., 1983. A method of calculating fluid inclusion volumes based on vapor bubble diameters and P-V-T-X properties on inclusions fluid. Economic Geology, 78(3): 535- 542.

Borisenko, A.S., 1977. Study of the salt composition of solutions in gas-liquid inclusions in minerals by the cryometric method. Geologiya i Geofizika (Soviet Geology and Geophysics), 18(8): 16-27 (11-19).

Bowman, J.R., O,Neil, J.R. and Essene, E.J., 1985. Contact skarn formation at Elkhorn, Montana.1I Origin and evolution of C-O-H skarn fluids. American Journal of Science, 285(7): 621- 660.

Boynton, W.V., 1984. Geochemistry of the rare earth elements: meteorite studies. In: P. Henderson (Editor), Rare earth element geochemistry, Elsevier, California, pp. 63- 114.

Cole, D.R., Horita, J., Eniamin, V., Polyakov, V.B., Valley, J.W., Spicuzza, M.J. and Coffey, D.W., 2004. An experimental and theoretical determination of oxygen isotope fractionation in the system magnetite-H2O from 300 to 800C. Geochimica et Cosmochimica Acta, 68(17): 3569- 3585.

Darvishzadeh, A., 1991. Geology of Iran. Danesh-e Emrooz Publication, Tehran, 635 pp. (in Persian)

De Sitter, J., Govaret, A., De Grave, E., Chamaere, D. and Robrecht, G., 1977. Mossbauer Study of Ca2+- containing magnetites. Physica Status Solidi, 43(2): 619- 624.

Dupuis, C. and Beaudoin, G., 2011. Discriminant digrams for iron oxide trace element fingerprinting of mineral deposit types. Mineralum Deposita, 46(4): 319- 335.

Faure, G. and Mensing, A., 2005. Principles of isotope geology. 2th Edition, Johm Weily and Sons, New York, 460 pp.

Frietsch, R. and Pendahl, J.A., 1995. Rare earth elements in apatite and magnetite in kiruna-type iron ores and some other Iron types. Ore Geology Reviews, 9(6): 489- 510.

Gehlen, K.V., Nielsen, H., Chunnett, I. and Rozendaal, A., 1983. Sulphur isotope in metamorphosed Percambrian Fe-Pb-Zn-Cu sulphides and barite at Aggeneys and Gamsberg, South Africa. Mineralogical Magazine, 47: 481- 6.

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

Hoefs, J. (Translated by Alirezaei, S.), 2008. Stable isotope geochemistry. Iran University Press, Tehran, 332 pp. (in Persian)

Jiang, S.Y., Chen, Y.Q., Ling, H.F., Yang, H.J., Feng, H.Z. and Ni, P., 2006. Trace and rare-earth element geochemistry and pb-pb dating of black shales and intercalated Ni-Mo-PGE-Au sulphide ores in Lower Cambrian Strata, Yangtze Platform, South China. Mineralum Deposita, 41(5): 435- 467.

Jiang, S.Y., Zhao, H.X., Chen, T.Y., Yang, T., Yang, J.H. and Ling, H.F., 2007. Trace and rare earth element geochemistry of phosphate nodules from the Lower Cambrian blak shale sequence in the Mufu Mountain of Nanjing, Jiangsu Province China. Chemical Geology, 244(3-4): 584- 604.

Karadag, M.M., Kupeli, S., Arik, F., Ayhan, A., Zedef, V., and Doyen, A., 2009. Rare earth element (REE) geochemistry and genetic implications of the Mortas bauxite deposit (Seydisehir/konya-Southern Turkey). Chemie der Erde- Geochemistry, 69(2): 143- 159.

Kato, Y., 1999. Rare Earth Elements as an Indicator to Origins of skarn deposits: Examples of the kamioka Zn-Pb and Yoshiwara-Sannotake Cu (-Fe) deposits in Japan. Resource Geology, 49(4): 183- 198.

Marschik, R., Spikings, R. and Kuscu, I., 2008. Geochronology and stable isotope signature of alteration related to hydrothermal magnetite ores in Central Anatolia, Turkey. Mineralium Deposita, 43(1): 111- 124.

Meinert, L.D., 1995.Coppositional variation of igneous rocks associated with skarn deposits- Chemical evidence for a genetic connection between petrogenesis and mineralization. In: J.F.H. Thompson (Editor), Magmas, fluids and ore deposits. Mineralogical Association of Canada, Canada, pp. 401- 418.

Ohmoto, H., 1972. Systematics of sulfur and carbon isotopes in hydrothermal ore deposits. Economic Geology, 67(5): 551-579.

Ohmoto, H. and Rye, R.O., 1979. Isotopes of sulfur and carbon. In: H.L. Barnes (Editor), Geochemistry of Hydrothermal Ore Deposits. John Wiley and Sons, pp. 509- 567.

Raju, P.V.S., 2009. Petrography and geochemical behavior of trace, REE and precious metal signatures of sulphidic banded iron formations from the Chikkasid- davanahalli area, Chitradurga schist belt, India. Journal of Asian Earth Science, 34(5): 663- 673.

Roedder, E., 1984. Fluid inclusions, 12. Mineralogical Society of America, Reviews in Mineralogy, Virginia, 646 pp.

Rollinson, H.R., (Translated by Moore F., Modaberi, S.), 2005. Using geochemical data. Iran University Press, Tehran, 422 pp. (in Persian)

Rose, A.W., Herrick, D.C. and Deines, P., 1985. An oxygen and sulfur isotope study of skarn-type magnetite deposits of the Cornwall type, Southeastern Pennsylvania. Economic Geology, 80(2): 418- 443.

Rye, R.O., 1993. The evolution of magmatic fluids in epithermal environment: the stable isotope perspective. Economic Geology, 88(3): 733- 752.

Shahabpour, J., 1994. Post-mineralization breccias dike from the sarcheshmeh porphyry copper deposit, Kerman, Iran. Exploration and Mining Geology, 3(1): 39- 43.

Sheppard, S.M.F. and Epstein, S., 1970. D/H and 18O/16O ratios of minerals of possible mantle or lower crustal origin. Earth and Planetary Science Letters, 9(3): 232- 239.

Stockiln, J., 1977. Structural correlation of the Apline range between Iran and central Asia. Memoire Hors Serve - Dela Societe Geologique De France, 8: 333- 353.

Sun, H., Wu, J., Yu, P. and Li, J., 1998. Geology, geochemistry and sulfur isotope composition of the Late Proterozoic Jingtieshan (Superior-type) hematite-jasper-barite iron ores deposits associated with stratabound Cu mineralization in the Gansu Province, China. Mineralium Deposita, 34(1): 102- 112.

Taylor, B.E. and O,Neil, J.R., 1977. Stable isotope studies of metasomatic Ca-Fe-Al-Si skarns and associated metamorphic and igneous rocks, Osgood Mountains, Nevada. Contributions to Mineralogy and Petrology, 63(1): 1- 49.

Taylor, H.P., 1979. Oxygen and hydrogen isotope relationships in hydrothermal mineral deposits. In: H.L. Barnes (Editor), Geochemistry of Hydrothermal Ore Deposits. Wiley, New York, pp. 229-302

Taylor, H.P. JR., 1980. The effects of assimilation of country rocks by magmas on 18O/16O and 87Sr/86Sr systematic in igneous rocks. Earth and Planetary Science Letters, 47(2): 243- 254.

Taylor, S.R. and McLennan, S.M., 1991. The continental Crust: its Composition and Evolution: An Examination of the Geochemical Record Preserved in Sedimentary Rocks. Blackwell Scientific Publications, 312 pp.

Wilkinson, J.J., 2001. Fluid inclusions in hydrothermal ore deposits. Lithos, 55(1-4): 229- 272.