Mineralogy and REE geochemistry at Gomish-Tappeh Zn-Pb-Cu (Ag) deposit, southwest of Zanjan

زمین شناسی اقتصادی

Article 4, Volume 2, Issue 2 - Serial Number 3, January 2011, Pages 235-254   

Document Type: Research Article

DOI: 10.22067/econg.v2i2.7853

Authors

Tooba Salehi; Majid Ghaderi^* ; Nematollah Rashidnejad Omran

Tarbiat Modares

Abstract

Gomish-Tappeh Zn-Pb-Cu (Ag) deposit is located 90 km southwest of Zanjan, in northwestern part of Urumieh-Dokhtar volcano-plutonic zone. Exposed rocks at the area include Oligo-Miocene volcano-sedimentary and sedimentary sequences as well as Pliocene volcano-plutonic sequence (andesite porphyry dykes, dacitic subvolcanic dome and rhyodacitic volcanics). Alteration in the deposit developed as silicic, silicic-sulfidic, sericitic, carbonate, argillic and propylitic. Main mineralization at the Gomish-Tappeh deposit is observed as veins occurring in a steeply-deeping normal fault defined by an NE-SW trend in host rocks such as dacitic crystal litic tuff, dacitic subvolcanic dome, specifically the rhyolitic tuff. Paragenetic minerals in the ore veins consist of pyrite, arsenopyrite, chalcopyrite, bornite, low-Fe sphalerite, galena, tetrahedrite and specularite. Gangue minerals accompanying the ores include quartz, calcite, chlorite, sericite and clay minerals. Based on geochemical data, average grades for samples from the ore veins at the Gomish-Tappeh deposit are: 4% Pb, 6% Zn, 2% Cu and 88 ppm Ag. Moreover, REE distribution patterns for altered samples of the dacitic subvolcanic dome and acidic tuff when campared with fresh samples, show enrichment in LREE, while HREE demonstrate various bahaviours. The negative Eu anomaly in chondrite-normalized REE patterns for these rocks is related to the increase in fluid/rock ratio and destruction of those grains of plagioclase enriched in Eu. REE distribution patterns for the silty tuff (footwall to the ore) campared with acidic tuff represent enrichment in all REE as well as positive Eu anomalies. However, the ore samples indicate more enrichment in LREE/HREE ratios and higher Eu contents when campared with wallrock of the ore veins (silty tuff). This is due to the influence of chloric magmatic-hydrothermal fluids that caused alteration along the ore zone, releasing LREE and Eu from the host rocks and finally, concentrating and transporting these elements in the ore fluid.

Keywords

Pliocene volcano-plutonic sequence; Alteration; Zn-Pb-Cu (Ag); Gomish-Tappeh; Zanjan

References

[1] قربانی م.، "دیباچه ای بر زمین شناسی اقتصادی ایران"، پایگاه ملی داده های علوم زمین کشور (1381)، 659 ص.

[2] صالحی ط.، "کانی شناسی، ژئوشیمی و ژنز کانسار روی- سرب (نقره) گمیش تپه، جنوب‌غرب زنجان"، پایان‌نامه کارشناسی ارشد، دانشگاه تربیت مدرس (1387)، 221 ص.

[3] شیرخانی م.، "کانی شناسی ، ژئوشیمی و ژنز کانه زائی روی- سرب و عناصر همراه در کانسار آی قلعه سی، جنوب‌خاوری تکاب"، پایان نامه کارشناسی ارشد، دانشگاه تربیت مدرس (1385) 143 ص.

[4] قربانی م.، تاجبخش، پ.، خویی، ن.، " کانسارهای سرب و روی در ایران"، سازمان زمین شناسی و اکتشافات معدنی کشور، طرح تدوین کتاب زمین شناسی، شماره 75 (1379).

[5] LeBas N.J.,"The role of aluminous in igneous clinopyroxenes with relation to their parentage". Am. J. Sci. 260 (1962) 267-288.

[6] مجیدی فرد ج.، "نقشه زمین شناسی 1:100000 مرزبان"، سازمان زمین‌شناسی و اکتشافات معدنی کشور (1385).

[7] Irvine T.N., Baragar, W.R.A., "A guide to the chemical classification of the common volcanic rocks", Can. J. Earth Sci. 8 (1971) 523-548.

[8] Pearce J.A., Harris, N.B.W., Tindle, A.G., "Trace element discrimination diagrams for the tectonic interpretation of granitic rocks", Journal of Petrology 25 (1984) 956-983.

[9] Lentz D.R., "Alteration and alteration processes associated with ore-forming system", Geological Association of Canada Short Course Notes 11 (1994) 16-22.

[10] Lovering T.G., Heyl, A.V., "Jasperoid as a guide to mineralization in the Taylor mining district and vicinity near Ely, Nevada", Economic Geology 69 (1974) 46-58.

[11] Pirajno F., "Hydrothermal Mineral Deposits, Principle and Fundamental Concept for the Exploration Geologist", Springer (1992) 706 p.

[12] Sillitoe R.H., "Epithermal models: genetic types, geometrical control and shallow features", Geological Association of Canada Special Paper 40 (1993) 403-417.

[13] Giggenbach W.F., "The origin and evolution of fluids in magmatic-hydrothermal systems", in Barnes, H.L, Geochemistry of Hydrothermal Ore Deposits, 3rd ed., New York, Wiley Interscience (1997) 737-796.

[14] Cox K.G., Bell, J.D., Pankhurst, R.J., "The Interpretation of Igneous Rocks", London, Allen and Unwin (1979) 450 p.

[15] Hitzman M.W., Reynolds, N.A., Sangster, D.F., Allen, C.R., Carman, C.E., "Classification, genesis, and exploration guides for nonsulfide zinc deposits", Economic Geology 98:4 (2003) 685-714.

[16] Sun S.S., McDonough, W.F., "Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes", Geol. Soc. Lon., Spec. Pub. 42 (1989) 313-345.

[17] Lottermoser B.G., "Rare earth elements and hydrothermal ore formation processes", Ore Geology Reviews 7 (1992) 25-41.

[18] Kikawada Y., Ossaka, T., Oi, T., Honda, T., "Experimental studies on the mobility of lanthanides accompanying alteration of andesite by acidic hot spring water", Chemical Geology 176 (2001) 137-149.

[19] Fulignati P., Gioncada, A., "Rare earth element bahaviour in the alteration facies of the active magmatic-hydrothermal system of volcano (Aeolian Island, Italy)", Journal of Volcanology and Geothermal Research 88 (1998) 325-342.

[20] Sverjensky D.A., "Europium redox equilibria in aqueous solution", Earth Planet. Sci. Lett. 67 (1984) 70-78.

[21] Henderson P., "Rare Earth Element Geochemistry", Elsevier (1984).

[22] Gramaccioli C.M., Diella, V., Demartin, F., "The role of fluoride complexes in REE geochemistry and the importance of 4f electrons: some complexes in minerals", Euro. J. Min 11:6 (1999) 983-992.

[23] Shangui G., Jianquan, M., Qihou, Z., "Hydrothermal redistribution of rare-earth element in Pingxiang dacite", Chinese Journal of

geochemistry 21:2 (2002) 170-174.

[24] Klein C., Hurlbut, C.S., "Manual of Mineralogy", John Wiley & Sons (1993) 681 p.

[25] Schwartz M., "Cadmium in zinc deposits: economic geology of a polluting element", Reviews in Economic Geology 13 (2000) 445-469.

[26] Simmons S.F., Browne, P.L., "Hydrothermal minerals and precious metals in the Broadlands-Ohaaki geothermal system: implications for understanding low-sulfidation epithermal environments", Economic Geology 95 (2000) 971-999.

[27] Hedenquist J.W., Arribas, A., Gonzalez-Urien, E., "Exploration for epithermal gold deposits", Reviews in Economic Geology 13 (2000) 245-277.

[28] Camprubi A., Albinson, T., "Epithermal deposits in Mexico, update of current knowledge, and an empirical reclassification", The Geological Society of America, Special Paper 422 (2007) 14-39.