Document Type : Original Research Paper


1 Assistant Professor, Department of Geology, University of Zanjan, Zanjan, Iran.

2 Professor, Department of Geology, Tarbiat Moallem University (Kharazmi), Tehran, Iran.

3 Assistant Professor, Department of Geology, Tarbiat Modares University, Tehran, Iran.

4 Assistant Professor, Research Institute for Earth Sciences, Geological Survey of Iran, Tehran, Iran.

5 Assistant Professor, Department of Geology, University of Tabriz, Tabriz, Iran.


Kamtal skarn zone is located in the 20km north of Kharvana in the Eastern Azarbaijan. Skarn-type metasomatic alteration is the result of Kamtal monzonitic intrusion into the Upper Cretaceous impure carbonates. Kamtal skarn include exoskarn and endoskarn zones. Exoskarn is the major zone that its thickness varies between 100-600m. Field and mineralogical studies demonstrate that exoskarn zone composed of garnet rich sub-zone (garnet skarn), epidote rich sub-zone (epidote skarn) and marble sub-zone. Garnet is the most important calc- silicate mineral within the garnet skarn sub-zone. They are mainly grossularitic in composition (Ad33-35), but along the fractures, andraditic composition (Ad66-73) is predominant. Clinopyroxene is the other dominant mineral within garnet skarn sub-zone that has diopsidic composition (Di82.8-85.7). In the epidote skarn sub-zone, epidote is the predominant mineral while garnet and clinopyroxene present in some places and have low concentration. Petrographic studies indicate that marly limestone was the primary rocks of the garnet skarn sub-zone while clay-bearing marl was the primary rocks of the epidote skarn sub-zone. Skarnification process can be categorized into two discrete stages: 1) prograde and 2) retrograde stages. Prograde stage began immediately after the initial emplacement of the Kamtal monzonitic magma into the enclosing impure carbonate rocks. The effect of heat flow from the intrusion caused the enclosing rocks to become isochemically marmorized in almost homogeneous limestone layers and bimetasomatized (skarnoid–hornfels) in thin interlayers of clay-rich carbonates. Invasion of segregated fluid phase of Kamtal intrusion into the fractures and micro-fractures of the marmorized and skarnoid–hornfelsic rocks incorporate considerable amounts of Fe, Si and Mg into the metasomatic aureole. During retrograde stage, due to relatively low temperature hydrothermal fluids and processes such as hydrolysis, carbonation and sulfidation, considerable amounts of hydrous calc-silicates, sulfides, oxides and carbonates replaced the anhydrous calc-silicates. Garnet and clinopyroxene are the most abundant mineral assemblage in Kamtal skarn zone, which were formed in temperature lower than 550°C. Lack of wollastonite in this mineral assemblage, intergrowth of garnet and clinopyroxene crystals and lack of any reaction rim between these crystals, and lack of emplacement texture indicate that they formed contemporaneously within the temperature and ƒO2 ranges of 430–550ºC and 10-26–10-23, respectively.


Berman, R. G., Brown, T. H. & Greenwood, H. J., 1985- An internally consistent thermodynamic data base for minerals in the system   Na2O–K2O–CaO– MgO–FeO–SiO2–Al2O3–Fe2O3–TiO2–H2O–CO2. Atomic Energy of Canada Technical Report TR-337, 62p.
Calagari, A. A. & Hosseinzadeh, G., 2005- The mineralogy of copper-bearing skarn to the east of the Sungun-Chay river, East-Azarbaijan, Iran. Journal of Asian Earth Sciences, V. 28, P. 423-438.
Deer, W. A., Howie, R. A. & Zussman, J., 1992- An Introduction to the rock- forming minerals. Second ed., Longman Scientific and Technical, London, 696p.
Einaudi, M. T. & Burt, D. M., 1982- Introduction- terminology, classification and composition of skarn deposits. Economic Geology and Bulletin of the Society of Economic Geologists, V. 7, N. 4, P. 745-754.
Einaudi, M. T., 1982a- Descriptions of skarns associated with porphyry copper plutons. In: Titley, S.R., (Eds.), Advances in geology of porphyry copper deposits, Southwestern North America, University of Arizona Press, Tucson, P. 1592-1606.
Einaudi, M. T., 1982b- General features and origin of skarns associated with porphyry copper plutons. In: Titley, S.R., (Eds.), Advances in geology of porphyry copper deposits, Southwestern North America, University of Arizona Press, Tucson, AZ, P. 185-210.
Einaudi, M. T., Meinert, L. D. & Newberry, R. J., 1981- Skarn deposits. Economic geology, 75th Anniv. V., P. 317-391.
Karimzadeh Somarin, A. & Moayed, M., 2002-  Granite and gabbro- diorite associated skarn deposits of NW Iran; Ore geology reviews, V. 20, P. 127-138.
Meinert, L. D., 1992- Skarns and skarn deposits, Geosciences Canada, V. 19, N.4, P. 145-162.
Meinert, L. D., 1995- Compositional variation of igneous rocks associated with skarn deposits- Chemical evidence for a genetic connection between Petrogenesis and mineralization. In: Thompson, J.F.H., (Eds.) magmas, Fluids and Ore Deposits. Mineralogical Association of Canada, Short Course Series, V. 23, P. 400-418.
Meinert, L. D., 1997- Application of skarn deposit zonation models to mineral exploration. Exploration and Mining Geology, V. 6, P. 185-208.
Mokhtari, M. A. A., Moinvaziri, H., Ghorbani, M. R., Mehrpartou, M., Padashi, S. M. & Baburek, J., 2010- Mineral chemistry of Kamtal Skarn (Eastern Azarbaijan, NW Iran). ACTA, Mineralogica-Petrogarphica Abstract Series; 20th General Meeting of the International Mineralogical Association, 21-27 Ague. 2010.
Mollaee, H., 1993- Petrochemistry and genesis of the granodiorite and associated Iron–copper skarn deposit of Mazraeh, Ahar, East-Azerbaijan, Iran. Unpublished Ph.D. thesis. University of Rookee, India, 287 pp.
Perkins, E. H., Brown, T. H. & Berman, R. G., 1986- PTX-SYSTEM: three programs for calculation of pressure–temperature–composition phase diagrams. Computers and Geoscience, V. 12, P. 749–755.
Ray, G. E., Webster, I. C. L. & Ettlinger, A. D., 1995- The distribution of skarns in British Columbia and the chemistry and ages of their related plutonic rocks. Economic geology, V. 90, P. 920-937.
Zharikov, V. A., 1991- Skarn types, formation and mineralization condition. In: Barto–Kyriakidis, A., (Eds.), Skarn, Their Genesis and Metallogeny. Theophrastus Publishing & Proprietary Co., Athen, Greece, P. 455-466.