Genetic Relations Between Intrusive Body And Skarn In Kharvana, Azarbaijan, NW. Iran

Category Economic geology & mineral exploration
Group GSI.IR
Location The 24 Symposium of Geosciences
Author Alirezaei S, Arjmandzadeh R, and Einali M.
Holding Date 13 August 2007

Kharvana Cu-Au prospect is located in East Azarbaijan, NW Iran, in Alborz-Azarbaijan tectonomagmatic province. Here a porphyritic pluton and associated dykes and sills intruded into a sequence of calcareous sandstones to sandy limestones, siltstones and shales of Paleocene age. The pluton is rhyodacite to dacite and andesite of chalc-alkaline affinity. The dykes and sills are hornblende-andesite to trachyandesite and dacite. Potassic, Phyllic, Propylitic, Argillic and silicic alteration zones are developed within the pluton and the dykes. The pluton is characterized by high Al2O3 and Sr, and low MgO, Y, and Yb and can be classified as adakite. This is clearly evident on Sr/Y–Y and La/Yb–Yb discrimination diagrams.

The intrusions caused extensive thermal metamorphism and metasomatism, leading to the formation of voluminous hornfels and skarns. Exoskarn occurs as banded and massive types rich in garnet (andradite) and epidote (pistacite). Endoskarn is locally developed. EMP analyses indicated high contents of fluorine in both garnet and epidote, implying a magmatic source for the reacting fluids. The high fluorine, garnet chemistry, and lack of pyrrhotite suggest that the fluids were oxidized.

Zones of As, Sb, Bi, Ag, Au, Cu anomalies are discovered in both intrusive bodies and in skarns. Mineralization occurs as disseminated, stockwork, veinlets and veins. Pyrite, chalcopyrite and subordinate bornite are the main sulfide minerals.

δ34SCDT values for 16 samples of sulfidic materials from the porphyry, dykes and skarns

fall in a narrow range around 0.0‰ 34SCDT = +1‰ to −2.5‰) implying a magmatic source for sulfur and ore fluids. Kharvana porphyry bears similarities to world-class Sungun porphyry and many other productive porphyries worldwide.

tags: QAZVIN