Mineralogy, geochemistry, and evolution of the Mivehrood skarn and the associated pluton, northwest Iran

摘要: An Upper Miocene (9.12 ± 0.19 Ma; biotite 40Ar/39Ar) shallow pluton and numerous dykes sills of felsic–intermediate compositions intruded the Cretaceous, flysch-type sediments in Mivehrood area, northwest Iran. The intrusions caused extensive thermal metamorphism metasomatism, leading to formation hornfels skarn. A massive skarn, 1–10 m thick, immediate intrusive contact, is bordered by a banded 100–400 that grades outward into original sediments. characterized steep REE pattern, high Al2O3 (14.64–16.4 wt%) Sr (380–786 ppm), low MgO (1.3–3.4 wt%), Y (4.8–10.7 Yb (0.35–0.95 characteristics typical high-silica adakites. Skarn started with metamorphism, followed anhydrous prograde hydrous retrograde stages. Prograde mineral assemblages are developed both skarns, represented garnet–clinopyroxene–wollastonite epidote–actinolite–scapolite–chlorite, respectively. Granditic F-bearing garnet dominates clinopyroxene skarns. skarn contains minor scapolite marialite composition. calc-silicate chemistry allow be classified as calcic, oxidized Mass balance assessments suggest Fe, Si, S were significantly enriched, Na, LILEs, LREEs strongly depleted, In K, enriched. Significant dehydration carbon degassing occurred Stockworks, veins, replacement bodies pyrite chalcopyrite locally occur δ34SCDT values for sulfides fall narrow range around 0.0 ‰, suggesting magmatic source sulfur possibly hydrothermal water solutes involved formation.