TY - JOUR T1 - Distribution of platinum-group elements (PGE) in chromitites of Sabzevar, NE of Iran TT - توزیع عناصر گروه پلاتین (PGE) در کرومیتیت‌های سبزوار، شمال شرق ایران JF - ijcmir JO - ijcmir VL - 27 IS - 1 UR - http://ijcm.ir/article-1-1229-en.html Y1 - 2019 SP - 109 EP - 122 KW - chromitite KW - platinum-group elements (PGE) KW - boninitic melt KW - toleiitic melt KW - sabzevar. N2 - The chromitite ores of Sabzevar ophiolitic zone could be divided into two groups of high Cr and high Al. The concentration of Cr2O3, As, S and some heavy metals (Cu, Ni, Ag, Co, Zn) is higher in high Cr samples; while high Al chromitites show higher concentration of Al2O3, SiO2, TiO2 and other trace elements. The high Cr chromitites have higher PGE than Al-rich samples and PGE concentration increases with Cr2O3. The high Cr chromitites have fractionated PGE chondrite- normalized patterns with negative slope (Pd/Ir = 0.25) and high IPGE/PPGE (average 6.22); while high Al chromitites show unfractionated and relatively flat patterns (Pd/Ir = 1.9, IPGE/PPGE = 2.88). The PGE composition of high Cr chromitites indicates they are formed by high degrees of partial melting (boninitic melt) in arc setting. In contrast, Al- enriched samples have been produced by low degrees of partial melting (toleiitic melt) beneath spreading centers (i.e., mid-ocean ridges or back-arc basins). The results of PGE composition of Sabzevar chromitites are coincident with chemical composition data of chromite crystals in these samples. M3 10.29252/ijcm.27.1.109 ER -