Petrography, mineral chemistry and geochemistry of granitoids of the Samen plutonic complex (SW Malayer, Hamedan)


1 دانشگاه لرستان، دانشکده علوم پایه، گروه زمین شناسی

2 دانشگاه بوعلی سینا


The Malayer plutonic complex is located in the northern Sanandaj-Sirjan zone of the western Iran. An intrusive body with granodioritic component known as the Samen granodiorite is in the center of this complex, which is accompanied by other granitic rocks and small mafic bodies. The major part of this intrusive body composed of tonalitic-granodioritic rocks. The monzogranitic rocks, unlike the other plutonic complexes of the Sanandaj-Sirjan zone such as the Alvand pluton constitute a small part of this complex, and probably formed and emplaced after tonalite-granodiorite body. In terms of geochemical characteristics these rocks are calc-alkaline, peraluminous and S-type, while tonalitic-granodioritic rocks are metaluminous and I-type in nature. These granitoids on the spider diagrams show enrichment in LILE (K, Rb and Th) and depletion in HFSE (Nb, P and Ti). Also they are enriched in LREE rather than HREE, the characteristics which are usually observed in the rocks from subduction environments and active continental margins. The biotites in the granodiorites are siderophyllite, amphiboles and plagioclases are hornblende and andesine type. Barometric calculations yield pressures of 1-1.2 kbar (equal to 3-4 km of depth) for intrusive rocks. Crystallization temperature of the granodioritic rocks in 1Kbar pressure is estimated to be 592.2 to 756.9 °C and in 1.2 Kbar pressure around 591.2 to 757.6 °C.