Petrography and geochemical characteristics of Nakhilab igneous complex, northwest of Zahedan


Department of Geology, Faculty of Sciences, University of Sistan and Baluchestan, Zahedan, Iran


Nakhilab igneous complex is located in 145 km northwest of Zahedan and is geologically situated between Lut block and the Sistan-suture zone. Rock units in the area range from Cretaceous to Quaternary and consist of sedimentary and igneous types. The igneous rocks occur as intrusive and extrusive in the Nakhilab. The extrusive rocks occur as lava and pyroclastic and consist of basalt, basaltic andesite, andesite and rhyolite. The intrusive rocks occur as stock and dyke and consist of gabbro, diorite and granodiorite. These rocks are porphyry and granular in texture. In these rocks, plagioclase, pyroxene, hornblende, biotite and quartz are the main minerals and apatite, sphene and magnetite are the accessory minerals. The intrusive rocks that were altered by hypogene and supergene processes are associated with Cu mineralization in the central part. The igneous rocks in the Nakhilab are metaluminus and calcalkaline. Patterns of minor and rare earth elements normalized to MORB and Chonderit show that LREE and LILE contents are sharply higher than HREE and HFSE contents, respectively. Higher contents of LREE and LILE compared to HREE and HFSE, respectively, negative anomalies of Zr, Ti, P and positive anomalies of K, Rb, Sr, suggest that the study samples may belong to an active continental margin. The studied igneous rocks were probably solidified from a basaltic magma by AFC processes that derived from partial melting a subducting oceanic crust and it`s above mantle wedge.