سنگ‌شناسی و جایگاه زمین‌ساختی سنگ‌های آذرین ترشیری در منطقه‌ی دوکوهه (جنوب غرب بیرجند)

In southwest of Birjand, the Tertiary igneous rocks have oxposed in Cretaceous flysch type deposits. These bodies are made of micro quartzmonzodiorite, trachyandesite, andesite and dacite. The main texture in these rocks is porphyry. Their phenocrysts are plagioclase, hornblende and biotite. Plagioclases contain zoning. Pyroxene, quartz and opaque minerals are in groundmass. Often, hornblendes have burned rims. These rocks have calc-alkaline nature and have formed in an active continental margin. These rocks enriched in LREE and LILE and depleted in HREE. However, negative Nb anomalies as well as enrichment in LILE implied in generation of these rocks by a low grade partial melting of an enriched mantle in a subduction zone or subducted oceanic slab that during ascend to higher level of crust, undergone crustal contamination.