University of Isfahan Petrological Journal 2228-5210 3 12 2013 02 19 Petrography, Geochemistry and Tectonomagmatic setting of the southwestern Salmas lamprophyres and related rocks Petrography, Geochemistry and Tectonomagmatic setting of the southwestern Salmas lamprophyres and related rocks 69 88 16115 FA Abdolnaser Fazlnia ارومیه، دانشگاه ارومیه، دانشکده علوم، گروه زمین شناسی Fahimeh Kouzekoulani Journal Article 2016 06 14 The Quaternary lamprophyres and related rocks from southwestern Salmas are laid on the old floodplain deposits in the border of Sanandaj-Sirjan and Urmia-Doukhtar zones. These rocks are all alkaline and include mostly camptonitic lamprophyres, contaminated Lamprophyres, basalt andesi-basalt and trachy-andesite. The rocks have been cropped out as prismatic and scoria structures with porphyritic and glomeroporphyritic textures. Lamprophyres are mostly composed of major minerals of augite, diopside, biotite, amphibole and tiny plagioclase in the matrix. Other rock types have augite, diopside and plagioclase as major phases. The presence of plagioclase and quartz xenocrystals with rounded margins, normative changes and variation in minor and trace elements content as well as their ratios are indicative of contamination with continental crust. Enrichment of LREE relative to HREE, the lack of Eu anomaly and the occurrence of Ta- and Nb-negative anomalies are important characteristics of all of the studied rocks. High ratios of Lan/Ybn, Lan/Smn and Smn/Ybn, the presence of spinel, augite and diopside and alkaline nature of all samples, indicate a melting process about 1 percent of a mantle with spinel lherzolite composition. The processes likely occurred following the Neotethys subduction beneath Central Iran ended. Slab break off in the remnants of the Neotethys oceanic crust occurred in location of the collision zone of Arabian-Eurasian plates. Arabian oblique tectonic pressure to the Eurasian plate and increasing activity of right-lateral strike-slip faults, which resulted of remnant slab break off the Neotethys, caused to decrease lithostatic pressure. As a consequence, the decompression melting occurred. The occurrence of these processes successively led to the rocks show tectonically within plate characteristic along with interacting of subduction elements. The mantle melts were erupted along these fault systems. The Quaternary lamprophyres and related rocks from southwestern Salmas are laid on the old floodplain deposits in the border of Sanandaj-Sirjan and Urmia-Doukhtar zones. These rocks are all alkaline and include mostly camptonitic lamprophyres, contaminated Lamprophyres, basalt andesi-basalt and trachy-andesite. The rocks have been cropped out as prismatic and scoria structures with porphyritic and glomeroporphyritic textures. Lamprophyres are mostly composed of major minerals of augite, diopside, biotite, amphibole and tiny plagioclase in the matrix. Other rock types have augite, diopside and plagioclase as major phases. The presence of plagioclase and quartz xenocrystals with rounded margins, normative changes and variation in minor and trace elements content as well as their ratios are indicative of contamination with continental crust. Enrichment of LREE relative to HREE, the lack of Eu anomaly and the occurrence of Ta- and Nb-negative anomalies are important characteristics of all of the studied rocks. High ratios of Lan/Ybn, Lan/Smn and Smn/Ybn, the presence of spinel, augite and diopside and alkaline nature of all samples, indicate a melting process about 1 percent of a mantle with spinel lherzolite composition. The processes likely occurred following the Neotethys subduction beneath Central Iran ended. Slab break off in the remnants of the Neotethys oceanic crust occurred in location of the collision zone of Arabian-Eurasian plates. Arabian oblique tectonic pressure to the Eurasian plate and increasing activity of right-lateral strike-slip faults, which resulted of remnant slab break off the Neotethys, caused to decrease lithostatic pressure. As a consequence, the decompression melting occurred. The occurrence of these processes successively led to the rocks show tectonically within plate characteristic along with interacting of subduction elements. The mantle melts were erupted along these fault systems. https://ijp.ui.ac.ir/article_16115_911e392464a7668d4a21899befe80ff0.pdf