پترولوژی (Jan 2018)
Using whole rock and mineral chemistry for determining the origin of lamprophyres from Deh-Bazargan-Sarasiab 6 (north of erman city, Kerman Province)
Abstract
In the north of Kerman city, between Deh-Bazargan and Sarasiab 6 villages and along the Koohbanan fault, several lamprophyric dykes have been intruded the Shemshak, Bidu and Hodjedk Formations. The dykes show porphyry and glomeroporphyry textures and contain coarse-grained phenocrysts of olivine (30 vol.%), pyroxene (20 vol.%) and amphibole (5 vol.%) crystals in a matrix containing 10 vol.% plagioclase and sanidine microlites, fine-grained pyroxene (20 vol.%) and amphiboles (5 vol.%). Electron microprobe analyses show that the pyroxenes are diopside (Fs7.84-15.11)-)Wo42.20-46.75)-)En41.57-49.24), olivines are chrysolite (Fo85/79-91.20), plagioclases are labradorite (An50.94-66.30) and opaque inclusions in olivines are chrome-spinel (Cr1.3-1.25)-(Fe0.708-0.548)-(Al0.518-0.433). Petrographical evidences such as lack of coarse-grained felsic minerals, the presence of porphyritic texture and the co-existence of coarse-grained pyroxene, olivine and amphibole minerals as well as the similar oxides contents of SiO2 (44.25-46.435 wt.%), MgO (5.81-19.125 wt.%), Na2O (1.55-2.035 wt.%), K2O (1.18-1.715 wt.%) to the average of the well-known alkaline lamprophyres (SiO2=42.5 wt.%, MgO=7.25 wt.%, Na2O=35 wt.%, K2O=25 wt.%), suggest that the studied dykes are similar to the alkaline lamprophyres (monchiquites) rather than calcalkaline spessartites. Thermo-barometric studies of pyroxenes show that the rocks under discussion have been formed under pressure of 5-10 Kb and temperature of 700-900 ºC with less than 10 percent water contents. Whole rock chemical analyses of the studied lamprophyres indicate that the parent magmas were alkaline type and originated from a metasomatized spinel-garnet-lhezrolite mantle source containing hydrous minerals, then they were emplaced in a post-collisional arc setting.
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