S. Z. Hosseini; M. Arvin
Abstract
Neogene volcanism in the Tel Gorban-Chah Breshk area, north of Shahre-Babak, occurs as dacitic to andesitic lava flows and domes. Petrographically the rocks consist of plagioclase, hornblende ±biotite and quartz phenocrysts setting in porphyritic and hyalopilitic matrix. Opacitization of hornblende ...
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Neogene volcanism in the Tel Gorban-Chah Breshk area, north of Shahre-Babak, occurs as dacitic to andesitic lava flows and domes. Petrographically the rocks consist of plagioclase, hornblende ±biotite and quartz phenocrysts setting in porphyritic and hyalopilitic matrix. Opacitization of hornblende and biotite and zoning and sieve texture in plagioclase are signatures of disequilibrium conditions through the magma cooling. Geochemical data and petrological diagrams show their medium potassic calc- alkaline nature. Enrichment in LILE’s and depletion in HFSE’s (eg. Nb,Ta,Ti) points to a subduction tectonic environment for Tel Gorban-Chah Breshk dacitic to andesitic rocks. Furthermore, their Al2O3>16,Sr/Y>80 and chondrite normalize REE pattern are quite similar to dakites. Distinctive geochemical features such as Rb/Sr< 0.04, La/Yb> 18, Yb< 1, (Sr/Y)n> 80, and Y
A. Ansari; S. J. Sheikh Zakariaee; S. Dargahi; M. Arvin
Abstract
The Chargonbad batholith is located close to Sirjan and southeast of Urumieh-Dokhtar magmatic zone . This batholith is acidic to intermediate in composition and intruded into the Eocene volcanic rocks. The main volume of these rocks consisted of granodiorite and monzogranite, but it also consists of ...
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The Chargonbad batholith is located close to Sirjan and southeast of Urumieh-Dokhtar magmatic zone . This batholith is acidic to intermediate in composition and intruded into the Eocene volcanic rocks. The main volume of these rocks consisted of granodiorite and monzogranite, but it also consists of quartzdiorite, tonalite and syenogranite. Their contacts are gradational. They have allotrimorphic granular texture with subordinate porphyritic texture. Their enclaves consist of xenoliths enclaves, microgranular mafic enclaves (diorite to quartzdiorite in composition) and autolith enclaves(tonalite, granodiorite and monzogranite in composition).The Chargonbad batholith rocks are also cut by different types of dykes which are mainly consisted of dykes and veins of pegmatitic stage, microgranular dykes (andesite and andesite basaltic in composition) and microgranular dykes that are similar to mafic enclaves. Evidenc show that the samples represent properties of I-type granitoids. Chargonbad granitoid has magnesium nature and shows cordellarian granites features. Based on the tectonomagmatic environment diagrams, all samples from the Chahargonbad plot in the island arc setting of a subduction zone and show active continental margin setting characteristics .
S Sedighian; S Dargahi; M Arvin
Abstract
Khunrang intrusive complex, as a one of the largest complexes in the southern part of the Sanandaj-Sirjan zone, is located at northwest of Jiroft, in Kerman province. The complex mainly consists of acidic-intermediate rocks such as diorite, quartzdiorite, tonalite, granodiorite, and granite with subordinate ...
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Khunrang intrusive complex, as a one of the largest complexes in the southern part of the Sanandaj-Sirjan zone, is located at northwest of Jiroft, in Kerman province. The complex mainly consists of acidic-intermediate rocks such as diorite, quartzdiorite, tonalite, granodiorite, and granite with subordinate amounts of mafic members such as hornblende gabbro and microgabbro. Field studies together with mineralogical and geochemical evidence show that the Khunrang intrusive complex belongs to calc-alkaline series and its felsic members are metaluminous to weakly peraluminous which display features typical of I-type granites. On the primitive mantle-normalized spider diagrams, all mafic and felsic samples are enriched in LILE (such as Rb, Cs and K) and depleted in Ti, Ta and Nb which is a main characteristic of subduction-related magmas. Based on geochemical data, the mafic rocks seems to be formed by melting of metasomatised mantle wedge; whereas felsic rocks are formed by melting of lower crust metabasic rocks as a result of the injection of mantle derived mafic magmas. It can be concluded that the Khunrang intrusive complex was formed in a volcanic arc setting due to subduction of the Neotethys oceanic crust beneath the Central Iranian Micro-continent in the Middle-Jurassic time.
D Raeisi; S Dargahi; S.H Moeinzadeh; M Arvin; B Bahrambeigi
Abstract
Gandom-Berian area, located on southern part of the Kavir-e Lut, covers an area around 480 km2 and morphologically is a covered messa by very dark basaltic lava flows. Their major minerals are olivine and clinopyroxene phenocrysts along with plagioclase microlites and their main textures are microlitic ...
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Gandom-Berian area, located on southern part of the Kavir-e Lut, covers an area around 480 km2 and morphologically is a covered messa by very dark basaltic lava flows. Their major minerals are olivine and clinopyroxene phenocrysts along with plagioclase microlites and their main textures are microlitic porphyry to glomeroporphiry with interestal to intergranular groundmass. The in line position of volcanic cones along the line of movements of Nayband fault show its effect on the formation of Gandom-Berian basaltic magma. The genetic realationship of these lava flows with deep seated lithospheric fractures as a result of Nayband fault, the presence of mantle xenoliths and alkaline nature of basalt all reveal a fast deep ascending of magmas. Based on geochemical analysis and occurrence of nepheline in the norm composition the Gandom-Berian basaltic lava flows belong to basanite-tephrite group. The investigation on Gandom-beriyan alkali basalts clearly shows their relationships to an intera-continental extensional environment. Low ratio of Ce/Nb, Th /Nb, U/Nb, Ba/Nb and High levels Zr with mean 234.81 indicate a none depleted asthenospheric mantle source the origin of Gandom-Berian basaltic lava flows. Enrichment and depletion of light and heavy rare earth elements respectively indicate the existence of garnet in the source rock.
