List of Articles Calc-alkaline.

• Open Access Article
  • Abstract Page
  • Full-Text
  
  1 - Magma mixing in Dehe Bala granodiorites and their mafic enclaves, SW of Boein Zahra: Evidence for I type calc-alkaline magmatism from both lithospheric mantle and lower crustal sources
  Zeynab Gharamohammadi Fatemeh  Najmi
  Dehe Bala granodioritic pluton with an E-W trend is exposed approximately 45 km south-west of Boein Zahra town, Qazvin province. This pluton includes several mafic microgranular enclaves (MMES) with diorite and quartz monzodiorite in composition. The ellipsoidal and rou More

  Dehe Bala granodioritic pluton with an E-W trend is exposed approximately 45 km south-west of Boein Zahra town, Qazvin province. This pluton includes several mafic microgranular enclaves (MMES) with diorite and quartz monzodiorite in composition. The ellipsoidal and rounded enclaves with 2 to 30 cm in sizes have been scattered in host granodiorites. The enclaves commonly have a sharp contact with the host granodiorites. Textural evidence indicative of disequilibrium condition, include plagioclase with oscillatory zoning and repeated resorption surfaces, acicular apatite and quartz ocelli as chemical and/or thermal changes in the melt during crystal growth and as evidence for occurrence of magma mixing. The enclaves enriched in LILES and LREES and are depleted in HFSES. The SiO2 content of the granodiorite ranges from 64.2 to 66.9 wt%. They are high-k calc-alkaline in composition, displaying a metaluminous character (A/CNK<1.1). Enrichment of incompatible elements such as La, Ce, Rb, Th, K and Nd coupled with negative anomalies of Ti, Ba, Eu, Nb and P implying the role of the lower crust in the formation of the granodioritic magma, but relatively high content of Mg value (0.39 – 0.43) suggest that the granodiorites were generated by mixing of mantle-derived mafic magma with felsic melt derived by partial melting of lower crust. The MMEs are characterized by relatively low contents of SiO2 = 52.8–58.2 wt%, moderate K2O=1.4-3.8 and high Mg (0.4 -0.46). Geochemical features and values of Dy/Yb=1.6 – 1.8 in MMES suggest that enclave magmas were derived by partial melting of the mantle wedge in the spinel–garnet transition zone and they have partially evolved in contact with fusion of crust-derived felsic magmas. Manuscript profile
• Open Access Article
  • Abstract Page
  • Full-Text
  
  2 - Magma mixing in Dehe Bala granodiorites and their mafic enclaves, SW of Boein Zahra: Evidence for I type calc-alkaline magmatism from both lithospheric mantle and lower crustal sources
  Zeynab  Gharamohammadi علی  کنعانیان Mohsen Zargham
  Dehe Bala granodioritic pluton with an E-W trend is exposed approximately 45 km south-west of Boein Zahra town, Qazvin province. This pluton includes several mafic microgranular enclaves (MMES) with diorite and quartz monzodiorite in composition. The ellipsoidal and rou More

  Dehe Bala granodioritic pluton with an E-W trend is exposed approximately 45 km south-west of Boein Zahra town, Qazvin province. This pluton includes several mafic microgranular enclaves (MMES) with diorite and quartz monzodiorite in composition. The ellipsoidal and rounded enclaves with 2 to 30 cm in sizes have been scattered in host granodiorites. The enclaves commonly have a sharp contact with the host granodiorites. Textural evidence indicative of disequilibrium condition, include plagioclase with oscillatory zoning and repeated resorption surfaces, acicular apatite and quartz ocelli as chemical and/or thermal changes in the melt during crystal growth and as evidence for occurrence of magma mixing. The enclaves enriched in LILES and LREES and are depleted in HFSES. The SiO2 content of the granodiorite ranges from 64.2 to 66.9 wt%. They are high-k calc-alkaline in composition, displaying a metaluminous character (A/CNK<1.1). Enrichment of incompatible elements such as La, Ce, Rb, Th, K and Nd coupled with negative anomalies of Ti, Ba, Eu, Nb and P implying the role of the lower crust in the formation of the granodioritic magma, but relatively high content of Mg value (0.39 – 0.43) suggest that the granodiorites were generated by mixing of mantle-derived mafic magma with felsic melt derived by partial melting of lower crust. The MMEs are characterized by relatively low contents of SiO2 = 52.8–58.2 wt%, moderate K2O=1.4-3.8 and high Mg (0.4 -0.46). Geochemical features and values of Dy/Yb=1.6 – 1.8 in MMES suggest that enclave magmas were derived by partial melting of the mantle wedge in the spinel–garnet transition zone and they have partially evolved in contact with fusion of crust-derived felsic magmas. Manuscript profile
• Open Access Article
  • Abstract Page
  • Full-Text
  
  3 - Tectonomagmatic setting of the Eocene volcanic rocks in Ahovan area (Semnan)
  Maryam Alipour Morteza Khalatbari-Jafari Mohsen Pourkermani Sedigheh Etesami Ali Sorbi
  Petrology and tectonomagmatic setting of the Eocene volcanic rocks exposed in the Ahovan area, east of Semnan are presented and discussed. The studied rocks include basic-intermediate and acidic volcanic lavas and dikes, accompanied by intercalations of nummulite-bearin More

  Petrology and tectonomagmatic setting of the Eocene volcanic rocks exposed in the Ahovan area, east of Semnan are presented and discussed. The studied rocks include basic-intermediate and acidic volcanic lavas and dikes, accompanied by intercalations of nummulite-bearing limestone, shallow water deposits, hyaloclastite and hyaloclastic breccia. The basic-intermediate lavas are exposed at the base and the rhyolitic and andesitic lavas are exposed at the top of the volcanic series, all of which may be attributed to a bimodal volcanism. It seems that Eocene volcanic activity occurred in shallow water to subaerial environments. Based on petrographical investigations, the volcanic lavas show basaltic, basaltic andesitic, andesitic, dacitic, rhyolitic and acidic tuffs compositions. The lavas have phyric to aphyric textures. The phyric lavas include plagioclase, augite and hornblend phenocrysts. They show microlitic, microcrystalline and intergranular groundmass in dikes. Disrupted zoning and sieve texture in plagioclase phenocrysts and heterogeneous groundmass might be interpreted by magma mixing. Study of the geochemical analyses, indicates high-k calc-alkaline to shoshonitic magmatic trends in the Ahovan area. Trace and REE spider diagrams, normalized with standard values, display enrichment of LILE and clear depletion of Nb and Ti. In tectonomagmatic diagrams, these samples plot in the arc field which tends toward an initial extensional back arc envirenment. It appears that partial melting of adjusted mantle wedge above a subducted slab provided the parental magma which was enriched by fluids-melt released from partial melting of the subducted slab. Manuscript profile
• Open Access Article
  • Abstract Page
  • Full-Text
  
  4 - Tectono-magmatic setting of diabase and basalt flows in north Makran ophiolite, southeast of Iran
  Azizollah Bazzi Mohammad Mahdi Khatib Mohammadhosein Zarrinkoub
  The north Makran ophiolite in southeast of Iran, as a part of Tethyan ophiolites, is located between Lut and Bajkan-Durkan continental blocks. Among the rocks of this ophiolite sequence, diabase and basalt flows are present more abundant in the outcrops in the eastern p More

  The north Makran ophiolite in southeast of Iran, as a part of Tethyan ophiolites, is located between Lut and Bajkan-Durkan continental blocks. Among the rocks of this ophiolite sequence, diabase and basalt flows are present more abundant in the outcrops in the eastern part of the studied north Makran ophiolite. Structural, petrographic and geochemical evidences suggest distinct geodynamic setting for the formation of these rocks. Based on geochemical characteristics, diabase and basalts fall into two groups: In the first group, tholeiitic diabase and basalt flows represent MORB-like affinity, and the second group include calc-alkaline basaltic to dacitic lavas with arc environment and supra-subduction affinities. These two lava types represent two major magmatic events: 1) MORB-type magmatism resulted from Early Cretaceous rifting/opening between two continental blocks and resulted in the formation of tholeiitic diabase and basalt. LREE enrichment, low La/Yb and relatively high U/Th ratios suggest continental influence in their melt source, and 2) subduction-related magmatism, that formed calc-alkaline basaltic, andesitic and dacitic lavas in Late Cretaceous. LILE, LREE enrichment, Nb and Ta negative anomaly, low TiO2 concentrations and relatively high Ce/Pb ratio document subduction influence in their composition. Manuscript profile