首页|Geochronology, geochemistry and petrology of the oligocene magmatism in SE segment of the UDMB, Iran
Geochronology, geochemistry and petrology of the oligocene magmatism in SE segment of the UDMB, Iran
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Despite diverse geochronological-geochemical studies on Cenozoic igneous rocks from the SE segment of the Urumieh-Dokhtar Magmatic Belt (UDMB) of Iran, the nature of the Oligocene magmatic rocks from the farthermost end of the SE segment- where it is linked to the Makran magmatic belt- has been ignored due to the difficulty of access. In this study, we focus on syn-collisional mafic to felsic igneous rocks of calc-alkaline and high-K calc-alkaline affinities from the SE segment of the Urumieh-Dokhtar Magmatic Belt (UDMB) near Nagisun, south of Bam. The Nagisun rocks have low Sr/Y and La(n)/Yb(n), similar to igneous rocks from typical arcs. Zircon U-Pb ages show comparable ages for plutonic (～ 34-25 Ma) and volcanic (～34-27 Ma) rocks. The eHf(t) values for zircons from plutonic rocks range from -0.3 to +12.8, whereas the eHf(t) values for the volcanic rocks vary from -2.6 to +13. Modelling of trace elements compositions using Nagisan basaltic samples indicate that an 87:2:11 mixture of the depleted MORB mantle, subducting (trench)-sediments and altered oceanic crust with 5% aggregated fractional melting closely matches the trace-element abundances of the Nagisun basaltic rocks. Indeed, the modelling of Sr and Nd isotopic data emphasizes that the Nagisun magmatic rocks could be products of bulk mixing between a depleted MORB mantle and/or a mixed, fertilized mantle with the Cadomian lower and upper continental crust. Furthermore, our compiled data display that the magmatism in the SE segment of the UDMB changed through time from normal calc-alkaline magmatism to adakitic magmatism at ~20 Ma, after the collision with Arabia began ca 27 Ma.
Hadi Shafaii Moghadam、William L. Griffin、Jose F. Santos
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School of Earth Sciences, Damghan University, Damghan 36716-41167, Iran
Arc Centre of Excellence for Core to Crust Fluid Systems and GEMOC ARC National Key Centre, DepL of Earth and Planetary Sciences, Macquarie University, NSW 2109, Australia
Geobiotec, Departamento de Geociencias, Universidade de Aveiro, 3810-193 Aveiro, Portugal
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