چند نقطه عطف در تاريخچه تكتونوماگمايي ايران

Some Turning points on Tectonomagmatic History of Iran

This article presents the interpretation of tectonomagmatic data of Iran, including the locations and movements of blocks in the past, the consequences of the breakage of the Neothetys oceanic crust in Upper Cretaceous, the magmatism originated from the obduction of crust and hot continental mantle over the serpentinized ophiolitic sheets, and the intereference of the two tectonic regimes such as the superposition of subduction and collision zones on the paleo hot spots which were already the agent for the formation of immature rifts within continents.It is inferred that the extension of Neothetys ocean was much more than that it was believed. Furthermore, its long time subduction beneath the Central Iran (and the Sannadaj-Sirjan zone, probably a series of island arcs at that time) was due to the northeastward movement of Africa, as well as a compensation for the oceanic crust generation. Superposition of the subduction and collision zones on paleo hot spots that created intracontinental rifts in Mesozoic, might have complicated the order of classical magmatism in those tectonic settings. The breakage of the Neothetys ocean in the Upper Cretaceous provided a situation that the collapsed and halted segments of this crust to be homogeneously heated up, causing intense and contemporaneous volcanism of the Eocene. This phenomenon then continued slightly during the Tertiary. Most of the Tertiary plutonic and subvolcanic bodies of Iran are comagmatic with the Eocene volcanism and resulted from the filter pressing of the deep magma chambers beneath the Eocene volcanoes during the Pyrenean and Styrian orogenies.Some of the magmatic activities occuring in the ophiolitic belts in hyper-collision zones millions of years after the obduction of oceanic crust might be the consequence of partial melting of mantle and the continental crust obducted over the sepentinizcd ophiolite slices.