New Evidences of Precambrian and Paleozoic Magmatism in the Gharebagh Intrusives, NW Iran

The Gharebagh intrusive complex which includes mafic, diorite and acidic rocks is a part of the Sanandaj-Sirjan zone in northwestern of Iran and a part of the Zagros orogenic belt. This complex has intruded into Precambrian metamorphic rocks. U-Pb daiting of zircons of a Lueicogranite has been identified 558.6 ± 3.8 Ma. The cores of some zircon grains are aged too old to 2400 Ma in this sample. These are the parts of remained original rocks. It can be inferred that the basement area is older than Precambrian intrusive, and maybe indicate the presence of Panafrican basement similar to which has been found mainly in the central Iran. Ages obtained in five Gabbro samples are 300.0 ± 1.3 Ma to 301.5 ± 1.3 Ma, in two Diorite samples 300.7 ± 1.5 Ma and in a Monzogranite sample 300.7 ± 1.7 Ma. Age obtained in Alkaligranite pach within the Gabbros is 303.4 ± 1.5 Ma. These rocks have the same ages and that can be inferred that all of them have been affected by one geology event in late Paleozoic. Based on chemical analysis data, a mantle source for mafic rocks is understanded. This Mafic magma has a very high temperature so that its heat causes melting of the lower crust and formation the Alkaligranitic magma simultaneously with it intrusion. These datings, shows polotonism of upper Paleozoic in the northwestern part of Sanandaj Sirjan zone. It can be inferred that this is the beginning of Neotethys opening in Iran.