Amalgamation Processes Of The Songliao And Jiamusi Massifs:Evidence From Detrital Zircons Of Late Paleozoic Terrestrial Strata

The Central Asia Orogenic Belt(CAOB) is one of the large scale accretionary orogenic belts in the world,of which eastern part is dominated by Paleo Asian Ocean tectonic system in Paleozoic,Paleo Pacific and Mongol-Okhotsk tectonic systems in Mesozoic.Songliao and Jiamusi massifs are situated in the easternmost part of the CAOB,that is the critical region of which issues are related to the overprinting processes of multiple tectonic regimes.It is generally recognized that the closure of Mudanjiang Ocean between the two massifs took place in the Mesozoic.Whereas the Early Paleozoic magmatism also developed along the Mudanjiang suture zone,while there are comparable Paleozoic strata on the two massifs,indicating that the two massifs had converged once during the Paleozoic.The tectonic history of the two massifs in the Late Paleozoic is still debatable.The Carboniferous-Permian continental facies stratum mainly developed in Binxian,Wuchang and Tieli region on the Songliao Massif,Baoqing and Mishan region on the Jiamusi Massif.For purposes of comparison,samples from the Songliao and Jiamusi massifs in the Late Carboniferous to Early Permian and Late Permian are obtained.The LA-ICP-MS zircon U-Pb dating results indicate that the maximum depositional age of Middle Permian Tumenling F.m.and Late Permian Hongshan F.m.in Songliao Massif is ~260 Ma,while that of Tatouhe F.m.and Zhenzishan F.m.in Jiamusi Massif are ~290 Ma and ~300 Ma,respectively.These results are compatible with the chronostratigraphic framework formerly founded.The age peaks of ~290–300 Ma,~400 Ma,and ~500 Ma showed in the Late Carboniferous to Early Permian strata of Jiamusi Massif and the Middle Permian strata of Songliao Massif.The age peak of ~500 Ma in the Middle Permian strata of Songliao Massif may derived from the Cambrian basement,Mashan Complex,of the Jiamusi Massif,while the age peak of ~420–440 Ma in the Carboniferous strata of the Jiamusi Massif may derived from the Silurian magmatic arc in the eastern periphery of the Songliao Massif,reveals the history that they had been potential sources region of each other,indicating they were combined together during the Paleozoic.In the Late Permian,The Hongshan F.m.of the Songliao Massif lacks the age peak of ~500 Ma,which indicate that the Jiamusi Massif ceased to be the provenance of the Songliao Massif in the Late Permian,that is,there was a palaeogeographic isolation between the two massifs.Combining with the ~210 Ma bimodal volcanic rocks developed along the suture zone,this work demonstrating the tectonic frame: the Songliao and Jiamusi massifs should have been connected till the Late Permian and the ocean between them was reopened during Late Permian to Late Triassic.