Temporal And Spatial Distribution Patterns Of Early Cretaceous A-type Granites In Northeast Asia And Their Significance

Northeast Asia is located in the superimposed area of the two major tectonic systems of Mongolia-Okhotsk Ocean and Paleo-Pacific.During the Late Mesozoic,especially the Late Jurassic-Early Cretaceous,a huge amount of magmatism and regional large-scale extensional structures developed.The scope and time limit of the structural system has always been controversial.The granites from the Erdene dome in Mongolia and alkaline from the Wulingshan in Hebei were selected for detailed study,including field survey,petrology and geochemistry,to elucidate their petrogenesis and tectonic significance.Geochemical data,using attribute-driven Arc GIS to compile maps,summarize the temporal and spatial distribution of granites in Northeast Asia,especially the A-type granites closely related to extension in the Early Cretaceous,and their relationship with minerals.The following results have been achieved:1?Erdene granite in southern Mongolia was intruded at 125 Ma.It is a high-potassium calcium-alkaline aluminum A1-type granite with dominate crust sources and formed in an intraplate setting.The ~130Ma Wulingshan syenite is also belong to the A1-type(intraplate)granite,but it is the product of crust-mantle magma mixing.2?The Early Cretaceous A-type granites in Northeast Asia formed in two stages of the early Early Cretaceous(148-134 Ma)and the late Early Cretaceous(134-104 Ma)and most of them are distributed in south of the Mongolia-Okhotsk orogenic belt.The early granites were mainly distributed in the west partfew in the east of Songliao basin;while the late Early Cretaceous granites were distributed throughout the region and relatively more concentrated in the east,generally parallel to the Pacific tectonic domain.3 ? A-type granites in the Northeast Asia were developed in the Early Cretaceous,also formed in two stages with a peak of ~135Ma.Early-stage A-type granites were mainly distributed in the west and occasionally developed in the east.Meanwhile,the late-stage A-type granites were mainly distributed in the central and eastern parts,and they are generally distributed parallel to the Pacific tectonic domainand do no show obvious spatial migration.4 ? The Early Cretaceous A-type granites in Northeast Asia were formed by cumulated affection of Mongolia-Okhotsk and Paleo-Pacific setting.The early Early Cretaceous A-type granite was more controlled by the intraplate extension and collapse after close of the Mongolia-Okhotsk Ocean and rollback of the subduction the Paleo-Pacific Ocean overlayed on the this area in late Early Cretaceous,and massive magmatism and extensional structures,such as domes,MCCs were formedin the Northeast Asia.with mineralization explosion.