Geochemistry and Zircon SHRIMP U-Pb Chronology of the mafic dyke swarms from Gaoligong magmatic zone and their geological significance

Gaoligong magmatic zone locates at the southeastern part of Eastern Himalayan Syntaxis, which is the east extension portion of the eastern Tethyan and Gangdese magmatic belt. This paper focuses on the mafic dyke swarms from Gaoligong zone of magma and presents particular research about the geochemical characteristics, Sr-Nd isotopic compositions and SHRIMP U-Pb zircon geochronology. Through these studies it can be concluded that the mafic dyke swarms basically consists of proterobase which is enriched in high field strength elements, lightly depleted in Nb-Ta and Ti. Besides, the proterobase's rare earth elements pattern shows light rare earth elements concentrations and flat curve of heavy rare earth elements. Sr-Nd isotopic compositions (ɛNd(T): -0.2- -5.9; ISr: 0.70523 - 0.70830) illustrate that these swarms originate from the enriched mantle. SHRIMP U-Pb zircon geochronological data demonstrate that the age of these mafic dyke swarms is 127±3 Ma. Consequently, this set of mafic dyke swarms is suggested to contain the features of active continental marginal arc derived from enriched mantle, moreover, some analysis proves that it is related to the hybridization of crust-derived and mantle-derived magma, or contaminated by crustal materials.