Petrogenesis of Borneo's Triassic granitoids in SE Asia and crustal growth of the southeastern margin of Pangea-Eurasia Continent
The Pangea supercontinent is the youngest one in Earth's history.It is generally believed that its main body was formed by the assembly of Gondwana and Laurasia continents in the Permian.During the Triassic period,the Southeast Asia continent continually grew around the southeastern edge of Eurasia Continent.It is the only conveyable zone connecting with the Panthalassa Ocean.However,the formation and convergence of many small-and medium-sized blocks in Southeast Asia during the final formation of the Pangaea supercontinent are still not clearly understood.The identification of Triassic magma source(ancient vs.juvenile)and block signatures(allochthonous vs.autochthonous)in Southeast Asia is crucial to understand processes of the convergence of many small-and medium-sized blocks and the growth of continental crust in the Tethys of Southeast Asia.Among many small-and medium-sized blocks in Southeast Asia,the Borneo Island is the largest block occupied the central part of Southeast Asia.It is generally considered to have recorded processes of convergence and collision of several ancient blocks(small continental blocks)in the Mesozoic era.Our research results show that the Western Borneo Triassic granitoids(in the Kuching and NW Schwaner zones)have mixed characteristics of the Indochina granitoids(with ancient crust signature)and the Northern Borneo granitoids(with juvenile crust signature)in terms of elemental and isotopic geochemistry,indicating that the juvenile components(mantle materials)had been developed in the area since the Triassic.The regional data compilation shows that all zircons of the Borneo granitoids are characterized with two-stage ages(about 240 Ma and 210 Ma)and positive εHf(t)values,indicating two-stage significant contributions of juvenile components to those granitic magmas.These contributions of juvenile components resulted in the autochthonous crustal growth of the Borneo terrane in the southeastern margin of Pangea-Eurasia Continent and the further crustal growth of the Pangea-Eurasia Continent margin(Sumatra,Java,and Borneo)to the southeast.This autochthonous crustal growth may not be attributed to a single subduction-accretion process of the paleo-Pacific or Tethys systems,as traditionally thought,but may be related to the exchange of matters and energy between two systems(the Tethys Ocean and the Panthalassa Ocean)in the Pangea's conveyable zone.
万方数据
维普
