<正>The Bayan Obo in the northern North China Craton is the world’s largest light rare earth element(LREE)deposit and the largest niobium(Nb)and thorium(Th)dep
<正>1 Introduction Biological markers or biomarkers(Eglinton et al.,1964;Eglinton and Calvin,1967)are molecular fossils,which were derived from once living orga