Platinum group element abundances in a peat layer associated with the Tunguska event,further evidence for a cosmic origin

【作者】 E.M.Kolesnikov； N.V.Kolesnikovat；

【Author】 Q.L.Hou~(a,c,*),E.M.Kolesnikov~b,L.W.Xie~a,N.V.Kolesnikova~b,M.F.Zhou~c,M.Sun~c a Laboratory of Lithosphere Tectonic Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,P.O.Box 9825,Beijing 100029,People’s Republic of China b Geological Faculty of Moscow State University,119899 Moscow,Russia c Department of Earth Science,University of Hong Kong,Pakfulam Road,Hong Kong,People’s Republic of China

【机构】 Geological Faculty of Moscow State University；

【摘要】 <正>We have measured excesses of Pd,Rh,Ru,REE,Co,Sr,and Y in a peat column from the Northern peat bog of the 1908 Tunguska explosion site.Earlier,in this peat column the presence of an Ir anomaly at the event layers(30-45 cm depth) has been found(Planet Space Sci.48(1998) 179).In these layers,Pd,Rh,Ru,Co,Sr,and Y show pronounced anomalies of a factor 4-7 higher than the background value.In the event layers there are also good correlations between the siderophile platinum group elements(Pd,Rh,Ru) and Co,indicators of cosmic material,which imply they might have the same source,i.e.the Tunguska explosive body.The patterns of CI-chondrite-normalized REE in the event layers are much flatter than those in normal peat layers and different from those in the nearby traps.Furthermore,in these layers the patterns of CI-chondrite-normalized PGEs and the element ratios(e.g.C/Pd,C/Rh,and between some siderophile elements) give evidence that the Tunguska explosive body was more likely a comet,although we cannot exclude the possibility that the impactor could be a carbonaceous asteroid.We have estimated the total mass of a solid component of the explosive body up to 10~3-10~6 tons.更多还原

【Abstract】 We have measured excesses of Pd,Rh,Ru,REE,Co,Sr,and Y in a peat column from the Northern peat bog of the 1908 Tunguska explosion site.Earlier,in this peat column the presence of an Ir anomaly at the event layers(30-45 cm depth) has been found(Planet Space Sci.48(1998) 179).In these layers,Pd,Rh,Ru,Co,Sr,and Y show pronounced anomalies of a factor 4-7 higher than the background value.In the event layers there are also good correlations between the siderophile platinum group elements(Pd,Rh,Ru) and Co,indicators of cosmic material,which imply they might have the same source,i.e.the Tunguska explosive body.The patterns of CI-chondrite-normalized REE in the event layers are much flatter than those in normal peat layers and different from those in the nearby traps.Furthermore,in these layers the patterns of CI-chondrite-normalized PGEs and the element ratios(e.g.C/Pd,C/Rh,and between some siderophile elements) give evidence that the Tunguska explosive body was more likely a comet,although we cannot exclude the possibility that the impactor could be a carbonaceous asteroid.We have estimated the total mass of a solid component of the explosive body up to 10~3-10~6 tons.更多还原