Study on the Weathering of a Dinosaur Fossil From Hami,Xinjiang
The discovery of dinosaursfrom the Early Cretaceous Pterosaur Fauna in Xinjiang has increased the diversity of the fauna and provided new information for the phylogenetic evolution of dinosaurs,which is of great scientific significance.However,when the Hami dinosaur fossils were preserved off-site from their original burial environment,they showed severe weathering due to changes in the preservation environment.In order to better preserve,study,and display the Hami dinosaurfossils,this paper used a variety of analytical techniques to examine the Hami dinosaur fossils that have shownsignificant weathering and to analyze the causes of weathering and fragmentation of the fossils.X-ray diffraction(XRD)showed that the severely weathered area of the Hami dinosaur fossils was the cancellous part of the bone.The main mineral components were quartz and calcite,containing less apatite,feldspar and clay minerals.Quartz and feldspar are foreign clastic particles in the cancellous pores of the filled bone.Calcite is a cement formed in the later diagenesis or fossilization process,and a small amount of apatite is mainly from the bone.The results of ion chromatography(IC),Fourier transform infrared spectroscopy(FTIR),Raman spectroscopy(Raman)and scanning electron microscopy(SEM-EDS)showed that the soluble salts in the weathering area of dinosaur fossilswere mainly NaCl,CaCl2 and Ca(NO3)2·4H2O,and a small amount of CaSO4.The soluble salt content was as high as 2.63％,and the preliminary conclusion is that the high soluble salt content was the main cause of the severe weathering of fossils.The mercury intrusion test(MIP)results show that the porosity of the weathering area of dinosaur fossilis 21.272 2％,which is significantly increased compared with the porosity of 16.420 6％in the unweathered area.In addition,there are two kinds of pore size distribution in the weathering area of dinosaur fossils,with the sizes of 0.005～0.04 and 17.3～283.2 μm,respectively.Compared with the unweathered area,the weathering area produces microcracks,and the number of large pore-sized pores increases sharply.It is concluded that the fossils contain a large number of deliquescent salts represented by CaCl2 and Ca(NO3)2·4H2O,which are easily affected by the changes intemperature and humidity in Beijingduring four seasons recycles.The deliquescent salts have a great destructive effect,thus increasing the porosity of the weathered areas of the Hami dinosaur fossils and increasing the pores.The internal filling structure is flimsy and heterogeneous,which eventually leads to the fragmentation of the Hami dinosaur fossils.This research work is of scientific significance for preserving and protecting dinosaur fossils from Hami in ex situ.
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