Conservation of Jiaohe ancient earthen site in China

Earthen sites, which are mainly made of earth, are cultural heritages with historical, artistic and scientific values. Many extremely valuable earthen sites have been preserved in the arid areas in China. The earthen site of Jiaohe Ancient City is one of the earliest National Protected Important Cultural Heritage Sites. The Jiaohe Ancient City site exhibits all kinds of deteriorations, which can be found in the earthen sites in arid environments in China. Through a case study of the Jiaohe ancient earthen site, we present in this paper the comprehensive conservation technologies, including the mud bricklaying and reparation, wooden rod anchorage, crack grouting, surface potassium silicate （PS） penetration consolidation, and suspended steel beam ceiling, etc. Results of this case study showed that better conservation effects could be achieved by selecting proper PS penetration and crack grouting processes based on the deterioration characteristics of the earthen sites. The technology of mud bricklaying and reparation was also an effective method for preventing the earthen body from collapsing. Compared with traditional conservation technologies, the suspended steel beam ceiling technology could effectively reduce the negative impacts to the original state of the earthen site. As for unstable cliffs, a new method using composite anchor rod of bamboo and steel with massive loose earth was applied. Deformation monitoring and temporary supports were critical and indispensable measures for the safe of site conservation projects. Through years of monitoring and practical operation at the Jiaohe ancient earthen site, deterioration at the site has been effectively controlled.

Deformation of the Subcontinental Lithospheric Mantle in NE China:Constraints from Rheological and Fabric Study of Mantle Peridotite Xenoliths from Jiaohe,Jilin Province

Mantle peridotite xenoliths in Jiaohe City,located near the northern part of the Tan-Lu fault,are key evidence for constraining the nature and evolution of the subcontinental lithospheric mantle(SCLM)of the NE China.Geochemical characteristics of Jiaohe peridotite xenoliths have been well studied,whereas the microstructures and associated fabrics remain poorly known.We report here major element composition of the constituent minerals,P-T conditions,microstructure,lattice preferred orientations(LPOs)of a set of xenoliths having coarse-grained and granuloblastic to porphyroclastic textures.These xenoliths are characterized by forsterite content of 89-91 in olivine.Dislocation microstructures,in olivine crystals revealed by oxidation decoration technique,are characterized by free dislocation,dislocation walls,dislocation loops and subgrains.Microstructures and deformation mechanism maps indicate that dislocation creep is the dominant deformation mechanism of almost anhydrous olivine in the SCLM.In most samples,the observed LPOs of olivine are typical A-type fabric.Stresses measured in the xenoliths using several olivine piezometers are~2.7-8.5 MPa.The equilibration temperature conditions,calculated using several geo-thermometers,indicate the equilibrium temperature condition of peridotites in a range of 891 to 993℃.These results provide rheological constraint on the deformation of the SCLM in Jiaohe.Combined with the data for mantle xenoliths from adjacent regions,a heterogeneous evolution of the lithosphere deformation is inferred at the Jiaohe region.We propose that characteristics of the studied peridotite may be related to the Tan-Lu fault.