| The North China craton is one of the world's oldest Archaean cratons, its lower crust and lithospheric mantle delaminated into asthenospheric mantle during the Mesozoic, which caused the material exchange between mantle and crust. The geochemicl characteristics of western Liaoning Cenozoic lavas and Longgan mantle xenoliths reveal the occurrence and the period of this process in this paper. Because the accurate analytical data are the basis of geological research, the proper sample preparations and analysing methods for geological samples are discussed in the first chapter.1. The research on the analytical method and the preparation ofgeological samplesThe pure quartz grains were grinded in both agate and tungsten carbide mortars and were then analysed by ICP-MS. The analytical results of grinded pure quartz grain compared with those of ungrinded show that tungsten carbide and agate mortars have no apparent contamination to geological samples for measured trace elements except for W, C and Co in tungsten carbide mortars.Major element concentrations of BCR-2, GSR-1 and GSR-3 were determined as unknown samples by XRF method that was established by using 38 national reference samples. The obtained values usually agree with recommended values within 1% relative, 5% relative for the oxide concentrations less than 0.5% and 3% relative for MgO and Na2O. Some trace element concentrations of GSR-9 were determined as unknown sample by XRF method that was also set up by using 38 national reference samples. The obtained values agree with recommended values within 10% relativeexcept for Ni, Cu, Zn, Pb and Nb.Trace element concentrations of USGS reference rokcs AGV-1 and BHVO-1 have been determined nearly 40 times within two years by ICP-MS solution method as unknown samples. The relative errors of obtained values from recommended values were less than 10%, most of which less than 5% except for transition elements, lighter mass elements and lower concentration elements.4 major and 38 trace elements of USGS glass reference materials BCR-2G, BIR-1G, BHVO-2G and AGV-2G were determined as unknown samples by LA-ICP-MS. The calibration was performed using NIST 610. The relative standard deviations and relative errors between obtained and recommended values were less than 10% for most elements, which were comparable with ICP-MS solution method.The weighted mean 206Pb/238U age of standard zircon TEMORA 1 determined by LA-ICP-MS method using standard zircon 91500 as external caliberate is 417.6+1.3Ma, which agrees with the age 416.75+0.48Ma determined by ID-TIMS method.The concentrations of trace elements Rb, Sr, Y, Z, Nb and Ba in Liaoning lavas determined by XRF and ICP-MS solution methods. The results obtained by XRF agree with those measured by ICP-MS within 10% relative for most elements. The Z-score for all 48 elements measued in GeoPTIO, GeoPTll and GeoPTIS respectively are between -2 and +2 except for Cu and Sc in GeoPT11. Most of them are in fact between +1 and -1.2. Characteristics of Mesozoic Liaoning intermediate-acidicvolcanic rocks and their tracing for delamination of lower crustMesozoic Liaoning intermediate-acidic volcanic rocks in Yixian and Xinglonggou Formations occur in isolated continental basins in the Yixian-Beipiao area of western Liaoning Province in the Eastern block of the North China craton. The features of the high-Mg volcanic rocks from these two formations include higher Sr (477 to 1618ug/g), lower Y (9-17ug/g) and Yb(0.98-1.65ug/g), depletion in HREE (LaN/YbN= 12-31), higher Sr/Y (32-119) ratio and Nb-Ta depletion relative to La inprimitive mantle normalized spider diagram. A striking feature of some lavas is the presence of zoned orthopyroxene phenocrysts which have lower Mg, Cr and Ni and higher Zr, Sr and Ga cores and just reversed mantles. The Nd isotopic model ages (TDM) of these lavas are as old as 1.8 Ga. The inherited zircon age populations include 2500, 1800, 780, 420, 310, 230, 160 and 130Ma and there is no correlation between initial 86Sr/87Sr ratio and Rb conte...
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