Abstract:The volcanic rocks in Junggar Basin are mainly basaltic and andesitic rocks, and subordinately dacite and rhyolite. Most of the rocks exhibit slight enrichment of LREE and somewhat low HFSE abundances relative to the LIFE. Such features are commonly regarded as characteristics of subduction-related magmatism. The rocks in the three regions have positive εNd(0) and relatively low (87Sr/86Sr)i, suggesting that the basement volcanic rocks were generated in the depleted mantle wedge that had been enriched in incompatible elements by subduction without old continental contamination. In addition, Nd single-stage model ages vary from 400 Ma to 700 Ma. The single-stage model age indicates that the subducted sedimentary rocks are younger than 700 Ma. The isotopic and trace element geochemical characteristics of basaltic volcanic rocks imply that these regions should belong to different arc accretionary systems. On such a basis, it can be inferred that the basement volcanics formed in the environment of arc accretion and the juvenile materials added to the crust through the arc volcanism, which constituted the most important mechanism at that time, and that the basement of Junggar Basin was presumably assembled by the three different arc accretion terrains which belonged to Middle Asian Kazakstan, Tarim, and Siberia Plate respectively.

Abstract:On the basis of the newly published clinopyroxene-melt equilibrium thermobarometer, the authors calculated the clinopyroxene-melt equilibium temperature and pressure of mantle xenoliths_bearing basalts at Kuandian, Hannuoba and Mingxi in eastern China. The res_ ults show that the crystallization temperature and pressure of cpx porphyritic crystals in alkali basalts are generally higher than those in subalkali basalts, and the crystallization temperature and pressure of cpx megacrysts are higher than those of phenocrysts, which further proves that the cpx megacrysts crystallize at higher pressure than cpx porphyritic crystals. The existence of cpx phenocrysts at various pressures indicates that the cpx can crystallize continually along the way through which the magma moves upward. Regression analysis shows that although the basalts which bear mantle xenoliths move up so fast, they are not adiabatic but have heat diffusion. The comparison of temperatures and pressures between the crystallization of cpx phenocrysts (or megacrysts) and that of xenolith in alkali basalts indicates that host magma exists originally deeper than the mantle xenoliths in terms of pressure and so the xenoliths are fragments of the upper mantle captured by magma along the ascending way instead of being the source residues of host magma as considered previously.

Abstract:The Early Paleozoic ophiolite melanges in Hongliugou of Altun fault belt (AFB) is composed of mantle peridotites, gabbros, diabases, basaltic dykes, pillow lavas, silicalites and flysches. Two types of basalt have been recognized in the ophiolite melanges: T_MORB and OIB, whose REE distribution patterns are flat_type and LREE_rich_type respectively. The presence of such rock assemblages indicates the existence of an ocean basin in this region in Early Paleozoic. This rock combination is comparable with its counterparts in northern Qilian Mountains.

Abstract:Petrological and petrochemical characteristics show that there exist such volcanic and subvolcanic rock types as basalt, iddingsite olivine basalt, olivine basaltic trachyandesite, trachybasalt, latite, trachydacite, trachyte, rhyolite, tuff and granite-porphyry in northeast Jiangxi Province. The volcanic rocks can be subdivided into high K calc-alkaline series, shoshonite series and alkaline basalt series. The high K calc-alkaline series is rich in Si, K, and poor in Mg, Fe, Ca, Al. The shoshonite series and alkaline series are rich in K,Al,Ti and poor in Si. It seems that shoshonite is richer in K,Ti,Si and poorer in Mg,Fe,Ca than alkaline basalt series. These complicated volcanic rocks might have resulted from strike-shift and angled subduction of Faralong, Izanagi and Kula plates relative to Asian continent and the NE-NNE trending strike-shift shearing and extension generated from the plates movement.

Abstract:Exposed on the northern edge of North China Platform, Xilin Gol complex has an age of 1.3~1.0 Ga. It is mainly composed of hornblende-plagioclase gneiss and biotite-pla-gioclase gneiss, plagioclase-hornblende schist, and amphibolite. Subjected to metamorphism of hornblende subfacies, its protolith comprises mostly calc_alkaline igneous rocks. This paper deals with mineral chemistry of amphiboles and feldspars in the complex and indicates that the metamorphism took place at temperature of 540~550℃and pressure of 0.5~0.6 Gpa.

Abstract:The Jinshan gold deposit hosted in the ductile shear zone is located in the well-known Dexing copper_gold concentration district, northeast Jiangxi Province. K-Ar ages of illite formed during fluid-rock interaction indicate that there existed an obvious Late Paleozoic tectonic hot event in Jinshan district. Baesd on the geological setting, the paper holds that the ore-forming process of the Jinshan gold deposit was related to this tectonic hot event. The ore-forming age of the Jinshan gold deposit is between 269.9 Ma and 317.9 Ma. The paper suggests that there is no direct evidence for the influence of Yanshanian magmatic activity on Jinshan mineralization. It is concluded that there is an obvious Herenian magmatic activity in Northeast Jiangxi or even in whole South China, which seems to be an important gold deposit_forming period.

Abstract:Principal component analysis (PCA) is aimed at explaining the covariance structure of multivariate data by way of reducing the whole data set to a smaller number of independent variables. By means of iso_ion spectrometry, the authors have analyzed 56 groups of trace elements data (Au, Ag, Sb, Cu, Pb, Zn, Sr, Ba, Mn, Co, Ti, Cr) along two sections of Gaojian Group in southwestern Hunan, and explained the geological implications of the calculated results and PCA figures. Components F1 in Section C and Section L have similar information, reflecting the main characteristics of original sediments in the two sections. As for the data of section L, 13 kinds of trace elements data are divided into 5 groups: Co-Zn-Cu(Mn, Ba), Ti-Cr, As-Sb, Au-Pb-Sr and Ag, as indicated in F1-F2 diagram. With regard to the data of Section C, the groups of variables are not identified very well. As, Cr, Sb and Ti are correlated closely with component F2, whereas Sr is in negative correction with component F2. The processes controlling the distribution of such noble metals as Au and Ag were complex. The oxidization environment controlled distribution of Au in Section L, and the reduction environment was beneficial to the precipitation of Au and Ag in Section C. As sedimentary environments are different, some trace elements in the northern part of the district are obviously different from those in the southern part. According to the squared distance (d k i) 2 of the "noise", the distribution of Ag and Pb was partly affected by the late tectonic movement.

Abstract:Hade 4 is the first large marine oilfield discovered recently in northern Manjiaer depression of Tarim basin. It was previously regarded as an oilfield formed in Himalayan (Neogene) period. Nevertheless, evidence from fluid inclusions, K/Ar dating of authigenic illite in the reservoir and retrospection of oil-water contact has revealed that the CⅢaccumulation (the major accumulation in the oilfield) was formed in Late Hercynian, whereas the C5 accumulation might be a secondary one formed by vertical adjustment of the CⅢaccumulation in Late Himalayan. Such a conclusion is of significance to the exploration and evaluation of western Manjiaer.

Abstract:Chemical leaching is widely applied to geochemical research of sediments. In this paper, 1 mol/L hydrochloric solution (HCl) and 1 mol/L acetic acid (HAc) were used to conduct leaching experiments on loess and paleosol samples. HAc leaches mainly the carbonate fraction in the loess and paleosols but has little effect on silicates or iron oxides. In contrast, 1 mol/L HCl solution dissolves not only carbonates but also some of iron oxides and chlorites, as evidenced by higher concentrations of Mg and Fe and higher leaching percentages of elements in the HCl leachate. Experimental results show that 1 mol/L HAc is an ideal dissolvent that caselectively leach the carbonate fraction in the loess and paleosols. On the basis of the leaching results, the average composition of the carbonate fraction, i.e., 1.71% of MgO, 490×10-6 of Sr and 6 7 0×1 0-6of MnO , was obtained . The leaching parameters reflect the degree of pedogenesis of the loess and paleosol sequence; moreover, the MnO content of HAc leachate is the best parameter to indicate the degree of pedogenesis.

Abstract:Pillared interlayered clay (called PILC for short), a novel class of material, has become a heated topic in the fields of geology, chemistry and material science. This paper has summed up new achievements in this aspect, which include pillaring of vermiculites, phlogopites and synthetic clays, three kinds of PILC of Ga/Al, Si/Al and REE/Al, pillaring of acid_activated clay, surfactant modification, and properties of ion exchange and adsorption of PILC. Moreover, some potential applications of PILC are also briefly described.

Abstract:Based on Mossbauer spectra and some related data, the authors have analyzed valence of Fe ion in sapphire and studied coloration mechanism of sapphire from Shandong Province. Absorption of visible light by Fe2+ -Ti4+ at 565 nm is the factor causing beautiful blue color, while black color results from Fe3+ absorbing visible light at 442 nm. Coloring experiments were carried out to remove Fe3+ as well as retain and add Fe2+ and Ti4+ , which prove to be successful.

Abstract:The mass percentage of different diameters of urban dust grains is as follows: there are no dust grains larger than 20 M; dust grains 20~30 M account for 13.54%; 30~50 M 23.00%; 50~80 M 14.04%; 80~100 M 10.40%; 100~120 M 5.52%; 120~140 M 3.02%; 140~160 M 7.90%; 160~180 M 1.74%; 180~200 M 7.52%; smaller than 200 M 11.98%. Generally the diameters of dust grains in Xi' an area are smaller than one millimeter, and hence they tend to form a repeated cycle of rising and sinking under the action of ex- ternal forces, and develop into particles that are likely to be breathed by human bodies, thus causing great harm to human health and environment.