Abstract:The Fuchuan ophiolite is preserved well in the Jiangnan orogen of South China. In Fuchuan area, ophiolite is composed of the largest mantle peridotite massif in the orogen, cumulated rocks, pillow lavas and some ribbon cherts. The mantle peridotite massif includes major massive harzburgite with high-Cr# value (54 to 60) spinels and U-shaped REE patterns. The cumulated rocks are composed of dunite, wehrlite and gabbro, thus being of the DPG type. All these features are consistent with those of the Izu-Bonin-Mariana peridotites, indicating that the Fuchuan ophiolite was formed in the supra-subduction zone (SSZ). The SHRIMP U-Pb ages of the co-magmatic zircon domains from gabbro that intruded the h arzburgite and the wehrlite are 848±12Ma (n=7, MSWD=1.9) and 827±9Ma (n=12, MSWD=1.4), respectively. The SSZ-type ophiolite and its ages suggest that the subduction of the ancient ocean between the Yangtze terrain and the Cathaysian (called “Jiangnan Ocean") terrain started before Neoproterozoic. It is inferred that the tectonic transform of the Jiangnan Ocean from spreading to subduction began before Neoproterozoic in southern Anhui Province, and the Yangtze terrain and the Cathaysian terrain started to collide before 848 Ma.

Abstract:The Yinmawanshan gabbro in southern Liaodong Peninsula is one of the youngest plutons in Northeast China. In this paper, the gabbro was investigated by petrologic and geochemical methods and calculated by means of PELE program (a silicate liquid crystallization program). The gabbro has high Al2O3（16.28%～19.27%） and low MgO（3.63%～5.57%）, belonging to high aluminum basalt. The gabbro has the assemblage of olivine + clinopyroxene + magnetite + ilmenite + biotite + plagioclase + K-feldspar. The ophitic and subophitic textures, elongated apatite crystals, low AlⅥ/AlⅣ ratios (0.00 ～0.28, 0.12 on average) in clinopyroxene, and low CaO content in olivine (0.04%～0.24%, average 0.12%) indicate that the gabbro was crystallized at a low pressure. The sequence of mineral crystallization in the gabbro is as follows: plagioclase, olivine, magnetite, clinopyroxene, ilmenite, apatite, biotite, K-feldspar, as revealed by petrography combined with the calculation using PELE program. The gabbro is indicative of intense magmatism in Cenozoic in Northeast China.

Abstract:Petrological, geochemical and Nd isotopic data are reported for the Ne oproterozoic Wasigou complex in the Kangdian rift on the western margin of the Yangtze block. This complex is an I-type granite, and its geochemical and Nd isotopic characteristics suggest that it was generated by partial melting of the pre-existing Late Mesoproterozoic-Early Neoproterozoic island arc crust. The early granite was produced by the tectonic transition from compression to intraplate extension on the western margin of the Yangtze block, whereas the late granodiorite was formed in an intraplate setting and might be related to the Neoproterozoic plume event. Their arc-like geochemical features such as Nb-Ta depletion must have been inherited from the protoliths rather than from their tectonic setting during the formation of the complex.

Abstract:The Tekesi Daban batholith can be divided into two intrusive series, i.e., Early Carboniferous Kulesayi series and Early Permian Qinaersayi series. The porphyry assemblage of the Kulesayi series is a calc-alkaline series formed in an island arc environment. SiO2 is 57.06％～70.74％, the Rittmann index (σ) is lower than 3.26, and（Na2O+K2O）/Al2O3 is lower than 0.9. It is enriched in Al2O3, Na2O, Sr and LREE, and poor in MgO, Y, Yb and HREE; Na2O / K2O is higher than 1, Sr/Y is 57. 67, δEu is 1.22，indicating O-type adakite. The Kulesayi series is enriched in Cu, Mo and W, and even contains Mo ore bodies. In the Qinaersayi series, SiO2 is 76.75％～77.83％, σ is higher than 3.3, （Na2O+K2O）/Al2O3 is higher than 0.9， andδEu is 0.07; this series is poor in Ba, Sr, Ni, Sc but enriched in Rb, Y, Zr, Th, Ta, with Sr/Y being 3.24. The protolith was partly derived from melting of argillaceous rocks of the earth crust, belonging to the alkaline series formed in an intrap late rift environment. Geochemical characteristics provide not only powerful evidence for the disintegration of the Tekesi Daban batholith but also abundant information for the improvement of native metallogenic regularity. In addition, these characteristics enrich types of tectonite assemblage, guide ore-prospecting work and contribute to researches on tectonic evolution.

Abstract:An analysis of sedimentary characteristics of Shangyoushashan and Xiayoushashan Formations and the features of seismic reflection in western Qaidam Basin su ggest that the Altyn Mountains were uplifted during the Mid_Late Miocene, which resulted in an eastward migration of the basin depocenter. Uplifting chron ological data from the surrounding mountains also indicate that the uplifting of the northern margin of the Qinghai-Tibet Plateau was coincident with the regional tectonic events of southern Qinghai-Tibet Plateau during the Mid_Late Miocene . It is also demonstrated that the Mid-Late Miocene is an important period for the northward growth of Qinghai-Tibet Plateau. The uplift event of the Altyn Moun tains was directly related to the wedging of the Tarim Plate underneath the Qaid am Plate. The plateau uplifting dynamic source was derived from the continuous northward subduction of the India Plate after its collision with the Eurasia continent

Abstract:Heilongjiang mélange distributed in Yilan area of Heilongjiang Province is regarded as the tectonic mélange with features of suture zone. Some metam orphic basic lavas consisting of quite a few metamorphic minerals without directional characteristics are named massive blue schist. The existence of large quan tities of glaucophane, a characteristic metamorphic mineral, indicates that these basic lavas have undergone high –P low –T metamorphism. Geochemical analyses of major elements show that all the samples have the following characterist ics: SiO2＜53%, TiO2＞2%，and Na2O+K2O=2.77%～6.41%. Geochemical analyses of trace elements reveal that the fractionation between LREE and HREE is quite obvious and the distribution pattern of REE is right oblique, with no negative Eu anoma ly in the chondrite-normalized diagram. Na2O+K2O-SiO2 variation diagram indicates that metamorphic basic lavas have characteristics of alkali basalt, and the Nb×2-Zr/4-Y, Ti/100-Zr-Sr/2, Ba-Th-Nb-La diagrams all suggest that these metamorphic basic lavas have characteristics of alkali ocean island basalt (OIB). The above understanding provides important evidence for the research on subduction of the palaeo-ocean crust between Jiamusi continental block and Songnen continental block.

Abstract:Reported in this paper are Fe isotope compositions of pyrites from Neo-Archean stratiform sulfide deposits，North China. Relative to IRMM-0 14, all pyrites analysed show light Fe isotope enrichment, with variations of -38.8～-13.1 ε57Fe units for those from Hebei, and -39.4～-15.1 ε57Fe units for those from Shandong. The results suggest that the Neo-Archean seawater where these sulfides originated are enriched in light Fe isotopes. As pyrites from Archean black shales worldwide show similar Fe isotope features to those from the two Chinese sulfide deposits, the enrichment of light Fe isotopes in early Precambrian ocean is likely to be regional, or even global. This is resulted from the prolonged and large-scale precipitation of iron oxides which show light Fe isotope depletion.

Abstract:On the basis of Fe isotope distribution in different reservoirs, the p resent situation of using Fe isotopes to trace mantle processes is reviewed in t his paper. Data obtained from mantle xenoliths hosted in Cenozoic basalts of North China confirm the existence of Fe isotope heterogeneity in the mantle. According to the previous and new data available, the mechanism for Fe isotope fractionation in mantle rocks is also discussed. It is pointed out that Fe isotopes have important potentials in tracing such mantle processes as mantle metasomatism, partial melting, and evolution of oxygen fugacity.

Abstract:A method for Mg isotope measurement using MC-ICP-MS has been set up. T he authors tried to make a high-precision analysis of magnesium isotopes by MC-ICP-MS for Mg reagent, waters and minerals. The "sample-standard" bracketing technique was used to correct spectrometer mass-dependent fractionation. By arranging narrow entry slit on MC-ICP-MS, the interferences of such molecules as C2+, C2H+, C2H2+, CN+ and NaH+ from Ar gas, air and acid can be decreased to the minimum. Keeping the concentration of samples the same as that of the standard is a good way to obtain high-precision Mg measurement. Through a lot of experiments on matrix element interference, matrix effects on Mg measurement can be realized. Keeping［element］/［Mg］concentration ratio lower than 0.05 can minimize isobaric interference and matrix effects. External repeatability (2SD) of Mg isotope measurement estimated by the authors' laboratory standard CAGS1-Mg relative to CAGS2-Mg is 0.180‰for δ26Mg and 0.090‰ for δ25Mg in a long period. The data in three 25Mg/24Mg versus 26Mg/24Mg plots all fall on the mass-dependent fractionation line with a slope of ～0.5. This means the method put forward by the authors is of high precision and suffers no interference. Relative to DSM3, Mg isotope composition of samples changes at 2.790‰ for δ26Mg and 1.282‰ for δ25Mg. 0.399‰ of δ26Mg from CAGS1-Mg is the maximum, whereas -2.091‰ of δ26Mg from Kanansi lake water is the minimum.

Abstract:Accurate determination of Mg isotopes using MC-ICP-MS requires an adequ ate separation of elements from bulk samples. Cation exchange chromatography has been used to separate Mg from the matrix elements. However, the removal of Fe and Al from Mg solution is not effective, and Fe and Al do affect the accurate de termination of Mg isotope by MC-ICP-MS. Methods for different kinds of samples were investigated based on exchange chromatography using AG50W-X12 and coprecipitation of Fe and Al using diluted NH3·H2O, and Mg isotope composition of natural sample was determined after purification. The results show that ① It is enough to separate Mg from the bulk samples using the resin column one time when m(Fe)/m(Mg) ≤0.1, m(Al)/m(Mg) ≤0.2 and m(Na)/m(Mg) ≤1 in solution; ② It is enough to separate Mg from the bulk samples using the resin column two times when m(Fe)/m(Mg) ≤ 0.1, m(Al)/m(Mg)≤0.2 and m(Na)/m(Mg)＞1 in solution; ③ It is essential to obtain Mg solution using coprecipitation of Fe and Al by NH3·H2O and separation of Mg by cation exchange chromatography one time when m(Fe)/m(Mg) ＞0.1, m(Al)/m(Mg) ＞0.2 and m(Na)/m(Mg) ≤1 in solution; ④ It is essential to obtain Mg solution using coprecipitation of Fe and Al by NH3·H2O and separation of Mg by cation exchange chromatography two times when m(Fe)/m(Mg)＞0.1, m(Al)/m(Mg)＞0.2 and m(Na)/m(Mg)＞1 in solution; ⑤ The Mg isotopic compositions of the sea water around Qingdao City are δ25MgDSM3＝-0.43‰ and δ26MgDSM3＝-0.84‰; The Mg isotopic compositions of the sea water around HLD are δ25MgDSM3＝-0.44‰ and δ26MgDSM3＝-0.85‰.

Abstract:With the improvement of analytical methods and the development of thermal ionisation mass spectrometry (TIMS) and multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS), the researches on geochemistry of non-traditional stable isotopes(Cu, Zn, Fe, Se, Mo, Cr, Hg) have made tremendous progress in the past ten years. Redox conditions are the primary reasons for Mo isotope fractionation, so Mo isotopic fractionation has been successfully employed to explain the evolution of paleo-environment. Mo isotopic fractionation studies have yielded considerable results in explaining ore fluids in ore deposits and Mo cycling in ocean. Mo stable isotope geochemistry is therefore becoming a new frontier subject in earth sciences. Based on summarizing the previous researches and synthesizing the authors' results of Mo isotope studies, this paper deals with the main advances in the study of Mo stable isotopes with the particular emphasis placed on the separation of Mo from the sample, the determination method and correction for instrumental mass-dependent isotopic fractionation of the isotope tracer sample, and the application prospects of the Mo stable isotopes in earth sciences.

Abstract:Zn isotopes is a new geochemical tracer, and a prerequisite for using them to constrain some important geochemical processes lies in the adequate understanding of the processes and mechanism of Zn isotope fractionation. This paper presents a review of current understanding of mass fractionation processes in low temperature environments, which include adsorption, precipitation, diffusion, reduction and biological processes. During the process of carbonate precipitation, the precipitates are depleted in heavy Zn isotopes; the mass fractionation increases with the increasing of diffusion distance; metallic Zn reduced from Zn( Ⅱ)aq is enriched in light Zn isotopes; during biologically related processes, the heavier Zn isotopes are preferentially adsorbed on the surface of diatoms, whereas lighter Zn isotopes are preferentially utilized for biological metabolism.

Abstract:As a major element in the earth, Magnesium (Mg) takes par t in all geochemical processes. It is also a component part of the 26Al-26Mg chronology for meteorites. The development of the high-precision Mg isotopic measurement technique using multiple-collector inductively coupled mass spectrometry (MC_ICP_MS) makes it possible for Mg isotopes to act as a research tool in geochemistry, cosmochemistry and medicine. Mg isotope studies can be used in such research fields as relative ages of inclusions in meteorite s, reconstruction of palaeo-envirment and intestinal Mg absorption

Abstract:Phosphate adsorption capabilities of different natural palygorskites and iron modified palygorskites in water with different phosphate concentrations were investigated, and the mechanisms of phosphate adsorption of natural and iron modified palygorskites were also studied through adsorption isotherms and adsorption kinetics experiments. The results show that the three palygorskite clays have different kinds of performance on removal of phosphate. For water quality o f Grade Ⅴ and lower than Grade Ⅴ, the more dolomite they contain, the higher removal efficiency they have. The iron modification treatments increase the phosp hate adsorption capabilities of natural palygorskite. The phosphate adsorption isotherm of natural palygorskite is an S-type isotherm, the Freundlich equation (R2=0.977 6) provides better fitting than the Langmuir equation (R2= 0.924 9) in terms of R2 values, suggesting that the adsorption of phosphate on palygorskite is inhomogeneous multilayer adsorption. On the basis of R2 values, the kinetics of phosphate adsorption on the palygorskite can be satisfactorily described by the pseudo-first-order equation, power function equation, parabolic diffusion equation and pseudo-second-order kinetic equation. However, the phosphate adsorption isotherm of iron modified palygorskites is an L-type isotherm, the Langmuir equation (Fe2+: R2=0.96, Fe3+： R2=0.967 7)provides better fitting than the Freundlich equation (Fe2+: R2=0.965 7, Fe3+： R2=0.936 1) in terms of R2 values, implying that the adsorption of phosphate on iron modified palygorskite is homogeneous monolayer adsorption. The results obtained reveal that, as the surface charges and adsorption activity sites of palygorskite are changed by iron modification, so do the phosphate adsorption mechanisms.

Abstract:Transmission electron microscopy (TEM) and STEM reveal the exsolution lamellar structure in labradorite, which is responsible for the iridescence of labradorite. The labradorite is made up of calc-poor and calc-rich plagioclase, and its thickness is mainly controlled by calc-rich plagioclase. The more the cal c content, the thicker the lamellar, and the longer the wavelength of the interf erence color. Furthermore, the increasing speed of calc-rich plagioclase will surpass that of the calc-poor one. The selected area electron diffraction (SAED) shows that the direction of exsolution lamellar structure is (153) , which is nearly parallel to （010）. The uniform interference color may have different calc con tents and exsolution directions, varying from place to place and from environment to environment.