Abstract:Large quantities of Precambrian volcanic-intrusive complexes are distributed between the northern side of Jiangshao suture and the southern side of Jiangnan orogenic belt in northeastern Jiangxi Province. They consist mainly of Neoproterozoic volcanic rocks and felsic-mafic igneous complexes, of which the largest one is Gangbian body covering 120 km2 in Hengfeng County. This complex body can be divided into felsic, mafic and transitional rock units at the mapping scale. The age of the upper intersection point on the U-Pb incongruent curve of zircon from the felsic rocks is 822±4 Ma.The Nd model ages of various rocks from Gangbian complex body are different from each other: felsic rocks are 1.49～1.68 Ga; mafic basaltic rocks are 1.51～2.21 Ga; Nd model ages of gabbro are approximately the same as those of basaltic rocks, being 1.54～2.13 Ga; the calculated Nd model ages of transitive rocks are 1.58～1.90 Ga. Therefore, the fractionation of mafic rocks inthis body from the mantle must have occurred much earlier than that of the felsic rocks. Nevertheless, the Nd model ages of these transitive rocks contain some information on mutual mixing and mingling of the two end-member magmatic bodies. The authors obtained quite a few isotopic data for various rocks in Gangbian complex body:εNd(t=822) values of the felsic rocks are -0.8～-4.4,87Sr/86Sr(822) ratios are 0.7068～0.70549,εNd(822) values of the mafic basaltic rocks are -2.6～+2.3, and 87Sr/86Sr(822) ratios are 0.70387～0.70527 These data show that the source of the basaltic magma was close to the bulk earth, whereas the source of Neoproterozoic felsic magma in the complex was derived from the EMⅠ mantle characterized by themixing of mantle and crust. It is thus considered that northeastern Jiangxi area developed magmatic underplating in Precombrian, and this process played an important role in the formation of the mama of Gangbian complex. The formation of the felsic magma was controlled by the melting of the crust because underplating of the basaltic magma along the boundary between the mantle and the crust supplied thermal energy which was accumulated in the magma chamber; temperature of the diapiric felsic magma chamber decreased in company with increasing extent of crystallization and viscosity in the felsic chamber; the physical state of the felsic magma chamber also changed simultaneously in order of liquid→(soild + liquid)→solid. The liquid basaltic magma entered the felsic magma chamber through the lower crust, in which the physical condition was changing. Finally, the successive chemical mixing and mechanical mingling of the two end-member magma bodies and the intrusion of magma took place. The time of magmatic mixing is defined by the age of the upper intersection point on the U-Pb incongruent curve of the zircon, i.e., 822±4 Ma. Based on the data of the Nd model age (tDM) and the Nd enrichment coefficient (fSm/Nd), it can be concluded that the middle Proterozoic Jiangnan orogenic belt was accreted on the southern margin of the Archean land nucleus in Yangtze paleocontinent, and that the Neoproterozoic terrestrial volcanic-intrusive complex zone was later accreted on the southern side of the Jiangnan orogenic belt. At that time, the accretion of Yangtze paleocontinent drew to its end and its piecing together with the Cathaysia paleocontinent began. Therefore, the Neoproterozoic volcanic-intrusive complex zone including Gangbian complex body became the link of these two paleocontinents.

Abstract:The volcanic suite of Guanfang area occurs in the north of South Lancangjiang magmatic tectonic zone within the Sanjiang Three-River tectonic belt. A volcanic suite composed of acidic volcanics of Manghuai Formation and basic volcanics of Xiaodingxi Formation was extruded in the Guanfang area in the middle-Late Triassic period. With high silica（SiO2=75.49% on average），rich potassium（K2O=3.88% on average）,low titanium（TiO2=0.136% on average）and A/CNK high than 1.1（1.53 on average）, the acidic volcanic rocks of Manghuai Formation belong to potassium-rich calc-alkali rhyolitic volcanic rock series. The rocks have an average ∑REE of 276.85×10-6 and show evident nagative Ti, P and Eu anomalies as well as positive K, Rb, Ba, Th anomalies in the trace element spider diagrams.Basic volcanic rocks of Xiaodingxi Formation are also enriched in potassium（K2O=2.68% on average），with their Rittmann index varies in the range of 65.92%～75.68%（σ=6.27 on average）, thus belonging to potassium_high calc-alkalibasalt-shoshonite series. The REE distribution pattern is slightly right oblique with an average ∑REE of 171.83×10-6，and there exist no or very weak nagative Eu anomaliesThe rocks show evident K, Rb, Ba, Th positive anomalies and Ti, Y, Yb, Cr nagative anomalies in the trace element distribution pattern. According to the rock assemblage as well as geological and geochemical haracteristics, it is suggested that the Triassic volcanic suite in Guanfang area along South Lancangjiang belt of Yunnan Province should be composed of epicontinental arc-volcanic rocks. 

Abstract:Kulehu ophiolite located in South Tianshan Mountains consists of two groups of basalts characterized by different geochemical types. The ∑REE(24×10-6 ～28.36×10-6),(La/Yb)N (0.35～0.37), Zr/Nb (39.91～95.12), Ta/Nb (0.07～0.09) and εNd(t) (8.85～12.25) values of the first group indicate that their mantle sources have been subjected to intense depletion, similar to things of the source of N_MORB. Furthermore, the enrichment of LILEs and the depletion of HFSEs, especially the appearance of Nb and Ta negative anomalies, show the affinity of this group to island arc tholeiite (IAT). On the contrary, the ∑REE (56.38×10-6～101.29×10-6) and (La/Yb)N (0.96～1.36) values, the contents of incompatible elements (REEs, LILEs and HFSEs) and the appearance of Nb and Ta positive anomalies all show that characteristics of the second group are between E-MORB and OIB, more close to E-MORB. TheεNd (t) (8.39), Zr/Nb (9.74～1094) and Ta/Nb (0.06) values are similar to those of E-MORB, suggesting that the mantle source of the second group is fertile relative to that of the first group. According to an integrated analysis of geochemical characteristics of these two groups of basalts, Kulehu ophiolite should have been formed in a back-arc basin setting. The first group of basalts, which have obvious SSZ features, are products of partial melting. They were formed at the early stage of back-arc basin, being products of the depleted residue of MORB-source mantle following earlier melt extraction. With the evolution of the back-arc system, mantle counterflow resulted in the formation of a relatively fertile mantle, and the upwelling of this mantle beneath the spreading ridge of theback-arc basin and the partial melting resulted in the generation of the secondgroup of basalts. The age of Kulehu ophiolite corresponds with the subduction age of the South Tianshan Ocean, and the formation of Kulehu ophiolite might havebeen related to the subduction that induced the back-arc extension of this ocean in a period from Late Silurian to Early Devonian. 

Abstract:Detailed field observations have identified basic and granitic plutons in Kumux area, whose intersections resulted in a white-black mosaic pattern at the surface. Geochemical analyses demonstrate that both granite and gabbro are strongly enriched in LREE and incompatible elements and depleted in HREE and other compatible elements. Very high Sr content and low Rb/Sr ratio of the gabbros can be attributed to some contamination of Sr-enriched fluids derived from sedimentary rocks. Such a geochemical feature suggests that the gabbros were derived from an enriched mantle wedge area in a magma arc environment. Weak fractionation of HREE indicates garnet crystallization during partial melting of the enriched mantle wedge. CL observations and SHRIMP U-Pb analyses of granitic zircons reveal that the granite is of S-type resulting from remelting of meta-sedimentary rocks at about 396 Ma. Taking into account the geological data from peripheral areas, the authors have reached the following conclusions: (1) the intensely deformed plutons of the Kumux area resulted from the northward subduction of the Paleo South Tianshan Ocean under the Central Tianshan terrane, (2) during the subduction, the Kumux area was located on the subduction-related continental magma arc zone, and (3) the boundary between the South Tianshan unit and the Central Tianshan unit should be re-located to the south of the Kumux and the north of the Yushugou ophiolite slice.

Abstract:The Neoproterozoic-Early Cambrian basic lava in Tianshan and its adjacent areas consists of two magma series, namely, tholeiitic and alkaline basaltic magma series. The tholeiitic magma series is the major component part of the early volcanic rocks (Early Nanhua Beiyixi Formation and Early Sinian Zamoketi Formation), the alkaline basaltic magma series is the main component part of the late volcanic rocks (Early Sinian Sugaitibulake Formation, Neosinian Suiquan Formation and Early Cambrian Xishanbulake Formation). REE, trace elements and Nd, Sr isotopic compositions reveal that the volcanic rocks were formed in a continental-rift environment, and their source resembled an asthenospheric mantle of ocean-island basalt and was contaminated by geosphere during the upward migration and eruption of the magma.

Abstract:Cenozoic volcanic units in Zhentouya area of north Qiangtang are mainly andesite and dacite lavas. The andesite, to some extent, shows an adakitic compositional characteristics, such as high Sr (>1000×10-6), Sr/Yratios >50 and low Yb contents (<2×10-6). Evidently plagioclase broke down in the andesitic magma source region under the p-Tconditions of partial melting. Compared with the dacite series, it seems that partial melting of the lower part of the thickened eclogite-facies Tibetan crust was responsible for the generation of the andesitic magma. The dacite is characterized by enriched LILE such as Rb, Ba, Th, U and K, and depleted HFSE such as Ti, Nb, Ta and Sr. It is noteworthy that the dacite exhibits a relatively low Sr (Sr<660×10－6), and this may imply that the plagioclase was still stable in the dacitic magma source region at the pressure and temperature of partial melting. Two_pyroxene granulite and clinopyroxene granulite xeneloths were discovered in the andesite and dacite volcanic rocks outcropped in north Qiangtang of central Tibetan Plateau. Based on electron microprobe analyses, the authors have concluded that the xenoliths provide constraints for the equilibrium temperatures of the two-pyroxene granulite, i.e., about 783 to 818℃ as determined by two_pyroxene thermometry, and that the formation pressure of the clinopyroxene granulite should be about 0.845 to 0.858 GPa, equal to 27.9～28.3 km in depth It is indicated that these granulite xenoliths represent the samples derived from the middlepart of the thickened Tibetan crust. This discovery is of great importance to the furtherinvestigation of the components and thermal regime of the deep crustof Tibetan Plateau. Geochemistry of dacite and characteristics of granulite xenolith suggest that partial melting of the middle part of thickened Tibetan crust might have produced the primary dacite magma series.

Abstract:By means of XRD, IR, DTA, SEM and chemical composition analysis, the authors studied mineralogical characteristics of kaolin from the newly discovered Xianrenwan kaolin orefield in Chenxi, Hunan Province and discussed ore genesis on the basis of geological and mineralogical properties of the ore deposit. It is shown that kaolin in this orefield is a halloysite type one dominated by 10 A halloysite and partially by 7 A halloysite. With very small amounts of clastic quartz and colloid quartz adsorbed on the outer surface, halloysite crystals are tubules about 1.0～1.5 μm in length and 0.05～0.1 μm in outer diameter. The authors hold that kaolin in this orefield is ancient karst cave colloidal precipitate in origin

Abstract:Researches on the weathering rate and products of primary silicate minerals are of great importance in the explanation of soil-forming process, cycling process of nutrient elements and global climate change. This paper has summed up the weathering of primary silicates through three different ways, i.e., natural, artificial and biochemical weathering processes, and dealt with the products formed. Biological weathering and biological mineralization as well as their significance are emphatically discussed. Field observations and laboratory experiments indicate that microbes can accelerate the weathering reactions of aluminosilicate minerals. Moreover, microbial cell surfaces and extracellular polymers serve as templates for the nucleation and precipitation of secondary mineral phases.

Abstract:The major composition of otoliths is biomineral aragonite. In the past two or three decades, quite a few achievements have been made in the study of fish otoliths, but no advances in researches on the thermoluminescence characteristics of the fish otoliths have been reported in literature. In this paper, thermoluminescence characteristics of otoliths of the wild carps (cyprinoid) in the Baiyangdian Lake of Hebei Province and the Miyun reservoir of Beijing were studied, and the difference of energy gap (E) between the fish otoliths in the two regions was analyzed. The experimental results indicate that such thermoluminescence curve parameters as Glow Peak (T), Thermoluminescence Intensity (I), Integral (S) and Half Width (W) of the fish otoliths from the Baiyangdian[JP3] Lake are greater than those from the Miyun reservoir, and the stability of thermoluminescence curve parameters and energy gap (E) of the former is weaker than that of the latter. Compared with things of the Miyun reservoir, the electrons and vacancies trapped in otoliths of the Baiyangdian Lake are more likely to escape. According to the investigation, the Baiyangdian Lake has suffered heavier pollution andeutrophication than the Miyun reservoir. Therefore, the thermoluminescence curve characteristics of the fish otoliths are quite sensitive to water quality and water environment, and this can be regarded as an important indicator to the contamination degree of the water.