Abstract:It is known that Mesozoic magmatism generated a series of granitic plutons in the northern segment of the Taihang Mountains. Among others, the Mapeng-Chiwawu pluton just crops out in the central part of the Neoarchean-Paleoproterozoic Fuping Complex, showing I-type calc-alkaline affinity, with low SiO₂ and high Al₂O₃ and alkali content. The pluton consists of quartz diorite, granodiorite and granite from edge to core, and these intrusions yielded LA-ICP-MS zircon U-Pb ages of 126.4±2.4 Ma, 125.4±2.0 Ma and 126.2±2.0 Ma, indicating that the pluton was emplaced in a short time around 126 Ma (Early Cretaceous). The total amount of Al in hornblende is 1.018, 0.880 and 0.871 for quartz diorite, granodiorite and granite, and accordingly the crystallization pressure of hornblende is 0.183, 0.118 and 0.114 GPa, with an average of 0.141 GPa, indicating a depth of ca. 5 km. This is significantly smaller than the thickness of Proterozoic to Jurassic sequences around the Fuping Complex, suggesting a dome-shaped structure for the Fuping Complex before the Early Cretaceous. Combined with other data, an average uplift rate of 0.07～0.08 km/Ma can be obtained for the Taihang Mountains since the Early Cretaceous.

Abstract:Biotite plagiogneiss samples from Hongqiyingzi Group in Chicheng County of northern Hebei Province have porphyroblastic texture with medium-fine grained lepido-granoblastic groundmass and gneissic structure. Blastopsammitic texture is preserved locally. The rocks mainly consist of plagioclase (28%～32%), quartz (35%～40%) and biotite (18%～25%), with minor garnet (2%～8%,as porphyroblast) and graphite (1%～4%). Garnet compositional characteristics reveal that the temperature and pressure fell contemporaneously during the main metamorphic evolution. All the biotite plagiogneiss samples have wider variation in major components. The total REE values are not very high and vary in the range of 49.45×10^-6～140.10×10^-6, displaying LREE-enriched and HREE-flattened patterns with chondrite-normalized (La/Yb)_CN of 5.07～8.70 and LREE/HREE of 5.23～9.16. Most of these samples show intermediate negative Eu anomalies and weak negative Ce anomalies, the chondrite-normalized Eu/Eu^* and Ce/Ce^* values are separately 0.63～0.81 and 0.82～1.01, and the rocks have lower Rb, Sr, Cs, Ba, Zr, Hf, Nb, Ta, Th and U and higher Sr/Ba and Th/U ratios relative to the upper crust. The geochemical characteristics of the biotite plagiogneiss samples from Hongqiyingzi Group suggest that their protolith might have been pelitic (or pelitic-bearing) sandstone and was formed in a tectonic environment similar to the continental island arc. This recognition is important with regard to understanding the tectonic evolution of the central part of the northern margin of the North China Craton.

Abstract:The Mahonondor granites, located in East Ujimqin Banner of Inner Mongolia, are predominated by monzogranite and syenogranite. SHRIMP zircon U-Pb dating shows that the crystallization age of the monzogranite is 307.0±1.9 Ma and that of the syenogranite is 299.7±5.3 Ma. The ages which are between the late Carboniferous and early Permian are consistent with the late Paleozoic magmatic activity age. Geochemical researches indicate that the granite from Mahonondor area in the East Ujimqin Banner of Inner Mongolia is rich in silica (SiO₂＝65.65%～71.86%), alkali (K₂O＋Na₂O＝9.59%～9.90%) and K (K₂O/Na₂O＝1.00%～1.73%), suggesting a typical high-K calc-alkaline to shoshonitic series with the metaluminous feature (A/CNK＝0.96～1.04). The rocks are poor in rare earth elements (∑REE＝82.60×10^-6～157.70×10^-6), enriched in LREE and LILEs (Rb, Th, K), and depleted in HFSE, especially Nb, Ta, Sr, P and Ti. Similar REE distribution patterns indicate that the Mahonondor granites have the same magma source. The δEu values vary from 0.44 to 0.87, with most rocks having moderate negative Eu anomalies. In addition, massive structure and miarolitic structure point to post-collisional granites. In a word, these characteristics suggest that these high-K calc-alkaline granites in the Mahonondor area were emplaced during post-collisional conversion from compression to extension, and were derived from fractional crystallization of medium-K calc-alkaline diorite-porphyrite, causing collision between the Sino-Korean and Siberian plates during late Devonian to early Carboniferous period. It is shown that the conversion time of the late Paleozoic orogenic process in East Ujimqin area was from 320.1±7.2 Ma to 307±1.9 Ma, the period 286～276 Ma was the developmental stage of post-collisional alkali granites, and Hegenshan oceanic basin had disappeared before 320.1±7.2 Ma. The above results provide new constraints on Mongolia Orogenic Belt tectonic-magmatic evolution in Late Paleozoic and closure of the Paleo-Asian Ocean.

Abstract:Based on studying the volcanic rocks in Qiongaxi Valley of northern Yining County, the authors found that the volcanic rocks in thia area belong to calc-alkaline volcanic rocks strongly enriched in LREE and weakly depleted in Eu. All the samples are enriched in large-ion-lithophile elements (LILE) such as Cs, Rb, Ba, Th and U, which are ten times higher than their values in the primitive mantle. In the primitive mantle-normalized trace elements diagram, the sample shows characteristics of the island-arc volcanic rock, such as distinct depletion of Nb-Ta. However, its (Th/Nb)_N>>1 and (La/Nb)_N>>1, the ratios of Ba/Nb and La/Nb vary in a large range, Zr/Nb and Zr/Hf ratios are similar to ratios of N-MORB, and Ta/Nb ratios are similar to ratios of the upper crust, which suggests that the volcanic rocks were mixed by the lithosphere during the upward migration of the magma. All the samples point to the intermediate potassium-high potassium series, and the dominance of such a potassium type also implies that the continental crust matrix must have played an important role in the magmatic activity. The features of Zr>300 and Zr/Y>4 of all the samples show characteristics of intraplate volcanic rocks. In the diagram of Zr-Zr/Y, most samples fall into the intralate basalt region. Combined with the geological features of the study area, the authors hold that the area experienced uplifting in Devonian, and in Carboniferous the collision terminated and the evolution entered into the post-collision extension stage. Some local places produced certain rifting characteristics. Therefore, the distinct depletion of Nb and Ta might have been caused by the mixing of the lithosphere, and the environment of the Qiongaxi Valley volcanic rocks should belong to the post-collision extension phase.

Abstract:The Yaguila Pb-Zn-Ag deposit is a large-size ore deposit on the north margin of Gangdise. Some experts considered that the ore deposit was formed by marine jet flow superimposed by magmatism, whereas others thought that it was formed only by magmatism. Detailed drill hole investigations into the Yaguila ore deposit show that both the light brown porphyry and the gray quartz porphyry contain a large volume of ore-bearing stockwork quartz veins. Meanwhile, large amounts of massive ores are developed along the contact zone between the two types of porphyries and limestone. Therefore, both the light brown porphyry and the gray porphyry must have played an important role in mineralization of the Yaguila ore deposit. In the present study, the authors analyzed zircon U-Pb ages for the two kinds of porphyries by using LA-ICP-MS. Mean ages of the concor- dant points for the two types of porphyries are 132.1±1 Ma and 62.4±0.6 Ma, respectively. Typical sedimentary ore bodies were not found during the field survey, but large volumes of skarn ores were found in most ore bodies, indicating that metals of the Yaguila Pb-Zn-Ag deposit were most likely derived from magmatic hydrothermal fluids related to both the light-brown porphyry and the gray porphyry. Therefore, two stages of magma events were found in this ore deposit. The first magma event occurred in the early Cretaceous, related to the light-brown porphyry, which was superimposed by the second mineralization event related to the gray porphyry in the Paleocene. Combined with the results of previous researchers, the authors hold that the ore-forming process dominated by Pb-Zn-Ag mineralization on the north margin of the Gangdise belt occurred during Cretaceous-Miocene period. Intense Pb-Zn-Ag mineralization implies that the paleo-basement of northern Gangdise belt might have played an important role in controlling the metal types of the mineralization in this area.

Abstract:The Xiongcun copper-gold deposit is an island arc porphyry copper-gold deposit newly discovered in the Gangdise metallogenic belt. It consists of three ore bodies. No.Ⅱ ore body is located 3 km northwest of No.Ⅰ ore body. Cu, Au, and Ag mineralizations occur in early K-silicate alteration zone and sericite-muscovite-quartz-sulphide zone. Early K-silicate alteration is characterized by biotite+magnetite±K-feldspar+chalcopyrite+pyrite, and is rich in magnetite. Element distribution characteristics and correlation analysis show that Cu is well correlated to Au and Ag. Au- and Ag-bearing chalcopyrite is mainly distributed at the center of the ore deposit. Cu is positively related to K, Rb and negatively related to Na, suggesting that the mineralization is mainly related to early K-silicate alteration. Later mineralization occurs around the ore body mainly as sphalerite and galena veins. From the center to the outer part, sixteen elements related to Cu, Au and Ag are zoned around the center, i.e., Cu, Au, Ag, K, Rb, Ba-Mo-Co, Ni-Pb, Zn, Mn, Ag, Sb-Na. The element distribution is similar to zoned alteration. They are controlled by such factors as hydrothermal fluid, translation condition, p-T and primary composition of the host rock. The zoned element characteristics and assemblies are of guiding significance for future exploration.

Abstract:The Jingangtai Formation constitutes an important component part of the Beihuaiyang Late Mesozoic volcanic rock belt. In this paper, the zircon U-Pb age of an ignimbrite sample was determined, and a trachyandesite sample from the Jingangtai Formation and an orthophyre sample collected near the volcanic rocks were dated by LA-ICP-MS method. According to the results, the ages of the 3 sample are almost identical within the error range, which means that the volcanic rocks of Jingangtai Formation and the orthophyre were formed in a very short period. Meanwhile, these ages are very close to the concentrated ages of the Cretaceous magmation in Sulu-Dabie orogen, which implies that they might have been generated under the same dynamic condition.

Abstract:Based on detailed researches on the species, abundances, crystal morphological features and stable C, O, S isotopes of the authigenic minerals in shallow core sediments of Site 5B and Site 4B within Shenhu area gas-hydrate potential deposits of northern South China Sea, the authors found that authigenic pyrites and carbonates are the dominating species in shallow sediments, and that great differences exist between Site 5B and Site 4B in abundance, distribution, morphology and grain size of pyrites and carbonates. Taking into account the same geological background of both sites in Shenhu area, the authors have inferred that the great differences might be related to the local methane flux and deep structures in different sites. Authigenic pyrites might have been formed by the anaerobic oxidation of methane or organic matter with sulfate reduction. Extremely negative sulfur isotope of pyrites might be related to the co-action of sulfate reduction bacteria and sulfur disproportionate bacteria. Authigenic carbonate was probably formed in a relatively complicated process, and carbon isotopic records might reflect mixed carbon sources of methane, organic matter and sea water.

Abstract:There exists a lead-zinc-copper polymetallic deposit of hydrothermal type in the Anji mining area. The ore samples from prospecting trenches and bore holes were analyzed and tested, and the results indicate that all kinds of ores contain high grade of silver, and hence the silver ore body can be distinguished from other ore bodies. Based on microscopic examination, SEM/EDS and EPMA analysis, the authors found that Cu, Pb and Zn occur respectively in chalcopyrite, galena and sphalerite, and silver may be closely coexistent with Pb-Zn-Cu sulfides. Based on studying tens of typical thin sections by using microscopic examination, SEM/EDS and EPMA, the authors also found that in most lead-zinc and copper ores, gold and silver exist as isomorphism in galena, chalcopyrite, sphalerite and pyrite, with the content of 0.03%～0.57% and 0.02%～3% respectively. In the hydrothermal filling type lead-zinc ores, silver exists mainly in the form of independent silver-bearing minerals, such as Ag-tetrahedrite and polybasite, which carry small amounts of isomorphic gold and occur mainly in galena as micro-inclusions in the subhedral crystal, short prismatic, blade, lath-shaped, dendritic and irregular forms. Actually, single particle sizes of Ag-tetrahedrite and polybasite are generally in the range of 10～60 μm, with only a few grains reaching 100 μm. In addition, the silver mineral aggregates canl be up to 200 μm in size. The silver and gold in the independent silver-bearing minerals can reach 10.98%～69.12% and 0.14%～0.35% respectively. The results obtained show that galena is a very important silver-carrying mineral, and the ores with rich galena are especially likely to contain independent silver-bearing minerals.

Abstract:Using the analytical means such as ordinary thin slice, cast thin slice, scanning electron microscope and X_diffraction, the authors conducted researches on the characteristics of petrology, diagenesis and pore evolution of the 2nd Member sandstone reservoirs of Xujiahe Formation in Hechuan area, and the result indicates that the sandstone reservoirs are mainly composed of feldspar lithic sandstone and lithic sandstone, which have mainly experienced compaction, cementation, dissolution and metasomatism, with the diagenetic phase reaching the middle diagenetic stage B. Primary pores decreased rapidly due to strong compaction during the early diagenentic stage A～B, and primary pores were reduced continuously due to the compaction and siliceous cementation, together with the increase of induced pores resulting from the dissolution of feldspars and the cutting of grains rich in feldspar during the middle diagenetic stage A. In addition, the metasomatism_filling of iron_bearing calcite and ankerite caused the tightness of the reservoir during the middle diagenetic stage B. The compaction and cementation seem to be the main diagenetic types which destroyed the primary pores. The dissolution was the main diagenetic action to form the induced pores. Controlled by diagenesis and diagenetic phase, there exist many types of reservoir space in the 2nd Member of Xujiahe Formation in Hechuan area: intragranular dissolving pores, intergranular dissolving pores and remnant intergranular pores are well developed, and the induced pores growing belt abnormally appears in the 2nd Member of Xujiahe Formation in Hechuan area, resulting from the corrosion of feldspars and the cutting of grains rich in feldspar.

Abstract:Altay is an important part of the Central Asian Orogenic Belt, and also the largest accretion orogen in the world. At present, scholars both in China and abroad are focusing their Altay studies on the evolution of various stages of orogenic movements as well as geochemical and geochronological time constraints on the orogenic activities. In contrast, the study of the Mesozoic-Cenozoic cooling history is relatively insufficient. To carry out the researches on the cooling as well as denudation and exposure history of the post-orogenic stage of the Altay orogenic belt is of great importance in the in-depth understanding of the formation of a large mountain range after the evolutionary stage. Researches on the post-orogenic uplift of the cooling as well as denudation and exposure history about Altay orogen are of great significance in that it make researchers obtain in-depth understanding of the formation of a large mountain range after the evolutionary stage. With the improvement of the fission track analysis technology, fission-track thermochronology represented by apatite has become the effective means for revealing the denudation and exposure age and speed of orogenic activity as well as the evolution of tectonic, topographic and thermal history. Low-temperature chronology records rock movement information of the upper crust within a few kilometers and on a million-year scale, and thus offers a good choice for the quantitative recovery of ancient orogenic terrain. This paper discusses uplifting-denudation and exposure history and paleotopographic reconstruction of this region based on fission track technology. AFT data from 11 samples show that the AFTA range from 99.2 Ma to 43.7 Ma. The average denudation and exposure rate has been 0.050 mm/ma since Late Cretaceous. Thermal history modeling results show that there have been multi-phase cooling and denudation and exposure evolutions since the Cretaceous period in the south margin of the Altay Mountains. From Early Cretaceous to Late Cretaceous (about 120～50 Ma), the denudation and exposure rate was 0.044 mm/a, and from Late Cretaceous to Eocene (about 75-70～50 Ma), the denudation and exposure rate was 0.070 mm/a. Since the Miocene (about 20-15 Ma～Present), the denudation and exposure rate has been 0.081 mm/a (the denudation and exposure rate was obtained from three methods, i.e., the age-closure temperature method, the cooling curve simulation and the age-elevation method). Early Cretaceous tectonic uplift of the Altay Mountains was contemporaneous with the final closure of the Mongol-Okhotsk Ocean, and the convergence and eventual collision of the Siberian and North China (Sino-Korean)/Mongolian continents. Tectonic activities from Late Cretaceous to Eocene were affected by long-distance effects of Lhasa block and Kohistan-Dras arc accretion. Rapid uplift since the Miocene may be related to distant effects of India-Eurasia convergence. Low-temperature thermochronology can be used to conduct paleotopographic reconstruction, and the specific process is shown as follows: First, the cooling history of rock samples is remolded. Then, the amount of stratigraphic erosion is estimated through temperature gradient. Finally, such affecting factors as balance role, climate and tectonics are considered. Paleotopographic reconstruction of the study area shows that the average denudation and exposure highness from Cretaceous up till now is about 5 km, while paleoelevation has been decreased by about 0.8 km. Cretaceous-Cenozoic paleoelevation of the south range of Altay Mountains has tended to decrease except for a stable period of 50～17.5 Ma.

Abstract:Harker diagram is considered to be fundamental in the study of magmatic fractionation. However, the conclusions drawn from the diagram are dependant on basic geological facts instead of on the diagram itself. Fractionation trend of magmas demonstrated on Harker diagram is derived from the study of layered intrusions formed from basaltic magmas, and hence Harker diagram is not suitable for the study of granitic rocks. Many conclusions based on Harker diagrams of granitic rocks are not consistent with the basic geological facts.

Abstract:To reveal palaeoclimatic evolution and aridification events of Early Oligocene-Early Miocene period on the northeast margin of Tibetan Plateau, the authors investigated micro-morphology, relative content of clay minerals and V(Ill+Chl)/V(Sme) ratios of sediments in Lanzhou Basin by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The relative content of clay minerals shows that the sediments are composed of illite, smectite, chlorite and minor illite-smectite mixed-layer clay (Ill/Sme), indicating that aridificati on prevailed in Lanzhou in that period, with intervals of relatively warm and humid climate conditions. According to relative content and V(Ill+Chl)/Ill(Sme) ratios, the palaeoclimate evolution in Lanzhou could be divided into four stages, i.e., (Ⅰ) relatively warm and dry and slightly humid period (31.5～28.8 Ma), (Ⅱ) relatively cold and dry period (28.8～26.2 Ma), (Ⅲ) relatively warm and humid period (26.2～22.1 Ma), and (Ⅳ) relatively warm and dry and slightly humid period (22.1～16.5 Ma). SEM results indicate that clay minerals were apparently corroded in the relatively warm and humid period and presented distinctly physical weathering characteristics in the relatively arid period. The aridification events probably resulted from the multi-stage uplifts of the Tibetan Plateau.

Abstract:In this study, the electronic structures of Fe- and/or V-doped rutile TiO₂ have been investigated using the first-principles calculations based on the density functional theory. Theoretical results show that the band gap of pure rutile is 1.98 eV. The top of the valence band is mainly formed by O2p and Ti3d states, in which O2p state plays a major role, while the conduction band is dominated by Ti3d state. In the calculations of doped models, a 2×2×2 super-cell structure (Ti₁₆O₃₂) is built based on the optimized geometric parameters of rutile. One Ti atom is replaced by a Fe or V atom with a doping amount of 6.25%. Fe and V are used to substitute the two nearest-neighbor Ti atoms parallel to the c-axis respectively so as to form the co-doped rutile with a doping quantity of 12.5%. The results show that Fe-doped rutile TiO₂ has a band gap of 2.18 eV, and the hybridization of Fe3d and O2p orbital introduce two intermediate bands in the middle of the forbidden band. The band gap of V-doped rutile is reduced to 1.80 eV and the intermediate state right below the bottom of the conduction band is attributed to the hybridization of V3d and O2p orbital, which acts as a shallow donor level. Fe- and V-codoping reduces the band gap of rutile to 1.73 eV and introduces a wide intermediate band into the forbidden gap. The emergence of the intermediate state and the decrease of the band gap make Fe- and V-codoped rutile possess a better responding capability to visible light. Meanwhile, isomorphous substitution of Fe or V atoms for Ti causes significant distortion to MO₆ octahedra, which could increase the concentration of surface defects, and thereby provide active sites for photocatalysis. These results supply theoretical aids to profound understanding of the photocatalytic mechanism of Fe- and V-bearing natural rutile under visible light.

Abstract:The layered double hydroxides (LDHs) were in-situ prepared by hydrolyses of copper, magnesium, and aluminium ions with sodium hydroxide solutions for removing copper ions from wastewater. The effects of medium pH, magnesium/copper molar ratio, reaction temperature and time on the removal efficiencies of copper ions were investigated. The results show that the removal efficiencies are significantly affected by the medium pH, and the removal efficiencies are more than 99% in the range of pH 8.0～11.0. Other factors have slight effects on the removal efficiencies. X-ray diffraction analyses of these prepared LDHs indicate that their layers are composed of copper, magnesium, and aluminium ions, and the copper ions are removed at the crystal formation stage of these LDHs. These Cu/Mg/Al-LDHs are formed by stepwise hydrolyses from aluminium to copper to magnesium ions, with the suitable pH value being 9.0.

Abstract:A series of heat-treatment experiments of zircons from Changle in Shandong Province were conducted at different temperatures in oxidizing and reducing atmosphere. The colors and their variations were studied by UV-NIR spectrometer. The formation mechanism of the zircon colors was discussed on the basis of the experiments. It is found that the color of the zircons after heat-treatment changed into colorless, yellow or orange in oxidizing atmosphere and colorless in reducing atmosphere. All the samples began to fade significantly at 400℃. The results also show that the red and redish brown colors of zircons are attributed to the color center and Fe³⁺ is responsible for the yellow coloration of zircons. Only a low temperature can make zircon change into perfect colorless, and hence the color enhancement of zircon has tremendous commercial value.

Abstract:In order to explore the cause for the existence of variegated substance in seawater cultured pearls,the authors observed the microstructure of variegated substance with scanning electron microscopy (SEM), and then used thermogravimetric analyzer and Fourier infrared spectrometer (FIR) to analyze the composition of variegated substance. Through SEM observation, the authors found that the variegated seawater cultured pearl contains nacre, prismatic layer, intermediate layer, variegated layer and nucleus from the outer part to the inner part. The thickness of the prismatic layer and the intermediate layer are 20 and 10 μm, respectively, whereas the thickness of variegated layer is nonuniform, even reaching 50 μm. The experimental result shows that the variegated substance mainly consists of aragonite and proteins which jointly constitute the laminated and reticular structure.