Abstract:This paper presents new geochronological, petrological, geochemical and Hf isotopic data of the intrusions from the Zongnaishan area in northern Alxa, Inner Mongolia, and discusses the tectonic settings and boundary of southernmost Central Asian Orogenic Belt (CAOB). Zircon U-Pb dating indicates that the Zongnaishan batholith includes the Middle Permian K-feldspar granite (272±1 Ma), Early Triassic diorite (249±1 Ma) and Early Triassic granodiorite (247±1 Ma). According to their geochemistry, the Middle Permian K-feldspar granite is weakly peraluminous and shoshonitic, belonging to the highly fractionated I-type granites; the Early Triassic diorite is calc-alkaline; and the Early Triassic granodiorite is metaluminous to slightly peraluminous and calc-alkaline. The REE patterns of all the three intrusions are high in LREEs and low in HREEs with week to moderate Eu negative anomalies. The primitive mantle normalized trace element diagrams are characterized by the enrichment of the LILE (K, Rb, Ba and Sr) and depletion of HFSE (Ta, Nb, P and Ti). Based on the zircon Hf isotopes, the authors hold that the intrusive rocks were mainly derived from juvenile material with high εHf(t) values (+0.3-+11.6) and young two-stage Hf model ages (1 275～533 Ma). The juvenile features of Zongnaishan-Shalazhashan terrane are similar to the most prominent features of the CAOB, but different from those of cratons or Precambrian blocks, such as the North China Craton and the Alxa Block, implying that the Zongnaishan-Shalazhashan terrane is part of the CAOB, and the southernmost boundary of CAOB here is to the south of the terrane. The recognition of Late Carboniferous typical adakite magmatism in this region provides evidence for the subduction of the oceanic crust of the CAOB. The Middle Permian magmatic activities (272～264 Ma) display a bimodal association with high-K calc-alkaline features and are interpreted as forming in a post-collision setting. These studies, in combination with regional geology, provide new constraints on the tectonic evolution of southern CAOB during the Late Paleozoic and the location of the southernmost margin of the CAOB.

Abstract:Located in the western Central Qilian Mountain, the Wuergelate pluton is mainly composed of granodiorite and monzonitic granite. In this paper, the authors studied its zircon LA-ICPMS U-Pb age and major and trace elements. The results show that the zircon ²⁰⁶Pb/²³⁸U weighted average age is 490.5±1.4 Ma (MSWD=0.85), indicating that the pluton was formed in the Late Cambrian. Compositionally, SiO₂ values range from 65.10% to 71.21%, Al₂O₃ from 14.94% to 16.82%, MgO from 0.23% to 1.24%, A/NKC from 0.9 to 1.0, and Na₂O/K₂O from 1.01 to 2.33, suggesting metaluminous rocks. In addition, the rocks are enriched in LILE(Ba, U, Sr) and LREE, and depleted in HREE and HFSE (Nb, Ta, Ti and P). The Sr values range from 345×10^-6 to 541×10^-6, averaging 402×10^-6, Yb from 0.72×10^-6 to 1.19×10^-6, averaging 0.97×10^-6, and Y from 6.09×10^-6 to 11.30×10^-6, averaging 8.67×10^-6, with no negative Eu anomalies (δEu=0.91～1.27). The geochemical characteristics imply that the Wuergelate pluton could represent adakite, and was formed in a subduction orogenic setting. Combined with the tectonic location of the granite and regional geology, the authors hold that the North Qilian oceanic plate subducted southward under the Central Qilian blocks in the late Cambrian, which resulted in the formation of Wuergelate pluton.

Abstract:In this paper,LA-ICP-MS zircon U-Pb dating was carried out for four samples of volcanic rocks from Qingshan Group in Jiaodong area and, as a result, their concordant ages were obtained, which are 119.4±0.9 Ma, 118.2±1.0 Ma,120.2±0.9 Ma and 120.0±0.8 Ma, respectively. The results show that all the volcanic rocks in Jiaodong area were formed from about 120 Ma to 118 Ma in the Early Cretaceous period. The ages of Qingshan Group volcanic rocks from Shandong Province controlled by Tan-Lu fault are similar to those from the Su-Wan segment of the Tan-Lu fault zone,but younger than those around the Tan-Lu fault zone,which indicates that the duration of volcanic eruption along Tan-Lu fault is probably longer than the duration in other areas under the background of lithospheric thinning in eastern China. Geochemically, all the intermediate and acidic volcanic rocks have high K₂O, ALK, LREE values and low MgO, TiO₂, Ni, Cr, HREE values. According to the geochemical features, the volcanic rocks can be subdivided into trachyte-trachydacite and rhyolite. The trachyte-trachydacite is characterized by LILE enrichment(Rb,Ba,K)and HFSE depletion(Nb,Ta,Ti,P), but the rhyolite exhibits stronger depletion of Ba,Sr and HFSE (Ti,P). Compared with the rhyolite,the trachyte-trachydacite possesses higher Sr and Ba values as well as La/Nb and Ba/Nb ratios,but lower Rb/Ba ratios and δEu values. All these data indicate that they might have been derived from different magma sources. It is inferred that the trachyte-trachydacite rocks were derived from the mixture of the partial melting of the lower crust(Yangtze Craton or North China Craton)and enriched lithospheric mantle. In addition, the rhyolites were related to the partial melting of the lower crust in the regional extension environment and high geothermal anomaly background with crystallization differentiation during the magma evolution.

Abstract:Following the discovery of the Yulong metallogenic belt and the Gangdise metallogenic belt, the Bangong Co-Nujiang River metallogenic belt is the third metallogenic belt found in Tibet, and the Duolong ore concentration area is a typical ore concentration area in this metallogenic belt. The authors investigated geochemical characteristics, tectonic setting and provenance of granodiorite porphyry by conducting whole rock analysis and Pb-Sr-Nd isotope analysis of Nadun, Bolong, Duobuza, Naruo, Tiegelong and Gaerqin deposits in the NE-trending tectonic belt of this ore concentration area. According to the results obtained, the granodiorite porphyry is mainly of the high K calc-alkaline and shoshonite rock series, with K₂O values being in the range of 2.03%～6.07%; it is enriched in LILE(Rb, K), but depleted in HFSE (Nb, Ta, P, Ti); ∑REE and LREE/HREE values are 48.95×10^-6～249.02×10^-6 and 4.09～21.47, respectively, suggesting the enrichment of LREE; δEu values are in the range of 0.56～1.03, with the average value being 0.78; ²⁰⁸Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, ²⁰⁶Pb/²⁰⁴Pb ratios are 38.554～39.419, 15.534～15.665 and 18.465～19.161, respectively, being 38.835, 15.615, 18.659 on average. In the lead isotope diagrams, the granodiorite porphyry is located around the evolution line of the orogenic lead. (⁸⁷Sr/⁸⁶Sr)_i vary in a wide range of 0.705 79～0.711 12, with the average value of 0.707 74. εNd(t) vary in the range of -15.3～-1.7, with the average value of -4.5. Sr and Nd isotope data show that the magma was mixed with the crust and the mantle. In combination with previous researches, the authors hold that the Duolong ore concentration area was formed at the accretionary orogen stage, and its geological setting was an island arc developed on the basis of an accretionary complex, and that the ore-forming materials were derived from the mantle with the addition of crustal material, with the activity conducted by the melt formed by subducting plate. The discovery of the Duolong ore concentration area, the Qingcaoshan deposit and the Xiongmei deposit indicate that more ore deposits are likely to be found in the Bangong Co-Nujiang River metallogenic belt.

Abstract:Located on the east margin of the Ordos Basin in the North China Craton, the Zijinshan alkaline complex,as a typical rock body in the Fenhe alkali-rich intrusive rock zone, consists of monzonite, diopside syenite, melteigite, malignite, nepheline syenite, pseudoleucite porphyry and trachyte porphyry. The results of SHRIMP zircon U-Pb dating, combined with previous researches, suggest that the Zijinshan complex was formed between 138.7 Ma and 125.0 Ma, thus belonging to the early Cretaceous epoch. The Zijinshan complex shows high K,enrichment of alkali, and low Ca and Mg content. These rocks all show high REE content, LREE enrichment, HREE depletion and no obvious Eu anomaly. In the PM-normalized diagram,trace element pattern exhibits enrichment of LILE (Rb, Ba, K, Sr) and LREE and relative depletion of HFSE (Th, U, Nb, Ta, Ti). Whole rocks Sr-Nd isotopic compositions are characterized by the data I_Sr=0.704 228～0.706 313 and εNd(t)=-12.3～-0.5. The monzonite shows a large variation in zircon Hf isotopic compositions with εHf(t)being -20.2～-16.4 and two-stage model ages from 2.22 Ga to 2.46 Ga. It can be inferred that the Zijinshan complex was formed in an extension setting after Mesozoic tectonic regime inversion in the North China Craton. Continuous ashenospheric upwelling caused by the strong stress during tectonic regime inversion resulted in several times of mixing of melts from asthenosphere mantle,lithosphere mantle and lower crust in different proportions, and then mixed magma of each episode migrated upward to the shallow area of the crust to form the Zijinshan complex. The Fenhe alkali-rich intrusive rock zone was formed between 138.7 Ma and 125.0 Ma. It served as the magma evidence of the destruction in the middle and west parts of the North China Craton, which happened almost at the same time as the destruction in the east part. The ashenospheric upwelling in tectonic weak areas caused by the strong stress during tectonic regime inversion led to the large-scale crust-mantle interaction, which might have been the principal mechanism of the Mesozoic destruction in the middle and west part of the North China Craton, and the mantle-derived magma in the crust-mantle interaction was gradually reduced from north to south.

Abstract:While petrologic characteristics and contact relations constitute the most direct and important evidence of the disintegration of granitic batholith, the accurate isotopic ages of the different series are important supplementary data. The Kulumusu granitic batholith is composed of Kulumusu and Shaque series. Detailed field investigation shows that the vein from Kulumusu series intruded into Shaque series. In addition, xenoliths of Shaque series are distributed in Kulumusu series. High-precision LA-ICP-MS zircon U-Pb dating of the Kulumusu series indicates that the weighted mean ²⁰⁶Pb/²³⁸U ages are 291.5±2.9 Ma and 290.9±2.9 Ma, and those of the Shaque series are 304.9±2.5 Ma and 304.1±2.9 Ma. The ages of the two series show that they were formed in different magma intrusion events, and the data obtained provide geochronological evidence for disintegration of the Kulumusu granitic batholith. The disintegration of the Kulumusu batholith not only provides new information on the geological features and facts of magmatic movements, but also is of significance and theoretical value in studying the tectonic evolution of this region.

Abstract:The Huize lead-zinc deposit has become one of world-famous deposit for its extremely high reserves of ores and a large number of dispersed elements (Ge, Ga, Cd and In, etc.). The hydrothermal dolomite is the most important host rock in this orefield. On the basis of identification of typical sections in combination with geological logging and inclusion investigation of dolomites, the authors divided the dolomites in the ore district into burial dolomites and HTD (Structure Controlled Hydrothermal Dolomite). Some conclusions have been reached based on the study of the HTD dolomites: ① The formation of HTD was controlled by NE-trending compresso-shear interlayer fractures, and the HTD dolomites are especially well-developed on the upper side of the fracture. ② There exist large quantities of fissure (hole) gaps which reflect the intensity of diagenesis. ③ Dolomites show coarse grains, are pink, gray or brown in color, and exhibit unique spire, anhedral saddle shape, curved face saddle shape, curved face contact, intracrystalline microcracks and dissolved pores as well as wavy extinction and fog core bright side. ④ Saddle-shaped dolomites are thick layered and have geode filled with hot brine. They are associated with disseminated spotted pyrite and some other hydrothermal minerals. ⑤ Saddle-shaped dolomites with microcracks are divided into matrix metasomatic type and pore fracture filling type. In the narrow transition zone between HTD and limestone, they form zebra-shaped structure and brecciated structure. ⑥ HTD inclusions related to NW-trending faults are characterized by high temperature (250～438 ℃) and wide salinity range (3.4%～17.2%), whereas HTD inclusions related to NE-trending faults have high temperature (180 ～354 ℃) and low salinity (1.1%～5.9%). Through analyzing the driving mechanism of fluid, fluid properties, and indicators of mineralization, the authors revealed the diagenetic mechanism of HTD, i.e., under compression, the formation of HTD was controlled by NE-trending compresso-shear interlayer fissures: ① The regional fold and thrust constituted the deep dynamic mechanism of fluid migration. ② Hot brine fluids with acidic high temperature and salinity were concentrated in the thrust fold system. With the CO₂ boiling occurring on the upper side and in the expansion position of NE-trending compresso-shear interlayer fissures related to the thrust fold system, the thick-layered dolomites were formed. ③ Crack (hole) gaps reflect the intensity of diagenesis. ④ lithologic zoning, diagenetic strength and structural characteristics (microstructures) of HTD are indicators of orebodies.

Abstract:Located in the Boluoke'nu metallogenic belt of the West Tianshan Mountains in Xinjiang, the newly discovered Halegati-Muzuke Fe-Cu-Pb-Zn deposit is a medium-sized skarn deposit, and may potentially become a large one. The orebodies occur at the contact zone between Dawabulake pluton and marble, marbleized limestone of the Upper Ordovician Hudukedaban Formation. Orebodies are controlled in trinity by the pluton, strata and structure of the contact zone. Dawabulake pluton consists mainly of monzogranite and granodiorite, and is rich in Si, Al, K, Na, LILE, and poor in Mg, HFSE. The pluton is I-type granite and has the magma characteris- tics of subduction zone. The carbonates of Hudukedaban Formation(O₃h)are rich in Cu and Zn, which is favorable for mineralization through hydrothermal metasomatism, and hence this horizon is likely to become a favorable formation for regional prospecting. As a geochemical barrier and a pathway of hydrothermal fluids, the structure of contact zone controls the skarn orebodies.

Abstract:In previous exploration, researchers commonly considered that the primary halo method is an effective geochemical means for studying the distribution, geochemistry and denudation of the anomaly, and this method can also help predict concealed orebodies and assess mineral resource potential in the depth. Based on previous exploration of the Zhaxikang lead-zinc polymetallic deposit in Tibet, the authors studied vertical zoning of the deposit, and the results achieved can provide reliable geochemical information in such aspects as factors affecting mineralization, metal source, wall rock alteration, metallogenic stages and ore genesis. Primary halo study was carried out by analyzing Cu, Pb, Zn, W, Mo, Sb, Bi, Ga, Sn, In, Au, Ag and some other metallogenic elements in rock samples from four selected drill holes of ZK006, ZK007, ZK009 and ZK010 along No. 0 exploration line in the mining area. It is shown that the element anomalies and primary halos mainly occur below the altitude of 4 400 m, metal sources might have been derived from both strata and concealed rock mass in the depth, and mineralization might have experienced multiple-stage superposition. The authors hold that the economic orebodies of the Zhaxikang deposit might have a good prospect of downward extension in the depth.

Abstract:The Galale skarn gold (copper) deposit in Tibet discovered by No. 2 Geological Party of Tibet in recent years is a deposit of a certain size and potential. In this paper, with the phlogopite from the Galale sharn gold-copper deposit as the study object and by using the method of ⁴⁰Ar/³⁹Ar isotopic dating, the authors determined the ore-forming age of the Galale sharn gold-copper deposit precisely. Phlogopite crystallized between the formation of garnet and diopside and the formation of pyrite and chalcopyrite, and was closely associated with garnet, tremolite and actinolite. Test results show that the ⁴⁰Ar/³⁹Ar plateau age of phlogopite from the Galale deposit is 85.41±0.64 Ma, consistent with the corresponding isochron age 85.9±2.4 Ma. It is thus inferred that mineralization might have been related to the magmatic activities induced by upwelling mantle caused by lithospheric delamination that occurred in the north of Lhasa block after the collision of Lhasa block with Qiangtang block.

Abstract:Most cathodoluminescence imaging studies are focused on zircons separated from rock samples. However, it is difficult for this method to reveal origins of zircons with complex formation and evolution histories. In order to overcome the shortage and better understand the influence of the environment on zircons, the authors carried out cathodoluminescence study of zircons in thin sections for three metamorphic rock samples from Daqingshan, a typical area of extensively distributed high-grade metamorphic rocks. The main conclusions are as follows: ① Zircons occurring as enclaves in rock-forming minerals, such as quartz and feldspar, have rare overgrowth rims but can undergo recrystallization in different degrees. ② Fluid is very important for the recrystallization of zircons and overgrowth, and can be derived outside or inside the rock system. ③ It seems that some recrystallized zircons were wrongly regarded as overgrowth rims in previous studies.

Abstract:The Bangong Co-Nujiang River metallogenic belt is an important Cu polymetallic ore belt in Tibet. The Galale copper gold deposit was found relatively late in this metallogenic belt. It is a representative skarn type copper gold deposit, but the study of this deposit is at a low level. The study of the modes of occurrence of gold and silver in the useful components of the ore remains very insufficient, which restricts the further development and utilization of the ore deposit. The authors made a detailed study of the ore components by such means as sampling and field geological integrated investigation, optical microscope identification, scanning electron microscopy, energy dispersive X-ray spectrometer, and chemical formula calculation of mineral crystals. The gold minerals occur mainly as native gold and electrum and subordinately as küstelite. There are also intergranular gold, fissure gold and a relatively small amount of inclusion gold. The gold-bearing minerals are mainly quartz, dolomite, calcite, metal oxides, sulfides and native bismuth. Silver minerals mainly exists in the form of gold and silver minerals, with a small amount of silver minerals coexistent with radioactive elements. In addition, there exists a small amount of argentite. The results achieved by the authors have filled the gap of understanding the modes of occurrence of gold and silver in this area, and also provide important implications for the develop- ment and utilization of mineral deposits.

Abstract:With synthetic wastewater, the authors investigated phosphorus recovery effect by seeded crystallization of precipitated calcium silicate, which is a byproduct of feldspar hydrothermal decomposition. The results showed that the remaining effluent phosphorus concentration could meet the wastewater discharge standard of 0.5 mg/L under the optimized conditions of seed concentration of 0.4 g/L, pH value of 8 and Ca/P molar ratio of 2. Phosphorus recovery efficiency of 79.5% showed that phosphorus recovery effect was still obvious after the precipitated calcium silicate was used for sixty times. The products obtained were analyzed by using powder X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) techniques. The results show that the product of phosphorus recovery is hydroxyapatite (HAP). P₂O₅ content of more than 35% shows that the product can meet the standard of the rich phosphate rock and the precipitated calcium silicate is a potential and perfect seed of phosphorus recovery.

Abstract:The kinetics and thermodynamics of the adsorption of aqueous iron (Ⅲ) on hydroxyapatite were investigated. The result indicates that the adsorption equilibrium follows Langmuir adsorption isotherm: c_t/q=0.006 4 c_t+0.018 3. The reaction of adsorption is in accord with the first reaction kinetics equation: lnC_R=-0.043 5 t+4.324 4, and the reaction of adsorption energy E_a is 36.26 kJ/mol. Thermodynamic parameters were calculated. The positive values of standard enthalpy of adsorption has revealed the enothermic nature of the adsorption process. The negative values of Gibbs free energy are indicative of the spontaneity of the adsorption process when the temperature is higher than 285.7 K.