Abstract:Baiganhu area is situated between East Kunlun-Qimantag tectonic zone and Altun block, where the Bashierxi granite series is the key to understanding the tectonic setting of this area during the Early-Middle Silurian. In this paper, a monzonitic granite (BGH-1) and a syenogranite (BGH-4) samples were collected from a single pluton and used for petrographic observations as well as geochronological and geochemical studies. This pluton contains muscovite and garnet, and its A/CNK and A/NK ratios are in the ranges of 1.07～1.12 and 1.41～1.59, respectively. Thus this pluton is peraluminous and high-K calc-alkaline S-type granite. In addition, this pluton is characterized by enrichment of LREE and LILEs and d epletion of HFSEs, with obvious negative anomalies of Nb, P and Ti. LA-ICP-MS zircon U-Pb dating reveals that the monzonitic granite and syenogranite were emplaced at 428.2±4.2 Ma and 422.5±2.3 Ma, respectively. The data obtained by the authors and previously published data show that the calc-alkaline S-type granites and A-type granites are coexisting in Bashierxi granite series and they were formed in a post-collisional environment during the Early-Middle Silurian (433～421 Ma). However, the Early-Middle Paleozoic magmatism in eastern Qimantag between Golmud and Baiganhu fault to the east of the Baiganhu fault has recorded a complete process of Late Ordovician to Early Silurian subduction, Middle Silurian to Early Devonian collision, and late Early Devonian post-collision. Apparently, the Early-Middle Silurian magmatic plutons in eastern Qimantag and the Bashierxi granite series, which are outcropped in Baiganhu area to the west of the Baiganhu fault, were formed in different tectonic environments, thus probably belonging to different tectonic evolution systems.

Abstract:A suite of Paleoproterozoic mafic-ultramafic rocks was discovered in the Wuyishan Block in southwest Zhejiang Province through 1:250000 regional geological survey of Quzhou Sheet. These mafic-ultramafic rocks comprising mainly pyroxene hornblendite, hornblendite, plagioclase actinolite, plagioclase pyroxenite and amphibolite are exposed perfectly in Zhangcun Village of Jinhua County and spatially exhibit planar-shaped distribution in Jinhua County and Longyou County. Zircon U-Pb dating with LA-ICP-MS shows that the formation age of pyroxene hornblendite is 1 834±14 Ma (MSWD=0.23, N=16), and that of actinolite is 1 839±17 Ma(MSWD =0.22, N=11), which suggest that these mafic-ultramafic rocks formed during the Paleoproterozoic magmatism. This discovery reveals that the Wuyishan Block was experiencing intraplate extension process at about 1 830 Ma and that the Wuyishan Block might have been a rigid continent at that time so that large-sized brittle fractures could be formed in the interior of the Wuyishan Block and induced basic magmatism resulting from mantle convection. Based on these facts and inference, the authors hold that the Wuyishan Block already had been cratonized at about 1.83 Ga.

Abstract:The Bayan Har block, as the main body of Tethys, is located in the northeast of the Tibetan Plateau. In-depth study in this area is not only of great importance for determining the evolution of Tethys but also of important practical significance for the research on metallogenesis related to tectonic evolution and minerals distribution in this area. The Bayan Har Group is located in the Bayan Har block, where the research on its provenance is insufficient. Its detrital and chemical components can reflect the features of the provenance and tectonic setting. The authors' researches on petrological characteristics, depositional setting, geochemical indices and geochemical discrimination diagrams of clastic rocks of the Bayan Har Group, together with previous researches on paleocurrent of Bayan Har Group clastic rocks, suggest that the Bayan Har Triassic sedimentary basin was based on the splitting of the old basement, the process of rift expansion did exist, the depth of water was increased, the tectonic setting was mainly characterized by the continental island arc and active continental margin, and the deposited sediments was derived from felsic rocks of upper continental crust of East Kunlun orogenic belt in the north.

Abstract:Lying at the junction of the Yangtze paleoplate and the Cathaysian paleoplate, Guangfeng and Yushan basins are characterized by red clastic rocks and mafic volcanic rocks. SHRIMP U-Pb dating of zircon shows that shoshonite in Guangfeng and Yushan basins has an age of 93±1 Ma, belonging to early Late Cretaceous. (⁸⁷Sr/⁸⁶Sr)_i values of shoshonite in Guangfeng are 0.706 191～0.706 352, εNd(t)=0.27～0.55, (²⁰⁶Pb/²⁰⁴Pb)_i=18.045～18.08, (²⁰⁷Pb/²⁰⁴Pb)_i=15.503～15.543, and (²⁰⁸Pb/²⁰⁴Pb)_i=38.240～38.256, whereas (⁸⁷Sr/⁸⁶Sr)_i values of shoshonite in Yushan basin are in the range of 0.705 856～0.706 024, εNd(t)=1.74～1.93, (²⁰⁶Pb/²⁰⁴Pb)_i=17.956～18.063, (²⁰⁷Pb/²⁰⁴Pb)_i=15.456～15.498, and (²⁰⁸Pb/²⁰⁴Pb)_i=38.195～38.232. In the (⁸⁷Sr/⁸⁶Sr)_i-(²⁰⁶Pb/²⁰⁴Pb)_i, (¹⁴³Nd/¹⁴⁴Nd)_i-(²⁰⁶Pb/²⁰⁴Pb)_i and (¹⁴³Nd/¹⁴⁴Nd)_i-(⁸⁷Sr/⁸⁶Sr)_i diagrams, the values fall exclusively between the DMM and EMⅡpositions, (⁸⁷Sr/⁸⁶Sr)_i and (²⁰⁶Pb/²⁰⁴Pb)_i show positive correlation, whereas (¹⁴³Nd/¹⁴⁴Nd)_i and (²⁰⁶Pb/²⁰⁴Pb)_i show negative correlation, which suggests that the source mantle of the shoshonite rocks probably had both DMM and EMⅡ magma, with a higher proportion of DMM in the Yushan basin.

Abstract:Located in Shangqimugan area of Akto County in Xinjiang,Shangqimugan plutons exhibit NW-SE trending zonal distribution along the Qiaolakeke-Sugaite-Ajiaerdong fracture. The plutons are mainly composed of monzonitic granite. The SiO₂ values range from 66.06% to 75.13% and Al₂O₃ from 12.45% to 14.78%. Average (K₂O+Na₂O) value is 8.82%, average K₂O/Na₂O ratio is 1.25, and aluminum index A/CNK (0.89～0.98)<1.1,suggesting that the plutons belong to high-K metaluminous calcic-alkaline series. The total REE values of the plutons are 231×10^-6～404×10^-6,and LREE and HREE show obvious fractionation. Chondrite-normalized REE patterns are of smoothly right-oblique type. Average value of δEu is 0.17, implying obvious depletion of Eu. Compatible elements (Ni, Co, Cr, V), incompatible elements (Rb, Th) and HFSE (Zr, Hf, etc.) are obviously concentrated; Ba, Sr, P and Ti are strongly impoverished; Nb and Ta are depleted in a certain extent. LA-ICP-MS zircon U-Pb dating yielded a ²⁰⁶Pb/²³⁸U weighted mean age of 225.4±1.9 Ma (MSWD=6.0), indicating that the plutons belong to early Late Triassic. Combined with geochemical characteristics and trace elements discrimination diagrams, the authors hold that the rocks resulted from the mixing of the crust and mantle magmas, belonged to A-type granite and formed in the tensional environment of a post-collision extensional phase, which marked the end of the orogeny of the West Kunlun orogenic belt and the beginning of intraplate tectonic evolution in early Late Triassic, implying a transition from the collision environment to the intraplate extensional environment. These data also demonstrate the complete closure of Paleo-Tethys in this region in early Late Triassic.

Abstract:Located in the northeast of Olongbuluck block on the northern margin of Qaidam Basin, the Hongliugoubei mafic-ultramafic intrusion is composed of harzburgite, olivine websterite, plagioclase-bearing clinopyroxene peridotite, olivine gabbro-norite, melaolivine-gabbro, norite and gabbro and belongs to a dike-shaped intrusion, with an exposed area of about 0.1 km². Various lithofacie belts show gradual transition relationship. Electron microprobe analyses show that the rock-forming minerals are composed of chrysolite, augite and plagioclase and their crystallization temperatures vary between 1 307 and 1 122℃. The intrusion is characterized by obvious mineralization of ilmenite, with main ore minerals being ilmenite, titanomagnetite and magnetite. The inversion of primary magma composition based on the compositions of most Fo-rich olivines indicates that the parental magma of Hongliugoubei intrusion belonged to common basalt magma containing about 8.49% MgO, 10.03% FeO and 1.63% TiO₂. Studies of temperature and oxygen fugacity conditions of rock-forming minerals reveal that oxygen fugacity of magma gradually increased from olive crystallization to augite crystallization and this seems to be the main factor that controlled the crystallization of Ti-Fe oxide.

Abstract:A core 40.92 m in length was drilled in Dalianhai, the terminal lake of the Shazhuyu River in Gonghe Basin, northeast Tibetan Plateau. The chronology of the core was established by normal and AMS ¹⁴C dating methods at 10 controlling points of lake plant relics. The oldest age of the core bottom is 14.5 cal ka BP. The clay minerals from the core were analyzed with the resolution of 20 cm/70 a. The evolutionary history of palaeoclimate and palaeoenvironment of Gonghe Basin since 14.5 cal ka BP was reconstructed mainly by clay minerals with particle fraction. During the deglaciation period (14.5～10.0 cal ka BP), the climate generally became dry and cold, with strong physical weathering. In the early-middle Holocene (10.0～5.0 cal ka BP), the climate was wet and warm, with the climatic optimum at about 6.0 cal ka BP. Chemical weathering of this period was strong. In the late Holocene (5.0～0.0 cal ka BP), the climate was similar to that of the deglaciation period, characterized by dryness and coldness and predominant physical weathering. The phases of climatic and environmental variation recorded by clay minerals were in accordance with those recorded by indices of other lakes on the plateau. The climatic and environment history of this basin shows some characteristics of Monsoon and Westerly models established since the last deglaciation period.

Abstract:The Laochang polymetallic deposit is one of the most important deposits in the south of the Sanjiang metallogenic belt and belongs to the polygenetic mineral deposit with superimposed metallogenic systems between the SEDEX ore-forming system and the hydrothermal porphyry metallogenic system. Based on an analysis of the typical minerals and rocks in different mineralization systems in the aspects of S, Pb, H, O isotopes, the authors compared the differences and similarities of deposit's geochemical characteristics in the different metallogenic systems, and the result shows that mineral sources of the two metallogenic systems were characterized by inheritance, regeneration and multiple sources. In the SEDEX ore-forming system S was mainly derived from volcanic hydrothermal solution, Pb mainly came from ancient continental crust basement and volcanic rocks, and ore-forming fluids were mainly derived from mixed magmatic water and brine as shown by H-O characteristics. In the porphyry-hydrothermal mineralization system, S mainly came from the mantle or crust-mantle magma homogenization, Pb was mainly from the crust-mantle mixing, ore-forming fluids were mainly derived from magmatic water and meteoric water, and ore fluids of the late stage had more characteristics of meteoric water. ⁸⁷Sr/⁸⁶Sr ratios of granite porphyry are between the average of the crust and that of the mantle, whereas isotope data of Sm-Nd is close to the EMⅡ, suggesting that the magma source was in the crust-mantle transition zone.

Abstract:Numerous breccias were identified as the host rocks of the Pb-Zn polymetallic deposit in Changchengling area, Hunan Province. These breccias are restricted to the intersections between the granite porphyry dykes and the NE-striking faults. Their distribution patterns, compositions, textures, and alteration characteristics suggest that they might have resulted from cryptoexplosion. The cryptoexplosive breccias can be divided into explosive breccias, shatter breccias and mixed breccias on the basis of the features of the cryptoexplosive breccias. These breccias can also be divided into igneous cryptoexplosive breccias and hydrothermal cryptoexplosive breccias according to their genesis. The geological and geochemical features of the granite porphyries indicate that the early Yanshanian hapabyssal granite porphyries were rich in volatiles and experienced strong fluid-melt, thus probably belonging to the cryptoexplosion type. The cryptoexplosion provided not only ore-forming elements and fluids for the Pb-Zn polymetallic mineralization but also convergent and precipitable space for ore-forming fluids. The discovery of cryptoexplosive breccias connected with Pb-Zn polymetallic mineraliza- tion in the Changchengling orefield is significant in the search for deep-seated mineralization in this orefield as well as in the southern Hunan W-Sn polymetallic concentration area and even in the whole central segment of Nanling region.

Abstract:Based on a study of mineral paragenetic relationship in combination with results obtained by previous researchers, the authors divided the metallogenic process of the Wulaga gold deposit into three ore-forming stages and figured out the ore-forming thermodynamic parameters of each stage according to thermodynamic data. The first stage was the pyrite-early white chalcedony-like quartz stage, during which Eh values varied in the range of -0.5～+0.3 V, implying a weak reduction environment, and sulfur fugacity should be higher than 10^-23; the second stage was the ash-gray chalcedony-like quartz- polymetallic sulfide stage, during which the ore-forming environment at low temperature was an intermediate-acid (pH=4) weakly reducing environment, the sulfur fugacity should be higher than 10^-40 but not in excess of 10⁰, and the lower limit of the sulfur fugacity decreased as compared with that of the first stage; the third stage was the carbonate-quartz stage, during which the formation of the carbonate minerals foreboded the ending of the mineralization, the pH values of the metallogenic media changed gradually from acid (pH=3) to intermediate-acid (pH=5), ore-forming Eh values also showed transition from weak reduction (-0.5 V) to weak oxidation (+0.3 V), the lower limit of the sulfur fugacity varied around 10^-23 and was not in excess of 10⁰, and the oxygen fugacity varied around 10^-20. The data obtained by the authors are of important reference value for the in-depth investigation of the hydrothermal ore-forming process.

Abstract:In the study of metallogeny, there isn't a unified nomenclature or classification for the sediment-hosted base-metal deposits. Among these deposits, one type of deposits, which is hosted by sediments and controlled by structure and characterized by vein orebody that contains Pb-Zn-Cu-Ag polymetals, lacks systematic summary. However, this type of deposits is a product of orogeny, and its study can provide information concerning the process of mineral migration and precipitation. The authors collected many data of this deposit type, in order to find out its metallogenic characteristics, ore-controlling structures, ore-forming fluids and sources of ore-forming material. Researches show that deposits of this type are mainly located in orogenic belts, and the mineralization is mostly related to orogeny or orogenic belt. The metallogenic materials of these deposits were mainly derived from basement rocks, probably with the contribution of magma and mantle source. The ore-forming fluids were mainly originated from basin brine, magmatic fluid and metamorphic fluid, and were partly affected by the meteoric water. Deposits of this type have some similarities to MVT deposits, but there are still many apparent differences between them in metallogenic environment, ore-bearing rock, ore-controlling structure type, source of ore-forming fluid and ore-forming material.

Abstract:Cordierite is a mineral material characterized by low thermal expansion coefficient and good thermal shock resistance. Cordierite mineral material is relatively rare in nature, so cordierite is synthesized usually by the method of artificial synthesis. Based on the newest investigation results of synthetic cordierite, this paper deals with the progress of researches on such synthesis methods of cordierite as high purity oxide solid reaction at high temperature, natural mineral solid reaction at high temperature, the utilization of industrial wasted materials, the employment of agricultural wasted materials, the sol-gel and the low-temperature combustion synthesis. At present, the method of natural mineral solid reaction at high temperature is used for the preparation of cordierite in industry. In spite of a lot of advantages, this method also has many disadvantages. Therefore, the development trend of cordierite synthesis seems to solve the problem as to how to apply other synthesis methods to industrial preparation.

Abstract:In the world, besides a number of high-grade or low-grade iron ore deposits in the Precambrian banded iron formation, there exist numerous associated deposits which contain large quantities of metallic and nonmetallic resources, particularly Au, Mn, Pb-Zn, Cu and Ni. These deposits are large to super-large in size, and some of them possess an important position in national economy of some countries. However, in China, only several small-medium sized Au deposits have been discovered, whereas large-sized Au deposits and other metallic ore deposits have not yet been found. Therefore, during the geological survey and integrated prospecting, researches on polymetallic deposits associated with the banded iron-formation must be strengthened. The geological characteristics and background of Precambrian greenstone belt and banded iron formation must be studied. Moreover, synthetic thought must be formed in looking for these mineral deposits which have favorable ore-prospecting potential. This paper deals with the research situation and basic geological characteristics of several typical ore deposits in China and abroad in the hope of providing some reference and expanding train of thought for China's prospecting work.

Abstract:Though geophysical observation and numerical modeling suggest that the oceanic crust have been subducted along convergent continental margins into the deep Earth, the exhumed UHP metamorphic terranes of oceanic affinity are rarely exposed. The UHP metamorphic belt of China's southwestern Tianshan was inherited from the ophiolitic complex as a result of the northward subduction of the paleo-Tianshan ocean beneath the Yili-Central Tianshan plate. With the in-depth investigations of many aspects in recent years, the UHP metamorphism of China's southwestern Tianshan has been better understood. In this paper, the authors focused the discussion on the progress in petrological studies of UHP rocks from this orogenic belt. The ubiquitous discovery of coesite in meta-basaltic and meta-sedimentary rocks indicates that the meta-ophiolitic belt of China's southwestern Tianshan have reached the mantle depths with extremely low goetherms, which is consistent with thermodynamic forward modeling. The rarity of coesite and the development of various coesite pseudomorphs suggest the intensive retrograde overprint at low temperatures. Only in the unfractured domain of porphyroblastic garnet could coesite be preserved. On the basis of detailed petrographical observation and phase diagram model, the UHP metamorphism in the north of the metamorphic belt of China's southwestern Tianshan is confirmed and a coherent UHP unit (referred to as Kebuerte-Habutengsu UHP unit) is proposed. To the south of this unit, no UHP evidence has been identified in eclogite or pelitic-felsic schist. The imbricate sequence relation between HP and UHP units points to the northward subduction polarity of the paleo-Tianshan ocean. The progress in the study of petrology is fundamental for further unraveling the physiochemical processes of cold oceanic crust subducted to great depths and for constructing a more reasonable tectonic model of the South Tianshan orogenic belt in Central Asia.

Abstract:Isotopic reference materials are crucial to isotopic measurement, and isotopic compositions of reference materials constitute basic parameters for isotopic measurement. This paper deals with the new reference material with basaltic matrix for Ti isotope measurement. The preparation of the reference material strictly followed the relevant metrological technical standard stipulated by the state, which included homogeneity and stability tests and certification analyses. The certified values and uncertainty at the 95% confidence level were δ⁴⁷Ti(‰)=-0.53±0.07, δ⁴⁸Ti(‰)=-1.05±0.09, δ⁴⁹Ti(‰)=-1.57±0.16 and δ⁵⁰Ti(‰)=-2.10±0.18. This newly certified reference material can be used for assessment of isotope fractionation during chemical separation of geological samples instrumental calibration in Ti isotope measurements, and data quality evaluation in the whole process of sample preparation and isotope measurement.

Abstract:The geodynamic implications of continental granite remain a controversial topic. The author believes that the granite can be divided into two series of ocean and continent. The granite produced in the ocean basin and the edge belongs to the ocean series, whereas the granite produced in the continent belongs to continental series. The most important geodynamic implications of ocean series granite is to distinguish tectonic settings, the same of continent series is to judge the crust thickness and temperature conditions. Granite can be divided into Adak-type, Himalaya-type, Zhemin-type, Guangxi-type and Nanling-type on the basis of Sr-Yb content. Different types of granite are related to the granite formation depth: Adak-type granite rich in Sr and poor in Yb is in equilibrium with eclogite facies and produced in the thickening crust; Himalaya-type granite with poor Sr and Yb is in equilibrium with granulite facies and produced in thick crust; Zhemin-type poor in Sr and rich in Yb and Guangxi-type rich in Sr and Yb are in equilibrium with amphibolite facies and produced in normal or thin crust; Nanling-type granite is also in equilibrium with amphibolite facies and produced in the thinnest crust. Himalaya-type granite belongs to the low temperature series, whereas Zhemin- type granite to the middle or high temperature series; Nanling-type and Guangxi-type belong to the high temperature series. Adak-type granite can appear in each temperature series. The application of classification of granite can restore ancient crustal thickness and temperature conditions at the bottom of the lower crust and can also trace changes of the situation and trend of the change of crustal thickness and temperature with time in some regions.