Abstract:During 2016-2018, aiming at the Zetso Salt Lake in the western of Qiangtang Basin, Tibet Autonomous Region, Tianjin Center of China Geological Survey joined The No.5 Geological Survey Party of Tibet Autonomous Region Geological and Mineral Exploration and Development Bureau to form a team to carry out the geological survey and assessment, eventually found it is a large scale brine-lithium-Boron deposit. Zetso Salt Lake, with a length of 16.3 km, width within 3.3-11.3 km, has an area of 113.8 km², also, it has a larger range in it depth, with shallow water around it but gradually becoming deeper and deeper to the middle of the lake with the deepest part of 44 m, average water depth of 24 m and the altitude of it is 4940 m. Zetso is located within the Qiangtang-Sanjiang Composite Plates. The Quaternary strata around Zetso can be divided into Pleistocene lacustrine sediments, Holocene alluviation, Holocene alluvial-diluvial, Holocene lacustrine sediments and Holocene surface brine. Lake basin can be divided into four hydrogeological units of bedrock fissure water, subsandy pore aquifer, subclayey pore aquifer and lake brine. By the authors statistics and calculation, the atmospheric precipitation adding into the Zetso directly is 1.081×10⁷ m³/a, the supplies of the surface water into it is 8.262×10⁷ m³/a, the supplies of the underground water into it is 2.052×10⁷ m³/a, as a result, the total watersupply amount per year into Zetso is about 11.395×10⁷ m³/a. Natural evaporation is the main discharge mode in Zetso lake. Its annual evaporation amount is 12.745×10⁷ m³/a, annual average amount value is 1.35×10⁷ m³/a, the total salt amount from surface water supplies into it is 7.8×10⁴ t/a. The main salt brine elements within Zetso are Cl^-, Na⁺, SO₄^2-, K⁺, CO₃^2-, HCO₃^-, B₂O₃, Mg²⁺, Li⁺, etc. The salt lake has an average salinity of 41.57 g/L, pH 9.31, therefore, the brine belongs to high salinity one and its water chemical type is due to sodium sulfate subtypes. The average grade of LiCl is 376.02 mg/L, its resources is 102.68×10⁴ t, thus, it has been proved to be a large scale brine-lithium deposit; in the meantime, the average grade of B₂O₃ is 840 mg/L, its resources is 229.38×10⁴ t, it also has been proved to be a large scale brine-boron deposit. On the foundation of the comprehensive analysis of lithium, boron resource requirements, extracting lithium technology, construction of salt field, and climatic conditions as well as economic value etc., the authors make a prospection of exploitation and utilization to Zetso salt lake in the future.

Abstract:On the basis of outcrop, drilling cores seismic, logging and geochemical data, the main sequence boundary surfaces of the Yan'an and Zhiluo Formation of Jurassic on the northeast margin of Ordos basin were systematically studied. On outcrop profiles and drilling cores, the sequence boundary surfaces show characteristics of iron weathering crust, truncation and lithologiclithofacies transformation. On seismic profiles, the boundaries are featured by onlap, downlap and truncation. The rock-electricity relation indicates different types of mutations. The trace elements also show mutation characteristics. Ten different orders of sequence boundaries were identified, including three I-type(TSB1-TSB3)and seven Ⅱ-type(SB1-SB7)sequence boundary surfaces. Ⅰ-type boundaries include TSB1 sequence boundary surface between Yan'an(J_1-2y)and Yanchang Formation(T₃y), corresponding to T_y in seismic profiles; TSB2 sequence boundary surface between Yan'an(_1-2y)and Zhiluo Formation(J₂z), corresponding to T_z-1 in seismic profiles; TSB3 sequence boundary surface between Jurassic and Lower Cretaceous, corresponding to T_k in seismic profiles. As regional unconformities,Ⅰ-type sequence boundaries including TSB1, TSB2, TSB3 reflected tectonic activity during Mesozoic period. The Ⅱ-type sequence boundaries were main climate transformation surfaces and showed the cyclic changes in climate factors. The vertical variations of values of Sr, Cu, Sr/Cu, FeO/MnO and Al₂O₃/MgO indicate that the paleoclimate and paleoenvironment experienced a changing process from warm-humid climate to dry-wet alternation, arid and semi-arid climate; TSB2 and SB6 were main climate transformation surfaces. Vertical zonation of stratigraphic structure is obvious between Yan'an and Zhiluo Formation on the 3D models of the study area. The uranium bodies mainly lie in the large sandstone overlying TSB2 sequence boundary surface, in the form of plate on the 3D models of sandstone and uranium mineralization bed. The uranium bed was obviously influenced by the vertical zonation of stratigraphic structure and paleoclimate transformation. The integrated identification of sequence boundaries will not only reduce the casualty of artificial empirical recognition but also provide a basis for the division of Jurassic sequences and the establishment of isochronous sequence stratigraphic framework. The research on space-time attributes and the indicated geological meanings of the main sequence boundary surfaces will be helpful to revealing the process of "Yanshan movement" and its influence on the paleoclimate transformation and sandstone-type uranium mineralization.

Abstract:In recent years, many Nb-REE deposits (ore spots) have been discovered in Hulunxibai area on the eastern margin of Beishan metallogenic belt. The deposits (ore spot) occur in the external contact zone of Permian adamellite, and the orebodies occur in the littoral-shallow marine carbonate and metamorphic detrital rocks. The morphology, attitude and scale of the orebody are controlled by tectonic-magmatic activity, and orebody position is consistent with the magnetic anomaly. The Nb₂O₅ grade of northeast Huishi Mountain mining area is generally between 0.02% and 0.56%, with an average of 0.11%, and the REO grade is between 0.13% and 2.63%, with an average of 0.93%. The Nb₂O₅ grade of the west Huisenwula mining area is between 0.01% and 0.1%. The metallogenic type is similar to that of the superlarge Nb-REE-Fe deposit in Bayan Obo. The metallogenic potential of NbREE deposits in this area is enormous. Combined with regional geological setting and metallogenic characteristics of the Nb-REE polymetallic mineralization zone, the authors hold that prospecting indicators for this type of Nb-REE polymetallic deposits in this area are as follows:ⅰ. Permian littoral-shallow marine carbonate and metamorphic detrital rocks strata; ⅱ. free space or transfer sites between ductile and brittle deformation from the tectonic compression; ⅲ. Permian adamellite outer contact zone; ⅳ. aeroradiometric anomaly gradient zone and magnetic anomaly; ⅴ. wall-rock alteration (limonitization, silicification, carbonatization, etc); ⅵ. fine quartz network veins development area. The study of the metallogenic characteristics and prospecting indicators of the Nb-REE polymetallic deposits in this area is helpful to promoting the prospecting ideas of rare earth, rare metal and rare-scattered elements mineral resources in Beishan area, and can also provide a reference for the prospecting direction of such deposits.

Abstract:In sediment-hosted copper deposits, altered volcanic rocks have special significance for diagenesis and mineralization. Based on the methods of tectonic lithofacies mapping, volcanic lithofacies classification, and electron microprobe analysis (EPMA), the authors studied lithofacies types of volcanic rocks, their geochemical characteristics, physical-chemical conditions of magmatic evolution and their relationship with copper (silver) enrichment. The following results show that mesogenetic intrusive facies, subvolcanic intrusive facies (sub-volcanic neck facies), volcanic overflow facies, pyroclastic facies and sink volcanic rocks are developed in the Tupiza copper deposit. The assemblage of rock types is diabase, gabbro, alkaline basalt, potash-trachybasalt, olivine basalt trachyandesite, and latite. In this area, alkaline basaltic magmatic emplacement has multiple stages and phases. In the Tupiza copper mining area, mineral geothermometer-geobarometer was used to do estimation. When the formation temperature and pressure of hornblende respectively are 630.97-748.43℃ and 55-251 MPa, the depth of diagenetic formation is estimated to be 2.04-9.27 km, revealing that the diagenesis evolution process under decreasing pressure-increasing temperature (decompression melting) and decreasing pressure-decreasing temperature had a high-temperature and high-oxidation diagenetic environment during magmatic decompression and emplacement, suggesting a multi-stage emplacement. Chlorite formation temperature is 112-305℃, lgf(O₂)=-45.03—-56.68, lgf(S₂)=-4.46—-18.07, suggesting a low temperature reduced diagenesis mineralization environment representing the main copper (silver) ore formation period. The Tupiza copper (silver) deposit was formed by the subvolcanic hydrothermal alteration diagenetic mineralization. Altered volcanic rock is a metallogenic material supply system for copper deposits. Copper (silver) orebody is concentrated in altered volcanic lithosphere and structural superposition, particularly concentrated in the intersection of NNE and NW-trending structures. In the pyrite glutenite at the top of the second lithologic section below the third lithologic alteration volcanic rock in the Upper Cretaceous Aroifilla Formation, the verifying drilling revealed a copper (cobalt) mineralized body, which was the sign of deep prospecting for hidden sedimentary rock type copper (cobalt) orebodies. In this paper, it is believed that, in the Tupiza copper deposit, the central phase of the sub-volcanic hydrothermal metallogenic system is distributed in the altered secondary volcanic neck phases, enriching the copper (silver) orebody. Peripheral veinlet vein-fractured-alteration zone is the transitional facies zone of the copper-lead-zinc metallogenic system, while the glutenite-type copper (cobalt) ore and Cu-Pb-Zn anomaly in the second lithologic zone of the Aroifilla Formation is the outer fringe facies zone of the copper (cobalt) lead-zinc metallogenic system. It has the prospecting potential for copper (silver), copper (cobalt) and copper-lead-zinc orebodies in the deep surrounding altered subvolcanic facies.

Abstract:The Huangyangshan deposit is a superlarge crystalline graphite deposit recently discovered in Xinjiang. The reserves of crystalline graphite in the deposit are estimated at least 72.64 Mt. The deposit is hosted in granite, and 90% of graphite is of spherulitic structure. The longest diameter of the spherulite can reach 20 cm. It is extremely rare in the world. Through drill core logging, prospecting trench logging and petrographic and zircon U-Pb geochronologic studies, the authors investigated mineralization, mineral assemblage and diagenetic age of the deposit, and discussed its ore genesis. The results reveal that the diagenetic age of the deposit is (306±4) Ma, which is Late Carboniferous. Graphite spherulite and matrix have the same lithology of alkali-feldspar granite. However, biotite, hornblende and clinopyroxene are relatively more concentrated in the spherulite. Metallic minerals associated with graphite are pyrrhotite, chalcopyrite, ilmenite and hematite. Due to strong reducibility of graphite, these metallic minerals are mainly distributed within graphite spherulite, forming typical zoning texture. Graphitization could be divided into two periods, namely magmatic hydrothermal period and hydrothermal superimposition period. The former was the principal oreforming period, producing spherulitic and disseminated graphite, while the latter produced vein graphite. Crystals of graphite are of flaky and colloform texture. The flaky graphite is in acicular form along the section and has preferred orientations. Graphite ores have low negative bulk-rock carbon isotopic composition, which implies that the carbon consisting of graphite was derived from organic matters in strata. Magma assimilated organic matters in strata during its ascending. At the late stage of magma evolution, with the separation of the melt and liquid phase, carbonaceous matters were incorporated into the liquid phase. When the temperature and pressure decreased, carbon precipitated from the magmatic hydrothermal to form graphite. Medium-grained arfvedsonite granite and fine and medium grained biotite granite contain graphite spherulites, and hence Huangyangshan pluton has considerable ore-prospecting potential.

Abstract:Chloritization is a type of hydrothermal alteration widely developed in the Huangsha uranium deposit in the middle part of the Nanling Mountains. Based on petrographic studies, the authors investigated the types and morphological characteristics of chlorite minerals in No. 221 and No. 223 uranium deposits by using electron microprobe analysis, and classified chemical types of chlorite. Four kinds of chlorite production status were recognized, and the temperature and environment of the formation of chlorite as well as the relationship between chlorite formation and uranium mineralization was discussed. The results are as follows:(1) The early chlorite was mainly of biotite pseudomorph or starlike shape characterized by mass output, and the metallogenic chlorite was mainly produced in the vein. (2) There are four types of genesis i.e., chlorite biotite alteration, feldspar alteration, fracture filling type and uranium deposit association. (3) The chlorite-forming temperature was 200-310℃, and the average formation temperature of chlorite coexisting with uranium minerals was 215℃, suggesting a middle-low temperature hydrothermal deposit. (4) Chlorite was mainly formed in a reductive environment, and the formation mechanism was dissolution-precipitation and dissolutionmigration-precipitation.

Abstract:The middle Zhuguangshan area is one of the main uranium-producing areas in South China. The characteristics of structural deformations and ore-controlling structural regularity were studied in order to identify the features of uranium deposits and provide scientific guidance for ore-prospecting in blind ore deposits, with Lujing uranium orefield in middle Zhuaguangshan as the study objects. The authors revealed that NE-trending faults are ore-controlling and ore-hosting faults in Lujing area, as shown by field detailed observation and microscopic structure analyses. NE-trending faults have characteristics of multi-stage tectonic and hydrothermal activities belonging to shallow surface tectonic deformation. Geological phenomena show that NE-trending faults had at least three stages of tectonic events:compression deformation at the early stage (Late Jurassic-Early Cretaceous), tensional and torsion at the late stage (Early Cretaceous-Paleogene), and the faults changed into compress-shear faults at the late stage (Neogene). The uranium orebodies were developed in the NE-trending fracture zone, and the mechanical properties of NE-trending faults were tensional and transtensional during the major ore-forming stage. The near EW, NW and NS (NEE) trending faults were induced from the NE-trending main faults in the later right twisting deformation in Neogene period. The earlier uranium orebodies were reformed by the later tectonic deformation. On the other hand, some parts of the uranium orebodies were concentrated in the later faults. According to the characteristics of structure combination and ore-controlling regularity, the authors hold that the blind uranium orebodies which occurred as veins and lenses existent in the NE-trending fracture zone, and the secondary enrichment of uranium may exist in other direction faults.

Abstract:The Dongji Au(Ag) deposit is a cryptoexplosive breccia deposit in the southeastern coastal area, with reserves of 12.5 tons Au and 135.9 tons Ag,and hosted in late Yanshanian Nanyuan Formation. To discuss metallogenic and metal material source of the Dongji deposit, the authors carried out multiple isotope (S-Pb) and electron microprobe analysis (EPMA). Pyrite Co/Ni ratio is 3-94 (averaging 23), Co is 500×10^-6-1070×10^-6 (averaging 799×10^-6), Fe/(S+As) is 0.827-0.871 (averaging 0.860), Au/Ag is 0.9-5.5 (averaging 2.6), which suggests that the Dongji Au(Ag) deposit is an epithermal deposit resulting from volcanism. δ³⁴S of pyrite ranges from -0.7‰ to -6.6‰, ²⁰⁶Pb/²⁰⁴Pb is 17.9801-18.4303, ²⁰⁷Pb/²⁰⁴Pb is 15.2689-15.9397, and ²⁰⁸Pb/²⁰⁴Pb is 37.9052-38.7871, which suggests that metal materials were mainly derived from crust-mantle granite magma and partly from metamorphic basement and volcanic wall rocks. Based on zircon U-Pb ages of crystal tuff and granite porphyry combined with regional mineralizaton in the Zhenghe-Jianou area, the authors hold that the metallogenic epoch of the Dongji deposit should be late early Cretaceous.

Abstract:The Shanwanzi gold deposit in Chifeng of Inner Mongolia which is located in the east of Chifeng-Chaoyang gold metallogenic belt occurs in the andesite of the early Cretaceous Yixian Formation. In order to discuss the metallogenic age and genetic characteristics of the deposit, the authors, through the study of petrography, microthermometry, hydrogen, oxygen isotope and chronology of the the fluid inclusions, have reached the following conclusions:The fluid inclusions are mainly composed of pure liquid inclusions and a small amount of gas-liquid two-phase inclusions, and the gas composition of the inclusions is mainly H₂O and CO₂, which reflects the NaCl^-H₂O-CO₂ system; uniform temperature range is 219-249℃, and salinity is 0.35%-3.23% NaCl eqv., suggesting that the temperature and salinity of the principal metallogenic period is low; the metallogenic pressure is 2.7-33.8MPa, and the metallogenic pressure depth is 2.78 km, indicating that the mineralization exhibits a shallow characteristic; the formation age of andesite determined by ICP-MS U-Pb zircon is 123.6 Ma and 124.5 Ma, which is consistent with the age of early Cretaceous period of the Chaoyang-Chifeng gold metallogenic belt. Combining ore deposit characteristics with the study of the metallogenic fluid, the authors hold that the Shanwanzi gold deposit is a low sulfur, low temperature hypabyssal hydrothermal deposit.

Abstract:The Gaozhuang gold deposit is one of the important Au deposits in Au polymetallic ore concentration area of northern Qinling Mountain, Henan Province. The Rb-Sr isochron age and H, O, S and Pb isotopes of ores from the Gaozhuang gold deposit were analyzed so as to constrain Au mineralization formation age and discuss the source of ore metals and the controlling factor of deep ore fluids discharge as well as the Au mineralization potential. The ⁸⁷Rb/⁸⁶Sr and ⁸⁷Sr/⁸⁶Sr ratios of pyrite and quartz from 7 ore samples are in the range of 0.0709-5.963 and 0.711139-0.721982, respectively. The initial ⁸⁷Sr/⁸⁶Sr ratios are in the range of 0.711025±0.000052 and the Rb-Sr isochron age is (129.8±1.4)Ma (MSWD=1.3), almost consistent with the age of the Yanzhen granitic intrusive and the Gaozhuang granitic aplite. It is suggested that they were nearly formed at the same time of -130Ma in early Cretaceous. The δ¹⁸O_V-SMOW and δD_V-SMOW values of 3 quartz samples are 11.6‰-12.1‰ and -60.9‰—-42.5‰, respectively. Their δ¹⁸O_H2O values range from 2.16‰ to 2.66‰, suggesting that ore-forming fluids of the Gaozhuang gold deposit were a mixed source. The δ³⁴SV-CTD values of 6 pyrite samples are from -2.8‰ to -1.6‰ with a tower shape in the δ³⁴S histogram, which indicates a mantle source. The ratios of ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb of 7 samples are 17.549-18.278, 15.461-15.619 and 37.593-38.428, respectively. Their μ, △α, Δβ and Δγ are 9.30-9.51, 59.52-75.10, 11.44-19.80 and 30.38-37.99. In ²⁰⁶Pb/²⁰⁴Pb-²⁰⁷Pb/²⁰⁴Pb and ²⁰⁶Pb/²⁰⁴Pb-²⁰⁸Pb/²⁰⁴Pb diagrams, sample points of the Gaozhuang gold deposit are close to the orogenic line. They fall into the crust-mantle subduction zone mixed lead source and the orogenic belt lead source in Δβ-Δγ of Pb isotopic diagram. It is suggested that metallogenic materials of the Gaozhuang gold deposit were derived from the lower crust and the upper mantle, with the addition of the upper crust materials in the ore-forming process. The formation of the Gaozhuang gold deposit was closely related to Yanshanian intraplate (intracontinental) orogenesis of northern Qinling Mountain. The Gaozhuang gold deposit, the Yanzhen granitic intrusive and the Gaozhuang granitic aplite are all products of regional lithosphere delamination. Deep fluids were rapidly discharged, and diverse sources of metallogenic materials at different depths were connected in the process of regional lithosphere delamination. The Gaozhuang gold deposit was formed when the mixed fluids stopped moving in shallow crust. It is suggested that the deep part beneath the Gaozhuang gold deposit and the Yanzhen area possessed endogenetic metallogenic potential with rapid discharging of deep fluids controlled by regional lithosphere delamination.

Abstract:The Zhujiawa molybdenum deposit is one of the large-size deposits recently discovered in the middle part of northern margin of North China Platform. The research on this deposit is relatively insufficient. The deposit is similar to the Caosiyao molybdenum deposit in metallogenetic mechanism in that they are both controlled by hypabyssal super-hypabyssal acidic rock from deep source. The characteristics of ore-forming fluid constitute the key problem in revealing the genesis of ore deposits. In this paper, eleven core samples of molybdenum mineralization were collected from No.ZK2-1 and No.ZK2-2 drill hole. The results show that the fluid inclusions can be divided into four types. They are liquid-rich phase inclusions, daughter-minerals three phase inclusions, gas-rich phase inclusions and CO₂-bearing three phase inclusions. Among them, CO₂-bearing three phase inclusions are less distributed, whereas the other three types of inclusions are common. Homogenization temperatures and salinities of daughter mineral-bearing three phase inclusions are the highest, at about 400℃ and 45% Na Cleqv respectively. Homogenization temperatures and salinities of liquid-rich phase inclusions are 277.43℃ and 20% Na Cleqv respectively. Homogenization temperatures and salinities of gas-rich phase inclusions and CO₂-bearing three phase inclusions are 380℃ and 30℃, 6%NaCleqv and 2.04% NaCleqv respectively. The initial fluid has the characteristics of high temperature, high salinity and rich CO₂, and the fluid inclusion has the characteristics of the porphyry mineralization system within the continent. The fluid inclusion composition of gas and liquid phase shows that ore-forming fluid mostly contains H₂O, Cl^-, F^-, Na⁺, K⁺, and minor Ca²⁺ and SO₄^2-. Diagnostic ion ratios indicate that ore-forming fluid was derived from magmatic fluid. The ore-forming fluid in general belongs to the H₂O-NaCl system. Hydrogen and oxygen isotopic composition of the fluid inclusion in quartz indicates that the water in ore-forming fluid was derived from magmatic. Boiling of the ore-forming stage led to the precipitation of molybdenite.

Abstract:The Xiashan Pb-Zn deposit is a large-sized Pb-Zn deposit discovered in Fujian Province in the 1950s. Although most researchers have classified this deposit as a sedimentary-reworked Pb-Zn deposit, some geologists still believe that it is a skarn type deposit formed by the intrusion of the Tongpenan pluton (syenite granite) in Yanshanian period. Based on geological survey, the authors hold that the distribution and morphology of orebodies are closely related to granite porphyry. Ore-related granite porphyry samples from the Xiashan Pb-Zn deposit were dated by zircon La-ICP-MS U-Pb chronology, which yielded an age of 173±1.7 Ma. This result confirms that the Xiashan Pb-Zn deposit involved a skarn mineralization process of Early Yanshanian period which was earlier than the intrusion of the Tongpenan pluton (155-150 Ma). In addition, the age of 173±1.7 Ma is consistent with the metallogenic epoch of Cu, Ag, Pb and Zn polymetallic deposits in northeastern Jiangxi Province, suggesting that the Wuyi Mountain metallogenic belt in Fujian Province had a positive response to the first large metallogeny of the Early Yanshanian period in southern China, and has the potential in the search for Cu, Ag, Pb and Zn polymetallic deposits. According to the results obtained by the authors and previous studies, two important metallogenic periods (173 Ma and 90-125 Ma) of Yanshanian period can be recognized in the Wuyi Mountain metallogenic belt, especially in the north region. These results are of great significance for discovering and studying the concealed and superimposed deposits in the Wuyi Mountain metallogenic belt.

Abstract:Located in the southern section of the CAOB (Central Asian Orogenic Belt), the Bianjiadayuan Pb-Zn-Ag polymetallic deposit belongs to the Sn-Cu-Zn-Pb metallogenic belt of Da Hinggan Mountains. In this study, a series of analyses, such as LAICP-MS zircon U-Pb isotopic dating, major element and trace elements testing and electron microprobe analysis of albite, were performed for the granite porphyry and augite diorite. The results show that the age of granite porphyry and pyroxene diorite are ca. 138 Ma and ca.137 Ma respectively, indicating that the intrusive rocks are products of the magmatic activities in the Early Cretaceous. The pyroxene diorite belongs to high K calc-alkaline series and calc-alkaline series with SiO₂ (50.99%-52.89%), CaO (7.4%7-7.51%), MgO (3.64%-4.68%), and alkali (Na₂O+K₂O) 4.91%-5.36%. Granitic porphyry with miarolitic structure and microscopic identification shows that feldspar is all alkaline feldspar. Non-mineralized granite porphyry is characterized by high SiO₂ (50.99%-52.89%), alkali (Na₂O+K₂O=4.83%-9.42%), A/CNK (1.13-2.40), LREE enrichment, strong negative Eu anomalies (δEu=0.12-0.32), enrichment of LILE such as Rb, Th, U and K, depletion of HFSE such as Ta, Nb, P and Ti and transition elements such as Sr and Ba. According to the electron microprobe analyses, the An values of the albite in granite porphyry are by far lower than 10 (0.03-4.64). These features are similar to the features of typical highly evolved A₂ post-orogenic alkali feldspar granite pluton, suggesting that the magma was derived from the lithospheric mantle and formed in the tensional setting. Combined with the geological characteristics and previous research results, the authors hold hat the metallogenic geological body of the Bianjiadayuan area is the granite porphyry pluton, and there is still a great potential for mineralization in the deep part of western mining area.

Abstract:The Dongtangzi Pb-Zn deposit is one of the typical Pb-Zn deposits in the Qinling metallogenic belt. Its mineralization has been studied by many researchers, but the study has been limited by the testing methods and the level of understanding. Its material source is still a problem of much controversy. Based on the study of the geological characteristics of the Dongtangzi Pb-Zn deposit, the authors carried out S and Pb isotope analysis of related samples. The analysis included different types of lead-zinc ore. The source of ore-forming materials of the lead-zinc deposit and the relationship between magmatic rocks and Pb-Zn mineralization in the study area were discussed. The results show that the δ³⁴S value of ore sulfides varies from 1.8‰ to 12.5 ‰ with an average of 7.50 ‰, whereas the δ³⁴S_∑S value in the ore-forming fluid is 7.7 ‰, which shows the characteristics of mixed sources of sulfate in sea water (evaporation paste rock) and magmatic sulfur. The Pb isotope composition of ores is stable in this deposit, which indicates that Pb sources were mainly derived from the upper crust with rich U-Th-Pb elements and deep surroundings, which might have been related to deep magmatic activity. The results show that the metallogenic process of the Dongtangzi Pb-Zn deposit was closely related to the large-scale multi-stage tectonic-magmatic-fluid activity in the Indosinian period, and this understanding provides a new idea for prospecting in the next stage.

Abstract:The Dongyan Pb-Zn deposit located in the Southeast Sichuan folded belt is a middle-low temperature hydrothermal type lead and zinc deposit, predicted amount of Zn metal is 101400 tons. The orebodies occur along NNE- and NWW-trending faults in veined or stratoid form in the interlayer fracture zone and are hosted in Ordovician carbonate rocks. The formation of this type of Pb-Zn deposit in the southeastern Sichuan fold belt and the relationship with the NNE-trending fault remain unclear. In this paper, Rb-Sr isotopic dating yielded an age of (157.7±3.3) Ma for the sphalerite in the Dongyan Pb-Zn deposit, which represents the main metallogenic age of this deposit and also constrains the formation time of NNE-trending fault of this area. The (⁸⁷Sr/⁸⁶Sr)_i ratio of the sphalerite is 0.71347, which is much more higher than the ratios of the same period or earlier period, and might have been related to atmospheric freshwater. The Southeast Sichuan folded belt of Sichuan Basin is a nappe-detachment thin skinned structure. The main period of the fold deformation was the early Yanshanian stage in the Middle-Late Jurassic period. Rb-Sr isochron age of Dongyan sphalerites is consistent with the tectonic deformation age mentioned above, indicating that the formation of the deposit was related to the Early tectonic deformation in Yanshanian stage.

Abstract:The Bagong Pb polymetallic ore spot is located in the west of the Bangong Co-Nujiang metallogenic belt, and its tectonic unit belongs to Ritu-Duolong early Cretaceous magma arc belt. Preliminary estimation of Cu+Pb+Zn 334₁ resources is 94900 tons. Based on the results of investigation and evaluation of Cu-Pb-Zn polymetallic ore resources in the eastern Aiyongcuo area in Ritu County of Tibet, The authors investigated their geological characteristics, genesis and prospecting significance. Samples of rare earth elements, trace elements, silicate and isotopes were systematically collected and studied through large scale mapping, and the pluton which is exposed in the ore spot consists of diabase, quartz monzodiorite, granodiorite porphyry and granite porphyry. Among them, granule porphyry formed on active continental margin in early Cretaceous((112.7±0.68)Ma) seems to be most closely related to mineralization. The ore-controlling factors are mainly composed of strata, magma and structure. The metallogenic wall rocks mainly include altered tuff sandstone, altered agglomerate, altered diabase and sericite-chlorite altered rock. The ore-controlling structure mainly includes NWW-, nearly EW- and NW-trending faults. The orebody exhibits disseminated, lentoid, stockwork and aggregation forms. The authors preliminarily hold that the origin of the Bagong Cu-Pb-Zn polymetallic ore spot is of medium and low temperature hydrothermal fracture filling type. The discovery of this ore spot provides a new prospecting clue for BangongNujiang junction zone and the volcanic-magma arc on both sides of the junction zone. In addition, the prospecting direction is further expanded in this area.

Abstract:Danghe South Mountain is located at the northern edge of South Qilian massif, bounded by the Danghe River, and neighbors the central Qilian massif in the north. It belongs to the South Qilian Au, Pb, Zn, Cu, Ni, W, and Cr metallogenic belt. The gold deposit is the main mineral species in the metallogenic belt. It is known as 72 gold ditches. At present, two large or medium-sized gold deposits have been discovered, and there are more than ten small gold ore spots. Wulandaban-Zhazigou area is located in the middle of the Danghe South Mountain. A large number of gulch-gold mining sites can be seen in the area, showing good geological conditions for prospecting in this area. Based on the investigation and study of the area, the authors analyzed the geochemical characteristics, elemental distribution characteristics, elemental correlation and abnormal elemental combination characteristics in the study area by using 1:50,000 stream sediment survey. Combined with the geological conditions such as strata, structures, magmatic rocks and mineralization alteration characteristics in the area, the authors delineated the metallogenic prospective areas. Through this work, 11 metallogenic prospective areas of gold were delineated which could be divided into three types. The first type includes the south of Zhazigou, Diaoyugounao, Diaoyugou, Hongmiaogou and Beijiazi-Wulandabangou metallogenic prospective areas. The authors also discussed the minerogenetic condition and put forward some suggestions concerning further work in the first type metallogenic prospective areas. Delineation of the metallogenic prospective areas provides important reference for further prospecting work.

Abstract:Through studying the geochemical characteristics and metallogenic potential of Maoershan granite and its adjacent basement strata, it is found that the granite is characterized by high silicon (SiO₂=67.61%-8.316%), rich potassium (K₂O=3.75%-6.28%) and iron (FeO^T=1.85%-5.38%), depleted sodium (Na₂O=0.08%-3.06%), poor magnesium (MgO=0.14%-1.28%), peraluminous nature (the average of A/CNK being 1.49), relatively high total amounts of rare earth elements, and enriched light rare earth elements, with Eu negative anomaly (δEu=0.15-0.46), suggesting that it was formed in the post-orogenic tectonic environment and belonged to strongly peraluminous S-type granite. At the same time, the results show that the element assemblages and hydrocarbon composition of Maoershan granite and its adjacent basement strata had inherited relationship. The granite was mainly derived from the partial melting of the basement strata. W, Sn and Bi had good metallogenic potential. All these data show that the basement strata in this area not only provided a material basis for large-scale magmatic activities but also provided a source of ore-forming materials for further differentiation of granite pulp to form tungsten-tin polymetallic deposits.

Abstract:

Abstract:

Abstract:

Abstract:

Abstract:

Abstract:

Abstract:

Abstract:

Abstract:

Abstract: