Abstract:The Sanweishan fault, an important branch of the eastern segment of the Altyn Tagh fault and located in the leading edge of the northwestern Tibet Plateau is a left- lateral strikeslip and thrusting activity. Field investigation and satellite image interpretation reveals that the main fault, after crossing through Mingsha Mountain, continues to extend westward and finally crops out in Danghe water reservoir segment (DHRS) and Yangguan County in the form of fault escarpment. The length of DHRS is almost 16 km, strikes near 90°. Morphology of the fault escarpment changes from simple to complicated with the fault crossing Yangguan County westward to DHRS and from Mingsha Mountain to Sanwei Mountain. The difference of the escarpment ranges from 2 to 6 m, but it tends to decrease and horizontal displacement also reduces. All of these phenomena reflect that the intensity of fault activity weakens gradually from west to east. The results of trenching and section interpretation show that the fault offsets the Lower Pleistocene sandstone and conglomerate (Yumen Formation, Qp1), the Middle Pleistocene gravel layers (Jiuquan Formation) and the Upper Pleistocene alluvial gravels. Satellite image interpretation, field investigation and magnetotelluric profiles indicate that the Nanjieshan fault intersects with the Sanweishan fault on the south side of the Mogao Grottoes, and the two faults merge to the Altyn Tagh fault at depth. The above three faults constitute an asymmetric positive half- flower structure with regional compression. The extension of the northern margin of the plateau may result from the activities of an array of NE- SW strike- slip faults and the northeast movement of the blocks between those faults.

Abstract:The paleogeographical location of the Tarim Block has long been a controversial issue. This paper conducted a systematical paleomagnetic study on 286 samples from the AK and AZ sections of the Upper Sugetbrak Formation in Aksu, Xinjiang. Three remanence components were separated from the 151 specimens available. The intermediate temperature component shows a negative fold test result, and then is interpreted as a remagnetization component during the Cenozoic time. The two high temperature characteristic remanence components HTC1 and HTC2 have positive fold test results, and the HTC1 component passed the reversal test at 95% confidence level. However, the corresponding paleomagnetic pole of the HTC2 locates between the Late Devonian and Middle Carboniferous paleomagnetic poles of the Tarim Block, whilst the corresponding paleopole of the HTC1, at λp/φp=4.5°S/93.0°E (dp/dm=7.6°/9. 9°), is significantly different from plaeomagnetic pole of the Tarim since Phanerozoic. Thus, we interpret the HTC1 component as a primary remanent magnetization acquired during the formation of the Upper Sugetbrak Formation. The detrital zircon geochronological dating yielded an age of ~588 Ma for the sampled sandstones. Combined with geological, geochemical and paleomagnetic data from Tarim and its surroundings, it can be concluded that the Tarim Block was very likely to locate in the periphery of the Rodinia supercontinent during the Neoproterozoic, the NW margin of AustraliaEast Antarctic plates. During the breakup of Rodinia supracontinent, the Tarim Block might keep drifting towards NW with the expansion of the ProtoTethyan ocean until it completely separated from the Australia plate in ~580 Ma.

Abstract:An integrated Cryogenian- Ediacaran sequence developed well in the Shennongjia area, northern margin of the Yangtze Craton, South China. Based on six Ediacaran sections bearing cap carbonates discovered recently in this area and a series of the sedimentary facies, this paper discussed the sedimentary environment of cap carbonates through systematically analyzing the stratigraphy, sedimentology and C- O isotope geochemistry. Cap carbonates in the western Shennongjia were composed of fine powder crystal dolomites have sharply contacts with the underlying tillites (and partly gradually transition), and have monotonous sedimentary structures which are mainly horizontal beddings or block stratifications. There are few other special sedimentary structures or lithological and mineral components, occasionally some cumular spharolite and leaf branchlike algae. The cap dolomites and overlying strata formed the rapid transgression sequence. The δ13 C values of the cap dolomites show a negative drift from extremely low (-6‰～-9‰) to medium low (-4‰～-5‰) in an ascending order, and a change from medium or low negative drift to much negative value, or a change around mediumlow negative values with high frequency oscillation, but δ13 C value of the overlying sediments remained medium- low negative. Sedimentary facies indicator and carbon isotopes study show that the cap carbonate rocks deposited in a shallow water shelf intertidal- supratidal flat, synchronously and diachronically with sea level rapidly rising. The 13 C value of the cap dolomite section at Shennongjia is basically similar to the change rule of the Ediacaran cap dolomite section in the world, with a wide range of global changes and correlation significance. Meanwhile, the 13 C value of the cap dolostone profile at Shennongjia is unique, which should be response to balancing the rapid rise of global sea level for the initial post- ice shallow water carbonate sedimentation. Further study found that the cap carbonates mainly developed in the shallow water shelf tidal in the central- west part of the Shennongjia area, but not in the deep- water basin, slope break and shelf.

Abstract:The late Neoproterozoic witnessed at least two glacial events on a global scale, namely, the Sturtian and Marinoan. In the Zouma area of West Hubei, the Nanhua System Gucheng Formation and Nantuo Formation belong to the Sturtian and Marinoan glacial deposits respectively. The Datangpo Formation represents the interglacial deposits and is also an important Manganese- forming period. This study conducted geochemcial analysis for fine clastic rock samples of the Guchegn, Dtangbo and Nantuo formations from the ZK702 drill core in the study area, and calculated the characteristic valuses of the CIA, CIW, PIA, Al/Ca, Rb/Sr, V/Cr and U/Th, to understand the paleoclimate and paleo- oxygen facies evolution from glacial to interglacial in the Nanhua period. Petrological evidence also suggests that the climate of Gucheng glacial period was cold and dry (CIA value changed from 69. 2 at the bottom to 57. 8, at the mean value of 62. 2), and the paleotemperature of early interglacial period in the Datangpo increased and tended to stable (CIA ranging from 54. 3 to 62. 7, with a mean of 59. 7), and the climate of late Datangpo returned to warm humid and tended to be stable (CIA value ranging from 70. 2 to 81. 1, with a mean of 75. 8). The climate of the Nantuo glacial period became cold and dry again (the CIA value decreased from 78. 6 to 61. 9). The paleoclimate evolution reflected by CIW, PIA and Rb/Sr values is consistent with that of CIA values. The change of Al/Ca values also reflects that the fluctuation of terrigenous clastic was input with paleoclimate. The V/Cr, U/Th and Ni/Co ratios show that the study area during Gucheng Period to early Nantuo Period was generally in an oxidation environment. Among them, the paleo- ocean during the early stage of Datangpo period was in sub- oxidation environment, while the other periods were in the oxidation environment. The manganese in Datangpo deposited in a sub- oxidation environment in the early interglacial cold climate, and the manganese stopped deposition after the climate became warmer. The mineralization of manganese deposits was coupled with paleoclimate and paleo- oxygen facies.

Abstract:With clastic rocks of the Lower Cretaceous Mogou Formation and the Pliocene Linxia Formation at Lintan area in the West Qinling orogenic belt as the study object, the authors used LA- ICP- MS zircon U- Pb isotope geochronological method to explore the provenance of Mogou Formation and Linxia Formation, which has important significance of study of Meso- Cenozoic tectonic evolution of the West Qinling orogenic belt. The results show that the detrital zircon ages are divided into 6 groups: (1)The Neoarchean- Paleoproterozoic (2627~1676 Ma); (2)The Mesoproterozoic (1487~1035 Ma); (3)The Neoproterozoic (996~812 Ma); (4)The Early Paleozoic (534~425 Ma); (5)The Late Paleozoic (409~252 Ma); (6)The Early Mesozoic (250~197 Ma), of which, the Neoarchean- Paleoproterozoic (2627~1676 Ma) ages data possess the largest proportion, accounting for about 5031% of the total data. The other ages possess a smaller proportion. The provenance source of Mogou Formation and Linxia Formation were much more complicated and characterized by obvious diversity. The Zircon age distribution of the two samples was consistent, with the Indosinian, Caledonian, and Neoproterozoic age peaks, as well as the unique peaks of 18 Ga and 25 Ga in the North China Block. The Lower Cretaceous Mogou Formation and the Pliocene Linxia Formation are characterized by proximal deposition. The Middle Qinling tectonic belt provides provenance, and the age patterns of the detrital zircon recorded the age information of multi- recycling zircons in the geological bodies of the provenance area.

Abstract:Nanpanjiang Basin is located in the junction area of the Tethys and Pacific Domains. Thick clastic sediments are developed in the Malipo Babu area, and therefore they are of important significance because of direct contact relationship with Babu ophiolite. Due to lacking of precise isotopic dating evidence, these sediments are still in great controversy. This study first reported the LA- ICP- MS dating age of 226±1 Ma (n=17, MSWD=1.1) for zircons from the tuff above these sediments. Combined with paleontological evidence and contact relationship, it can be confirmed that these clastic sediments are Middle- Upper Triassic Banna- Lanmu- Pinzhai Formations. Onshore- tidal- flat facies sedimentary rocks were firstly discovered, which contains quartzose fine- grained conglomerate, quartzose sandstone, fine sandstone. Sedimentary structures such as parallel bedding, wave- ripple cross beddings, lenticular beddings and interfered ripples are well developed. The evolution from huge succession of deep- water siliciclastic rocks of the Middle Triassic (Bannan- Lanmu Formation) to shallow water sediments of late Triassic (Pingzhai Formation) represents the tectonic evolution of Nanpanjiang forland basin in the Middle- Late Triassic. The unconformity between Ladinian (Gejiu Formation) and Carnian (Pingzhai Formation) represents the Indosinian orogeny II.

Abstract:The Ganzi- Litang ophiolite mélange belt, which is located in the eastern margin of the ‘Three- River’ island- arc basin in southwest of China, is an important window of studying the development and evolution of the Tethys Ocean. This paper carried out a geochemcial investigation on the Jiaokuolongwa siliceous rocks in the middle part of the Ganzi- Litang Ophiolite Mélange Belt. Geochemical analysis shows that the siliceous rocks have SiO2 content of 88.19%~94.57%, Al2O3 of 1.60%~5.33%, TiO2 of 0.05%~0. 19%, (Ce/Ce*)SN ratios of 0.63~1.77 and (La/Ce)SN ratios of 0.35~1.11, generally reflecting the influence of the terrigenous components. The trace element characteristics (V and V/Y) are similar to that of the siliceous rocks in ocean basins, suggesting that the Jiaokuolongwa siliceous rocks were probably formed in a contintental rifting basin, which was affected by terrigenous materials and relatively far away from the continental margin. A large number of late Paleozoic conodonts and radiolarian fossils have been found in the siliceous rocks through fossil identification, indicating that the Zhongzan Block had gradually split from the Yangtze Plate during the middle- late Devonian, accompanied by the formation of the rifting basin in the western margin.

Abstract:In this paper, the diabase from the Akbastao ophiolitic mélange in West Junggar was taken as the research target. A detail field geological survey, LA- ICP- MS zircon U- Pb isotopic dating and geochemical analysis were carried out to shed light on its petrogenesis, petrogenic age and tectonic setting and provide new data support for understanding the tectonic evolution of West Junggar. The geochemical characteristics show that the diabase is characterized by high SiO2 (51. 15%~54. 34%), Na2O (4. 95%~6. 36%), TiO2 (1. 79%~2. 08%), and low MgO (3. 90%~5. 15%), K2O (0. 13%~0. 80%), and Na2O>K2O. The total REEs of 117. 52×10-6 to 143. 12×10-6, LREE/HREE ratios of 1. 79 to 2. 04, and (La/Yb)N ratios of 1. 04 to 1. 22 displays unapparent differentiation between LREE and HREE with an average δEu of 0. 93. The diabase is enriched in LILEs (K, Rb, Sr) and strongly depleted in high HFSEs (Th, Nb, Ti), showing the similar characteristics of both N- MORB and IAT. 176Hf/177Hf values of zircons from diabase range from 0. 282783 to 0. 282993 with an average value of 0. 282926 and εHf(t) values range from +8. 0 to +15. 2 with the average value +12. 8. The geochemical characteristic study of the diabase implies that the source area of the diabase was the product of 25%~30% partial melting of the depleted mantle spinel lherzolite metasomatized with subduction fluid. Meanwhile, the magma underwent some extent of crystallization differentiation during its evolution. The zircon U- Pb geochronology study shows that the diabase from the Akbastao ophiolitic mélange formed at 357. 6±2. 4 Ma (n=24, MSWD=5. 3), suggesting the Early Carboniferous in age. This dating age also verifies that the evolution of the oceanic basin in the West Jungger area continued to the Early Carboniferous, and provides evidence for extinction time of the Late Paleozoic residual oceanic basin in West Junggar. Combined with regional geological background and diagenetic age, it can be concluded that the Akbastao ophiolitic mélange formed in the back- arc basin which was associated with the subduction in the Early Carboniferous.

Abstract:The amalgamation timing of the Xing’an and Songneng Blocks is still on controversy. The Xinsheng, Xinli and Niuqiuhe intermediate to felsic plutons in the southeast of Xing’an Block were systematically studied using geochronology, petrology and geochemical analysis, with the aim to understand its tectonic and magmatic evolution during the Late Paleozoic. Zircon LA- ICP- MS U- Pb dating results suggest these plutons formed in the Late Carboniferous (315~298 Ma). The Xinli monzogranite has a zircon U- Pb age of 304±2 Ma. The Xinsheng monzogranite and monzonite formed at 312±2 Ma and 303±2 Ma, respectively. The Niqiuhe alkali- feldspar granite and gabrroic diorite were formed at 315±2 Ma and 298±6 Ma, respectively. Geochemical analysis shows that these rocks are high- K calc- alkaline/shoshonite series and metaluminous. The Niuqiuhe gabbroic diorite has high MgO content (68%~8%) and Mg values (64~68), low Al2O3 and TiO2 contents, with affinity of sanukite. The Niqiuhe alkali- feldspar granite has high SiO2 and K2O and low CaO, rich in LREE and LILEs and depleted in Eu, which belongs to A2- type granitoids. The Xinli monzogranite and Xinsheng monzogranite are rich in SiO2, strong REE differentiation, and moderate depletion in Nb, Ta, P and Ti, suggesting the characteristics of highly fractionated I- type granitoids. Furthermore, the Xinsheng monzogranite is characterized by high Sr/Y ratios (132~140). The Xinsheng monzogranite and Niqiuhe alkali- feldspar granite formed likely from partial melting of the lower crust, while the Xinsheng mozonite and Xinli monzogranite were hybid melts by crust- mantle derived magma mixing. The Niqiuhe gabbro diorite originated from slab- derived sediment metasomatized mantle. According to the geochemical difference between Early Carboniferous and Late Carboniferous magmatism, along with regional geological data, it is deduced in this study that the Xing’an and Songnen Blocks had amaglmated together before 315 Ma and these Late Carboniferous intrusions formed in a post- collisional setting.

Abstract:The Zhongtiaoshan region in Shanxi Province is an important copper metallogenic belt in China, which hosts the Hujiayu porphyry copper deposit and the ‘HujiayuBizigou’type copper deposit.In this paper, we analyzed the helium and argon isotopic compositions of fluid inclusions from pyrite and chalcopyrite in Tongkuangyu and pyrite in Hujiayu.For the Tongkuangyu deposit, 4 He content of fluid inclusions ranges from 46. 23×10 -8 cm 3 STP/g to 1195. 75×10 -8 cm 3 STP/g, with 3 He/ 4 He ratios between 0. 01 Ra to 0. 06 Ra; 40 Ar content varies from 1. 69×10 -8 cm 3 STP/g to 74. 11×10 -8 cm 3 STP/g, with 40 Ar/ 36 Ar ratios of 407 to 2327. 8.For the Hujiayu deposit, 4 He content, 3 He/ 4 He ratios, 40 Ar content and 40 Ar/ 36 Ar ratios range from 314. 06×10 -8 cm 3 STP/g to 3815. 87×10 -8 cm 3 STP/g, 0. 003 Ra to 0. 014 Ra, 25. 62×10 -8 cm 3 STP/g to 761. 51 ×10 -8 cm 3 STP/g and 963. 1 to 4108. 6, respectively.The 3 He/ 4 He ratios of the Zhongtiaoshan copper deposit show typical feature of crustal He.The mantlesourced He contents of samples in the Tongkuangyu and Hujiayu copper deposits range from 0 to 0. 56%, contribution of which to mineralizaiton can be ignored.The diagrams of 40 Ar/ 36 Ar vs.R/Ra as well as 40 Ar * / 4 He vs.R/Ra show that all the samples fall into the crustal source area, suggesing Ar crustal origin.Therefore, the largescale copper mineralization in the Zhongtiaoshan region resulted from crustal fluid, without involvement of mantle fluid into mineralization.

Abstract:The Bengge gold deposit, which is located in the northern region of the Ailaoshan- Jinshajiang alkali- rich porphyry metallogenic belt, is a hydrothermal type gold- polymetallic deposit related to alkaline rocks in the Sanjiang area of southwest China. The collisional orogen of India- Asia plates occurring in the Himalayan made it multi- stage and composite mineralizations, but research on its metallogenic chronology of the deposit is still poor and restricts the understanding of metallogenic mechanism. Apatite fission- track (AFT) thermochronology technique is one of the most effective approaches to study the thermal evolution of mineralization in recent years. This study carried out the apatite fission track testing, and three groups of fission track ages of 30 Ma, 25 Ma and 15 Ma have been obtained. Simulation analysis reveals the main metallogenic thermal history of the Bengge gold deposit since the Himalayan epoch. The period of 42Ma～32Ma had a decreasing amplitude of 20～30℃, with a cooling rate of 3～3. 8℃/Ma; the period of 32Ma and 16Ma had a temperature decreasing of 20～10℃ with a cooling rate of 1. 5～0. 71℃/Ma; the period of 16Ma～6Ma witnessed a temperature decreasing of obviously 50～45℃, with cooling rate of 11～6. 25℃/Ma. The former two phases were in a slow decreasing of temperature, indicating a setting of squeezing and shorting. While the last was rapid cooling phase, indicating a extension- dominated tectonic activity. Fission track thermal history simulation reflects that the Bengge gold deposit has undergone two stages of metallogenic process. The first stage was in the environment of extrusion and shortening, which coincides with the tectonic background of compression and torsion in the Sanjiang area at that time; while the fission track age of 30Ma represents the formation time of major gold mineralization. The second stage reflects that the environment of tectonic extension is the same as the extensional setting in which the Sanjiang area was located. 15Ma is the specific time limit for mineralization, indicating that the metallogenic tectonic activity has undergone an evolutionary mechanism from compression to extension. Based on the fission track data for apatite and metallogenic simulation, this paper established the ore- forming thermal events of the Bengge gold deposit in the Himalaya period. The results in this study demonstrates that evolution mechanism of the Bengge gold deposit is similar to the main metallogenic event occured for the alkaline magmatic belt in Sanjiang area, and also shows that the Bengge gold deposit was part of the composite metallogenic system in the Sanjiang area in southwest China, suggesting that the two have similar geodynamic mechanism.

Abstract:The Huayangchuan uranium- niobium polymetallic deposit which is located on the southern margin of the North China Craton, is a large carbonatite- related uranium deposit.Based on detailed field geological work, this paper focus on the petrography, mineral chemistry and chronology of the uranium minerals, using field emission scanning electron microscopy (FE- SEM) combined with energy Disperse spectrum (EDS) and electron microprobe analysis (EMPA). The results show that primary uranium mineral is betafite, followed by uraninite. Uraninite chemical U- Th- Pb geochronology and mineralogical evidences provide the timing constraints and insights into the formation of the Huayangchuan uranium- niobium deposit. Two types of mineralization are identified and documented here: magmatic uranites and betafites related to (aegirine- augite) biotite calcite carbonatitic and syenite pegmatitic veins, formed during the peak (~201 Ma) associated with a large number of altered betafites, and high- temperature vein- hosted uraninites and betafites related to granitic gneiss, formed during the peak (~129 Ma) with few unaltered betafite grains. Minerology and mineral chemistry study indicate that the uraninite and betafite formed at the late stage may precipitate from the Yanshanian magmatic hydrothermal fluid which leached the uranium element from the early betafites. It is demonstrated that the early uranium mineralization related to the (Aegirine- augite) biotite calcite carbonatitic veins, is the primary stage for the deposit, while the late uranium mineralization may be only the altered produced due to the Yanshanian magmatic activity. In summary, the Huayangchuan uranium- niobium deposit show the genetic relationship with the Indosinian- Yanshanian carbonatitic veins but superimposed by the Yanshanian magmatism activity.

Abstract:The Huoshenmiao intrusion, which is located in the western section of the Luanchuan ore cluster district, southern margin of the North China Craton (NCC), comprises quartz diorite, monzo- granite and granite porphyry. The quartz diorite distributed mainly in the periphery is the main part of the intrusion. Four major rock- forming minerals including plagioclase, K- feldspar, amphibole and biotite were analyzed using electron microprobe to constrain the formation process and physicochemical conditions of the quartz diorite, and to reveal the genesis of the Huoshenmiao Mo deposit. Mineralogical study shows that plagioclase belongs to andesine, which can be divided into three types including normally zoned, reverse zoned and oscillatory zoned; K- feldspar is orthoclase; amphibole is magnesium amphibole; and biotite belong to magnesium biotite and iron biotite. The formation process of quartz diorite experienced multiple- stage magma evolution: the early stage of magma evolution, at which plagioclase was crystallized with An=30~35; the middle stage, at which increased water content in magma gave rise to the formation of plagioclase with An=39~42; the late stage, at which magma with less water was stabely crystallized to form plagioclase with An=42~28. The quartz diorite formed under the conditions of high- temperature (798℃ to 830℃), high- pressure (198～242MPa) and high- oxygen fugacity (-14～-13). Therefore, the high oxygen fugacity, temperature and Cl contents of mafic magma are directly related to the formation of the Huoshenmiao Mo deposit.

Abstract:The Shuangjianzishan Pb- Zn- Ag deposit, located in the northeast section of the Huanggang- Ganzhuermiao polymetallic metallogenic belt, is currently the largest silver deposit discovered in China. In this paper, the mineral characteristics of metal minerals in the deposit were studied in detail using field geological survey, identification of the ore facies, back scattering image of the electronic probe and chemical composition of electronic probe. At the same time, the chemical formula of metallic minerals was calculated and the mechanism of silver enrichment was discussed. Silver- bearing minerals occur mainly in the form of visible silver (>50 μm), including independent silver minerals such as polybasite, canfieldite, aguilarite, pyrargyrite, stephanite, freibergite, argentite, kustelite and native silver. Invisible silver content is low and occurs mainly in galena in the form of homomorphism. The metallogenic stage of the deposit can be divided into four stages: (1) Quartz- high iron Se- rich and bismuth galena - rich selenium, tin and antimony silver mineral stage; (2) Quartz- galena- rich iron sphalerite- arsenopyrite- rich antimony and tin, low selenium silver mineral stage; (3) Quartz- sphalerite- galena- silver mineral stage; and (4) Pyrite- carbonate stage. Precipitation order for metallic mienrals is pyrite+chalcopyrite+sphalerite+galena → silver sulfosalt minerals → silver sulfide, and → natural silver. The metal ions such as Fe+, Cu+, Zn+, Pb+ and Ag+ in the deposit are mainly transported in the form of sulfur- hydrogen complexes in the early stage of medium temperature and high sulfur degree. With decreasing of metallogenic hydrothermal temperature, metal S- H complexes such as lead and zinc begin to decompose to form sulphides such as galena, chalcopyrite and sphalerite. During this process, some silver were entraped within these sulphides in the form of microscopic and sub- microscopic enclaves. Precipitation of a large amount of of lead- zinc sulfide significantly changed the composition and properties of metallogenic hydrothermal fluids, eventually resulting in the complete disintegration of silver from its S- H complexes and thus forming a large number of independent silver- bearing mienrals (such as pyrargyrite, polybasite, etc.) through combination with ions such as Cu+ and Sb 3+.With continuous decreasing of temperature and salinity, when sulphur fugacity decreased gradually and pH values increased, free Ag+started to accumulate in the metallogenic fluid and gradually reached saturation, resulting in the precipiation of silver minerals, i.e. argentite due to reaction of Ag+ to H2 S. The mass appearance of natural silver marks the end of the precipitation process of silver.

Abstract:The Huzhagaitu molybdenum deposit is a newly discovered porphyry deposit in the middle segment of the Derbugan metallogenic belt in Inner Mongolia. The molybdenum orebodies are mainly hosted within the Early Yanshan granodiorite, and its contact zone with rhyolite. The deposit is dominated by molybdenum mineralization and pyrite mineralization, accompanied by lead- zinc mineralization and a small amount of copper mineralization. The ore- forming process can be divided into four stages: silicification stage, quartz- molybdenum stage, quartz- polymetallic sulphide stage, and quartz- calcite stage. There are four types of fluid inclusions: liquid- rich phase inclusions, vapor- rich phase inclusions, multiphase inclusions including daughter minerals and CO2- bearing three- phase inclusions. With the main mineralization stage as the focus of our research, this study carried out microscopic temperature measurement and laser Raman microprobe analysis for the inclusions in quartz or calcite in different mineralization stages (stage II to IV). The results show that the homogenization temperatures of the inclusions in the quartz- molybdenum- pyrite stage are mainly concentrated between 280℃ and 400℃, and the salinities vary from 2.57% to 51.68%. In this stage, vapor- rich phase inclusions and multiphase inclusions including daughter minerals coexist with CO2- bearing three- phase inclusions. The liquid phase composition of L- type inclusions is mainly H2O- NaCl. The gas phase composition of V- type inclusions is mainly H2O, and some of them also contain CO2. Characteristic peak of laser Raman shift of daughter mineral chalcopyrite was detected in halite- bearing three phase inclusions. In the quartz- pyrite stage with lead- zinc mineralization and chalcopyrite mineralization, the homogenization temperatures of the inclusions are concentrated between 180℃ and 280℃, and the salinities vary from 0.18% to 9.73%. In late stage, only L- type inclusions occur in quartz- calcite veins, with the homogenization temperatures mainly ranging between 140℃ and 240℃, salinities varying from 0.35% to 7.17%. Combined with the latest research results, this paper suggests that the initial fluid of the deposit was magmatic fluid characterized by medium salinity and medium density. In the main stage of mineralization, the boiling of ore- forming fluid due to pressure release resulted in sudden change of the physical and chemical conditions of the ore- forming fluid system and the oxidation- reduction environment, causing the unloading and precipitation of molybdenite and other sulfide minerals in vein fractures.

Abstract:This article has systematically collected global coordinates of carbonatite complexes with different ages, and obtained the distribution map of the main carbonatite complexes and their related minerals of the world using Arcgis. Based on the main structures worlwide, this study investiged the relationship of carbonatites and deepseated faults. Spatial distribution of carbonatites is often associated with extensional lithospheric tectonic background within intraplate and orogenic extensional environment. Under such tectonic setting, deep faults of tensional tectonic background can cut into the depth of the earth and provide upwelling channels for carbonatitic magma, thereby controlling the formation and distribution of carbonatites. Carbonatites occurred through all the geological periods from Archean to Cenozoic. But more carbonatites formed in later ages. The most significant petrological characteristic of carbonatite complexes is fenitization, containing aegirine, arfvedsonite, albite, phlogopite, potash feldspar and so on. The carbonatite complexes present certain of regularity in distribution of assocated alkaline rocks and ultramafic rocks in both plane and section. Major elements of carbonatites contain CO2, CaO, MgO, FeO, Fe2O3, MnO and SiO2. Carbonatites can divided into calcareous carbonatites, magnesial carbonatites, iron carbonatites and alkali carbonatites according to weight percentage of CaO, MgO, (FeO+Fe2O3+MnO) and alkali. Trace elements of carbonatite are LREE, Nb (Ta), Zr (Hf), F, P, alkali metals (K, Na, Rb, Cs, Li), alkaline earth metals (Sr, Ba), and Fe derived from above. Those trace elements are usually products of low partial melting of deep mantle caused by extensional deep faults which can form numerous important metal and nonmetal deposits in carbonatite complexes. The isotope and inclusion study of carbonatite complexes reflect the deep origin and evolution characteristics of the carbonate magma in different degrees. Therefore, carbonatite occurrence, unique mineral assemblages, wall rock alteration, petrology and geochemistry research data can provide evidence for understanding the evolution of deep magma and exploring the information of deep earth. In a recent decade’s study, there is high possibility to find existence of a new crustderived carbonatite.

Abstract:The determination of thermal maturity of the Lower Paleozoic sediments has long been a difficult problem for evaluation of the hydrocarbon source rocks due to lack of vitrinites. Based on microscopic observation of graptolite- bearing shale and laboratory simulated maturation of low mature graptolite- bearing shale and coal, optical characteristics and thermal evolution of the graptolites in marine shale was investigated to anlayze the feasbility of graptolite random reflectance as an indicator of the thermal maturity. The non- granular graptolite of lower Paleozoic marine shale occurs in banded- shaped parallel to the bedding or in the fragmented shape, and has similar optical characteristics as that of vitrinite, therefore, it can be used to measure its reflectance. The relationship between non- granular graptolite reflectance (R′gr) and vitrinite reflectance (R′vr) can be presented as following: R′vr = 1.055R′gr－0.053. The distribution characteristic of thermal maturity of the Wufeng- Longmaxi Formation in the eastern Upper Yangtze area has been determined using the non- granular graptolite random reflectance. The results indicate that the non- granular graptolite random reflectance is a practical indicator for the thermal maturity of the lower Paleozoic sediments and provides a reliable method to determine the thermal maturity of the Lower Palaeozoic sediments.

Abstract:The micro- fractures in shale reservoirs are not only the reservoir space of shale gas, but also the important channel of shale gas migration and loss. The structural characteristics of shale micro- fractures of the Longmaxi Formation in the Jiaoshiba area were determined using micro- CT, field emission scanning electron microscopy (FE- SEM) and core observations data. The opening degree of micro- fractures under different conditions (surface or formation) and their contribution to shale permeability were compared to preliminarily understand the influence of micro- fracture on the preservation of shale nanoporosity. The results show that: (1) Based on micro- CT, three sections including matrix components, high- density minerals (such as pyrite) and fractures can be distinguished in shale samples, with volume ratio of 97. 88%, 0. 88% and 1. 24%, respectively; (2) Micro- fractures are mainly isolated, slender, or zigzag bending, and have length of 3. 4~299 μm, mostly around 3. 4~20μm, with an average of 12. 44 μm; (3) The opening degree of micro- fractures in the formation is about 2. 2~30. 33 μm, with an average of 3. 97 μm, which is 36. 38% lower than the surface opening degree (average 6. 24 μm). Although the micro- fractures accounts only for 0. 7% of the total volume in the shale samples, it provides more than 70% of the permeability in the shale reservoirs. This study shows that a large amount of reticular micro- fractures developed in the Longmaxi Formation shale in JYA well is the important channels for the intensive “desorption, migration and dispersal” of shale gas along the path of “porosity, micro- fracture and fracture”. Correspondingly, the decreasing pressure of fluids resulted in deformation and closure of porosities, which is not conducive to the preservation of nano- pores. The conclusion is of great practical significance to the study of micro- fractures in shale reservoirs mainly as reservoir space or dispersal channel.