Abstract:Submarine volcanics-hosted iron deposits refer to those that are hosted in submarine volcanic-sedimentary succession. They are one of the most important types of iron deposits in China. Almost all of these deposits are distributed in western China, and have received much attention in recent years. Most researchers consider them to be formed in an active continental margin. However, it is still poorly understood why these iron deposits were formed in minor active continental margins. This key issue is crucial to the prospecting for this type of iron deposits in future. The previous isotopic dating shows that iron mineralization is coeval with the ore-bearing volcanic rocks, which suggests that the iron deposits are genetically related to submarine volcanism. Studies of the ore-bearing volcanic rocks show that they are a succession of tholeiitic to calc-alkaline basalt-basaltic andesiteandesite-dacite-rhyolite association with arc-like geochemical signature of negative Nb, Ta and Ti anomalies coupled with positive ε_Nd values, which implies that the primary magmas were derived from asthenospheric mantle, and experienced extensive crystal fractionation within the crust-level magma chamber. The above geochemical characteristics reflect partial melting of the mantle with no involvement of oceanic crust, which suggests a thermal structure of warm mantle-cool crust in the subduction zone. Considering the scenario that the iron deposits occur in submarine volcanic rocks in active continental margin, the authors hold that they resulted from high-angle subduction of oceanic lithosphere. The general characteristics and genesis of the submarine volcanics-hosted iron deposits can be plausibly interpreted by this thermal structure model. The formation of the early stage of high-salinity magmatic fluids was correlated to crystal fractionation in the magma chamber in a compressional setting, whereas the magmatic fluids mixed with sea water can be attributed to the releasing of magmatic fluids in an extensional setting. Furthermore, this model can also explain why submarine volcanics-hosted iron deposits are not associated with porphyry Cu deposits in one continental arc, and even if they occur in one continental arc in some special backgrounds, the submarine volcanics-hosted iron deposits are always located on the margin of the arc, whereas the porphyry Cu deposits are developed in the main arc.

Abstract:In order to understand the characteristics of magma activities in the southern part of Siberian plate and their influence on the closing time of Hegenshan Ocean during Late Palaeozoic, the authors studied petrography, zircon U-Pb chronology, zircon Hfisotope and geochemistry of the diorite and monzonitic granite to constrain the genesis and tectonic setting of the rock in Bayan Dulan of Dong Ujimqin Banner, Inner Mongolia. The zircon U-Pb dating results show that the diorite was formed at 319.8±0.9 Ma (Late Carboniferous), and the monzonitic granite was formed at 300.8±1.7 Ma (Early Permian). The ε_Hf(t) values and the crust model ages (t_DM^c) of diorite are14.6-17.1 Ma and 335-466 Ma respectively. The Bayan Dulan diorite is enriched in such LILE as Rb and K and depleted in Ba, Sr, Ta、Nb and Ti. The formation of diorite resulted from partial melting of juvenile oceanic crust mixed with mantle wedge during the subduction of the oceanic crust from Middle-Ordovician to Early-Carboniferous. The monzonitic granite is enriched in K and alkali, suggesting the weak peraluminous feature. The monzonitic granite is also enriched in some LILE and LREE, Rb and K with weak negative Zr anomaly and weak positive Hf anomaly, and depleted in Sr, Nb, Ta, P and Ti, suggesting characteristics of post-orogenic granite. The monzonitic granite was produced in an extension environment,and was formed by post-orogenic evolution after closing of Hegenshan Ocean.In addition, the formation of the rock was caused by partial melting of juvenile continental crust resulting from subducted oceanic crust.

Abstract:The Shaoguoyingzi intrusion is located in the Chifeng-Chaoyang gold concentration area on the northern margin of the North China Craton, surrounded by Shaoguoyingzi and Zhuanshanzi gold deposits or gold ore spots. The lithology of the intrusion is monzogranite which shares the same source with the gold deposits. The zircon U-Pb age data obtained by using laser ablation ICPMS technique are 159.1±1.5 Ma, 160.2±4.4 Ma and 160.1±1.1 Ma, which indicate that the Shaoguoyingzi intrusion was formed in Late Jurassic and the gold deposits were formed at the same time or a little later. The major and rare elements are characterized by high Si, low Al, medium alkali, poor Mg and Ca, rich Th, Zr, Nd, Rb and K and comparatively low Ba, Sr, P and Ti, with obvious negative Eu(δ Eu=0.08-0.60)and Sr anomalies; which indicates that the Shaoguoyingzi intrution is a high-K calc-alkaline I-type granite that has experienced a high degree of crystallization and differentiation. The depth of the source is about 30km, as shown by the characteristics of Sr-Yb-Y. This area was a tectonic transition period in late Jurassic, and the intrusion was formed by back-arc extension in the Pacific plate subduction environment, as shown by an analysis of the regional tectonic environment.

Abstract:This paper reports LA-ICP-MS zircon U-Pb ages of spillite-keratophyre in Pingshui Formation, northwest Zhejiang Province. The Th/U ratios in the range of 0.42-2.28 show that the zircon is a typical magmatic mineral. Analytical results show that the weighted mean ,²⁰⁶Pb/²³⁸U age of the spillite is (952±5) Ma (n=18, MSWD=0.19), and that of the keratophyre is (954±8) Ma (n=15, MSWD=0.51). Combined with previous studies and geological facts, the authors hold that the diagenetic epoch of the spillitekeratophyre in the Pingshui Formation was the Neoproterozoic (about 950 Ma). It is further suggested that the amalgamation between the Yangtze and Cathaysia Blocks in the eastern segment of the Jiangnan orogen was completed between 1.0 Ga and 0.9 Ga. It can be inferred that the Pingshui area and even Qin-Hang metallogenic belt have the potential in search for VMS deposits.

Abstract:Located in Mengyang area of the Tengchong block in western Yunnan, the Mengyang intrusion consists of biotite monzogranite (128 Ma) and granodiorite (113 Ma) with abundant gabbroic enclaves (123 Ma) and dioritic enclaves (120 Ma). The dark enclaves, which are mainly gabbroic enclaves and dioritic enclaves, are mainly distributed in the granodiorite. The dark enclaves have igneous texture, and some of them are characterized by plastic flow deformation, quenching boundary, reverse pulse and acicular apatite, suggesting petrographic characteristics of magma mixing. Geochemical data show that the host granitoids and mafic enclaves are all metaluminous to peraluminous and high-K calc-alkaline enclaves enriched in LILE ( such as Rb,Th,U, Nd and Pb) and depleted in HFSE ( such as Nb,Ta,Sr,Zr) . The host rock and dark enclaves are metaluminous, calc-alkaline and high-K calc-alkaline series rocks. Geochemical data show that the host granitoids and mafic enclaves are all metaluminous to peraluminous, calc-alkaline and high-K calc-alkaline series rocks enriched in LILE ( such as Rb,Th,U, Nd and Pb) and depleted in HFSE ( such as Nb,Ta,Sr,Zr) . The REE patterns and primitive mantle normalized trace element spider diagrams of the host rock and dark enclaves are nearly of the same shape,which indicates that they have a close relationship in magma mixing. The Early Cretaceous granitoids are considered to be of the volcanic island arc tectonic setting. The gabbroic enclaves and dioritic enclaves are characterized by low SiO₂, high MgO, high K₂O and high Mg^#(Mg^# = 48.1-68.5). Zircon in the dioritic enclaves has ε_Hf(122 Ma) values of 3.6-6.2, T_DM1Hf ratios of 535-665 Ma, and Nb/Ta ratios of 12.1-15.4, suggesting that the dioritic enclaves had the nature of mantle derived magmas, and that mafic magma was directly derived from depleted mantle source region and was subjected to magma mixing in late reformation. The Mg^# value of biotite monzogranite is 33.5, and Nb/Ta ratio is 10.9. The Mg^# value of granodiorite is 44 and Nb/Ta ratio is 12.5. It is thus held that the biotite monzogranite and the dark enclaves were derived from partial melting of the Mid-Proterozoic metamorphosed basement (Gaoligong Group), and granodiorite from the mixing of mantlederived magma and partial melting crust. The early Cretaceous intrusive rocks in the Tengchong block were intimately related to the oceanic crust of Zuogong -Baoshan plate subducted to the bottom of the Bomi-Tengchong block in the southwest; as a result, the regional crustal was continuously thickening and led to continuous regional gravity isostatic uplift; deep crustal partial melting occurred after heating uplift during decompression and formed lots of granite. Because of plate subduction and collision, the mantle magma and melting substances produced magma mixing, and formed granodiorite and dark enclaves.

Abstract:This paper first reports the characteristics of volcanic rocks in the Dazuozishan copper polymetallic deposit of Inner Mongolia. The deposit is located on the northern margin of the North China Platform, between Sila Mulun River great fault and Shaolang River great fault. The rhyolites and trachytes in the deposit are closely related to the mineralization. The rhyolites contain 74.93%-76.36 % of SiO₂ and 11.22%-11.70% of Al₂O₃. The rhyolites exhibit slightly alkali-rich form and the ratio between K₂O and Na₂O is approximately between 1.29 and 1.54. Meanwhile, the trachytes contain 65.52%-68.04% of SiO₂ and 15.05%-16.38% of Al₂O₃. They are of the alkali-rich type and the ratio between K₂O and Na₂O is approximately between 0.85 and 1.64. Both of the two rocks belong to the metaluminous-weak peraluminous series. Meanwhile, the rhyolites belong to the high potassium calc alkali series. The trachytes, on the other hand, belong to the high potassium calc alkali ~ shoshonite series. The rare earth element (REE) patterns of these two volcanic rocks are generally rightly-inclined. The rhyolites show strong Eu negative anomaly, while the trachytes show weak Eu positive anomaly. Except the elements of Ba, Sr and Ti whose values are notably lower in rhyolites than in trachytes, the trace elements in these two rocks are comparable in composition. In addition, they are both enriched in LILE and are depleted in HFSE. These two rocks have similar initial ratios of (⁸⁷Sr/⁸⁶Sr)_i and (¹⁴³Nd/¹⁴⁴Nd)_i. The ratio of (⁸⁷Sr/⁸⁶Sr)_i is approximately between 0.7046 and 0.7063, while the ratio of (¹⁴³Nd/¹⁴⁴Nd)_i is between 0.5119 and 0.5122 (t=155 Ma) , and ε_Nd is in the range of -4.24 to-10.37. These two rocks are the products of the anatexis of plagioclase amphibolite in the middle Proterozoic lower crust. The environment for the formation of the rhyolites and the trachytes in the Dazuozishan ore district is the intraplate environment of post-orogenic extension. In other words, under the condition of the post-orogenic extension of Mongolia-Okhotsk scissor-type closed orogeny and lithospheric thinning in late Jurassic (150-160 Ma), the anatexis of plagioclase amphibolite in the middle Proterozoic lower crust formed the volcanic rocks of metaluminous-weakly peraluminous series.

Abstract:On the basis of regional gravity data and through gravity anomaly separation and potential field transformation, the authors revealed the deep structural features of the orogenic belt. In this study, the authors found that the positive linear gravity and magnetic anomaly belt and the details of each order wavelet can clearly reflect the location of the suture belt at the southern edge of the Tongbai-Dabie and East Qinling orogenic belt. The fourth order approximation of the gravity anomaly wavelet can especially obviously reveal the deep structural features. In the"overpass style" two-tier structure displayed in the lithosphere in northwest Hubei, the free space gravity, the isostatic gravity, the residual gravity anomaly and the wavelet details of each order can reflect the nearly EW-extending structural features of the relatively shallow orogenic belts clearly. Each order approximation result reflects the north-south stretching structural features of the relatively deep crust-lithosphere mantle. The analysis and study of the gravity field space form of the orogen belt are of important scientific and practical significance for the study of tectonic deformation of the central orogenic processes, the reconstruction of ancient suture position, the detection of the tectonic framework of the central orogenic belt and the recovery of the flatten process of the North China and South China Plates.

Abstract:Recent studies of Middle Tianshan Mountains are reviewed in this paper, with particular interest placed on magmatism and related mineralization. The Tianshan Mountains in Kyrgyzstan are composed of three major structural units, i.e., the northern, middle and southern Tianshan Mountains, which are separated by the Nikolaev Line and Atbashi-Inylchek fault. The suture zones on both sides of the Middle Tianshan Mountains were formed as a result of progressive subduction and subsequent closure of the Terskey Ocean in Early Paleozoic and the Paleo-Turkestan Ocean in Late Paleozoic. Various Precambrian continental domains joined to form the basement of the Middle Tianshan Mountains. The Paleozoic was generally a passive stage in the history of the Middle Tianshan Mountains. The Late Carboniferous magmatism had distinct metallogenic affinities with subduction-related rocks, and the post-collisional intrusions and orogenic Au deposits in the Early Permian were formed coevally and controlled by tectonics.

Abstract:Based on analyzing the model parameters of continental extension, the temporal-spatial evolution of igneous rock's geochemical characteristics, the geometry and kinematics of multi-level extension within lithosphere , the match and evolution between stress and deformation fields, this paper focuses on the Bohai Bay basin and its adjacent areas to discuss the dynamic mechanism of rifting in Late Mesozoic-Cenozoic. The continent extended by the way of core complex mode in the north and west of Bohai Bay basin, but by the way of wide rift mode in the south and east in Late Mesozoic. In the process of lithospheric extension, the crust was deformed by simple shear whereas the lithospheric mantle deformed by pure shear. In addition, the geochemical characteristics of igneous rock indicate that the basin was located in a back-arc tensional regime due to the subduction of ocean crust, the lithospheric mantle was of EM1 pattern under the basin and in its north and west, whereas the lithospheric mantle was of the EM2-like pattern in the south and the east of the basin because of the subduction of Yangtze plate. Combined with the stress and deformation fields of the basin, the stress source of rifting should be the tension mainly generated by the relative motion within the plate, and the basin was transformed by the strike slip of Tanlu fault. However, the continent extended by the way of narrow rift mode within Bohai Bay basin in Cenozoic. Additionally, the crust and the lithospheric mantle were deformed exclusively by pure shear, but the latter extended more intensively. On the other hand, the geochemical characteristics of igneous rocks indicate that the basin was involved in the continental rift, and the asthenosphere upwelled and transformed the lithospheric mantle. Apparently, the tension produced by the upwelling of asthenosphere played the crucial role in basin rifting.

Abstract:In this paper, the stratigraphic framework of the SDQ buried hill reservoir was built through using the drilling cores, loggings and seismic data of northern Shaya uplift in the Tarim Basin, and the rock lithofacies were analyzed through drilling cores and petrographic thin section. The stratigraphic age was determined through the U-Pb zircon geochronology of the drilling core samples, and was compared with the outcrops of the Kuruketag area in northeast Tarim Basin. The result shows that the SDQ buried hill is composed of some metamorphic marine sedimentary clastics and carbonate rocks, whose thickness is between 700 to 800 m. The minimum zircon concordia age is about 522 ±16 Ma from 3 clastics rock samples, which indicates that the deposition or diagenetic age should not be earlier than the middle Proterozoic. The SDQ buried hill reservoir is the oldest buried hill reported in the Tarim Basin.

Abstract:Progressive metamorphic belts occur extensively in Chinese Altay. The depositional time and provenance of the metasediments in the metamorphic belts are critical for understanding the rock-forming process and the evolution of the orogen. Based on petrological analysis, the authors conducted LA-ICP-MS U-Pb analysis of detrital zircons from the quartzite narrowly interbedded in the metamorphic belt and yielded 100 concordant or nearly concordant ages with a range from (443±5) Ma to (2682± 19) Ma. Most of the detrital zircons have Cambrian ages of 486~540 Ma with the peaks between 527 and 535 Ma. One fourth of the zircon grains show Neoproterozoic ages. A few detrital zircon grains formed in the Meso-Paleoproterozoic period and even in the Archean period. Combining the youngest detrital zircon age with the emplacement time of the tonalite which directly intruded in the metamorphic belt, it could be inferred that the protolith of the quartzite deposited between the Early Silurian and the Early Devonian and later experienced metamorphism. The Cambrian and even younger detrital zircons were possibly derived from the contemporaneous igneous rocks in the region. Since the lack of Precambrian rocks in the Chinese Altay, the Precambrian detrital zircons may imply a hidden ancient basement in the region or could be ascribed to a faraway source from the neighboring block.

Abstract:Controlled by both Huangzhuang-Gaoliying fault and Nanyuan-Tongxian fault, Beijing depression was formed in the Tertiary period. The northern margin of Beijing depression in Quaternary disintegrated due to the strong activity of the Shunyi fault, and formed two new depressions, i.e., Houshayu depression and Fengbo depression. In this study, the authors conducted the research on Quaternary magnetic strata in drill hole ZK19. In combination with the OSL results, the bottom depths of early Pleistocene, Middle Pleistocene, late Pleistocene and Holocene strata in drill hole ZK19 were determined, which are 434 m, 128 m, 29.9 m and 1.35 m respectively. By comparative analysis of the sedimentary thickness and deposition rate of drill hole ZK12-2 in Fengbo depression, the authors investigated the Shunyi fault activity characteristics since the Quaternary, and discussed the evolution of the basin on the northern margin of Beijing depression. The results show that the intense activity of Shunyi fault in the early Pleistocene resulted in the disintegration of the basin on the northern margin of Beijing depression. In the Middle Pleistocene, the activity of Shunyi fault was indistinct relative to Huangzhuang-Gaoliying fault. In the late Pleistocene, Shunyi fault had a strong activity again relative to Huangzhuang-Gaoliying fault, which accelerated the disintegration of the basin on the northern margin of Beijing depression. In the Holocene, the strong activity of Shunyi fault caused the growth of ground fissures and the destruction of buildings.

Abstract:On the basis of field geological investigation, old well reexamination and analysis results, the reservoir characteristics of Leping Formation shale in Pingle depression was discussed in such aspects as distribution characteristics, geochemical characteristics, mineral composition features and micro-pore features. The results show that Leping Formation shale is widely distributed and its thickness is above 100 m. The total organic carbon content of shale is high, reaching up to 0.21%-23.4%, averagely 1.74%, the thermal evolution degree of shale is also high, with Ro in the range of 0.7%-4.06%, averagely 1.88%, and the organic matter type is mainly of type II₂. The shale has abundant brittle minerals consisting mainly of quartz(averagely 47.94%)and shows a good fracturing potential; the clay minerals content is moderate(averagely 34.93%)composed mainly of illite and andreattite. The shale reservoirs have an average porosity of 3.5% and average permeability of 0.01×10^-3μm², implying a good physical property. The types of micropores include intergranular pores, intragranular pores and organic pores, as shown by scanning electron microscope. Shale reservoir pore shapes show opening state, including two-end opened cylindrical shape and four sides opened parallel pores. Further analyses show that the organic carbon content and quartz content were the major factor to control the shale reservoir porosity development, the effect of total organic content on shale micro-pores was mainly manifested in the development of micropores and mesopores, and the quartz mineral content contributed to macropores.

Abstract:The Changhanboluo Pb-Zn-Ag deposit is located on the northern margin of North China Craton. The concealed orebodies are hosted in quartz porphyry, quartz monzonite, andesite and the contact zone of different lithofacies as lodes and lens. The hydrothermal ore-forming process of the Changhanboluo deposit includes three stages, i.e., the early, middle and late stages: The early stage is disseminated metallogenic stage; the middle stage is lode metallogenic stage which can be divided into quartzpyrite±chalcopyrite±arsenopyrite sub-stage (Ⅰ) and quartz-polymetallic sulfide sub-stage (Ⅱ); the late stage is quartz-carbonate stage. The disseminated metallogenic stage developed NaCl-H2O (W-type) and H2O-CO2 (C-type) fluid inclusions (Fls). The homogeneous temperatures of the W-type and C-type fluids in the disseminated metallogenic stage are mainly 272℃-349℃, with salinities ranging from 1.40% to 7.31% NaCl eqv. The lode metallogenic stage mainly developed W-type fluids. Therefore, fluids of stage 1 mainly have homogenization temperatures between 198 and 348℃, with salinities ranging from 1.40% to 5.86% NaCl eqv.. The stage Ⅱ fluids yield homogenization temperatures of 118℃-199℃ and salinities of 1.40%-4.80% NaCl eqv. In the late stage, the fluids have homogenization temperatures of 106° C-157° C and salinities of 0.88%-2.24% NaCl eqv. The depth of the disseminated mineralization is about 1.8-2.5 km. The mineralization depth of the middle stage (Ⅰ) is possibly at 0.1-1.5 km, while the middle stage (Ⅱ) shows much shallower depth, which is near the surface. The fluid inclusions in the Changhanboluo Pb-Zn-Ag deposit are characterized by low temperatures and low salinities. The mixing of hot magmatic fluids and meteoric water resulted in rapid precipitation of ore-forming materials.

Abstract:There are many medium and small karst depressions, karst pits and karst ditches with varied morphology in the NE-SW karst basin of the Houcao mining area in the middle of Zunyi bauxite belt. The bauxite-bearing rock series of Lower Carboniferous Jiujialu Formation was deposited in these corroded depressions. The sedimentary types were mainly debris flow-like deposition, swamp deposition, peat bog deposition and flooding sheetflood deposition. Sediments of these sedimentary types were alternatively deposited in multiple depositional cycles. This shows that the depositional environment changed repeatedly and periodically. Debris flow deposit and flooding sheetflood deposit seem to have been the main sedimentary types in the bauxite mineralization process. Bauxite orebodies were formed by flooding sheetflood deposition, called "mainstream planar orebodies", which constituted the main sedimentary type and covered all the corroded depressions in the mining area. After the formation of "mainstream planar orebodies", the conversion of the original laterite weathering crust material to the sediments of bauxite ore-bearing rock series in Jiujialu Formation drew to an end. The formation of bauxite-bearing rock series in corroded depressions was mainly affected by complex continental deposition.

Abstract:Based on analyzing the distribution, thickness, total organic carbon content, degree of organic metamorphism of the shale of Turpan-Hami Basin, evaluating the formation of fractures and the capability of adsorbing gas in consideration of the mineral composition, and studying the conditions of shale gas accumulation by analyzing the distribution of cap rocks, the physical property of reservoir, and the data of gas surveying, the authors consider that the shales in Middle-Lower Permian Taodonggou Group and the Middle-Upper Triassic Xiaoquangou Group have the bigger thickness, higher brittle mineral content, higher degree of thermal evolution, and preferable situation of cap rock, thus probably being the potential horizons of shale gas exploration. The Taodonggou Group of Tainan depression, the north of Taiben depression and the northwest of Tuokexun depression and the Xiaoquangou Group shale of Sanbao depression are favorable areas for gas exploration.

Abstract:This study used 40 shale samples from the seventh member of Dameigou Formation in 4 drilling wells and the Jurassic standard profile in the Dameigou area to illustrate the organic geochemical characteristics, the petrographic and mineralogical features, and the reservoir properties. According to the results obtained, the average content of total organic carbon is 5.22%; the kerogen is of I-II type, dominated by sapropel; the average value of organic maturity is 0.52%, belonging mainly to immaturity to low maturity; the reservoir space has various types, and micro-fractures are developed in favor of the adsorption and storage of the shale oil, and the content of brittle minerals in the mineral composition is more than 40% in favor of the production fracturing in the future. In addition, the fracture surface and the bedding planes with fluorescent provide the direct evidence for the presence of shale oil. A comprehensive analysis shows that the seventh member of the Dameigou Formation in Dameigou area with the geological conditions of the shale oil formation is the most favorable section for the development of Middle Jurassic shale oil. Moreover, the single layer of the shale in this member has larger thickness and the lateral distribution of this member is stable in the plane within the northern margin of Qaidam Basin. Combined with the existing results, it is tentatively held that the favorable areas for the shale oil development are Lenghu area, Saishiteng depression, Yuka depression and Dachaidan-Dameigou area.

Abstract:Based on the result of the stream sediment survey in Shijinpo-Nanjintan area of Gansu Province, the authors studied the characteristics of the elements distribution, the single element anomaly and the element assemblage. According to the distribution of element anomalies, the types of assemblages and theanomaly controlling factors, thestudy area is subdivided into 11 anomalous zones. The eleven anomalous zones can be further divided into four types: the first kind of anomalies is related to the intermediate acid intrusive rocks and the fracture structures, and Au is the main metallogenic element. The anomalous zones are the potential areas of quartz vein type and broken belt type gold deposits. The second type of the anomalies is related to the formation of the Jixian system, and these anomalous zones are the important potential areas of Pb, Zn, Fe and polymetallic deposits. The third type of the anomalous zones is related to the Dunhuang system, and the anomalous zones are potential areas of metamorphic hydrothermal type gold deposits. The fourth type of the anomalous zones is related to the intrusion of basic-ultrabasic complex, and the anomalous zones are the potential areas of magmatic liquation Cu-Ni sulfide deposits.

Abstract:Through analyzing the aeromagnetic and aeroradiometric results obtained in the Bayan Obo REE-Nb-Fe deposit in combination with the comprehensive comparative study of its geological characteristics, the authors found that the Bayan Obo REENb-Fe ore deposit has unique and typical aeromagnetic and aeroradiometric characteristics. The aeromagnetic anomaly characteristics show that the ore deposit is characterized by a high-intensity banded and nearly EW positive magnetic anomaly associated with a parallel positive anomaly, which is the reflection of the contact between strong magnetic orebodies and poor magnetic wall rocks. The aeromagnetic ΔT_max value is over 5000 nT, and the ΔTmin value is about -2000 nT. There are over 30 survey lines which indicate obvious positive-negative magnetic anomaly development and show that the superimposed anomaly characteristics are the reflection of magnetic rocks of varying ages and intensities. It indicates that the ore deposit has experienced superposition and transformation activities of tectonic thermal events of varying ages. The scale of ore deposit decreases gradually with the increasing depth of downward extension, but it still shows obvious positive magnetic characteristics while aeromagnetic ΔT contour exhibits upward continuation to 3000 m, which indicates that the ore deposit has obvious mineralization in the depth. In addition, the aeroradiometric characteristics of the Bayan Obo ore deposit show marked high value halos of total counting rate and potassium and uranium and thorium elements, and they all show nearly EW banded distribution. The mining area is located in the high value zone, with values between 3000 and 15381 cps and partially in lumpy form, and the range of the high value zone exceeds the range of the mining area. The potassium content is high with values between 2.0% and 2.8%, and partially even reaching 2.8%-12% in the ore deposit and adjacent areas. The thorium values are in the range of 26×10^-6-223×10^-6, and the range of thorium high value zone is larger than the range of the second intrusive carbonatite that hosted the ore deposit in the middle Caledonian. The uranium values are generally in excess of 1.6×10^-6, with higher values between 2.8×10^-6 and 9.1×10^-6 in the ore deposit and adjacent areas. Through the comprehensive analysis, it is proved that the aeromagnetic and aeroradiometric characteristics are of highly consistent with ore deposit information. The aeromagnetic positive anomalies information can be used as favorable information to look for the iron-bearing polymetallic deposits, and the radioactive elements mainly including potassium, uranium and thorium with high values can be used as favorable information to look for rare earths ore. This understanding is of great guiding significance for the further prospecting work.

Abstract:The region in middle and lower reaches of the Yangtze River is rich in minerals, and many mining areas in this region are covered by the alluvium. In consideration of the characteristics of hydrocarbon and mercury such as strong volatile, penetrability and faraway migration distance, the authors conducted an ore prospecting test research on the special landscape of alluvium cover area by using the integrated hydrocarbon and mercury method. In this paper, based on the study of the background of hydrocarbon and mercury and their primary anomaly halos in different types of deposits in middle and lower reaches of the Yangtze River, the effectiveness test of hydrocarbon and mercury method for ore-prospecting, and the contrastive analysis of the microstructures of hydrocarbon component, the authors revealed that primary anomaly halos of hydrocarbon and mercury were formed during mineralization in most deposits of this region. Meanwhile, the alluvial materials contain the anomaly information of hydrocarbon similar to the information in deep deposits. The results obtained by the authors preliminarily indicated that integrated hydrocarbon and mercury method is suitable for ore-prospecting in alluvium landscape.

Abstract:As the main mineralization information, high natural gamma anomaly in coalfield lays a foundation for the fast discovery of a series of uranium ores in uranium geological survey. In order to improve efficiency and accuracy of coalfield data's secondary development, the authors chose the exploration of the ZS uranium deposit in Erlian basin as a study case and constructed a new uranium exploring technical system for coalfield data's secondary development. On such a basis, the authors established coalfield's uranium geological survey model of "quaternary" involving "natural gamma anomaly sieving and prospective area forecasting", "drilling verification in situ and geochemical environment discrimination", "isochronous stratigraphic framework establishing and sedimentary system analysis" and "comprehensive study and target localization". This model which provides a new thought and technological route may play an important role in northern China's uranium exploration.

Abstract:Top (0-20 cm)and sub-layer (20-40 cm)soils were collected at twenty-seven tea gardens in Anxi, Fujian Province, which is the source area for Tieguanyin tea production. Air-dried soils after sieving through 10 mesh (2 mm nylon screen) were partitioned into 5 aggregate-size fractions by vibration sieving with supersonic wave generators. It is found that the macro aggregates of 2000-840 μm and 840-250 μm fractions are composed of 73% of the total particle weight, and micro aggregates of 250-125 μm, 125-63 μm and <63 μm fractions occupy less than 30%. Soils with higher Al₂O₃, Fe₂O₃ and lower SiO₂ are in favor of macro aggregate formation. There is a concentration difference between macro and micro aggregates for most elements such as Cd, Cr, Hg, Ni, P and Al. The concentrations of most geochemical indicators such as P, Zn, Zr and organic carbon become increasingly higher with the decrease of the aggregate size. Extractable concentrations of As, Cu, Pb and Zn are enhanced in order of water, ammonium nitrate, dilute hydrochloric acid, and DTPA extraction. However, the extractable Cd, Hg, Mn, Ni and Se present higher concentrations in the particular extraction method. Generally the extractable content of top soils is higher than that of sublayer soils due to soil physical-chemical characteristics including organic carbon content and soil structure.

Abstract:161 carbon isotope samples of the Ordovician carbonate from well GL1 and SN1 were analyzed. According to the standard of the carbon isotope established for the Central Uplift Zone, the authors divided the Ordovician carbonate layer system according to the features of carbon isotope, lithology and conodont. Based on the summary of lithology and electric features, the authors divided well GL3 and SN2 through correlation of lithology and electric features. On such a basis, the authors further studied the thickness variation of Yijianfang Formation. The results show that the thickness of Yijianfang Formation in the east of the Shuntuogule Uplift is thicker than that of Yijianfang Formation in the Guchengxu Uplift, possibly because of the difference of the sedimentary environment. According to the evolution characteristics of conodont from the interface between the Yijianfang Formation and the Qrebake Formation in well GL1 and the seismic reflection termination of the T₇⁴ interface of well SN1, the authors have reached the conclusion that the T₇⁴ interface is a unconformity interface near the Tazhong Uplift, because the upper part of the Yijianfang Formation was subjected to obvious erosion. Nevertheless, the T₇⁴ interface should be a conformity interface in other areas. In other words, the strata between the Yijianfang Formation and the Qrebake Formation are continuous in other areas.

Abstract:The Lower Devonian Xiangyangsi Formation is located in the west of Changning-Menglian suture belt at the junction of the Gondwanaland and the Pan-Cathaysian continent in Gengga, Changning, western Yunnan. The chert was discovered in the Xiangyangsi Formation for the first time, and the geochemistry of the chert was studied. Crinoidal stems with radiolarians and diatoms are distributed in chert. An analysis of the data of major elements shows that the values of SiO₂ are relatively high, being in the range of 85.43%-93.50%, the average ratio of Al/(Al + Fe + Mn) obtained in chert is 0.77, suggesting that the chert of the Xiangyangsi Formation is characteristic of biogenesis activity, along with some chemical activity. An analysis of the data of REE shows that the values of REE are 53.208×10^-6, δ Ce has a value of 1.02, and δEu has a value of 1.01. The average ratio of La_N/Yb_N and La_N/Yb_N is 0.99 and 0.84, suggesting the continental margin and deep-sea environment. With the rapid expansion of Changning- Menglian Ocean, a wide chert deposition took place due to the regional synsedimentary fault on the continental margin of Baoshan massif from Early Devonian. In combination with the characteristics of chert geochemical and the paleontological research, the authors hold that the Xiangyangsi Formation in Gengga is characterized by deep-sea deposition on the continental margin of Baoshan massif of Gondwanaland close to Changning-Menglian Paleo-Tethys Ocean.

Abstract:Soil salinization is a worldwide ecological problem. In Tianjin coastal area, soil has long suffered from sea water and high mineralization diving, so salinization is widely distributed. Choosing Taiping Town of Tianjin coastal area as a typical soil salinization coastal area, the authors determined the correlation between main salt ions in the soil, carried out the random uniform thinning test for sampling points in the study area, and discussed the influence of different sampling densities on the interpolation results and the evaluation results of soil salinization. The results show that the farmland soil in Tianjin coastal area has mainly anions of Cl^-, and cations of Na⁺, and that the total Cl and Cl^- have good correlation with total salt in the soil. The authors extracted randomly a small number of samples to test total salt, and established an equation of total Cl and total salt, which could accurately calculate the total salt values for the whole samples. High-density sampling can improve the representation of the samples: when the sampling density is more than 4 points per square kilometers, the acceptance rate of the relative error is equal or greater than 80%; in addition, sampling density of evaluating salinization levels should not be less than 1 points per square kilometers.

Abstract:The method of calculating groundwater nitrate background level was explored in Liujiang Basin as a research object. Based on a comparison and analysis of methods adopted both in China and abroad, the authors firstly used an absolute concentration and milliequivalent percentile double factors method to eliminate outliers macroscopically, and then employed hierarchy clustering analysis combined with principal component analysis to investigate hydrochemical characteristics and identify anomaly category for further candidate selection. The last remaining data were examined for distribution type with the range of groundwater nitrate background level being determined by the cumulative frequency method. The results show that, although the absolute concentration and milliequivalent percentile double factors method cannot completely eliminate outliers, it helps to reduce abnormal information and subset for subsequent hierarchical clustering analysis identifying outliers. Hierarchical clustering analysis method takes advantage of identification of artificial and natural anomaly in that it emphasizes groundwater hydrochemical characteristics analysis. Compared with the mathematical methods, it is more efficient to identify outliers and more reasonable to calculate groundwater nitrate background level by using the two methods in combination. The outliers analysis shows that the high nitrate content in shallow groundwater is closely related to overuse of agricultural fertilizer and living sewage and faeces infiltration in Liujiang basin.

Abstract:Two hundred and twenty topsoil samples were collected successively in Shijiazhuang City, Hebei Province. All topsoil samples were analyzed for concentrations of Al₂O₃, As, Cd, Cr, Cu, Ni, Pb and Zn. The results indicated that, compared with the background values of soil in China, metal concentrations of topsoil have increased on the whole, except those of As and Al₂O₃ in Shijiazhuang City. Correlation coefficient analysis and principal component analysis (PCA) were performed and three main sources were identified: (1) Pb, Zn and Cu are mainly derived from industrial production and traffic exhaust; (2) Ni, Cr and Cd are probably related not only to industrial production but also to coal combustion; (3) Al₂O₃ and As are mainly derived from soil parent material. High concentrations of heavy metals in topsoil are consistent with the distribution of industrial areas and traffic distribution.

Abstract:The implementation of the National Exploration and Development Planning is the major measure for safeguarding China's economic and social sustainable development, and also for improving the guarantee capacity of mineral resources. The integrated exploration is an important way to perform the National Exploration and Development Planning. Based on geological data management and geological data related to mineral prospecting, this paper proposes the geological data integration and service in the equipped exploration area, in which data and maps are collected, the data are integrated, the public data are produced, and the system for publishing data is developed. On such a basis, geologists inquire about the finished data. The research on the geological data integration and service can provide reference for the development of the geological data.