LI Shuanglin, ZHAO Qingfang, WANG Jianqiang, DONG Heping
The geochemical characteristics of saturated hydrocarbon in the surface sediments of the southern central Laoshan uplift in the South Yellow Sea Basin were studied by organic geochemistry method and the relationship between saturated hydrocarbon and deep oil and gas was analyzed.The n-alkane chromatograms of seabed sediments from 25 sites show two types of distribution:front peak and back peak in the south central Laoshan uplift of the South Yellow Sea Basin.Some of chromatograms exist distinct "UCM" bulges, which indicate that there may be theromgenic hydrocarbons imported into seabed sediments and suffer biodegradation in these sites.In m/z191 mass spectrogram, the hopane series of seabed sediments exhibit geological, biological and mixed configurations, in which Ts/Tm and C31-litre hopane 22S/(22S+22R)indicate high thermal maturity of organic matter, also mean the importation of exogenous thermogenic hydrocarbons with high thermal maturity.The 20S/(20S+20R)-C29 and αββ/(ααα+αββ)-C29 steroids parameters of seabed sediments at some sites reflect that the maturity of organic matter has reached maturity, which is obviously deviated from the immature-low maturity characteristics of modern sediments, and also indicates the importation of exotic high maturity thermogenic hydrocarbons.The three main sources of organic matter including terrigenous organic matter, marine endogenous organic matter and thermogenic hydrocarbon input in seabed sediments in the south central Laoshan Uplift of the South Yellow Sea.The vertical seepage of deep reservoirs along boundary faults and unconformity in strata towards the seafloor is the main mechanism of thermogenic hydrocarbon input of seabed sediments.
ZHANG Yong, LI Yanjing, PAN Lan, YU Ruoshui, ZHANG Yitao
Starting from the structural characteristics of the Nanchuan block in the transition zone of the southeast basin margin of Chongqing, in-depth analysis of the layered differential structural characteristics, regional differential structural characteristics, and structural evolution characteristics, so as to clarify the influence of different structural characteristics on shale gas preservation conditions in the Nanchuan area.The research results show that, ①The Nanchuan area is divided into four detachment strata in the vertical direction, creating four deformation layers in the vertical direction.②The structural force in the Nanchuan area is gradually weakened from east to west in the horizontal direction, changing from thrust characteristics.It is a fracture feature, and finally becomes a slip feature.③The main structural features of Nanchuan area were formed in the Middle Yanshanian and Late Yanshanian.④The overall preservation conditions of the thrust structure belt in Nanchuan area are poor, which is not conducive to the exploration and development of shale gas; the fault extension structure belt has good preservation conditions and is a favorable area for shale gas exploration and development.The detachment structural belt has good overall preservation conditions, but due to the deep shale formation, it is a favorable target area for shale gas exploration in the next step.
DONG Fangsheng, PENG Hu, ZHANG Chengyong, WANG Shengwen, ZHANG Song, AN Yonghai
The Heishui area lies in the northern Pingzhuang Basin, where the Cretaceous Sunjiawan Formation is targeted for uranium exploration. Better oxidized zones and industrial uranium mineralization have been observed on the margins of the basin in recent years. However, the choice of the next exploration direction puzzles us because the pattern and type of mineralization are still unclear. To improve our understanding of the oxidation of aim stratum and geological characteristics of uranium mineralization, we conducted an integrated analysis of samples collected in study area, including microscopic identification, major element, environmental geochemical indicators, clay minerals, EPMA, and SEM in this study. The results show that the maturity of sandstone of ore bearing aim stratum is low, indicating a proximal provenance. There is strong post-growth oxidation and significant alteration zoning. Furthermore, the target layer reductant is dominated by pyrite. The uranium enrichment pattern is that uranium-oxygenated water continuously infiltrates the sand body. Enrichment and mineralization occurred in the oxidation-reduction transition zone of the frontal interlayer oxidation zone. Pitchblende, followed by coffinite, is the predominant uranium mineral type. The geological characteristics of the uranium mineralization in the study area are in accord with oxide zone-stratified sandstone-type uranium mineralization model, which has a high potential for mineralization.
The northwest margin of the Junggar Basin in Xinjiang belongs to the Central Asia orogenic metallogenic belt, which is one of the important copper polymetallic metallogenic belts in China. The study of the genesis and ore bearing properties of the intrusive rocks in the area has important practical significance for further improving the degree of geological and mineral exploration in the area. Based on the study of its geological characteristics and mineralization occurrence characteristics, Jieledikezeng diorite sequence in Tacheng, Xinjiang, has been systematically sorted and analyzed by using its rock geochemical data. Combined with the previous chronological data, the rock genesis, tectonic environment, ore bearing property and its relationship with mineralization of this rock mass have been preliminarily discussed, providing some basic references for geological prospecting in this area. Jieledikezeng diorite sequence in Tacheng, Xinjiang is composed of four intrusive periods, namely, gray fine-grained diorite porphyrite, coarse-grained diorite porphyrite, fine medium grained diorite and gray white biotite quartz diorite.The rock mass is low in silicon, magnesium and potassium and high in sodium, aluminum and iron; weakly quasi aluminous, subalkaline series rocks; Rb, Ba, Th and other large ion lithophile elements are enriched, while Nb, Ta, Y, Yb and other high field strength elements are depleted; the rare earth content is low, and the distribution pattern shows a right leaning curve.It is a light rare earth enriched rock, There is weak loss anomaly of cerium and europium.The intrusive diagenetic age of the rock mass is the end of the Early Carboniferous, formed in the island arc tectonic environment, and belongs to the pre orogenic I-type Cordillera granite, Its source rocks may be derived from partial remelting of island arc volcanic rocks or homologous magmatic evolution.Through comparative study, the contents of Au, Ag, Cu, As, Pb and other major metal elements in this rock mass at each intrusive stage are relatively high, and its element concentration is different, and the differentiation of copper, gold and other ore-forming elements is relatively high, reflecting that the polymetallic mineralization in the area is closely related to the strong magmatic hydrothermal process of the rock mass.This rock mass has the magmatic conditions for forming porphyry copper deposits and hydrothermal gold deposits.
The Baitoushan rubidium deposit is located in the Beishan orogenic belt, which is a newly discovered super-large rubidium deposit.The garnet-bearing leucogranite is the important ore-bearing rock and is crucial for understanding the mechanism of rubidium enrichment and mineralization of the deposit.The Baitoushan garnet-bearing leucogranite is enriched in silicon(SiO2=73.56%~75.60%), alkali(Na2O+K2O=8.84%~10.39%), and aluminum(Al2O3 14.41%~15.01%), lower in Mg, Fe, Ca, P, and Ti.The Al saturation index is high(A/CNK=0.98~1.14).In terms of trace elements, the Baitoushan garnet-bearing leucogranite is enriched in Rb, Th, U, and Ta, relatively depleted in Ba, Sr, P, and Ti, with strong Eu negative anomalies(Eu/Eu*=0.02~0.03).The petrological, mineralogical, and geochemical characteristics of the Baitoushan garnet-bearing leucogranite indicate that it is a highly fractionated S-type granite.Fractional crystallization of mica, plagioclase, and zircon may have occurred in this granitic system during magmatic evolution.The total amount of rare earth elements is low(REE=32.06×10-6~45.33×10-6), with an obvious tetrad effect(TE1.3=1.28~1.31).Combined with the non-CHARAC(no radius-controlled) behavior of the characteristic element pairs(Zr/Hf, Nb/Ta, Y/Ho, K/Rb), it reflects that they also underwent a strong differentiation evolution with melt fluid interaction.The extensive magmatic differentiation of highly fractionated granites and F-rich fluid interaction are the key controlling factors for the enrichment and mineralization of rubidium and other rare metals.Zircon U-Pb dating shows that the crystallization age of the garnet-bearing leucogranite is 226±3.8 Ma.Combined with previous studies, it is suggested that the Triassic is an important period for the formation of highly fractionated granites and associated rare metal mineralization in the Eastern Tianshan-Beishan region, which will provide a new direction for prospecting rare metals in the study area.
TANG Minggao, CHEN Haowen, ZHAO Huanle, YANG Wei, DENG Wenfeng
The Qinghai-Tibet Plateau is one of the most frequent glacial lake outburst floods(GLOFs)areas in the world.The GLOF poses a serious threat to the safety of human beings and engineering construction.Based on the remote sensing images and data of Landsat 8 OLI_TIRS from 2015 to 2018, this paper interprets the GLOFs where located within 10 km range of more than 40000 glaciers and its area is greater than 900 m2.This paper analyzes the distribution and development characteristics of glacial lakes, establishes the identification index system of GLOFs, and evaluates the hidden danger points by the catastrophe progression method(CPM).The following results the shown.①There are 16481 glacial lakes in Qinghai-Tibet Plateau, which are mainly distributed at 5000~5500 m above sea level, accounting for 43.69% of the total.The area is concentrated between 0.01~0.05 km2, accounting for 47.40% of the total.In terms of administrative distribution, the Tibet Autonomous Region has the largest number of glacial lakes, 12664, accounting for 76.84% of the total.In terms of basin distribution, the Yarlung Zangbo River Basin has the largest number of glacial lakes, with 8321, accounting for 50.49% of the total.②369 potential GLOFs were identified, including 126 low-risk points, 177 medium risk points and 66 high-risk points.③The area of hidden danger of GLOFs is mostly 0.1~0.2 km2.The altitude is mainly distributed between 5000 ~5500 m above sea level.The distance between the hidden danger point and the mother glacier is less than 100 m, and the width of the moraine dam is mostly less than 300 m.The backwater slope is mostly less than 50°, the slope of the ice tongue of the mother glacier is between 10° and 20°, and most of the GLOFs burst to the north direction.
YUAN Dong, ZHANG Guangze, WANG Dong, MAO Bangyan, YOU Yong, LIU Jinfeng
Affected by topography and tectonics, the eastern part of the Qinghai-Tibet Plateau is characterized by high density, diverse types and frequent outbreaks of debris flows.In order to provide support for the planning, selection, and later operation of the line engineering, we study the development characteristics of debris flows in the transportation corridor and their impact on the project.In this paper, through high resolution remote sensing interpretation, field surveys, and grain analysis tests, the types and distribution of debris flow in the study area have been systematically studied, and corresponding route selection strategies have been proposed.The results show that: ①Rainstorm debris flows and glacier debris flows are mainly developed in the study area, which has the characteristics of wide distribution, multiple types, large scale, and long disastrous chain.The adjacent lines are mostly rainstorm debris flows.②The study area has problems such as difficulty in investigating and identifying potential debris flow ditches, difficult design of disaster chain prevention and control, and harsh plateau construction environment.③The Sichuan-Tibet railway line selection should implement the risk control principle, take disaster mitigation line selection as the leading factor, and actively use InSAR, LiDAR, and UAV technology to conduct surveys on complex sources such as difficult source estimation and unclear identification of potential debris flow gully.The geological conditions of debris flow gully investigation should adopt the "air, space and earth" integrated comprehensive survey technology, and different types of debris flow should be combined with the characteristics of the debris flow to take diverse prevention and control measures.
LIU Hanlun, MAO Jingwen, DUAN Shigang, WANG Mengqi, WANG Yingchao, DONG Zebao
In order to deepen the understanding of the Cretaceous tectonic setting in the eastern part of South China, the petrological, geochemical and Sr-Nd-Hf isotope analyzes of the basalt in the Zhilingtou area of Zhejiang Province were carried out.The basalt are massive and porphyritic, and the phenocrysts consist of plagioclase and hornblende.LA-ICP-MS zircon U-Pb dating shows that the age is 101±1 Ma, which is the product of Early Cretaceous magmatic activity.The results of geochemical analyzes show that the basalt has the characteristics of rich alkali, high K2O/Na2O ratio, high K2O+Na2O value, and high Al2O3 content, enrichment in large ion lithophile elements(Rb, Sr)and light rare earth elements, depletion in high field strength elements(Nb, Ta, Ti, Hf).The distribution curve of rare earth elements is generally right-sloping, with a weak positive Eu anomaly, which should belong to potash basalt series, and has experienced a certain degree of fractional crystallization during the magma evolution process.The ratios of Th/La, Th/Ce and Lu/Yb are closer to the ratio of mantle-derived magma.(87Sr/86Sr)i=0.70729-0.71029, εNd(t) and εHf(t) values range from -19.7 to -11.8 and -9.7 to -0.8, respectively, indicating that the source area of basalt has the characteristics of EMⅠ-enriched mantle, and a small amount of crustal material is also involved.Structural discriminant diagrams show that basalt was formed in an intraplate extensional environment.In combination with the spatiotemporal distribution and geochemical characteristics of Late Mesozoic basic magma in South China, and with the continuous rollback of the paleo-Pacific plate, South China was a backarc spreading tectonic environment in the Early Cretaceous.The EMⅠ-type enriched mantle formed by fluid metasomatism generated by dehydration of subduction plates partially melted and ejected from the surface to form the basalt in the Zhilingtou area.
WANG Meng, PEI Xianzhi, ZHANG Jinjiang, CHEN Youxin, ZHAO Shaowei, ZHANG Bo, CAO Ming
There are massive Carboniferous magmatic rocks in the northern Yili Block.However, rare middle-late Early Carboniferous (340~320 Ma) magmatic rocks were reported, which limited our understanding for the tectonic evolution of the northern Chinese West Tianshan of this period.In order to constrain the tectonic setting of the northern Yili Block, we conducted detailed petrology, geochemistry, zircon U-Pb dating and Lu-Hf isotope analyses on a newly identified middle Early Carboniferous dioritic pluton along the Alasitan river in the northern Yili Block.Microgranular dioritic enclaves are widely developed within the diorites.The two types of rocks display different evolutionary trends in multiple bivariate diagrams of major and trace elements, indicating different petrogenesis and magma sources.Both types of rocks are enriched in LILEs, depleted in HFSEs (Nb, Ta, Ti), which are characteristics of magmatic arc rocks.Combined with regional geology, we suggested that the northern Yili Block experienced regional extension since the middle-late Early Carboniferous, which might be related to the slab roll back or retreat of the North Tianshan oceanic crust.
SHI Zhongming, LI Baolong, PENG Bo, ZHU Dequan, FAN Haibin
Granitic magmatism is one of the key processes of continental crust evolution,explosive volcanic activity,and rare metal mineralization.Yanhu composite batholith is located in the western section of Bangonghu-Nujiang suture zone in the north of Lhasa terrane,and is an important part of the response of Bangonghu-Nujiang Tethys Ocean subduction.In this paper,the petrography,zircon U-Pb chronology and petrogeochemistry of the granite porphyry in the Yanhu composite batholith from Geji County were studied,and its petrogenesis was discussed.The results show that the zircon U-Pb age of the Yanhu composite batholith granitic porphyry is 103.8±0.8 Ma(MSWD=3.0,n=25),and the intrusion occurred in the late Early Cretaceous.Aluminum saturation index(A/CNK)of Yanhu composite batholith granitic porphyry ranges from 1.05 to 1.08,showing weak peraluminous characteristics with high K2O,Na2O and low Mg#(12.43~22.36),indicating the high K calc-alkaline type Ⅰ-type granite.The Yanhu composite batholith granitic porphyry is enriched in K and depleted in Ba,Nb,P,Zr and Ti,and has strong negative Eu anomaly(δEu= 0.20~0.48).The REE distribution curves are characterized by right-leaning type,ΣREE=81.33×10-6~121.61×10-6,LREE/HREE=5.75~6.74,higher Y(20.14×10-6~ 24.38×10-6,> 18×10-6)and Yb(2.11×10-6~2.62×10-6,> 1.9×10-6),lower Sr/Y ratio(4.05~6.54,< 20),La/Yb=6.79~8.94.Rb/Sr = 0.50~1.12.The calculated zircon saturation temperature is 812~823℃,and the formation depth of magmatic melt is estimated to be 34~40 km,indicating that the granitic porphyry formed in the Yanhu composite batholith was partially melted products of basaltic lower crust under the high temperature background of the collision between the North Lhasa terrane and the South Qiangtang terrane.It belongs to a set of highly differentiated Ⅰ-type granites formed by remelting of the basic lower crust caused by plate fragmentation events.
LUO Ya'nan, XU Dong, YU Shaohua, XIN Fengpei, XIAN Yuanhong, LUO Shuai
The structural-magmatic evolution of East Qinling-North Dabie Mountains is a popular issue.The eruption time of the volcanic rocks in the belt still has a greater dispute for a long time, which is still unclear during rock formation and diagenetic tectonic environment.Based on the studies of geochemistry, zircon LA-ICP-MS U-Pb dating of dacite in Xianqiao bentonite deposit in the western segment of North Dabie Mountains, it is shown that acidic volcanic rocks from Xianqiao area display high contents of K2O(3.96%~5.01%), are enriched in K2O+Na2O(7.97%~8.96%)and weak peraluminous, with A/CNK values of 1.0~1.15.The volcanic rocks should belong to high-K calc-alkaline to shoshonite series.The rocks are enriched LREE and depleted HREE, with weak negative Eu anomaly, strongly depleted in the high field strength elements Nb and Ta and high Nb / Ta ratio, and has high(La/Yb)N(25.68~28.25)and Sr/Y(34.92~41.42)ratios, which has obvious geochemical characteristics of adakite.Zircon LA-ICP-MS U-Pb dating result shows that the Xianqiao ore-forming rocks(dacite)was erupted at 133±1 Ma, consistent with the age of volcanic rocks of Chenpeng Formation in Shuangqiao bentonite deposit and Huangchengshan silver deposit.This research reveals that the Mesozoic acidic volcanic rocks from Xianqiao area with the characteristics of adakitic rocks were formed by partial melting of the thickened lower crust, which were formed at post-collisional tectonic setting in Mesozoic.The large-scale magma activity resulting from lower crust delamination and thinning of the lithosphere has not yet occurred in the Xianqiao area of North Dabie Mountains at about 133 Ma.
NIU Jinghui, TIAN Fuquan, QIU Dunfang, XU Daoxue, FAN Dejiang, ZHANG Yonglin, CUI Qingqi, ZHANG Peng, SONG Zichong, WANG Haihong, WU Minggang, ZHONG Shihua
The Jiudian gold deposit from Shandong province is located in the south of the Zhaoping fault zone in Jiaodong Peninsula.It is a medium-sized gold deposit dominated by quartz-vein type mineralization.The granitoids in the district are widespread and of various types,but the formation ages and genesis of these granites have not been well studied,which limits the understanding of the metallogenic geodynamic background of this deposit.In this study,a detailed LA-ICP-MS zircon U-Pb dating of granite gneiss,garnet-bearing monzogranite,biotite monzogranite and granite pegmatite in Nos.4,6 and 12 veins of the Jiudian deposit shows that the granite gneiss age is 709.1±4.1 Ma(No.6),the garnet-bearing monzogranite is 164.1±1.9 Ma(No.4),the biotite monzogranite are 157.5±1.1 Ma(No.4)and 145.2±1.5 Ma(No.6),and the granitic pegmatite is 146.5±0.7 Ma(No.12).Combined with the geological characteristics and previous studies,it is indicated that there are three periods of magmatic activity in the Jiudian gold deposit:Neoproterozoic,Late Jurassic and Early Cretaceous.The Late Jurassic garnet-bearing monzogranite and biotite monzogranite are formed in lithosphere transition stage from extrusion to extend and they show characteristics of the S-type granite.They are not only the main host rocks of the deposit,but also may be the ore-forming rocks.
ZHU Dong, LIU Shuai, WU Jianhua, YANG Dongguang, HUANG Meihua, MA Shusong
The Ganhang uranium metallogenic belt is located at the junction of the Yangzi plate and the Huaxia plate. The Maquan basin is a uranium-bearing volcanic basin in the middle of this belt, and the uranium ore body is hosted in andesite. However, there is controversy over the rock types and lithological affiliation, and there is a lack of precise rock ages. Therefore, this paper focuses on the study of neutral volcanic rocks in Maquan basin, with the aim of investigating their chronology, petrology, and geochemical characteristics. The results show that the SHRIMP zircon U-Pb age of neutral volcanic rocks is 137.1±1.1 Ma (n=15, MSWD=1.5), which is a product of Early cretaceous magmatism. The neutral volcanic rocks in Maquan basin have a massive and porphyritic texture, with plagioclase as the main phenocryst, and contain a small amount of pyroxene, hornblende, and biotite. They are rich in alkali, high in potassium, low in iron, and poor in titanium, and they are enriched in light rare earth elements and large ion lithophile elements (Rb, Ba, K), but lack high field strength elements (Nb, Ta, Ti). These geochemical characteristics indicate that they are andesites, belonging to the typical high-potassium calc-alkaline volcanic rock series. The andesites have (87Sr/86Sr)i=0.70855~0.70882, εNd(t)=-9.77~-7.02, (206Pb/204Pb)i=18.17~18.27, (207Pb/204Pb)i=15.56~15.62, (208Pb/204Pb)i=38.43~38.61. The (87Sr/86Sr)i-(206Pb/204Pb)i and (143Nd/144Nd)i-(206Pb/204Pb)i as well as (143Nd/144Nd)i-(87Sr/86Sr)i diagrams indicate that the andesite source region in Maquan basin has the characteristics of enriched mantle EM Ⅱ. The tectonic discrimination diagrams indicate that the andesites in Maquan basin were formed in an intraplate extensional environment. The comprehensive study shows that the andesites in Maquan basin were produced by partial melting of enriched mantle EM Ⅱ mobilized by mantle fluids in an early cretaceous extensional tectonic setting.
XIE Xuejing, XIE Zhong, MA Kai, CHEN Jianguo, QIU Qinjun, LI Hu, PAN Shengyong, TAO Liufeng
Extracting geological named entities from geological texts is of great significance for deep mining and application of geological big data.In this paper, we define the concept of geological named entities, formulate annotation specifications, and design an object-oriented representation model for geological entities.Geological texts have a large number of long entities and complex nested entities, which increase the challenge of geological named entity recognition tasks.To address these problems, ①the BERT model is introduced to generate high-quality word vector representations that take into account contextual information; ②BiGRU-Attention-Conditional Random Field(BiGRU-Attention-CRF)is used to sequence label and decode the semantic encoding output from the previous layer.Compared with mainstream deep learning models, the F1 value of this model is 84.02%, which shows better performance than other models and can have better recognition effects on small-scale geological corpora.