The Baguamiao superlarge gold deposit in Shaanxi Province is one of the typical cases in China that are hosted by sedimentary rocks. Explorers and researchers have discussed the gold mineralization enrichment conditio...The Baguamiao superlarge gold deposit in Shaanxi Province is one of the typical cases in China that are hosted by sedimentary rocks. Explorers and researchers have discussed the gold mineralization enrichment conditions by studying sulphur, oxygen, carbon, silicon stable isotopes and mineralizing fluid features of the Baguamiao gold deposit and proposed a hydrothermal sedimentation-magmatic reconstructing gold mineralization model featuring multi-sources of ore-forming materials and multistage mineralizations. In addition, prospecting for “Baguamiao-type” gold deposits was started in the Fengtai Basin and a great number of important prospecting targets such as Tonglinggou, Simaoling, Guoansi and Dachaigou were discovered.展开更多
Tin,as one of the most important critical metals,has at-tracted great attention worldwide(Jiang et al.,2023,2020).China has the largest amount of tin resources in the world,ac-counting for nearly one-fourth of the wo...Tin,as one of the most important critical metals,has at-tracted great attention worldwide(Jiang et al.,2023,2020).China has the largest amount of tin resources in the world,ac-counting for nearly one-fourth of the world’s total(Jiang et al.,2020;Chen and Sheng,2015).Tin deposits in China mainly occur in the Nanling Range in southern China,the Sanjiang Basin in southwestern China,and the Great Xing’an Range in northeastern China,which account for 98%of the country’s tin resources,whereas tin deposits are relatively rare in north-western China(Ni et al.,2023;Chen et al.,2014,1992).展开更多
In China's long-term social and economic development process, mineral energy plays an important role in promoting the pace of development. At present, China contains relatively low reserves of mineral resources, a...In China's long-term social and economic development process, mineral energy plays an important role in promoting the pace of development. At present, China contains relatively low reserves of mineral resources, and some shallow mineral resources have basically been developed. In order to obtain more geological and mineral resources, it is necessary to further develop the deep mineral resources in China. Most of the mining areas in our country are mainly concentrated in the western mountainous and desert areas. In order to obtain accurate and comprehensive geological and mineral resources, the survey data are relatively difficult, especially the data of deep mining areas, which have higher requirements for the prospecting work. In this paper, the exploration work of geology and mineral resources is analyzed by mainly studying the way of deep prospecting, mainly in order to improve the efficiency of deep prospecting of mineral resources and the reserve content of geological and mineral resources in our country. First of all, the direction and present situation of deep prospecting are briefly analyzed, and then three new prospecting methods for deep deposits and concealed deposits are proposed, mainly including geochemical survey method, deep penetration geochemical method and geochemical prospecting method. At last, the paper applies the method of reduplication to the actual operation of the prospecting work, and analyzes the effect of the application, thus inferring that some mineral information within the fault structure is helpful to the further development of mineral resources in the western region of our country.展开更多
The North China Craton(NCC)experienced significant lithospheric thinning of over 100 km during the Mesozoic,accompanied by extensive magmatic activity and extensional tectonics.However,the timing and mechanism of this...The North China Craton(NCC)experienced significant lithospheric thinning of over 100 km during the Mesozoic,accompanied by extensive magmatic activity and extensional tectonics.However,the timing and mechanism of this thinning remain the subjects of debate.This study presents zircon U-Pb ages,Hf isotopic data and whole-rock elemental and Sr-Nd isotopic compositions of the Guanshui monzonites and diorites in the eastern NCC.Zircon U-Pb dating reveals that both rock types formed at ca.130 Ma.The monzonites,characterized by high Mg^(#)(50.9-57.9),low Nb/U ratios(2.53-3.89)and depleted isotopic compositions,suggest derivation from asthenospheric mantle modified by slab-derived fluids.The diorites,distinguished by low SiO_(2)(49.5-50.8),high Mg^(#)(66.7-68.5)and an EM2-type enriched mantle isotopic signature,point to a lithospheric mantle source modified by subducted sediment melts.The coexistence of monzonites and diorites suggests a transition in magma source from lithospheric to asthenospheric mantle,implying that lithospheric thinning may have commenced around 130 Ma.The destruction of the NCC was likely driven by localized,small-scale drip-style detachment processes,rather than wholesale lithospheric removal.展开更多
The deep geologic processes between the Xing’an-Mongolian Orogenic Belt and the North China Craton in the Mesozoic are crucial to reveal the magmatic and tectonic evolution and their constraints on mineralization in ...The deep geologic processes between the Xing’an-Mongolian Orogenic Belt and the North China Craton in the Mesozoic are crucial to reveal the magmatic and tectonic evolution and their constraints on mineralization in the Jiapigou-Haigou collage zone.In this paper,We have presented the geochronology,geochemistry and Sr-Nd-Hf isotopic compositions of the Middle Jurassic granitic complexes in the Songjianghe area,Jilin Province.The granitic complexes can be categorized into four groups based on their geologic characteristics,with corresponding zircon U-Pb isotope ages of 177 Ma,172 Ma,169 Ma and 168-167 Ma,respectively.These granitoids exhibit calcalkaline to high-K calc-alkaline,metaluminous to weakly peraluminous Ⅰ-type characteristics,which show relative enrichment in LILEs(Rb,Sr,Ba)and depletion in HFSEs(Nb,Zr).Geochemical analyses reveal high initial^(87)Sr/^(86)Sr ratios of 0.70633-0.70740,coupled with lowεNd(t)values ranging from−10.65 to−13.23.The zircon analyses show similarly negativeεHf(t)values ranging from−16.9 to−3.2.The integrated elemental and Hf-Sr-Nd isotopic signatures demonstrate that the primitive magmas of the four group rocks were primarily derived from partial melting of thickened Archean lower crust,with the exception of the Group Ⅳ rocks,which exhibit significant evidence of crustal contamination.The residual mineral assemblages during the magma-forming process varied from amphibole to eclogite facies.These findings indicate that magmatism in the Songjianghe region likely resulted from the accretion and delamination of the Archean crust in the collage zone during the subduction of the Paleo-Pacific Plate beneath the Eurasian continent.展开更多
Vegetation ecological quality(VEQ)is not only influenced by meteorological drought(MD)but also exerts a certain degree of regulatory effect on it.Clarifying the relationship between the two is crucial for ecological c...Vegetation ecological quality(VEQ)is not only influenced by meteorological drought(MD)but also exerts a certain degree of regulatory effect on it.Clarifying the relationship between the two is crucial for ecological conservation efforts.However,the interactions between VEQ and MD and its driving mechanisms in karst mountain regions with high surface heterogeneity remain unclear,and the lack of exploration of this interaction under different subregions hinders further progress in ecological conservation.This study took Guizhou Province,characterized by significant surface heterogeneity and extensive karst formations,as a research case.By dividing the region into different landform regions,we quantified the coupling coordination degree(CCD)between VEQ and MD using the coupling coordination degree model to elucidate their interaction and analyzed its driving forces using the Geodetector model.Results indicated that:(1)From 2001 to 2020,the CCD between VEQ and MD in Guizhou remained at a moderate coordination level,with increasing benign interactions,though significant variations in CCD trends were observed across landform regions.MD is the pivotal subsystem that determines CCD changes.(2)The dominant driving factors of CCD vary by landform,with soil moisture,precipitation,or population density as primary influences.Soil moisture has a stronger effect in karst regions,and its interaction with other factors surpasses the effects of individual factors.(3)To achieve benign development between VEQ and MD.In karst regions,attention should be focused on the impact of soil moisture and human activities on CCD.While non-karst regions have favorable vegetation and hydrothermal conditions,improper development can lead to vegetation degradation,and abnormal hydrothermal conditions,which could trigger a decline in CCD.Therefore,regulating human activities in non-karst regions is also crucial.This work serves as a scientific foundation for formulating ecological preservation strategies in Guizhou and other karst mountain regions.展开更多
Medium-low temperature geothermal resources are abundant in the Guanxian fault depression.An essential foundation for the effective development and use of geothermal resources is the study of the genetic model and res...Medium-low temperature geothermal resources are abundant in the Guanxian fault depression.An essential foundation for the effective development and use of geothermal resources is the study of the genetic model and resource assessment of the geothermal system.This study examines the geothermal geological circumstances,hydrochemical features,and geothermal field characteristics based on the regional geological structure and prior research findings.The appraisal of geothermal resources is done,and a conceptual model of the geothermal system in the research area is built.The findings indicate that the Guan xian fault depression's geothermal resources are primarily Guantao Formation sandstone heat reservoirs.The geothermal water at the wellhead has a temperature between 54℃and 60℃,and its primary chemistry is Cl·SO_(4)-Na.Deep thermal conduction heats the geothermal water,which is then laterally supplied to the reservoir after being largely restored by air precipitation from the western Taihang Mountains.With an annual exploitable geothermal resource of 6,782×10^(12)J,or 23.14×10^(4)tons of standard coal,the Guantao Formation sandstone reservoir in the Guanxian depression has a geothermal resource of about 620.10×10^(16)J.An area of 18 million m^(2)can be heated by geothermal extraction per year,demonstrating the potential for geothermal resources and their high development and use value.展开更多
The Phapon gold deposit, located in northern Laos, is a unique large-scale gold deposit in Luang Prabang-Loei metallogenic belt. It is hosted in the Lower Permian limestone and controlled by a NE-trending ductile-brit...The Phapon gold deposit, located in northern Laos, is a unique large-scale gold deposit in Luang Prabang-Loei metallogenic belt. It is hosted in the Lower Permian limestone and controlled by a NE-trending ductile-brittle fault system. There are three types of primary ore including auriferous calcite vein type, disseminated type, and breccia type, and the first two are important in the Phapon gold deposit. Based on fluid inclusion petrography and microthermometry, three types of primary fluid inclusions including type 1 liquid-rich aqueous, type 2 vapor-rich aqueous and type 3 daughter mineralbearing aqueous were identified in hydrothermal calcite grains. The ore-forming fluids are normally homogeneous, as indicated by the widespread type 1 inclusions with identical composition. The coexistence of type 1 and type 2 inclusions, showing similar final homogenization temperature but different compositions, indicate that fluid immiscibility did locally take place in both two types of ores. The results of microthermometry and H-O isotopes geochemistry indicate that there are little differences on ore-fluid geochemistry between the auriferous calcite vein-type and disseminated type ores. The oreforming fluids are characterized by medium-low temperatures(157–268 oC) and low salinity(1.6 wt.%–9.9 wt.% NaCl eq.). It is likely to have a metamorphic-dominant mixed source, which could be associated with dehydration and decarbonisation of Lower Permian limestone and Middle–Upper Triassic sandstones during the dynamic metamorphism. The fluid-wallrock interaction played a major role, and the locally occurred fluid-immiscible processes played a subordinate role in gold precipitation. Combined with the regional and ore deposit geology, and ore-fluid geochemistry, we suggest that the Phapon gold deposit is best considered to be a member of the epizonal orogenic deposit class.展开更多
There are many factors affecting the chemical characteristics of groundwater in the forming process of groundwater chemical fields, such as freshening due to meteoric water leaching downwards, freshening due to mudsto...There are many factors affecting the chemical characteristics of groundwater in the forming process of groundwater chemical fields, such as freshening due to meteoric water leaching downwards, freshening due to mudstone compaction and water release, concentration due to infiltration and freshening due to dehydration of clay minerals. As a result, the groundwater chemical fields are characterized by lengthwise stages and planar selectivity. The former arouses vertical chemical zonality of groundwater. Five units could be identified downwards in the Songliao basin： （1） freshening zone due to downward-leaching meteoric water, （2） concentration zone due to evaporation near the ground surface, （3） freshening zone due to mudstone compaction and water release, and concentration zone due to compaction and infiltration, （4） freshening zone due to dehydration of clay minerals, and （5） filtration-concentration zone; whereas the latter determines the planar division of groundwater chemical fields： （1） the freshening area due to meteoric water, asymmetrically on the margin of the basin, （2） the freshening area due to mudstone compaction and water release in the central part of the basin, （3） the leaky area, which is a transitional zone, and （4） leakage-evaporation area, which is a concentration zone. In the direction of centrifugal flows caused by mudstone compaction in the depression area, the mineralization degree, concentrations of Na^＋ and Cl^-, and salinity coefficient （SC） increase, while concentrations of （CO3^2- ＋HCO3^-） and SO4^2-, metamorphism coefficient （MC） and desulfuration coefficient （DSC） decrease. However, all these parameters increase in the direction of gravity-induced centripetal flows.展开更多
Based on element geochemical studies of the main Permian exploitable coal measure strata in Western Guizhou, the element geochemical distribution characteristics of the main exploitable coal measures were revealed in ...Based on element geochemical studies of the main Permian exploitable coal measure strata in Western Guizhou, the element geochemical distribution characteristics of the main exploitable coal measures were revealed in the regions of Dafang, Qianxi, Weining, Hezhang, Zhijin, etc., of Guizhou Province, and the results show that their element contents are mainly affected by terrestrial material supply. Coal measures formed in the delta plain environment where sufficient terrestrial materials are supplied contain relatively abundant trace elements and rare-earth elements, whereas those formed in the tidal-fiat environment influenced greatly by seawater have relatively low contents of trace elements and rare-earth elements, mainly con- trolled by the geological fact that basalts the parent rocks from source regions contain high trace elements and rare-earth elements. In addition, coal measures affected by later hydrothermal activities and fault tectonics contain a large amount of harmful elements. According to the rules of distribution of elements in coal measures, a new idea was put forward to classify coal-forming environments by using the geochemical composition characteristics, which is of great significance in dissolving the problem of whether coal measures were fbrmed either in delta environments or in tidal-flat environments in Western Gui- zhou. At the same time, the rules of distribution of elements in the main exploitable coal measures in Western Guizhou were fully understood, which is of direct significance in utilizing coal resources on the basis of classification of coals, as well as in developing the coal chemical industry.展开更多
The early Mesozoic marked an important transition from collisional orogeny to post-orogenic extension at the northern margin of the North China Craton(NCC). In this study, we undertook zircon U-Pb dating and whole-roc...The early Mesozoic marked an important transition from collisional orogeny to post-orogenic extension at the northern margin of the North China Craton(NCC). In this study, we undertook zircon U-Pb dating and whole-rock majorand trace-element geochemical analyses of early Mesozoic granitic rocks in the Chifeng area to establish their geochronological framework, petrogenesis, and implications for the tectonic evolution of the eastern Central Asia Orogenic Belt(CAOB). Zircon U-Pb dating results show that these rocks were emplaced in three stages during the Triassic:(1) syenogranites during 250-248 Ma,(2) granodiorites during 244-243 Ma, and(3) monzogranites and granodiorites during 232-230 Ma. These Triassic granitoids belong to the high-K calc-alkaline series and are evolved I-type granites. They have high SiO2 and low Mg O contents with enrichments in light rare-earth elements, Zr, Hf, Rb, Th, and U, and depletions in Ba, Nb, Ta, Sr, and Eu. These geochemical data indicate that the granitoids were derived from partial melting of a lower-crustal source under relatively low-pressure conditions and subsequently underwent extensive fractional crystallization. Considering both the geochemical data and regional geological information, we propose that the 250-248 Ma syenogranites were emplaced in an extensional environment linked to slab break-off after closure of the Paleo-Asian Ocean(PAO) along the Solonker-Xra Moron-Changchun suture zone. The 244-243 Ma granodiorites were formed in a compressional orogenic setting during collision between the Erguna-Xing’an-Songliao composite block and the NCC. The 232-230 Ma granodiorites and monzogranites were emplaced during the transition from compressional orogeny to post-orogenic extension. Overall, the early Mesozoic tectonic evolution of the Chifeng area can be divided into three main stages:(1) closure of the Paleo-Asian Ocean and extension related to slab break-off during the Early Triassic;(2) continuous collisional compression during the Middle Triassic after closure of the PAO;and(3) post-orogenic extension during the Late Triassic, most probably due to lithospheric delamination after amalgamation of the Erguna-Xing’an-Songliao composite block and the NCC.展开更多
Hot dry rock(HDR)is an important geothermal resource and clean energy source that may play an increasingly important role in future energy management.High-temperature HDR resources were recently detected in deep regio...Hot dry rock(HDR)is an important geothermal resource and clean energy source that may play an increasingly important role in future energy management.High-temperature HDR resources were recently detected in deep regions of the Gonghe Basin on the northeastern edge of the Tibetan Plateau,which led to a significant breakthrough in HDR resource exploration in China.This research analyzes the deep temperature distribution,radiogenic heat production,heat flow,and crustal thermal structure in the Qiaboqia Valley,Guide Plain,and Zhacanggou area of the Gonghe Basin based on geothermal exploration borehole logging data,rock thermophysical properties,and regional geophysical exploration data.The results are applied to discuss the heat accumulation mechanism of the HDR resources in the Gonghe Basin.The findings suggest that a low-velocity layer in the thickened crust of the Tibetan Plateau provides the most important source of constant intracrustal heat for the formation of HDR resources in the Gonghe Basin,whereas crustal thickening redistributes the concentrated layer of radioactive elements,which compensates for the relatively low heat production of the basal granite and serves as an important supplement to the heat of the HDR resources.The negative effect is that the downward curvature of the lithospheric upper mantle caused by crustal thickening leads to a small mantle heat flow component.As a result,the heat flows in the Qiaboqia Valley and Guide Plain of the Gonghe Basin are 106.2 and 77.6 m W/m2,respectively,in which the crust-mantle heat flow ratio of the former is 3.12:1,indicating a notably anomalous intracrustal thermal structure.In contrast,the crust-mantle heat flow ratio in the Guide Plain is 1.84:1,which reflects a typical hot crust-cold mantle thermal structure.The Guide Plain and Zhacanggou area show the same increasing temperature trend with depth,which reflects that their geothermal backgrounds and deep high-temperature environments are similar.These results provide important insight on the heat source mechanism of HDR resource formation in the Tibetan Plateau and useful guidance for future HDR resource exploration projects and target sites selection in similar areas.展开更多
The Wenquan molybdenum deposit is a kind of large-sized porphyry molybdenum deposit found in re-cent years.In this paper,on the basis of deposit geology,geochemistry and isotope geochronology data,the metal-logenic mo...The Wenquan molybdenum deposit is a kind of large-sized porphyry molybdenum deposit found in re-cent years.In this paper,on the basis of deposit geology,geochemistry and isotope geochronology data,the metal-logenic model of this deposit was established.The Wenquan granitic batholith belongs to the K-rich(alkali-rich) calc-alkaline rock series,which is the mineralization parent rock.The rock massif shows the characteristics of both crust-remelting granite and mantle-source granite.At the same time,the data of REE contents,hydrogen and oxygen isotopes and inclusion temperatures showed that the metallogenic hydrothermal solution is a mixed mesothermal solution of magmato-hydrothermal fluid and meteoric water.Mineralization was dated at 214±7.1 Ma,basically identical with the parent rock's age(207-226 Ma).This reflects that molybdenum mineralization has a close relation to tectonic magmatism evoked by orogenic processes,and molybdenum mineralization occurred mainly at the petrogenesis stage at the late stage of magma emplacement.Mixing with meteoric water led to a decrease in the sa-linity of magmato-hydrothermal solution and changes in other physical and chemical properties.During the tectonic process,ore-bearing hydrothermal solution ascended along favorable fault structure channels.With physicochemical changes,it filled in the surrounding rock joints on both sides of faults,forming ore deposits.展开更多
The Zhou＇an PGE-Cu-Ni deposit was recently discovered in the Qinling orogenic belt bound by the Yangtze and the North China Cratons. It is a blind deposit thoroughly covered by the Cenozoic alluvial sediments in the ...The Zhou＇an PGE-Cu-Ni deposit was recently discovered in the Qinling orogenic belt bound by the Yangtze and the North China Cratons. It is a blind deposit thoroughly covered by the Cenozoic alluvial sediments in the Nanyang Basin. As the first large PGE-Cu-Ni deposit discovered in the Qinling-Dabie-Sulu orogenic belt, its geological and geochemical characteristic, isotope age, genesis and tectonic setting are of wide concern in both scientific studies and ore exploration. In this contribution, we report the results obtained from a pioneering study. The Zhou＇an ultramafic complex is ferruginous, with m/f = 4.79-5.08, and shows the nature of tholeiite series. It is rich in light rare earth elements, Rb, Th, U, La, Sm, Zr and Hf, and poor in heavy rare earth elements, Nd and Ta, suggesting an intraplate setting. It has high S7Sr/S6Sr and low 143Nd/144Nd ratios. The ratios of Zr/Nb, La/Nb, Ba/ Nb, Rb/Nb, Th/Nb, Th/La and Ba/La, suggest the magma originated from lithosphere mantle. The Fo values of olivine and Pd/Ir-Ni/Cu diagram suggest primary magma was High Mg basalt. The laser ablation inductively coupled plasma atomic emission spectroscopy zircon U-Pb age is 641.5 ± 3.7 Ma.展开更多
The sequence stratigraphy framework of Paleogene of Qikou Sag has been built in this paper. The evolution law of episodic subsidence in Qikou Sag has been expounded, with the analysis of the characteristic of sequence...The sequence stratigraphy framework of Paleogene of Qikou Sag has been built in this paper. The evolution law of episodic subsidence in Qikou Sag has been expounded, with the analysis of the characteristic of sequence thickness, as well as the study of consedimental tectonic activity, subsidence history, paleogeomorphology and the coupling relationship among them. The faults controlling action was the dominant mechanism during rifting stage I , as the depression was the dominant mechanism during rifting stage III, which embodies a process from intense disparity fault depression to integral subsidence. Meanwhile, under the control of regional faulting and later stage depression, subsidence rate centers and paleogeomorphic concave centers are always corresponding to the sequence thickness centers, and the changes of subsidence centers and paleogeomorphology concave centers are consistent with the migration of thickness centers, which presents the restriction, coupling and response among them and clarifies the law that tectonic activity controls the basin fill by means of controlling the subsidence rate and paleogeomorphology from contributing factor angle. On this basis, the dynamic evolution of the composite pattern of structure-subsidence-deposition in the fault controlling actic region during the three rifting stages and their petroleum geological significance has been discussed.展开更多
The Heyuan Fault,is one of the main NE-trending faults in the southernmost South China Block and is close to the northernmost South China Sea to the south.The fault features multi-stage deformation and controlled the ...The Heyuan Fault,is one of the main NE-trending faults in the southernmost South China Block and is close to the northernmost South China Sea to the south.The fault features multi-stage deformation and controlled the formation of late Cretaceous to Cenozoic basins.Based on detailed field investigations and comprehensive geochronological research,including zircon U-Pb,Rb-Sr isochron,zircon U-Th-He dating,two episodic tectono-thermal events are recognized.The first occurred during~79 Ma to 66 Ma,which is characterized by large-scale quartz-fluid emplacement.The other occurred at~34 Ma,which features the eruption of a set of basalts.The two events show a changing on material source from siliceous hydrotherm to basalt magma,supporting obvious lithospheric thinning of the southernmost South China Block,which shed light on the geological evolution and the interaction mechanisms between the SCB and the northern South China Sea since the Late Cretaceous.展开更多
The Qingkuangshan Ni-Cu-PGE deposit, located in the Xiaoguanhe region of Huili County, Sichuan Province, is one of several Ni-Cu-PGE deposits in the Emeishan Large Igneous Province （ELIP）. The ore-bearing intrusion ...The Qingkuangshan Ni-Cu-PGE deposit, located in the Xiaoguanhe region of Huili County, Sichuan Province, is one of several Ni-Cu-PGE deposits in the Emeishan Large Igneous Province （ELIP）. The ore-bearing intrusion is a mafic-ultramafic body. This paper reports major elements, trace elements and platinum-group elements in different types of rocks and sulfide-mineralized samples in the intrusion. These data are used to evaluate the source mantle characteristics, the degree of mantle partial melting, the composition of parental magma and the ore-forming processes. The results show that Qingkuangshan intrusion is part of the ELIP. The rocks have trace element ratios similar to the coeval Emeishan basalts. The primitive mantle-normalized patterns of Ni-Cu-PGE have positive slopes, and the ratios of Pd/Ir are lower than 22. The PGE compositions of sulfide ores and associated rocks are characterized by Ru depletion. The PGE contents in bulk sulfides are slightly depleted relative to Ni and Cu, which is similar to the Yangliuping Ni-Cu-PGE deposit. The composition of the parental magma for the intrusion is estimated to contain about 14.65 wt% MgO, 48.66 wt% SiO2 and 15.48 wt% FeOt, and the degree of mantle partial melting is estimated to be about 20%. In comparison with other typical Ni-Cu-PGE deposits in the ELIP, the Qingkuangshan Ni-Cu-PGE deposit has lower PGE contents than the Jinbaoshan PGE deposit, but has higher PGE contents than the Limahe and Baimazhai Ni-Cu deposit, and has similar PGE contents to the Yangliuping Ni-Cu-PGE deposit. The moderate PGE depletions in the bulk sulfide of the Qingkuanghan deposit suggest that the parental magma of the host intrusion may have undergone minor sulfide segregation at depth. The mixing calculations suggests that an average of 10% crustal contamination in the magma, which may have been the main cause of sulfide saturation in the magma. We propose that sulfide segregation from a moderately PGE depleted magma took place prior to magma emplacement at Qingkuangshan, that small amounts of immiscible sulfide droplets and olivine and chromite crystals were suspended in the ascending magma, and that the suspended materials settled down when the magma passed trough the Qingkuangshan conduit. The Qingkuangshan sulfide-bearing intrusion is interpreted to a feeder of Emeishan flood basalts in the region.展开更多
A systematic analysis of the inorganic and organic geochemistry of Middle Permian source rocks comprising carbonate rocks and mudstones was carried out, with samples collected from the outcrop and bore of the Junggar,...A systematic analysis of the inorganic and organic geochemistry of Middle Permian source rocks comprising carbonate rocks and mudstones was carried out, with samples collected from the outcrop and bore of the Junggar, Turpan and Ili basins in northern Xinjiang. This study confirmed that sedimentary parameters for an ancient water body, such as inorganic geochemistry and paleosalinity, have a close relation to the organic matter of source rocks. It is also disclosed that phytane predominance in the source rocks is mainly due to a reducing environment. Biomarkers, such as gammacerane and β-carotene, in the samples reflect a specific salinity in the sedimentary environments. Sedimentary zones with a strong reducing environment are more likely to produce deposits of primary organic matter, which will be buried and preserved contemporarily. Consequently, the source rocks are generally high in organic content and better in organic type than ordinary ones, and vice versa.展开更多
Two Permian-Triassic boundary(PTB) sections(Pojue and Dala) are well exposed in an isolated carbonate platform(Napo Platform) on the southwestern margin of the Nanpanjiang Basin, South China. These sections provide an...Two Permian-Triassic boundary(PTB) sections(Pojue and Dala) are well exposed in an isolated carbonate platform(Napo Platform) on the southwestern margin of the Nanpanjiang Basin, South China. These sections provide an insight into the transition across the PTB and a detailed investigation of the conodont biostratigraphy and inorganic carbon isotopes is presented. The PTB at the Pojue Section is placed at the base of Bed 10 B(a dolomitized mudstone found below a microbialite horizon), defined by the first occurrence of Hindeodus parvus. At the Dala Section, four conodont zones occur. They are, in ascending order, the Hindeodus parvus Zone, Isarcicella staeschei Zone, Isarcicella isarcica Zone and Clarkina planata Zone. Comparison with the Pojue Section suggests the PTB at Dala also occurs at the base of dolomitized mudstone below a microbialite horizon, although the first occurrence of Hindeodus parvus is near the top of a microbialite bed: an occurrence that is also seen in other platform sections. The succeeding microbialite beds developed during the ongoing PTB mass extinction phase. This time was characterized by low carbon isotope values, and a microbialite ecosystem that provided a refuge for selected groups(bivalves, ostracods and microgastropods) that were likely tolerant of extremely high temperatures.展开更多
Deep-water facies sections have advantages of recording complete information across the Permian-Triassic boundary(PTB). Here we present a detailed study on the conodont biostratigraphy and carbon isotope profile range...Deep-water facies sections have advantages of recording complete information across the Permian-Triassic boundary(PTB). Here we present a detailed study on the conodont biostratigraphy and carbon isotope profile ranges from the Wuchiapingian-Changhsingian boundary(WCB) to the PTB of two deep-water facies sections at Zhuqiao and Shiligou in the Middle Yangtze region, western Hubei, South China. Fifteen species and three genera are identified. Eight conodont zones are recognized which in ascending order are the Clarkina orientalis, C. wangi, C. subcarinata, C. changxingensis, C. yini, C. meishanensis, Hindeodus parvus and Isarcicella isarcica zones. The onset of deposition of the deep-water siliceous strata of Dalong Formation in western Hubei began in the Late Wuchiapingian and persisted to the Late Changhsingian. Carbon isotope negative excursions occur near both the WCB and PTB in both sections. The WCB δ13 Ccarb negative excursion is in the C. orientalis and C. wangi zones. The PTB δ13 Ccarb negative excursion began in the C. yini Zone and extended to the I. isarcica Zone. The absence of several Changhsingian zones may indicate the difficulty of extracting conodonts from siliceous strata or the presence of an intra-Changhsingian hiatus.展开更多
文摘The Baguamiao superlarge gold deposit in Shaanxi Province is one of the typical cases in China that are hosted by sedimentary rocks. Explorers and researchers have discussed the gold mineralization enrichment conditions by studying sulphur, oxygen, carbon, silicon stable isotopes and mineralizing fluid features of the Baguamiao gold deposit and proposed a hydrothermal sedimentation-magmatic reconstructing gold mineralization model featuring multi-sources of ore-forming materials and multistage mineralizations. In addition, prospecting for “Baguamiao-type” gold deposits was started in the Fengtai Basin and a great number of important prospecting targets such as Tonglinggou, Simaoling, Guoansi and Dachaigou were discovered.
基金financially supported by projects from the National Natural Science Foundation of China (Nos. 92162323, 42321001)the Qinghai Provincial Non-ferrous Metal Geological and Minerals Exploration Bureau (No.2023jgky01)the Kunlun Talents project of Qinghai Province (2023)
文摘Tin,as one of the most important critical metals,has at-tracted great attention worldwide(Jiang et al.,2023,2020).China has the largest amount of tin resources in the world,ac-counting for nearly one-fourth of the world’s total(Jiang et al.,2020;Chen and Sheng,2015).Tin deposits in China mainly occur in the Nanling Range in southern China,the Sanjiang Basin in southwestern China,and the Great Xing’an Range in northeastern China,which account for 98%of the country’s tin resources,whereas tin deposits are relatively rare in north-western China(Ni et al.,2023;Chen et al.,2014,1992).
文摘In China's long-term social and economic development process, mineral energy plays an important role in promoting the pace of development. At present, China contains relatively low reserves of mineral resources, and some shallow mineral resources have basically been developed. In order to obtain more geological and mineral resources, it is necessary to further develop the deep mineral resources in China. Most of the mining areas in our country are mainly concentrated in the western mountainous and desert areas. In order to obtain accurate and comprehensive geological and mineral resources, the survey data are relatively difficult, especially the data of deep mining areas, which have higher requirements for the prospecting work. In this paper, the exploration work of geology and mineral resources is analyzed by mainly studying the way of deep prospecting, mainly in order to improve the efficiency of deep prospecting of mineral resources and the reserve content of geological and mineral resources in our country. First of all, the direction and present situation of deep prospecting are briefly analyzed, and then three new prospecting methods for deep deposits and concealed deposits are proposed, mainly including geochemical survey method, deep penetration geochemical method and geochemical prospecting method. At last, the paper applies the method of reduplication to the actual operation of the prospecting work, and analyzes the effect of the application, thus inferring that some mineral information within the fault structure is helpful to the further development of mineral resources in the western region of our country.
基金supported by the Jiangsu Innovation and Entrepreneurship Project(JSSCBS20211225).
文摘The North China Craton(NCC)experienced significant lithospheric thinning of over 100 km during the Mesozoic,accompanied by extensive magmatic activity and extensional tectonics.However,the timing and mechanism of this thinning remain the subjects of debate.This study presents zircon U-Pb ages,Hf isotopic data and whole-rock elemental and Sr-Nd isotopic compositions of the Guanshui monzonites and diorites in the eastern NCC.Zircon U-Pb dating reveals that both rock types formed at ca.130 Ma.The monzonites,characterized by high Mg^(#)(50.9-57.9),low Nb/U ratios(2.53-3.89)and depleted isotopic compositions,suggest derivation from asthenospheric mantle modified by slab-derived fluids.The diorites,distinguished by low SiO_(2)(49.5-50.8),high Mg^(#)(66.7-68.5)and an EM2-type enriched mantle isotopic signature,point to a lithospheric mantle source modified by subducted sediment melts.The coexistence of monzonites and diorites suggests a transition in magma source from lithospheric to asthenospheric mantle,implying that lithospheric thinning may have commenced around 130 Ma.The destruction of the NCC was likely driven by localized,small-scale drip-style detachment processes,rather than wholesale lithospheric removal.
基金supported by the Natural Science Foundation of Jilin Province of China(grant no.20230101075JC)the National Natural Science Foundation of China(grant no.42072085).
文摘The deep geologic processes between the Xing’an-Mongolian Orogenic Belt and the North China Craton in the Mesozoic are crucial to reveal the magmatic and tectonic evolution and their constraints on mineralization in the Jiapigou-Haigou collage zone.In this paper,We have presented the geochronology,geochemistry and Sr-Nd-Hf isotopic compositions of the Middle Jurassic granitic complexes in the Songjianghe area,Jilin Province.The granitic complexes can be categorized into four groups based on their geologic characteristics,with corresponding zircon U-Pb isotope ages of 177 Ma,172 Ma,169 Ma and 168-167 Ma,respectively.These granitoids exhibit calcalkaline to high-K calc-alkaline,metaluminous to weakly peraluminous Ⅰ-type characteristics,which show relative enrichment in LILEs(Rb,Sr,Ba)and depletion in HFSEs(Nb,Zr).Geochemical analyses reveal high initial^(87)Sr/^(86)Sr ratios of 0.70633-0.70740,coupled with lowεNd(t)values ranging from−10.65 to−13.23.The zircon analyses show similarly negativeεHf(t)values ranging from−16.9 to−3.2.The integrated elemental and Hf-Sr-Nd isotopic signatures demonstrate that the primitive magmas of the four group rocks were primarily derived from partial melting of thickened Archean lower crust,with the exception of the Group Ⅳ rocks,which exhibit significant evidence of crustal contamination.The residual mineral assemblages during the magma-forming process varied from amphibole to eclogite facies.These findings indicate that magmatism in the Songjianghe region likely resulted from the accretion and delamination of the Archean crust in the collage zone during the subduction of the Paleo-Pacific Plate beneath the Eurasian continent.
基金supported by the Geological Research Project of Bureau of Geology and Mineral Exploration and Development Guizhou Province(Qian Di Kuang Ke He(2020)No.27)the Guizhou Provincial Science and Technology Project(no.Qian Ke He Zhi Cheng(2022)General 199)the Guizhou Provincial Science and Technology Project(no.Qian Ke He Zhi Cheng(2023)General 169)。
文摘Vegetation ecological quality(VEQ)is not only influenced by meteorological drought(MD)but also exerts a certain degree of regulatory effect on it.Clarifying the relationship between the two is crucial for ecological conservation efforts.However,the interactions between VEQ and MD and its driving mechanisms in karst mountain regions with high surface heterogeneity remain unclear,and the lack of exploration of this interaction under different subregions hinders further progress in ecological conservation.This study took Guizhou Province,characterized by significant surface heterogeneity and extensive karst formations,as a research case.By dividing the region into different landform regions,we quantified the coupling coordination degree(CCD)between VEQ and MD using the coupling coordination degree model to elucidate their interaction and analyzed its driving forces using the Geodetector model.Results indicated that:(1)From 2001 to 2020,the CCD between VEQ and MD in Guizhou remained at a moderate coordination level,with increasing benign interactions,though significant variations in CCD trends were observed across landform regions.MD is the pivotal subsystem that determines CCD changes.(2)The dominant driving factors of CCD vary by landform,with soil moisture,precipitation,or population density as primary influences.Soil moisture has a stronger effect in karst regions,and its interaction with other factors surpasses the effects of individual factors.(3)To achieve benign development between VEQ and MD.In karst regions,attention should be focused on the impact of soil moisture and human activities on CCD.While non-karst regions have favorable vegetation and hydrothermal conditions,improper development can lead to vegetation degradation,and abnormal hydrothermal conditions,which could trigger a decline in CCD.Therefore,regulating human activities in non-karst regions is also crucial.This work serves as a scientific foundation for formulating ecological preservation strategies in Guizhou and other karst mountain regions.
基金funded by the Hebei Province Natural Resources Science and Technology Project(13000024P00F2D410443X).
文摘Medium-low temperature geothermal resources are abundant in the Guanxian fault depression.An essential foundation for the effective development and use of geothermal resources is the study of the genetic model and resource assessment of the geothermal system.This study examines the geothermal geological circumstances,hydrochemical features,and geothermal field characteristics based on the regional geological structure and prior research findings.The appraisal of geothermal resources is done,and a conceptual model of the geothermal system in the research area is built.The findings indicate that the Guan xian fault depression's geothermal resources are primarily Guantao Formation sandstone heat reservoirs.The geothermal water at the wellhead has a temperature between 54℃and 60℃,and its primary chemistry is Cl·SO_(4)-Na.Deep thermal conduction heats the geothermal water,which is then laterally supplied to the reservoir after being largely restored by air precipitation from the western Taihang Mountains.With an annual exploitable geothermal resource of 6,782×10^(12)J,or 23.14×10^(4)tons of standard coal,the Guantao Formation sandstone reservoir in the Guanxian depression has a geothermal resource of about 620.10×10^(16)J.An area of 18 million m^(2)can be heated by geothermal extraction per year,demonstrating the potential for geothermal resources and their high development and use value.
基金financially supported by the China Geological Survey Project (No. 121201010000150013)
文摘The Phapon gold deposit, located in northern Laos, is a unique large-scale gold deposit in Luang Prabang-Loei metallogenic belt. It is hosted in the Lower Permian limestone and controlled by a NE-trending ductile-brittle fault system. There are three types of primary ore including auriferous calcite vein type, disseminated type, and breccia type, and the first two are important in the Phapon gold deposit. Based on fluid inclusion petrography and microthermometry, three types of primary fluid inclusions including type 1 liquid-rich aqueous, type 2 vapor-rich aqueous and type 3 daughter mineralbearing aqueous were identified in hydrothermal calcite grains. The ore-forming fluids are normally homogeneous, as indicated by the widespread type 1 inclusions with identical composition. The coexistence of type 1 and type 2 inclusions, showing similar final homogenization temperature but different compositions, indicate that fluid immiscibility did locally take place in both two types of ores. The results of microthermometry and H-O isotopes geochemistry indicate that there are little differences on ore-fluid geochemistry between the auriferous calcite vein-type and disseminated type ores. The oreforming fluids are characterized by medium-low temperatures(157–268 oC) and low salinity(1.6 wt.%–9.9 wt.% NaCl eq.). It is likely to have a metamorphic-dominant mixed source, which could be associated with dehydration and decarbonisation of Lower Permian limestone and Middle–Upper Triassic sandstones during the dynamic metamorphism. The fluid-wallrock interaction played a major role, and the locally occurred fluid-immiscible processes played a subordinate role in gold precipitation. Combined with the regional and ore deposit geology, and ore-fluid geochemistry, we suggest that the Phapon gold deposit is best considered to be a member of the epizonal orogenic deposit class.
基金supported by the National Important Basic Research and Development Program(973)(Grant No.2001CB209104).
文摘There are many factors affecting the chemical characteristics of groundwater in the forming process of groundwater chemical fields, such as freshening due to meteoric water leaching downwards, freshening due to mudstone compaction and water release, concentration due to infiltration and freshening due to dehydration of clay minerals. As a result, the groundwater chemical fields are characterized by lengthwise stages and planar selectivity. The former arouses vertical chemical zonality of groundwater. Five units could be identified downwards in the Songliao basin： （1） freshening zone due to downward-leaching meteoric water, （2） concentration zone due to evaporation near the ground surface, （3） freshening zone due to mudstone compaction and water release, and concentration zone due to compaction and infiltration, （4） freshening zone due to dehydration of clay minerals, and （5） filtration-concentration zone; whereas the latter determines the planar division of groundwater chemical fields： （1） the freshening area due to meteoric water, asymmetrically on the margin of the basin, （2） the freshening area due to mudstone compaction and water release in the central part of the basin, （3） the leaky area, which is a transitional zone, and （4） leakage-evaporation area, which is a concentration zone. In the direction of centrifugal flows caused by mudstone compaction in the depression area, the mineralization degree, concentrations of Na^＋ and Cl^-, and salinity coefficient （SC） increase, while concentrations of （CO3^2- ＋HCO3^-） and SO4^2-, metamorphism coefficient （MC） and desulfuration coefficient （DSC） decrease. However, all these parameters increase in the direction of gravity-induced centripetal flows.
文摘Based on element geochemical studies of the main Permian exploitable coal measure strata in Western Guizhou, the element geochemical distribution characteristics of the main exploitable coal measures were revealed in the regions of Dafang, Qianxi, Weining, Hezhang, Zhijin, etc., of Guizhou Province, and the results show that their element contents are mainly affected by terrestrial material supply. Coal measures formed in the delta plain environment where sufficient terrestrial materials are supplied contain relatively abundant trace elements and rare-earth elements, whereas those formed in the tidal-fiat environment influenced greatly by seawater have relatively low contents of trace elements and rare-earth elements, mainly con- trolled by the geological fact that basalts the parent rocks from source regions contain high trace elements and rare-earth elements. In addition, coal measures affected by later hydrothermal activities and fault tectonics contain a large amount of harmful elements. According to the rules of distribution of elements in coal measures, a new idea was put forward to classify coal-forming environments by using the geochemical composition characteristics, which is of great significance in dissolving the problem of whether coal measures were fbrmed either in delta environments or in tidal-flat environments in Western Gui- zhou. At the same time, the rules of distribution of elements in the main exploitable coal measures in Western Guizhou were fully understood, which is of direct significance in utilizing coal resources on the basis of classification of coals, as well as in developing the coal chemical industry.
基金financially supported by the National Key Research and Development Program (Grant Nos. 2018YFC0603804)the China Geological Survey (Grants DD20190042, DD20190039 and DD20160048-05)
文摘The early Mesozoic marked an important transition from collisional orogeny to post-orogenic extension at the northern margin of the North China Craton(NCC). In this study, we undertook zircon U-Pb dating and whole-rock majorand trace-element geochemical analyses of early Mesozoic granitic rocks in the Chifeng area to establish their geochronological framework, petrogenesis, and implications for the tectonic evolution of the eastern Central Asia Orogenic Belt(CAOB). Zircon U-Pb dating results show that these rocks were emplaced in three stages during the Triassic:(1) syenogranites during 250-248 Ma,(2) granodiorites during 244-243 Ma, and(3) monzogranites and granodiorites during 232-230 Ma. These Triassic granitoids belong to the high-K calc-alkaline series and are evolved I-type granites. They have high SiO2 and low Mg O contents with enrichments in light rare-earth elements, Zr, Hf, Rb, Th, and U, and depletions in Ba, Nb, Ta, Sr, and Eu. These geochemical data indicate that the granitoids were derived from partial melting of a lower-crustal source under relatively low-pressure conditions and subsequently underwent extensive fractional crystallization. Considering both the geochemical data and regional geological information, we propose that the 250-248 Ma syenogranites were emplaced in an extensional environment linked to slab break-off after closure of the Paleo-Asian Ocean(PAO) along the Solonker-Xra Moron-Changchun suture zone. The 244-243 Ma granodiorites were formed in a compressional orogenic setting during collision between the Erguna-Xing’an-Songliao composite block and the NCC. The 232-230 Ma granodiorites and monzogranites were emplaced during the transition from compressional orogeny to post-orogenic extension. Overall, the early Mesozoic tectonic evolution of the Chifeng area can be divided into three main stages:(1) closure of the Paleo-Asian Ocean and extension related to slab break-off during the Early Triassic;(2) continuous collisional compression during the Middle Triassic after closure of the PAO;and(3) post-orogenic extension during the Late Triassic, most probably due to lithospheric delamination after amalgamation of the Erguna-Xing’an-Songliao composite block and the NCC.
基金supported by National Key R&D Program of China(Grant No.2018YFB1501803)。
文摘Hot dry rock(HDR)is an important geothermal resource and clean energy source that may play an increasingly important role in future energy management.High-temperature HDR resources were recently detected in deep regions of the Gonghe Basin on the northeastern edge of the Tibetan Plateau,which led to a significant breakthrough in HDR resource exploration in China.This research analyzes the deep temperature distribution,radiogenic heat production,heat flow,and crustal thermal structure in the Qiaboqia Valley,Guide Plain,and Zhacanggou area of the Gonghe Basin based on geothermal exploration borehole logging data,rock thermophysical properties,and regional geophysical exploration data.The results are applied to discuss the heat accumulation mechanism of the HDR resources in the Gonghe Basin.The findings suggest that a low-velocity layer in the thickened crust of the Tibetan Plateau provides the most important source of constant intracrustal heat for the formation of HDR resources in the Gonghe Basin,whereas crustal thickening redistributes the concentrated layer of radioactive elements,which compensates for the relatively low heat production of the basal granite and serves as an important supplement to the heat of the HDR resources.The negative effect is that the downward curvature of the lithospheric upper mantle caused by crustal thickening leads to a small mantle heat flow component.As a result,the heat flows in the Qiaboqia Valley and Guide Plain of the Gonghe Basin are 106.2 and 77.6 m W/m2,respectively,in which the crust-mantle heat flow ratio of the former is 3.12:1,indicating a notably anomalous intracrustal thermal structure.In contrast,the crust-mantle heat flow ratio in the Guide Plain is 1.84:1,which reflects a typical hot crust-cold mantle thermal structure.The Guide Plain and Zhacanggou area show the same increasing temperature trend with depth,which reflects that their geothermal backgrounds and deep high-temperature environments are similar.These results provide important insight on the heat source mechanism of HDR resource formation in the Tibetan Plateau and useful guidance for future HDR resource exploration projects and target sites selection in similar areas.
文摘The Wenquan molybdenum deposit is a kind of large-sized porphyry molybdenum deposit found in re-cent years.In this paper,on the basis of deposit geology,geochemistry and isotope geochronology data,the metal-logenic model of this deposit was established.The Wenquan granitic batholith belongs to the K-rich(alkali-rich) calc-alkaline rock series,which is the mineralization parent rock.The rock massif shows the characteristics of both crust-remelting granite and mantle-source granite.At the same time,the data of REE contents,hydrogen and oxygen isotopes and inclusion temperatures showed that the metallogenic hydrothermal solution is a mixed mesothermal solution of magmato-hydrothermal fluid and meteoric water.Mineralization was dated at 214±7.1 Ma,basically identical with the parent rock's age(207-226 Ma).This reflects that molybdenum mineralization has a close relation to tectonic magmatism evoked by orogenic processes,and molybdenum mineralization occurred mainly at the petrogenesis stage at the late stage of magma emplacement.Mixing with meteoric water led to a decrease in the sa-linity of magmato-hydrothermal solution and changes in other physical and chemical properties.During the tectonic process,ore-bearing hydrothermal solution ascended along favorable fault structure channels.With physicochemical changes,it filled in the surrounding rock joints on both sides of faults,forming ore deposits.
基金granted by the National Natural Science Fund of China (No. 41072058)the Scientific Research Special Subject for Public Welfare Profession (200911007 and201011058)China central college fund(CHD2011TD007)
文摘The Zhou＇an PGE-Cu-Ni deposit was recently discovered in the Qinling orogenic belt bound by the Yangtze and the North China Cratons. It is a blind deposit thoroughly covered by the Cenozoic alluvial sediments in the Nanyang Basin. As the first large PGE-Cu-Ni deposit discovered in the Qinling-Dabie-Sulu orogenic belt, its geological and geochemical characteristic, isotope age, genesis and tectonic setting are of wide concern in both scientific studies and ore exploration. In this contribution, we report the results obtained from a pioneering study. The Zhou＇an ultramafic complex is ferruginous, with m/f = 4.79-5.08, and shows the nature of tholeiite series. It is rich in light rare earth elements, Rb, Th, U, La, Sm, Zr and Hf, and poor in heavy rare earth elements, Nd and Ta, suggesting an intraplate setting. It has high S7Sr/S6Sr and low 143Nd/144Nd ratios. The ratios of Zr/Nb, La/Nb, Ba/ Nb, Rb/Nb, Th/Nb, Th/La and Ba/La, suggest the magma originated from lithosphere mantle. The Fo values of olivine and Pd/Ir-Ni/Cu diagram suggest primary magma was High Mg basalt. The laser ablation inductively coupled plasma atomic emission spectroscopy zircon U-Pb age is 641.5 ± 3.7 Ma.
基金support from the National Natural Science Foundation of China (Grant No.40872077)National Major Science and Technology Project of China (Grant No. 2011ZX05009-002)Open Project Foundation of Ministry of Education Key Laboratory of Tectonics and Petroleum Resources (Grant No. TPR-2011-09)
文摘The sequence stratigraphy framework of Paleogene of Qikou Sag has been built in this paper. The evolution law of episodic subsidence in Qikou Sag has been expounded, with the analysis of the characteristic of sequence thickness, as well as the study of consedimental tectonic activity, subsidence history, paleogeomorphology and the coupling relationship among them. The faults controlling action was the dominant mechanism during rifting stage I , as the depression was the dominant mechanism during rifting stage III, which embodies a process from intense disparity fault depression to integral subsidence. Meanwhile, under the control of regional faulting and later stage depression, subsidence rate centers and paleogeomorphic concave centers are always corresponding to the sequence thickness centers, and the changes of subsidence centers and paleogeomorphology concave centers are consistent with the migration of thickness centers, which presents the restriction, coupling and response among them and clarifies the law that tectonic activity controls the basin fill by means of controlling the subsidence rate and paleogeomorphology from contributing factor angle. On this basis, the dynamic evolution of the composite pattern of structure-subsidence-deposition in the fault controlling actic region during the three rifting stages and their petroleum geological significance has been discussed.
基金jointly supported by projects,including the Study on the Lithospheric Thermal Structure,the Formation Mechanism of Geothermal Systems,and the Assessment of Geothermal Resources of the Guangdong-Hong Kong-Macao Greater Bay Area(Grant No.U20A2096)The Huizhou Multi-factors Urban Geological Survey Project(Grant No.DD20190287)the Update and Sharing of China Geological Maps of Land and Sea areas(Grant No.DD20190370)。
文摘The Heyuan Fault,is one of the main NE-trending faults in the southernmost South China Block and is close to the northernmost South China Sea to the south.The fault features multi-stage deformation and controlled the formation of late Cretaceous to Cenozoic basins.Based on detailed field investigations and comprehensive geochronological research,including zircon U-Pb,Rb-Sr isochron,zircon U-Th-He dating,two episodic tectono-thermal events are recognized.The first occurred during~79 Ma to 66 Ma,which is characterized by large-scale quartz-fluid emplacement.The other occurred at~34 Ma,which features the eruption of a set of basalts.The two events show a changing on material source from siliceous hydrotherm to basalt magma,supporting obvious lithospheric thinning of the southernmost South China Block,which shed light on the geological evolution and the interaction mechanisms between the SCB and the northern South China Sea since the Late Cretaceous.
基金financially supported by the Chinese Academy of Sciences (grant no.KZCX2-YW-Q04-06)the National Key Basic Research Program of China (grant no. 2009CB421005)the National Science Foundation of China (grant no.40973039)
文摘The Qingkuangshan Ni-Cu-PGE deposit, located in the Xiaoguanhe region of Huili County, Sichuan Province, is one of several Ni-Cu-PGE deposits in the Emeishan Large Igneous Province （ELIP）. The ore-bearing intrusion is a mafic-ultramafic body. This paper reports major elements, trace elements and platinum-group elements in different types of rocks and sulfide-mineralized samples in the intrusion. These data are used to evaluate the source mantle characteristics, the degree of mantle partial melting, the composition of parental magma and the ore-forming processes. The results show that Qingkuangshan intrusion is part of the ELIP. The rocks have trace element ratios similar to the coeval Emeishan basalts. The primitive mantle-normalized patterns of Ni-Cu-PGE have positive slopes, and the ratios of Pd/Ir are lower than 22. The PGE compositions of sulfide ores and associated rocks are characterized by Ru depletion. The PGE contents in bulk sulfides are slightly depleted relative to Ni and Cu, which is similar to the Yangliuping Ni-Cu-PGE deposit. The composition of the parental magma for the intrusion is estimated to contain about 14.65 wt% MgO, 48.66 wt% SiO2 and 15.48 wt% FeOt, and the degree of mantle partial melting is estimated to be about 20%. In comparison with other typical Ni-Cu-PGE deposits in the ELIP, the Qingkuangshan Ni-Cu-PGE deposit has lower PGE contents than the Jinbaoshan PGE deposit, but has higher PGE contents than the Limahe and Baimazhai Ni-Cu deposit, and has similar PGE contents to the Yangliuping Ni-Cu-PGE deposit. The moderate PGE depletions in the bulk sulfide of the Qingkuanghan deposit suggest that the parental magma of the host intrusion may have undergone minor sulfide segregation at depth. The mixing calculations suggests that an average of 10% crustal contamination in the magma, which may have been the main cause of sulfide saturation in the magma. We propose that sulfide segregation from a moderately PGE depleted magma took place prior to magma emplacement at Qingkuangshan, that small amounts of immiscible sulfide droplets and olivine and chromite crystals were suspended in the ascending magma, and that the suspended materials settled down when the magma passed trough the Qingkuangshan conduit. The Qingkuangshan sulfide-bearing intrusion is interpreted to a feeder of Emeishan flood basalts in the region.
文摘A systematic analysis of the inorganic and organic geochemistry of Middle Permian source rocks comprising carbonate rocks and mudstones was carried out, with samples collected from the outcrop and bore of the Junggar, Turpan and Ili basins in northern Xinjiang. This study confirmed that sedimentary parameters for an ancient water body, such as inorganic geochemistry and paleosalinity, have a close relation to the organic matter of source rocks. It is also disclosed that phytane predominance in the source rocks is mainly due to a reducing environment. Biomarkers, such as gammacerane and β-carotene, in the samples reflect a specific salinity in the sedimentary environments. Sedimentary zones with a strong reducing environment are more likely to produce deposits of primary organic matter, which will be buried and preserved contemporarily. Consequently, the source rocks are generally high in organic content and better in organic type than ordinary ones, and vice versa.
基金supported by the National Natural Science Foundation of China (No. 41572324)the Special Project on Basic Work of Science and Technology from the National Ministry of Science and Technology of China (No. 2015FY310100-11)the China Geological Survey (No. DD20160120-04)
文摘Two Permian-Triassic boundary(PTB) sections(Pojue and Dala) are well exposed in an isolated carbonate platform(Napo Platform) on the southwestern margin of the Nanpanjiang Basin, South China. These sections provide an insight into the transition across the PTB and a detailed investigation of the conodont biostratigraphy and inorganic carbon isotopes is presented. The PTB at the Pojue Section is placed at the base of Bed 10 B(a dolomitized mudstone found below a microbialite horizon), defined by the first occurrence of Hindeodus parvus. At the Dala Section, four conodont zones occur. They are, in ascending order, the Hindeodus parvus Zone, Isarcicella staeschei Zone, Isarcicella isarcica Zone and Clarkina planata Zone. Comparison with the Pojue Section suggests the PTB at Dala also occurs at the base of dolomitized mudstone below a microbialite horizon, although the first occurrence of Hindeodus parvus is near the top of a microbialite bed: an occurrence that is also seen in other platform sections. The succeeding microbialite beds developed during the ongoing PTB mass extinction phase. This time was characterized by low carbon isotope values, and a microbialite ecosystem that provided a refuge for selected groups(bivalves, ostracods and microgastropods) that were likely tolerant of extremely high temperatures.
基金supported by the Natural Science Foundation of China(Nos.41572002,41830320,41272044,41472087,4183000426,41802016)
文摘Deep-water facies sections have advantages of recording complete information across the Permian-Triassic boundary(PTB). Here we present a detailed study on the conodont biostratigraphy and carbon isotope profile ranges from the Wuchiapingian-Changhsingian boundary(WCB) to the PTB of two deep-water facies sections at Zhuqiao and Shiligou in the Middle Yangtze region, western Hubei, South China. Fifteen species and three genera are identified. Eight conodont zones are recognized which in ascending order are the Clarkina orientalis, C. wangi, C. subcarinata, C. changxingensis, C. yini, C. meishanensis, Hindeodus parvus and Isarcicella isarcica zones. The onset of deposition of the deep-water siliceous strata of Dalong Formation in western Hubei began in the Late Wuchiapingian and persisted to the Late Changhsingian. Carbon isotope negative excursions occur near both the WCB and PTB in both sections. The WCB δ13 Ccarb negative excursion is in the C. orientalis and C. wangi zones. The PTB δ13 Ccarb negative excursion began in the C. yini Zone and extended to the I. isarcica Zone. The absence of several Changhsingian zones may indicate the difficulty of extracting conodonts from siliceous strata or the presence of an intra-Changhsingian hiatus.
