238 marine carbonate samples were collected from seven sedimentary sections ofthe entire late Palaeozoic (Permian, Carboniferous and Devonian) in the Upper Yangtze Plat-form, southwest China. Based on the absence of c...238 marine carbonate samples were collected from seven sedimentary sections ofthe entire late Palaeozoic (Permian, Carboniferous and Devonian) in the Upper Yangtze Plat-form, southwest China. Based on the absence of cathodoluminescence and very low Mn (gener-ally<50 ppm) contents of the samples, it is thought that they contain information on the orig-inal sea water geochemistry. The results of isotopic analyses of these samples are presented interms of δ^(13)C and ^(87)Sr/^(86)Sr ratios versus geological time. The strontium data, consistent withother similar data based on samples from North America, Europe, Africa and other areas inAsia, support the notion of a global consistency in strontium isotope composition of marinecarbonates. The strontium data exhibit three intervals of relatively low ^(87)Sr/^(86)Sr ratios in thelate Middle Devonian to early Late Devonian, Early Carboniferous and Early Permian, corre-sponding to global eustatic high sea level stands. The lowest ^(87)Sr/^(86)Sr ratio recorded in theLate Permian was probably caused by substantial basalt eruptions in the Upper Yangtze Plat-form at the time. Three corresponding periods of relatively high δ^(13)C values at roughly the samethe intervals were caused by a relatively high rate of accumulation of organic carbon duringsea level rises at these times. The deposition of coal was probably responsible for the increaseof sea water δ^(13)C at other times. The δ^(13)C values drop dramatically near theDevonian/Carboniferous, Carboniferous/Permian and Permian/Triassic boundaries, con-sistent with other similar data, which further support the notion that geological time boundariesare associated with mass extinction and subsequent rejuvenation.展开更多
Power-law patterns appear in a variety of natural systems on the modern Earth;nevertheless,whether such behaviors appeared in the deep-time environment has rarely been studied. Isotopic records in sedimentary rocks, w...Power-law patterns appear in a variety of natural systems on the modern Earth;nevertheless,whether such behaviors appeared in the deep-time environment has rarely been studied. Isotopic records in sedimentary rocks, which are widely used to reconstruct the geological/geochemical conditions in paleoenvironments and the evolutionary trajectories of biogeochemical cycles, offer an opportunity to investigate power laws in ancient geological systems. In this study, I focus on the Phanerozoic sedimentary records of carbon, oxygen, sulfur, and strontium isotopes, which have well documented and extraordinarily comprehensive datasets. I perform statistical analyses on these datasets and show that the variations in the sedimentary records of the four isotopes exhibit power-law behaviors. The exponents of these power laws range between 2.2 and 2.9;this narrow interval indicates that the variations in carbon, oxygen, sulfur, and strontium isotopes likely belong to the same universality class, suggesting that these systematic power-law patterns are governed by universal, scale-free mechanisms. I then derive a general form for these power laws from a minimalistic model based on basic physical principles and geosystem-specific assumptions, which provides an interpretation for the power-law patterns from the perspective of thermodynamics. The fundamental mechanisms regulating such patterns might have been ubiquitous in paleoenvironments, implying that similar power-law behaviors may exist in the sedimentary records of other isotopes.展开更多
The calibration of sedimentary rock absolute dates is one of the difficulties in sedimentological and stratigraphic research.Since strontium(Sr)resides in seawater much longer(≈10^(6) a)than the seawater intermixing ...The calibration of sedimentary rock absolute dates is one of the difficulties in sedimentological and stratigraphic research.Since strontium(Sr)resides in seawater much longer(≈10^(6) a)than the seawater intermixing time(≈10^(3) a),the Sr isotopic composition of global seawater is uniform at any time and results in a stable system throughout geological history,based on which a global Sr isotope composition dating database has been established for age-calibration of marine strata.The Permian stratigraphic sections in the northern part of the Upper Yangtze block,southern China,record continuous marine sediments with clear stratigraphic boundaries and is suitable for stratigraphic dating of Sr isotopes.Based on sampling and Sr isotopic compositions of Permian carbonate strata in the northern part of the Upper Yangtze,a Permian Sr isotope evolution curve was established.According to the basic principles of Sr isotope stratigraphy,the global Strontium isotope age database can be used to calibrate the Permian stratigraphic dates in the northern Upper Yangtze.The results show that the Sr isotope evolution curves for the marine carbonate rocks in the Permian stratigraphic section of the Upper Yangtze present a decreasing trend from the mid-Qixia stage(P_(2))to the mid-Wujiaping stage(P_(3)),and then rise from the middle Wujiaping stage to the end of Changxing stage(P_(3)).When the Permian Sr-isotope evolution curve is compared with the global Sr isotope evolution curve in the northern Upper Yangtze,the two are consistent in their long-term evolutionary trend,indicating that Permian global geological events are important controlling factors for the composition and evolution of Sr isotopes.The 87 Sr/86 Sr value decreased gradually in the background of large-scale regressions at the turn of middle to late Permian period,revealing that the Emeishan basalt eruption occurred near the Maokou/Wujiaping boundary(GLB).Srisotope stratigraphy dating was performed on the boundaries of the Qixia Formation/Maokou Formation,Maokou Formation/Wujiaping Formation(GLB),Wujiaping Formation/Changxing Formation(WCB)and the Permian/Triassic(PTB)using the Global Strontium Isotope Age Database.The results are 270.4 Ma,261.2 Ma,254.5 Ma and 249.7 Ma,respectively.Based on this,the eruption age of the Emeishan basalts is defined at about 261.2 Ma.,which is more coincident with that acquired from other previous dating methods on the eruption age of the Emeishan basalts,and therefore proves that the application of Sr isotopic stratigraphy to dating marine sedimentary units is an effective method.展开更多
Groundwater from karst subterranean streams is among the world's most important sources of drinking water supplies,and the hydrochemical characteristics of karst water are impacted by both natural environment and ...Groundwater from karst subterranean streams is among the world's most important sources of drinking water supplies,and the hydrochemical characteristics of karst water are impacted by both natural environment and people.Therefore,the study of hydrochemistry and its solutes'sources is very important to ensure the normal function of life support systems.In this paper,thirty-five representative karst groundwater samples were collected from different aquifers(limestone and dolomite)and various land use types in Chongqing to trace the sources of solutes and relative hydrochemical processes.Hydrogeochemical types of karst groundwater in Chongqing were mainly of the Ca-HCO3 type or Ca(Mg)-HCO3 type.However,some hydrochemical types of karst groundwater were the K+Na+Ca-SO4 type(G25 site)or Ca-HCO3+SO4 type(G26 and G14 site),indicating that the hydrochemistry of these sites might be strongly influenced by anthropogenic activities or unique geological characteristics.The dissolved Sr concentrations of the studied groundwater ranged from 0.57 to 15.06~tmmol/L,and the STSr/S6Sr varied from 0.70751 to 0.71627.The j34S-SO42-fell into a range of-6.8%o-21.5%o,with a mean value of 5.6%o.The variations of both 87Sr/S6Sr and Sr values of the groundwater samples indicated that the Sr element was controlled by the weathering of limestone,dolomite and silicate rock.However,the figure of STSr/S6Sr vs.Sr2+/[K++Na+]showed that the anthropogenic inputs also obviously contributed to the Sr contents.For tracing the detailed anthropogenic effects,we traced the sources of solutes collected karst groundwater samples in Chongqing according to the j34S value of potential sulfate sources.The variations of both j34S and 1/SO42-values of the groundwater samples indicated that the atmospheric acid deposition(AAD),dissolution of gypsum(GD),oxidation of sulfide mineral(OS)or anthropogenic inputs(SF:sewage or fertilizer)have contributed to solutes in karst groundwater.The influence of oxidation of sulfide mineral,atmospheric acid deposit and anthropogenic inputs to groundwater in Chongqing karst areas was much widespread.展开更多
The Yunkai Area is located at the southern South China Block and is part of the Qinzhou Bay-Hangzhou Bay Metallogenic Belt, which is a famous polymetallic mineralization belt. The Xinhua Pb–Zn–(Ag)deposit is located...The Yunkai Area is located at the southern South China Block and is part of the Qinzhou Bay-Hangzhou Bay Metallogenic Belt, which is a famous polymetallic mineralization belt. The Xinhua Pb–Zn–(Ag)deposit is located in the western part of Yunkai Area, with an abundance of Pubei batholiths. Zircon U–Pb geochronology of Pubei batholiths shows that crystallization age ranges from 251.9 ± 2.2 to 244.3 ± 1.8 Ma, thus belonging to Indosinian orogeny. Geochemistry and Sr isotopic compositions of the Pubei batholiths show that it is derived from the partial melting of large scale crustal melting during the stage of exhumation and uplifting of the lower-middle crust. In addition, strontium isotope of sphalerite from the Xinhua Pb–Zn–(Ag) deposit, has limited ranges in ^(87)Rb/^(86)Sr and ^(87)Sr/^(86)Sr, ranging from 0.4077 to 1.0449, and 0.718720 to 0.725245, respectively. The initial ^(87)Sr/^(86)Sr ratios of sphalerite ranges between 0.718720 and 0.725245, which is higher than that of upper continental crust and lower than that of the Pubei batholiths, illustrating the fluid might be derived from the mixing of Pubei pluton and upper continental crust.展开更多
Hydrothermal barite is a typical low-temperature mineral formed during the mixing of hydrothermal fluid and seawater.Because of its extremely low solubility,barite behaves as a close system after crystallization and p...Hydrothermal barite is a typical low-temperature mineral formed during the mixing of hydrothermal fluid and seawater.Because of its extremely low solubility,barite behaves as a close system after crystallization and preserves the geochemical fingerprint of hydrothermal fluid.In this study,the elemental contents and Sr isotope compositions of hydrothermal barites from the Yonaguni IV were determined using electron microprobe and LA-MC-ICP-MS respectively.On these bases,the fluid/sediment interaction during the hydrothermal circulation and physicochemical condition of barite crystallization were discussed.Results show that the 87 Sr/86 Sr values of hydrothermal barites from the Yonaguni IV are apparently higher than those of the seawater and associated volcanic rocks,indicating the sufficient interaction between the hydrothermal fluid and overlying sediment.Monomineral Sr abundance shows large variations,reflecting the changes in barite growth rate during the fluid mixing.The mineralization condition in the Yonaguni IV was unstable.During the crystallization of barite,hydrothermal fluid and seawater mixed in varying degrees,with the pro-portions of hydrothermal fluid varied from 36%to 72%.The calculated crystallization temperatures range from 109 to 220℃.Sediment plays a critical role during the mineralization process in the Yonaguni IV and incorporation of sediment component into hydrothermal system was prior to barite crystallization and sulfide mineralization.展开更多
The research on the trace elements of Ordovician carbonates plays an important part in the whole work on reservoir in Tazhong （塔中 ） area. This paper systematically studies the characteristics and sedimentary setti...The research on the trace elements of Ordovician carbonates plays an important part in the whole work on reservoir in Tazhong （塔中 ） area. This paper systematically studies the characteristics and sedimentary settings of Ordovician dolomites in Tazhong area, Tarim basin, and debates their enrichment of mechanisms and different element existing patterns. The study makes use of ICP-MS analysis technology to test the strontium and manganese content of 109 samples from four wells in the Tazhong area, Tarim basin and strontium isotope composition tests have also been done on 25 samples from wells Zhong-1 and Zhong-4 on VG354 solid isotope mass spectrograph. By means of analyzing contents of strontium and manganese elements, doing research on the strontium isotope composition characteristics from wells Zhong-1 and Zhong-4 and comparing the results of strontium analysis to the global Ordovician marine carbonate and its evolution trend, in the combination of sedimentary facies characteristics of isolated wells in this area, we can come to the following cognitions： （1） The marine carbonate strontium isotope curve in the Tazhong area of Tarim basin is consistent to the global evolution trend which is overall descending with time, the direct reason of which is the evolution of paleogeographic environment. The Ordovician paleogeographic environment goes through restricted platform to open platform and then shallow marine shelf in Tazhong area, Tarim basin. Dolomitization is another subordinate reason and the inversion of fluid with high manganese can lead to heavy strontium; （2） The fact that the 87 Sr/86 Sr ratios of the Upper Ordovician in Tazhong area have an apparent mono-decline trend with the time going by, which is similar to the global strontium isotope ratio, is suggesting that the variation of the Upper Ordo- vician sea level is starting, the overall trend of which is the rising of the sea level; （3） Compared to the global seawater strontium ratios, the ^87Sr/^86 Sr ratio of the Lower Ordovician is much high, and ^87Sr/^86Sr ratio of the Lower Ordovician is overall increasing with its maximum value reaching 0. 709 727, the reasons of which are dolomitization, evaporation of the supratidal and the reflux of high manganese haline, those reasons can lead to the increasing amount of the strontium and the rising of the ^87 Sr/^86 Sr ratio; （4） The manganese element content changes little. Dolomitization has little impact on it; （5） Big variation occurs in the strontium values of Ordovician carbonate in the region of Tazhong. Apart from paleogeographic environment and petrography, the factors which can affect the values of strontium are the content of the terrestrial clastics and the diagenesis modification which may result in the further changing of the strontium values.展开更多
Hydrogeochemical processes that would occur in polluted groundwater and aquifer system,may reduce the sensitivity of Sr isotope being the indicator of hydraulic fracturing flowback fluids(HFFF)in groundwater.In this p...Hydrogeochemical processes that would occur in polluted groundwater and aquifer system,may reduce the sensitivity of Sr isotope being the indicator of hydraulic fracturing flowback fluids(HFFF)in groundwater.In this paper,the Dameigou shale gas field in the northern Qaidam Basin was taken as the study area,where the hydrogeochemical processes affecting Sr isotope was analysed.Then,the model for Sr isotope in HFFF-polluted groundwater was constructed to assess the sensitivity of Sr isotope as HFFF indicator.The results show that the dissolution can release little Sr to polluted groundwater and cannot affect the εSr(the deviation of the 87Sr/86Sr ratio)of polluted groundwater.In the meantime,cation exchange can considerably affect Sr composition in the polluted groundwater.The Sr with low εSr is constantly released to groundwater from the solid phase of aquifer media by cation exchange with pollution of Quaternary groundwater by the HFFF and it accounts for 4.6% and 11.0% of Sr in polluted groundwater when the HFFF flux reaches 10% and 30% of the polluted groundwater,respectively.However,the Sr from cation exchange has limited impact on Sr isotope in polluted groundwater.Addition of Sr from cation exchange would only cause a 0.2%and 1.2% decrease in εSr of the polluted groundwater when the HFFF flux reaches 10% and 30% of the polluted groundwater,respectively.These results demonstrate that hydrogeochemical processes have little effect on the sensitivity of Sr isotope being the HFFF indicator in groundwater of the study area.For the scenario of groundwater pollution by HFFF,when the HFFF accounts for 5%(in volume percentage)of the polluted groundwater,the HFFF can result in detectable shifts of εSr(Δ_(εSr)=0.86)in natural groundwater.Therefore,after consideration of hydrogeochemical processes occurred in aquifer with input of the HFFF,Sr isotope is still a sensitive indicator of the Quaternary groundwater pollution by the HFFF produced in the Dameigou shale of Qaidam Basin.展开更多
The global Hangenberg Crisis or Hangenberg Extinction is a mass extinction near the Devonian-Carboniferous boundary.Comprehensive research of petrology and geochemistry on the Devonian-Carboniferous boundary,as expose...The global Hangenberg Crisis or Hangenberg Extinction is a mass extinction near the Devonian-Carboniferous boundary.Comprehensive research of petrology and geochemistry on the Devonian-Carboniferous boundary,as exposed in the Nanbiancun auxiliary stratotype section,South China,elucidates paleoenvironmental changes and controls on marine strontium(^(87)Sr/^(86)Sr)and carbonate carbon(δ^(13)C_(carb))isotopes during the Hangenberg Crisis.The new^(87)Sr/^(86)Sr data reveal a regression in the Middle Siphonodella praesulcata Zone,while the Hangenberg Extinction was occurring in South China.Moreover,theδ^(13)C_(carb)data records a negative excursion near the base of the Middle Siphonodella praesulcata Zone that may have been connected with the Hangenberg Extinction.A positiveδ^(13)C_(carb)excursion,corresponding with the Upper Siphonodella praesulcata Zone,may reflect the effects of a vigorous biological pump.The magnitude of the Hangenberg Carbon Isotopic Excursion in peakδ^(13)carb values andδ^(13)C_(carb)gradient in carbonate Devonian-Carboniferous boundary sections of the South China Craton during the Hangenberg Crisis,are a function of depositional water depth and distance from the shore.The carbon cycling during the Hangenberg Carbon Isotopic Excursion had a much stronger impact on oceanic surface waters than on the deep ocean and theδ^(13)C_(carb)gradient of local seawater was likely caused by enhanced marine productivity,associated with biological recovery in platform sediments during the Hangenberg Crisis.展开更多
Clay minerals of 34 sediments collected from the northwestern continental shelf of the East China Sea have been determined by X-ray diffraction analysis. The clay mineral distribution is mainly controlled by the sedim...Clay minerals of 34 sediments collected from the northwestern continental shelf of the East China Sea have been determined by X-ray diffraction analysis. The clay mineral distribution is mainly controlled by the sediment source and the dominant circulation pattern. The predominant clay mineral in our study area is illite comprising more than 67% of the whole clay fraction. The highest concentration of illite （〉68%） is found in the southeastern offshore parts beyond the reach of terrigenous input from the Jeju Island. It means that these illites are largely transported by the Kuroshio Current from the South China Sea （SCS）. Smectite is highly concentrated in the northwest middle part and in the outer-shelf mud patch. It seems to be due to the high supply of smectite transported from China where fine-grained sediments are discharged from modern and ancient Huanghe （Yellow） River. The relatively high abundant kaolinite is likely derived from the Changjiang （Yangtze） River via the Taiwan Warm Current. In contrast, large amounts of chlorite and high chlorite/kaolinite ratios occur in the northwestern area, reflecting the transportation by the Yellow Sea Coastal Current from the southern Yellow Sea. The discrimination diagrams clearly show that the sediments in the northwestern East China Sea are ultimately sourced from Chinese rivers, especially from the Huanghe River, whereas the sediment in the northeast part might come from the Jeju Island. The muddy sediments of the Changjiang River＇s submerged delta have much lower 87Sr/S6Sr ratios （0.716 2-0.718 0） than those of the Shandong Peninsular mud wedge （0.721 6-0.724 9）, which are supposed to be originated from the Huanghe River, suggesting the distribution pattern of 87Sr/86Sr ratios as a new tracer to discriminate the provenance of shelf sediments in the study area. The 87Sr/86Sr ratios of the outer-shelf muddy sediments ranged from 0.7169 to 0.7216 in a wide range and was between those of the Huanghe River and Changjiang River sediments, suggesting multiple sources of the sediment in the area.展开更多
Four types of apatite have been identified in the Ningwu region. The first type of apatite is widely distributed in the middle dark colored zones （i.e. iron ores） of individual deposits. The assemblage includes magn...Four types of apatite have been identified in the Ningwu region. The first type of apatite is widely distributed in the middle dark colored zones （i.e. iron ores） of individual deposits. The assemblage includes magnetite, apatite and actinolite （or diopside）. The second type occurs within magnetite-apatite veins in the iron ores. The third type is seen in magnetite-apatite veins and （or） nodules in host rocks （i.e. gabbro-diorite porphyry or gabbro-diorite or pyroxene diorite）.The fourth type occurs within apatite-pyrite-quartz veins f＇dfing fractures in the Xiangshan Group. Rare earth elements （REE） geochemistry of apatite of the four occurrences in porphyry iron deposits is presented. The REE distribution patterns of apatite are generally similar to those of apatites in the Kiruna-type iron ores, nelsonites. They are enriched in fight REE, with pronounced negative Eu anomalies. The similarity of REE distribution patterns in apatites from various deposits in different locations in the world indicates a common process of formation for various ore types, e.g. immiscibility. Early magmatic apatites contain 3031.48-12080 ×10^-6 REE. Later hydrothermal apatite contains 1958 ×10^-6 REE, indicating that the later hydrothermal ore-forming solution contains lower REE. Although gabbro-diorite porphyry and apatite show similar REE patterns, gabbro-diorite porphyries have no europium anomalies or feeble positive or feeble negative europium anomalies, caused both by reduction environment of mantle source region and by fractionation and crystallization （immiscibility） under a high oxygen fugacity condition. Negative Eu anomalies of apatites were formed possibly due to acquisition of Eu^2＋ by earlier diopsite during ore magma cooling. The apatites in the Aoshan and Taishan iron deposits yield a narrow variation range of ^87Sr/^86Sr values from 0.7071 to 0.7073, similar to those of the volcanic and subvolcaulc rocks, indicating that apatites were formed by liquid immiscibility and differentiation of intermediate and basic magmas.展开更多
The Callovian-Oxfordian carbonate reservoirs are the most important hydrocarbon reservoir in the Samandepe gas field,Amu Darya basin,Turkmenistan.Based on the analysis of Fe,Mn and Sr trace elements,and carbon,oxygen ...The Callovian-Oxfordian carbonate reservoirs are the most important hydrocarbon reservoir in the Samandepe gas field,Amu Darya basin,Turkmenistan.Based on the analysis of Fe,Mn and Sr trace elements,and carbon,oxygen and strontium isotopes,the genesis and evolutionary characteristics of the carbonate reservoirs were studied,and the conclusions were follows：1） Sustained transgressive-regressive cycles played an important role during Callovian-Oxfordian.The reservoir of reef-bank facies was well developed in the period of transgression,while the regional dense cap rocks developed in the period of regression;2） The 87 Sr/86 Sr ratio measured from rudist shells yields an age of 157.2 Ma according to the global strontium isotope curve;3） As diagenetic intensity increased,δ 13 C changed little,and δ 18 O showed strong negative deviation but was still limited to the range of Late Jurassic seawater.High Fe and Sr contents,and low Mn content,and the evolutionary trend of δ 13 C and δ 18 O all indicate that diagenesis occurred in a relatively confined environment,where the fluids were relatively reducing and contained hot brine.The stage of diagenesis reached is mesodiagenesis,which is very favorable for preservation of primary pores in carbonates;4） Strong dissolution of reef limestones,burial dolomitization and hydrothermal calcite precipitation were all the results of the interaction between the 87 Sr-rich diagenetic fluid and rocks;5） The analysis results of isotopes,fluid inclusions and vitrinite reflectance show that the diagenetic fluid was compaction-released water that originated from the deep,coal-bearing clastic strata.展开更多
Petrogenesis of lacustrine dolostone is closely related with paleo-lake water conditions.Here we report the high spatial-resolution petrographic and geochemical results of a lacustrine dolomite nodule from the Qingsha...Petrogenesis of lacustrine dolostone is closely related with paleo-lake water conditions.Here we report the high spatial-resolution petrographic and geochemical results of a lacustrine dolomite nodule from the Qingshankou Formation,the Songliao Basin.Sedimentary and elemental signatures confirm the protogenetic origin of this nodule and its effectiveness in recording geochemical characteristics of paleo-lake water during dolomitization.The low Y/Ho ratios,middle rare earth element(MREE)enrichment and subtle positive Eu anomalies within the nodule indicate a fresh water source.However,the Sr isotope values in the core of the nodule(0.7076-0.7080)are close to contemporaneous seawater(0.7074),yet different from the modern river(0.7120)and the host black shale(0.7100).On the premise of excluding the influence of hydrothermal fluids,the significantly low strontium isotope values of the lacustrine dolomite might be caused by seawater interference during dolomitization.Our findings demonstrate that lacustrine dolomite within black shales is not only a faithful tracer of diagenetic water environment,but also a novel and easily identified mineralogical evidence for episodic seawater intrusion event(91 Ma)in the Songliao Basin,which supplements other paleontological and geochemical evidence.展开更多
Karst rocks from the Huanglong Formation exposed at the margin of the Eastern Sichuan Basin can be divided into four types：slightly corroded, moderately corroded porous, intensely corroded brecciated and intensely co...Karst rocks from the Huanglong Formation exposed at the margin of the Eastern Sichuan Basin can be divided into four types：slightly corroded, moderately corroded porous, intensely corroded brecciated and intensely corroded and replaced secondary calcic karstic rocks. The carbon, oxygen and strontium isotope compositions of the various karst rocks are analyzed systematically and compared to rocks without karst corrosion. The results indicate that（1） the Huanglong Formation in the eastern Sichuan Basin was a restricted bay supplied and controlled by freshwater in which mudmicrite and mud-dolomicrite exhibit low δ13C and δ18O values and high 87Sr/86 Sr ratios;（2） all types of karstic rocks in the paleokarst reservoirs of the Huanglong Formation in the research area are affected by atmospheric freshwater with the δ13C and δ18O values and 87Sr/86 Sr ratios in the original formation approaching those of atmospheric freshwater, which reflects ancient hydrological conditions, fluid properties, isotopic source and the fractionation effect;（3） the intensely corroded and replaced secondary limestone is affected by a variety of diagenetic fluids, often reflected by δ13C and δ18O values, while the 87Sr/86 Sr ratios exhibit the strong degree of the corrosion;（4） after comparing the 87Sr/86 Sr ratios of each type of karst rock, the diagenetic fluids are determined to be mainly atmospheric freshwater, and depending on the strength of corrosion, and the low 87Sr/86 Sr ratio fluids in the layer will participate in the karst process. The carbon, oxygen, and strontium isotopes of different karstic reservoirs can provide meaningful geochemical information for forecasting and evaluating the development and distribution rules of the Huanglong Formation at the margin of the eastern Sichuan Basin in time and space.展开更多
The karst groundwater of Cambrian limestone may become an important water source for industry and agriculture in the Pingdingshan area,and is also a potential threat to mining safety.Therefore,to find out the origin,f...The karst groundwater of Cambrian limestone may become an important water source for industry and agriculture in the Pingdingshan area,and is also a potential threat to mining safety.Therefore,to find out the origin,flow paths,and hydrogeochemical processes of karst groundwater beneath the Pingdingshan coalfield,a total of 16 water samples were collected.Our findings confirmed that the karst groundwater is mainly recharged by precipitation.The precipitation can directly supply the deep aquifer of the karst water system through the southwest limestone outcrops,and this area mostly includes the southern part of mines No.11,No.9,and the hidden outcrops in the southern part of mine No.2.What is more,the areas adjacent to the synclinal axis,including mines No.10,No.12,and No.8,may be the main discharge areas.A mixing model of^(87)Sr/^(86)Sr and Sr showed that in the southwest Pingdingshan coalfield,the proportion of precipitation decreased gradually from the recharge area to the discharge area,ranging from 89.1%to 17.1%.Besides,the northeast Pingdingshan coalfield is another recharge area for the whole karst system,thus,the infiltrating groundwater will indirectly supply the deep aquifer through Quaternary deposition near the mine No.13.Our research results can provide theoretical support for the prevention and control of groundwater disasters and the development and utilization of regional groundwater resources in the coalfield in Northern China.展开更多
The Erlitou site is located at Yanshi City,Henan Province.This site is a large settlement site of Erlitou culture,and it is dated to 3800-3500 a BP.Five kinds of domestic animals,i.e.,dogs,pigs,sheep,goats,and cattle ...The Erlitou site is located at Yanshi City,Henan Province.This site is a large settlement site of Erlitou culture,and it is dated to 3800-3500 a BP.Five kinds of domestic animals,i.e.,dogs,pigs,sheep,goats,and cattle were found from the site.In this paper,two problems have emerged in studies involving the estimation of local isotope levels and the distinction of migrants from locals.Tooth enamel samples from 17 domestic animals individuals were analyzed for strontium isotope ratio(87Sr/86Sr),by the thermal ionization mass spectrometry,including 10 pigs,5 sheep and 2 cattle.The results show that the mean 87Sr/86Sr ratios of 10 pigs enamel samples were 0.712078,Based on the local strontium isotopes ratio range determined by the mean 87Sr/86Sr ratios ±2 of 10 pig enamel samples(0.712256-0.711900),we found that five sheep and one cattle from the Erlitou site fell well outside the local strontium isotopes ratio range and were considered to be non-local.展开更多
^(87)Sr/^(86)Sr ratios of marine carbonate samples collected from a sedimentary section of the Late Cretaceous in the south of Tibet were measured.Based on the absence of cathodoluminescence and a very low Mn/Sr ratio...^(87)Sr/^(86)Sr ratios of marine carbonate samples collected from a sedimentary section of the Late Cretaceous in the south of Tibet were measured.Based on the absence of cathodoluminescence and a very low Mn/Sr ratio(average 0.06)of the samples,it is thought that they contain information on the original seawater strontium isotope composition.The strontium isotope evolution curve of the Late Cretaceous in Tibet we established here,is consistent with other coeval curves from Europe,North America and Antarctica,supports the notion that the strontium isotope composition of seawater is governed by global events,which provides a new approach for the inter-continental and inter-basinal correlations of Late Cretaceous in the area and is a complementarity for biostratigraphy.In addition,we attempt to determine the age of the boundaries for Campanian/Santonian and Maastrichtian/Campanian by ^(87)Sr/^(86)Sr ratios for Gamba section in southern Tibet.The two boundaries are located in the thickness of 217 m(83.5 Ma)and 291 m(71.3 Ma),respectively.展开更多
In the Ordovician, a carbonate platform system grading from the platformal interior eastwards to basin was developed in the Tazhong area of the Tarim Basin, and the study column is located in the place where the paleo...In the Ordovician, a carbonate platform system grading from the platformal interior eastwards to basin was developed in the Tazhong area of the Tarim Basin, and the study column is located in the place where the paleoslope occurred. The isotope compositions of the carbonates there are thus considered as having reflected those of simultaneous sea waters in view of its good connection with the open seas. The carbon and strontium isotope compositions of the Ordovician carbonates in the Tazhong area are analyzed, and their relationships to the sea-level fluctuations are discussed as well. Studies have revealed that the carbon isotope composition is related positively with the sea-level fluctuations, whereas an opposing situation occurs to the strontium isotope variation. Similar responses of carbon and strontium isotope compositions to the sea-level fluctuations are reported elsewhere in the world, suggesting that the Ordovician sea-level fluctuations of the Tarim Basin were of eustatic implication.展开更多
The Lopingian is one of the fastest rising periods of seawater strontium isotopic ratios （^87Sr/^86Sr） in earth history, and its mechanisms and increasing rates of the ^87Sr/^86Sr evolution were still disputed widel...The Lopingian is one of the fastest rising periods of seawater strontium isotopic ratios （^87Sr/^86Sr） in earth history, and its mechanisms and increasing rates of the ^87Sr/^86Sr evolution were still disputed widely. These disputations among researchers were caused mainly by timeframe selection （sections＇ thickness or data of radiometric ages）, and different stratigraphic boundaries and un-upmost dated ages. This paper examined published ^87Sr/^86Sr data of the Lopingian, and projected them on timescales based on evolutionary and age constrained conodonts fossils. ^87Sr/^86Sr evolution vs fossil constraining timescales was re-established in this period. This research suggests： （1） ^87Sr/^86Sr excursion projects on fossil zones can truly support ^87Sr/^86Sr evolutionary pattern in the period; （2） ^87Sr/^86Sr evolution provides a new approach for stratigraphic research of marine carbonate sections in lieu of biostratigraphic data; （3） ^87Sr/^86Sr stratigraphy works on marine carbonate sections of different sedimentation rates even between different basins; （4） the ^875r/^86Sr data and its shift was dependent on samples materials and chemical treatment methods; （5） the increasing rate of marine water ^875r/^86Sr in the Late Permian is suggested as 5.4× 10^-5/Ma or slightly lower; （6） sedimentation age and its ^875r/^86Sr of the Lopingian marine carbonate suggested as： Dpro=259-（Rs- 0.70695）/5.4×10^-5 （Ma）.展开更多
The Ediacaran to early Cambrian Blovice accretionary complex,Bohemian Massif,hosts abundant chert bodies that formed on an oceanic plate and were involved in subduction beneath the northern margin of Gondwana.Field re...The Ediacaran to early Cambrian Blovice accretionary complex,Bohemian Massif,hosts abundant chert bodies that formed on an oceanic plate and were involved in subduction beneath the northern margin of Gondwana.Field relationships of cherts to their host,their microstructure and elemental as well as isotopic compositions revealed diverse processes of chert petrogenesis reflecting depositional environment and position on the oceanic plate.The deep-water cherts formed through a hydrothermal precipitation of silica-rich gels on outer trench swell of the subducted slab with none or only minor addition of terrigenous material.On the contrary,the shallow-water cherts formed in lagoons on seamount slopes,and at least some of them represent a product of hydrothermal replacement of former carbonate and/or evaporite precursors.For both chert types,the hydrothermal fluids were of low temperature and continuous pervasive hydrothermal alteration of oceanic crust,together with an elevated Si content in Neoproterozoic seawater,served as the major source of silica.On the other hand,minor carbon enrichment in chert is mostly linked to variable incorporation of organic matter that was deposited on the seafloor.Rare earth element(REE)systematics of the cherts indicate predominantly oxygenated environment for the shallow-water cherts whereas the deep-water cherts were deposited in diverse redox conditions,depending on their distance from hydrothermal vent.Using these data,we demonstrate that the cherts once formed a part of Ocean Plate Stratigraphy(OPS)now dismembered and mixed with terrigenous siliciclastic material to form OPS mélanges.Combining our data with those from the existing literature,we show that cherts can serve as significant markers of OPS since the Archean,recording a complex interplay between seafloor-related volcanic(production of MORB-and OIB-like magmas)and sedimentary processes,hydrothermal activity at mid-ocean ridges and seamount chains as well as at outer slopes of subducting slabs.However,the cherts also exhibit a secular change in composition and petrogenesis most profoundly affected by an overturn in seawater silica cycle across the Precambrian-Phanerozoic boundary.展开更多
基金This study was supported by the National Natural Science Foundation of China Grant No.48970116
文摘238 marine carbonate samples were collected from seven sedimentary sections ofthe entire late Palaeozoic (Permian, Carboniferous and Devonian) in the Upper Yangtze Plat-form, southwest China. Based on the absence of cathodoluminescence and very low Mn (gener-ally<50 ppm) contents of the samples, it is thought that they contain information on the orig-inal sea water geochemistry. The results of isotopic analyses of these samples are presented interms of δ^(13)C and ^(87)Sr/^(86)Sr ratios versus geological time. The strontium data, consistent withother similar data based on samples from North America, Europe, Africa and other areas inAsia, support the notion of a global consistency in strontium isotope composition of marinecarbonates. The strontium data exhibit three intervals of relatively low ^(87)Sr/^(86)Sr ratios in thelate Middle Devonian to early Late Devonian, Early Carboniferous and Early Permian, corre-sponding to global eustatic high sea level stands. The lowest ^(87)Sr/^(86)Sr ratio recorded in theLate Permian was probably caused by substantial basalt eruptions in the Upper Yangtze Plat-form at the time. Three corresponding periods of relatively high δ^(13)C values at roughly the samethe intervals were caused by a relatively high rate of accumulation of organic carbon duringsea level rises at these times. The deposition of coal was probably responsible for the increaseof sea water δ^(13)C at other times. The δ^(13)C values drop dramatically near theDevonian/Carboniferous, Carboniferous/Permian and Permian/Triassic boundaries, con-sistent with other similar data, which further support the notion that geological time boundariesare associated with mass extinction and subsequent rejuvenation.
文摘Power-law patterns appear in a variety of natural systems on the modern Earth;nevertheless,whether such behaviors appeared in the deep-time environment has rarely been studied. Isotopic records in sedimentary rocks, which are widely used to reconstruct the geological/geochemical conditions in paleoenvironments and the evolutionary trajectories of biogeochemical cycles, offer an opportunity to investigate power laws in ancient geological systems. In this study, I focus on the Phanerozoic sedimentary records of carbon, oxygen, sulfur, and strontium isotopes, which have well documented and extraordinarily comprehensive datasets. I perform statistical analyses on these datasets and show that the variations in the sedimentary records of the four isotopes exhibit power-law behaviors. The exponents of these power laws range between 2.2 and 2.9;this narrow interval indicates that the variations in carbon, oxygen, sulfur, and strontium isotopes likely belong to the same universality class, suggesting that these systematic power-law patterns are governed by universal, scale-free mechanisms. I then derive a general form for these power laws from a minimalistic model based on basic physical principles and geosystem-specific assumptions, which provides an interpretation for the power-law patterns from the perspective of thermodynamics. The fundamental mechanisms regulating such patterns might have been ubiquitous in paleoenvironments, implying that similar power-law behaviors may exist in the sedimentary records of other isotopes.
基金financially supported by the National Key Research and Development Program(Grant No.2016YFC0601003)the scientific team foundation of Department of Geology,China Northwest Universitythe National Natural Science Foundation of China(Grant No.41172101)。
文摘The calibration of sedimentary rock absolute dates is one of the difficulties in sedimentological and stratigraphic research.Since strontium(Sr)resides in seawater much longer(≈10^(6) a)than the seawater intermixing time(≈10^(3) a),the Sr isotopic composition of global seawater is uniform at any time and results in a stable system throughout geological history,based on which a global Sr isotope composition dating database has been established for age-calibration of marine strata.The Permian stratigraphic sections in the northern part of the Upper Yangtze block,southern China,record continuous marine sediments with clear stratigraphic boundaries and is suitable for stratigraphic dating of Sr isotopes.Based on sampling and Sr isotopic compositions of Permian carbonate strata in the northern part of the Upper Yangtze,a Permian Sr isotope evolution curve was established.According to the basic principles of Sr isotope stratigraphy,the global Strontium isotope age database can be used to calibrate the Permian stratigraphic dates in the northern Upper Yangtze.The results show that the Sr isotope evolution curves for the marine carbonate rocks in the Permian stratigraphic section of the Upper Yangtze present a decreasing trend from the mid-Qixia stage(P_(2))to the mid-Wujiaping stage(P_(3)),and then rise from the middle Wujiaping stage to the end of Changxing stage(P_(3)).When the Permian Sr-isotope evolution curve is compared with the global Sr isotope evolution curve in the northern Upper Yangtze,the two are consistent in their long-term evolutionary trend,indicating that Permian global geological events are important controlling factors for the composition and evolution of Sr isotopes.The 87 Sr/86 Sr value decreased gradually in the background of large-scale regressions at the turn of middle to late Permian period,revealing that the Emeishan basalt eruption occurred near the Maokou/Wujiaping boundary(GLB).Srisotope stratigraphy dating was performed on the boundaries of the Qixia Formation/Maokou Formation,Maokou Formation/Wujiaping Formation(GLB),Wujiaping Formation/Changxing Formation(WCB)and the Permian/Triassic(PTB)using the Global Strontium Isotope Age Database.The results are 270.4 Ma,261.2 Ma,254.5 Ma and 249.7 Ma,respectively.Based on this,the eruption age of the Emeishan basalts is defined at about 261.2 Ma.,which is more coincident with that acquired from other previous dating methods on the eruption age of the Emeishan basalts,and therefore proves that the application of Sr isotopic stratigraphy to dating marine sedimentary units is an effective method.
基金supported by the National Natural Science Foundation of China(No:41072192)the Natural Science Foundation Project of Chongqing,CSTC(No.CSTC2010BC7004)+2 种基金the Special Fund for Public Benefit Scientific Research of Ministry of Land and Resources of China(201111022)the Guangxi Natural Science Foundation Project(2012GXNSFBA053137)IGCP/SIDA 598 Project
文摘Groundwater from karst subterranean streams is among the world's most important sources of drinking water supplies,and the hydrochemical characteristics of karst water are impacted by both natural environment and people.Therefore,the study of hydrochemistry and its solutes'sources is very important to ensure the normal function of life support systems.In this paper,thirty-five representative karst groundwater samples were collected from different aquifers(limestone and dolomite)and various land use types in Chongqing to trace the sources of solutes and relative hydrochemical processes.Hydrogeochemical types of karst groundwater in Chongqing were mainly of the Ca-HCO3 type or Ca(Mg)-HCO3 type.However,some hydrochemical types of karst groundwater were the K+Na+Ca-SO4 type(G25 site)or Ca-HCO3+SO4 type(G26 and G14 site),indicating that the hydrochemistry of these sites might be strongly influenced by anthropogenic activities or unique geological characteristics.The dissolved Sr concentrations of the studied groundwater ranged from 0.57 to 15.06~tmmol/L,and the STSr/S6Sr varied from 0.70751 to 0.71627.The j34S-SO42-fell into a range of-6.8%o-21.5%o,with a mean value of 5.6%o.The variations of both 87Sr/S6Sr and Sr values of the groundwater samples indicated that the Sr element was controlled by the weathering of limestone,dolomite and silicate rock.However,the figure of STSr/S6Sr vs.Sr2+/[K++Na+]showed that the anthropogenic inputs also obviously contributed to the Sr contents.For tracing the detailed anthropogenic effects,we traced the sources of solutes collected karst groundwater samples in Chongqing according to the j34S value of potential sulfate sources.The variations of both j34S and 1/SO42-values of the groundwater samples indicated that the atmospheric acid deposition(AAD),dissolution of gypsum(GD),oxidation of sulfide mineral(OS)or anthropogenic inputs(SF:sewage or fertilizer)have contributed to solutes in karst groundwater.The influence of oxidation of sulfide mineral,atmospheric acid deposit and anthropogenic inputs to groundwater in Chongqing karst areas was much widespread.
基金supported by grants by the National Natural Science Foundation of China (No.41272097)the China Geological Survey Project (No.12120114016601)+1 种基金the Special Fund for Basic Scientific Research of Central Colleges, China University of Geosciences (Wuhan) (No.CUG120702)the Teaching Laboratory Foundation of China University of Geosciences (Wuhan) (No.SKJ2013085,SKJ2014010)
文摘The Yunkai Area is located at the southern South China Block and is part of the Qinzhou Bay-Hangzhou Bay Metallogenic Belt, which is a famous polymetallic mineralization belt. The Xinhua Pb–Zn–(Ag)deposit is located in the western part of Yunkai Area, with an abundance of Pubei batholiths. Zircon U–Pb geochronology of Pubei batholiths shows that crystallization age ranges from 251.9 ± 2.2 to 244.3 ± 1.8 Ma, thus belonging to Indosinian orogeny. Geochemistry and Sr isotopic compositions of the Pubei batholiths show that it is derived from the partial melting of large scale crustal melting during the stage of exhumation and uplifting of the lower-middle crust. In addition, strontium isotope of sphalerite from the Xinhua Pb–Zn–(Ag) deposit, has limited ranges in ^(87)Rb/^(86)Sr and ^(87)Sr/^(86)Sr, ranging from 0.4077 to 1.0449, and 0.718720 to 0.725245, respectively. The initial ^(87)Sr/^(86)Sr ratios of sphalerite ranges between 0.718720 and 0.725245, which is higher than that of upper continental crust and lower than that of the Pubei batholiths, illustrating the fluid might be derived from the mixing of Pubei pluton and upper continental crust.
基金financially supported by the National Basic Research Program of China(No.2013CB429702)
文摘Hydrothermal barite is a typical low-temperature mineral formed during the mixing of hydrothermal fluid and seawater.Because of its extremely low solubility,barite behaves as a close system after crystallization and preserves the geochemical fingerprint of hydrothermal fluid.In this study,the elemental contents and Sr isotope compositions of hydrothermal barites from the Yonaguni IV were determined using electron microprobe and LA-MC-ICP-MS respectively.On these bases,the fluid/sediment interaction during the hydrothermal circulation and physicochemical condition of barite crystallization were discussed.Results show that the 87 Sr/86 Sr values of hydrothermal barites from the Yonaguni IV are apparently higher than those of the seawater and associated volcanic rocks,indicating the sufficient interaction between the hydrothermal fluid and overlying sediment.Monomineral Sr abundance shows large variations,reflecting the changes in barite growth rate during the fluid mixing.The mineralization condition in the Yonaguni IV was unstable.During the crystallization of barite,hydrothermal fluid and seawater mixed in varying degrees,with the pro-portions of hydrothermal fluid varied from 36%to 72%.The calculated crystallization temperatures range from 109 to 220℃.Sediment plays a critical role during the mineralization process in the Yonaguni IV and incorporation of sediment component into hydrothermal system was prior to barite crystallization and sulfide mineralization.
基金This paper is supported by the 973 Project of China ( No .2005CB422103) and by the China Petrochemical Corporation ( SI N-OPEC) .
文摘The research on the trace elements of Ordovician carbonates plays an important part in the whole work on reservoir in Tazhong （塔中 ） area. This paper systematically studies the characteristics and sedimentary settings of Ordovician dolomites in Tazhong area, Tarim basin, and debates their enrichment of mechanisms and different element existing patterns. The study makes use of ICP-MS analysis technology to test the strontium and manganese content of 109 samples from four wells in the Tazhong area, Tarim basin and strontium isotope composition tests have also been done on 25 samples from wells Zhong-1 and Zhong-4 on VG354 solid isotope mass spectrograph. By means of analyzing contents of strontium and manganese elements, doing research on the strontium isotope composition characteristics from wells Zhong-1 and Zhong-4 and comparing the results of strontium analysis to the global Ordovician marine carbonate and its evolution trend, in the combination of sedimentary facies characteristics of isolated wells in this area, we can come to the following cognitions： （1） The marine carbonate strontium isotope curve in the Tazhong area of Tarim basin is consistent to the global evolution trend which is overall descending with time, the direct reason of which is the evolution of paleogeographic environment. The Ordovician paleogeographic environment goes through restricted platform to open platform and then shallow marine shelf in Tazhong area, Tarim basin. Dolomitization is another subordinate reason and the inversion of fluid with high manganese can lead to heavy strontium; （2） The fact that the 87 Sr/86 Sr ratios of the Upper Ordovician in Tazhong area have an apparent mono-decline trend with the time going by, which is similar to the global strontium isotope ratio, is suggesting that the variation of the Upper Ordo- vician sea level is starting, the overall trend of which is the rising of the sea level; （3） Compared to the global seawater strontium ratios, the ^87Sr/^86 Sr ratio of the Lower Ordovician is much high, and ^87Sr/^86Sr ratio of the Lower Ordovician is overall increasing with its maximum value reaching 0. 709 727, the reasons of which are dolomitization, evaporation of the supratidal and the reflux of high manganese haline, those reasons can lead to the increasing amount of the strontium and the rising of the ^87 Sr/^86 Sr ratio; （4） The manganese element content changes little. Dolomitization has little impact on it; （5） Big variation occurs in the strontium values of Ordovician carbonate in the region of Tazhong. Apart from paleogeographic environment and petrography, the factors which can affect the values of strontium are the content of the terrestrial clastics and the diagenesis modification which may result in the further changing of the strontium values.
基金This study was supported by the National Natural Science Foundation of China(No.41302192)Natural Science Foundation of Hebei Province of China(No.D2018504011)+1 种基金China Geological Survey(No.DD20190555)the Ministry of land and resources of the People’s Republic of China(No.201411052).
文摘Hydrogeochemical processes that would occur in polluted groundwater and aquifer system,may reduce the sensitivity of Sr isotope being the indicator of hydraulic fracturing flowback fluids(HFFF)in groundwater.In this paper,the Dameigou shale gas field in the northern Qaidam Basin was taken as the study area,where the hydrogeochemical processes affecting Sr isotope was analysed.Then,the model for Sr isotope in HFFF-polluted groundwater was constructed to assess the sensitivity of Sr isotope as HFFF indicator.The results show that the dissolution can release little Sr to polluted groundwater and cannot affect the εSr(the deviation of the 87Sr/86Sr ratio)of polluted groundwater.In the meantime,cation exchange can considerably affect Sr composition in the polluted groundwater.The Sr with low εSr is constantly released to groundwater from the solid phase of aquifer media by cation exchange with pollution of Quaternary groundwater by the HFFF and it accounts for 4.6% and 11.0% of Sr in polluted groundwater when the HFFF flux reaches 10% and 30% of the polluted groundwater,respectively.However,the Sr from cation exchange has limited impact on Sr isotope in polluted groundwater.Addition of Sr from cation exchange would only cause a 0.2%and 1.2% decrease in εSr of the polluted groundwater when the HFFF flux reaches 10% and 30% of the polluted groundwater,respectively.These results demonstrate that hydrogeochemical processes have little effect on the sensitivity of Sr isotope being the HFFF indicator in groundwater of the study area.For the scenario of groundwater pollution by HFFF,when the HFFF accounts for 5%(in volume percentage)of the polluted groundwater,the HFFF can result in detectable shifts of εSr(Δ_(εSr)=0.86)in natural groundwater.Therefore,after consideration of hydrogeochemical processes occurred in aquifer with input of the HFFF,Sr isotope is still a sensitive indicator of the Quaternary groundwater pollution by the HFFF produced in the Dameigou shale of Qaidam Basin.
基金financially supported by the National Natural Science Foundation of China(92055208)Guangxi Natural Science Foundation for Distinguished Young Scholars(2018GXNSFFA281009)+3 种基金the CAS‘Light of West China’Program(2018-XBYJRC-003)the Guangxi Science Innovation Base Construction Foundation(Guike ZY21195031)the Fifth Bagui Scholar Innovation Project of the Guangxi Province(to Xu Jifeng)the grant of the Laboratory for Marine Geology,Qingdao National Laboratory for Marine Science and Technology(MGQNLM201901)。
文摘The global Hangenberg Crisis or Hangenberg Extinction is a mass extinction near the Devonian-Carboniferous boundary.Comprehensive research of petrology and geochemistry on the Devonian-Carboniferous boundary,as exposed in the Nanbiancun auxiliary stratotype section,South China,elucidates paleoenvironmental changes and controls on marine strontium(^(87)Sr/^(86)Sr)and carbonate carbon(δ^(13)C_(carb))isotopes during the Hangenberg Crisis.The new^(87)Sr/^(86)Sr data reveal a regression in the Middle Siphonodella praesulcata Zone,while the Hangenberg Extinction was occurring in South China.Moreover,theδ^(13)C_(carb)data records a negative excursion near the base of the Middle Siphonodella praesulcata Zone that may have been connected with the Hangenberg Extinction.A positiveδ^(13)C_(carb)excursion,corresponding with the Upper Siphonodella praesulcata Zone,may reflect the effects of a vigorous biological pump.The magnitude of the Hangenberg Carbon Isotopic Excursion in peakδ^(13)carb values andδ^(13)C_(carb)gradient in carbonate Devonian-Carboniferous boundary sections of the South China Craton during the Hangenberg Crisis,are a function of depositional water depth and distance from the shore.The carbon cycling during the Hangenberg Carbon Isotopic Excursion had a much stronger impact on oceanic surface waters than on the deep ocean and theδ^(13)C_(carb)gradient of local seawater was likely caused by enhanced marine productivity,associated with biological recovery in platform sediments during the Hangenberg Crisis.
基金This work was supported by the research grant of the Cheju National University of Year 2006.
文摘Clay minerals of 34 sediments collected from the northwestern continental shelf of the East China Sea have been determined by X-ray diffraction analysis. The clay mineral distribution is mainly controlled by the sediment source and the dominant circulation pattern. The predominant clay mineral in our study area is illite comprising more than 67% of the whole clay fraction. The highest concentration of illite （〉68%） is found in the southeastern offshore parts beyond the reach of terrigenous input from the Jeju Island. It means that these illites are largely transported by the Kuroshio Current from the South China Sea （SCS）. Smectite is highly concentrated in the northwest middle part and in the outer-shelf mud patch. It seems to be due to the high supply of smectite transported from China where fine-grained sediments are discharged from modern and ancient Huanghe （Yellow） River. The relatively high abundant kaolinite is likely derived from the Changjiang （Yangtze） River via the Taiwan Warm Current. In contrast, large amounts of chlorite and high chlorite/kaolinite ratios occur in the northwestern area, reflecting the transportation by the Yellow Sea Coastal Current from the southern Yellow Sea. The discrimination diagrams clearly show that the sediments in the northwestern East China Sea are ultimately sourced from Chinese rivers, especially from the Huanghe River, whereas the sediment in the northeast part might come from the Jeju Island. The muddy sediments of the Changjiang River＇s submerged delta have much lower 87Sr/S6Sr ratios （0.716 2-0.718 0） than those of the Shandong Peninsular mud wedge （0.721 6-0.724 9）, which are supposed to be originated from the Huanghe River, suggesting the distribution pattern of 87Sr/86Sr ratios as a new tracer to discriminate the provenance of shelf sediments in the study area. The 87Sr/86Sr ratios of the outer-shelf muddy sediments ranged from 0.7169 to 0.7216 in a wide range and was between those of the Huanghe River and Changjiang River sediments, suggesting multiple sources of the sediment in the area.
基金This paper is financially aided by the National Natural Science Foundation of China （Grant No. 40472055）.
文摘Four types of apatite have been identified in the Ningwu region. The first type of apatite is widely distributed in the middle dark colored zones （i.e. iron ores） of individual deposits. The assemblage includes magnetite, apatite and actinolite （or diopside）. The second type occurs within magnetite-apatite veins in the iron ores. The third type is seen in magnetite-apatite veins and （or） nodules in host rocks （i.e. gabbro-diorite porphyry or gabbro-diorite or pyroxene diorite）.The fourth type occurs within apatite-pyrite-quartz veins f＇dfing fractures in the Xiangshan Group. Rare earth elements （REE） geochemistry of apatite of the four occurrences in porphyry iron deposits is presented. The REE distribution patterns of apatite are generally similar to those of apatites in the Kiruna-type iron ores, nelsonites. They are enriched in fight REE, with pronounced negative Eu anomalies. The similarity of REE distribution patterns in apatites from various deposits in different locations in the world indicates a common process of formation for various ore types, e.g. immiscibility. Early magmatic apatites contain 3031.48-12080 ×10^-6 REE. Later hydrothermal apatite contains 1958 ×10^-6 REE, indicating that the later hydrothermal ore-forming solution contains lower REE. Although gabbro-diorite porphyry and apatite show similar REE patterns, gabbro-diorite porphyries have no europium anomalies or feeble positive or feeble negative europium anomalies, caused both by reduction environment of mantle source region and by fractionation and crystallization （immiscibility） under a high oxygen fugacity condition. Negative Eu anomalies of apatites were formed possibly due to acquisition of Eu^2＋ by earlier diopsite during ore magma cooling. The apatites in the Aoshan and Taishan iron deposits yield a narrow variation range of ^87Sr/^86Sr values from 0.7071 to 0.7073, similar to those of the volcanic and subvolcaulc rocks, indicating that apatites were formed by liquid immiscibility and differentiation of intermediate and basic magmas.
文摘The Callovian-Oxfordian carbonate reservoirs are the most important hydrocarbon reservoir in the Samandepe gas field,Amu Darya basin,Turkmenistan.Based on the analysis of Fe,Mn and Sr trace elements,and carbon,oxygen and strontium isotopes,the genesis and evolutionary characteristics of the carbonate reservoirs were studied,and the conclusions were follows：1） Sustained transgressive-regressive cycles played an important role during Callovian-Oxfordian.The reservoir of reef-bank facies was well developed in the period of transgression,while the regional dense cap rocks developed in the period of regression;2） The 87 Sr/86 Sr ratio measured from rudist shells yields an age of 157.2 Ma according to the global strontium isotope curve;3） As diagenetic intensity increased,δ 13 C changed little,and δ 18 O showed strong negative deviation but was still limited to the range of Late Jurassic seawater.High Fe and Sr contents,and low Mn content,and the evolutionary trend of δ 13 C and δ 18 O all indicate that diagenesis occurred in a relatively confined environment,where the fluids were relatively reducing and contained hot brine.The stage of diagenesis reached is mesodiagenesis,which is very favorable for preservation of primary pores in carbonates;4） Strong dissolution of reef limestones,burial dolomitization and hydrothermal calcite precipitation were all the results of the interaction between the 87 Sr-rich diagenetic fluid and rocks;5） The analysis results of isotopes,fluid inclusions and vitrinite reflectance show that the diagenetic fluid was compaction-released water that originated from the deep,coal-bearing clastic strata.
基金supported by Project of Basic Science Center of National Natural Science Foundation of China(72088101)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA14010101)+3 种基金National Key Research and Development Program of China(2017YFC0603101)National Natural Science Foundation of China(41872125,42002158)Scientific and Technological Project of RIPED(2021ycq01)the subject development project of RIPED(yjkt2019-3).
文摘Petrogenesis of lacustrine dolostone is closely related with paleo-lake water conditions.Here we report the high spatial-resolution petrographic and geochemical results of a lacustrine dolomite nodule from the Qingshankou Formation,the Songliao Basin.Sedimentary and elemental signatures confirm the protogenetic origin of this nodule and its effectiveness in recording geochemical characteristics of paleo-lake water during dolomitization.The low Y/Ho ratios,middle rare earth element(MREE)enrichment and subtle positive Eu anomalies within the nodule indicate a fresh water source.However,the Sr isotope values in the core of the nodule(0.7076-0.7080)are close to contemporaneous seawater(0.7074),yet different from the modern river(0.7120)and the host black shale(0.7100).On the premise of excluding the influence of hydrothermal fluids,the significantly low strontium isotope values of the lacustrine dolomite might be caused by seawater interference during dolomitization.Our findings demonstrate that lacustrine dolomite within black shales is not only a faithful tracer of diagenetic water environment,but also a novel and easily identified mineralogical evidence for episodic seawater intrusion event(91 Ma)in the Songliao Basin,which supplements other paleontological and geochemical evidence.
基金supported by the National Major Science of China (Grant NO. 2011ZX05030-003-002)Natural Science key project of Education Department in Sichuan (NO.13ZA0058)
文摘Karst rocks from the Huanglong Formation exposed at the margin of the Eastern Sichuan Basin can be divided into four types：slightly corroded, moderately corroded porous, intensely corroded brecciated and intensely corroded and replaced secondary calcic karstic rocks. The carbon, oxygen and strontium isotope compositions of the various karst rocks are analyzed systematically and compared to rocks without karst corrosion. The results indicate that（1） the Huanglong Formation in the eastern Sichuan Basin was a restricted bay supplied and controlled by freshwater in which mudmicrite and mud-dolomicrite exhibit low δ13C and δ18O values and high 87Sr/86 Sr ratios;（2） all types of karstic rocks in the paleokarst reservoirs of the Huanglong Formation in the research area are affected by atmospheric freshwater with the δ13C and δ18O values and 87Sr/86 Sr ratios in the original formation approaching those of atmospheric freshwater, which reflects ancient hydrological conditions, fluid properties, isotopic source and the fractionation effect;（3） the intensely corroded and replaced secondary limestone is affected by a variety of diagenetic fluids, often reflected by δ13C and δ18O values, while the 87Sr/86 Sr ratios exhibit the strong degree of the corrosion;（4） after comparing the 87Sr/86 Sr ratios of each type of karst rock, the diagenetic fluids are determined to be mainly atmospheric freshwater, and depending on the strength of corrosion, and the low 87Sr/86 Sr ratio fluids in the layer will participate in the karst process. The carbon, oxygen, and strontium isotopes of different karstic reservoirs can provide meaningful geochemical information for forecasting and evaluating the development and distribution rules of the Huanglong Formation at the margin of the eastern Sichuan Basin in time and space.
基金granted by the National Natural Science Foundation of China(42102297,41972254)Innovative Science and Technology Talents Team Construction Project of Henan Province(CXTD2016053)+2 种基金China Postdoctoral Science Foundation(2021M701098)Special Funds for Higher Education Basic Scientific Research Funds of Henan Province(NSFRF200103NSFRF210304)。
文摘The karst groundwater of Cambrian limestone may become an important water source for industry and agriculture in the Pingdingshan area,and is also a potential threat to mining safety.Therefore,to find out the origin,flow paths,and hydrogeochemical processes of karst groundwater beneath the Pingdingshan coalfield,a total of 16 water samples were collected.Our findings confirmed that the karst groundwater is mainly recharged by precipitation.The precipitation can directly supply the deep aquifer of the karst water system through the southwest limestone outcrops,and this area mostly includes the southern part of mines No.11,No.9,and the hidden outcrops in the southern part of mine No.2.What is more,the areas adjacent to the synclinal axis,including mines No.10,No.12,and No.8,may be the main discharge areas.A mixing model of^(87)Sr/^(86)Sr and Sr showed that in the southwest Pingdingshan coalfield,the proportion of precipitation decreased gradually from the recharge area to the discharge area,ranging from 89.1%to 17.1%.Besides,the northeast Pingdingshan coalfield is another recharge area for the whole karst system,thus,the infiltrating groundwater will indirectly supply the deep aquifer through Quaternary deposition near the mine No.13.Our research results can provide theoretical support for the prevention and control of groundwater disasters and the development and utilization of regional groundwater resources in the coalfield in Northern China.
基金supported by National Science and Tech-nology Program of China (Grant No.2006BAK21B03)
文摘The Erlitou site is located at Yanshi City,Henan Province.This site is a large settlement site of Erlitou culture,and it is dated to 3800-3500 a BP.Five kinds of domestic animals,i.e.,dogs,pigs,sheep,goats,and cattle were found from the site.In this paper,two problems have emerged in studies involving the estimation of local isotope levels and the distinction of migrants from locals.Tooth enamel samples from 17 domestic animals individuals were analyzed for strontium isotope ratio(87Sr/86Sr),by the thermal ionization mass spectrometry,including 10 pigs,5 sheep and 2 cattle.The results show that the mean 87Sr/86Sr ratios of 10 pigs enamel samples were 0.712078,Based on the local strontium isotopes ratio range determined by the mean 87Sr/86Sr ratios ±2 of 10 pig enamel samples(0.712256-0.711900),we found that five sheep and one cattle from the Erlitou site fell well outside the local strontium isotopes ratio range and were considered to be non-local.
基金supported by the National Natural Science Foundation of China(Grant No.40272059)the Preresearch Project of the National Basic Research Priorities Prugram(Grant No.2001CCA01800)
文摘^(87)Sr/^(86)Sr ratios of marine carbonate samples collected from a sedimentary section of the Late Cretaceous in the south of Tibet were measured.Based on the absence of cathodoluminescence and a very low Mn/Sr ratio(average 0.06)of the samples,it is thought that they contain information on the original seawater strontium isotope composition.The strontium isotope evolution curve of the Late Cretaceous in Tibet we established here,is consistent with other coeval curves from Europe,North America and Antarctica,supports the notion that the strontium isotope composition of seawater is governed by global events,which provides a new approach for the inter-continental and inter-basinal correlations of Late Cretaceous in the area and is a complementarity for biostratigraphy.In addition,we attempt to determine the age of the boundaries for Campanian/Santonian and Maastrichtian/Campanian by ^(87)Sr/^(86)Sr ratios for Gamba section in southern Tibet.The two boundaries are located in the thickness of 217 m(83.5 Ma)and 291 m(71.3 Ma),respectively.
基金the National Natural Science Foundation of China (Grant No. 49872042).
文摘In the Ordovician, a carbonate platform system grading from the platformal interior eastwards to basin was developed in the Tazhong area of the Tarim Basin, and the study column is located in the place where the paleoslope occurred. The isotope compositions of the carbonates there are thus considered as having reflected those of simultaneous sea waters in view of its good connection with the open seas. The carbon and strontium isotope compositions of the Ordovician carbonates in the Tazhong area are analyzed, and their relationships to the sea-level fluctuations are discussed as well. Studies have revealed that the carbon isotope composition is related positively with the sea-level fluctuations, whereas an opposing situation occurs to the strontium isotope variation. Similar responses of carbon and strontium isotope compositions to the sea-level fluctuations are reported elsewhere in the world, suggesting that the Ordovician sea-level fluctuations of the Tarim Basin were of eustatic implication.
基金This research was supported by National Basic Research Program of China （Grant No. 2011CB808905）, National Natural Science Foundation of China （Grant Nos. 41227801, 41273004, and 412003028）, Knowledge Innovation Program of the Chinese Academy of Sciences （Grant No. KZCW2-YW-Q08-4） and Instrument Developing Project of the Chinese Academy of Sciences （Grant No. YZ201433）. We thank anonymous reviewers for their generous helps to improve the manuscript, and also appreciate members of experimental paleontology research group for their stimulating discussions and constructive suggestions.
文摘The Lopingian is one of the fastest rising periods of seawater strontium isotopic ratios （^87Sr/^86Sr） in earth history, and its mechanisms and increasing rates of the ^87Sr/^86Sr evolution were still disputed widely. These disputations among researchers were caused mainly by timeframe selection （sections＇ thickness or data of radiometric ages）, and different stratigraphic boundaries and un-upmost dated ages. This paper examined published ^87Sr/^86Sr data of the Lopingian, and projected them on timescales based on evolutionary and age constrained conodonts fossils. ^87Sr/^86Sr evolution vs fossil constraining timescales was re-established in this period. This research suggests： （1） ^87Sr/^86Sr excursion projects on fossil zones can truly support ^87Sr/^86Sr evolutionary pattern in the period; （2） ^87Sr/^86Sr evolution provides a new approach for stratigraphic research of marine carbonate sections in lieu of biostratigraphic data; （3） ^87Sr/^86Sr stratigraphy works on marine carbonate sections of different sedimentation rates even between different basins; （4） the ^875r/^86Sr data and its shift was dependent on samples materials and chemical treatment methods; （5） the increasing rate of marine water ^875r/^86Sr in the Late Permian is suggested as 5.4× 10^-5/Ma or slightly lower; （6） sedimentation age and its ^875r/^86Sr of the Lopingian marine carbonate suggested as： Dpro=259-（Rs- 0.70695）/5.4×10^-5 （Ma）.
基金the Czech Science Foundation through project no.20-13644S(to Lukas Ackerman)The Scientific Program RV067985831 of the Institute of Geology of the Czech Academy of Sciences+3 种基金Charles University through Cooperation Programme(Research Area GEOL)Center for Geosphere Dynamics(UNCE/SCI/006)Operational Programme Prague-Competitiveness(Project CZ.2.16/3.1.00/21516)Strategic Research Plan of the Czech Geological Survey(DKRV02018-2022)
文摘The Ediacaran to early Cambrian Blovice accretionary complex,Bohemian Massif,hosts abundant chert bodies that formed on an oceanic plate and were involved in subduction beneath the northern margin of Gondwana.Field relationships of cherts to their host,their microstructure and elemental as well as isotopic compositions revealed diverse processes of chert petrogenesis reflecting depositional environment and position on the oceanic plate.The deep-water cherts formed through a hydrothermal precipitation of silica-rich gels on outer trench swell of the subducted slab with none or only minor addition of terrigenous material.On the contrary,the shallow-water cherts formed in lagoons on seamount slopes,and at least some of them represent a product of hydrothermal replacement of former carbonate and/or evaporite precursors.For both chert types,the hydrothermal fluids were of low temperature and continuous pervasive hydrothermal alteration of oceanic crust,together with an elevated Si content in Neoproterozoic seawater,served as the major source of silica.On the other hand,minor carbon enrichment in chert is mostly linked to variable incorporation of organic matter that was deposited on the seafloor.Rare earth element(REE)systematics of the cherts indicate predominantly oxygenated environment for the shallow-water cherts whereas the deep-water cherts were deposited in diverse redox conditions,depending on their distance from hydrothermal vent.Using these data,we demonstrate that the cherts once formed a part of Ocean Plate Stratigraphy(OPS)now dismembered and mixed with terrigenous siliciclastic material to form OPS mélanges.Combining our data with those from the existing literature,we show that cherts can serve as significant markers of OPS since the Archean,recording a complex interplay between seafloor-related volcanic(production of MORB-and OIB-like magmas)and sedimentary processes,hydrothermal activity at mid-ocean ridges and seamount chains as well as at outer slopes of subducting slabs.However,the cherts also exhibit a secular change in composition and petrogenesis most profoundly affected by an overturn in seawater silica cycle across the Precambrian-Phanerozoic boundary.
