期刊文献+
共找到17,252篇文章
< 1 2 250 >
每页显示 20 50 100
碳、氮稳定同位素在构建海洋食物网及生态系统群落结构中的研究进展 预览
1
作者 张硕 高世科 +1 位作者 于雯雯 李士虎 《水产养殖》 CAS 2019年第7期6-10,共5页
该文综述了碳、氮稳定同位素在海洋生态系统中的最新研究进展及应用,着重讨论了海洋食物网中不同层级消费者的营养级时空变化及食性特征,为海域生态系统及其动态关系提供了重要手段,也为现代同位素全球生物化学提供理论基础。
关键词 碳稳定同位素 氮稳定同位素 海洋营养生态学 营养结构
在线阅读 下载PDF
河南省西峡县水地沟金矿地质特征及S、Pb同位素示踪 预览
2
作者 马玉见 梁涛 +1 位作者 卢仁 谢小芳 《地质与勘探》 CAS CSCD 北大核心 2019年第2期472-483,共12页
水地沟金矿是河南省北秦岭高庄-二郎坪金多金属矿成矿带内新发现的金矿,为探讨其成矿物质来源及成矿物质释放机制,对水地沟金矿矿石进行了S、Pb同位素分析。4件黄铁矿样品的δ34S值介于0. 5‰~4. 5‰,平均值为2. 5‰,具有塔式分布特征,... 水地沟金矿是河南省北秦岭高庄-二郎坪金多金属矿成矿带内新发现的金矿,为探讨其成矿物质来源及成矿物质释放机制,对水地沟金矿矿石进行了S、Pb同位素分析。4件黄铁矿样品的δ34S值介于0. 5‰~4. 5‰,平均值为2. 5‰,具有塔式分布特征,峰值在2‰~4‰之间,显示幔源硫特征。7件样品的206Pb/204Pb、207Pb/204Pb和208Pb/204Pb的比值范围分别为15. 80~18. 32、15. 11~15. 68和35. 17~38. 39,它们的μ值、△α值、Δβ值和Δγ值的范围依次为8. 97~9. 85、32. 93~74. 31、-1. 98~30. 64和4. 10~50. 61。在206Pb/204Pb-207Pb/204Pb比值图解中,水地沟金矿样品点位于下地壳铅演化趋势线和上地壳铅演化趋势线之间,在206Pb/204Pb-208Pb/204Pb比值图解中,它们集中于上地幔和造山带铅演化趋势线两侧,铅同位素Δβ-Δγ图解表明它们位于地幔Pb、上地壳Pb和上地壳与地幔混合的俯冲带Pb三个源区内。S、Pb同位素特征表明水地沟金矿成矿物质来源于上地幔-下地壳,成矿过程中有上地壳物质加入。水地沟金矿床的形成与北秦岭燕山期陆内(板内)造山过程密切相关,它是区域岩石圈拆沉作用的产物。在这一区域岩石圈灾变过程中,不仅使水地沟岩石圈-软流圈系统内不同源区的流体混合,造成了"宽泛"的S、Pb同位素示踪结果,而且有利于深部流体的大规模快速释放,说明水地沟金矿及其邻区具有大的成矿潜力。 展开更多
关键词 水地沟金矿 西峡县 S同位素 PB同位素 岩石圈拆沉 成矿潜力 北秦岭 河南省
在线阅读 下载PDF
Interplay of S and As in Mekong Delta sediments during redox oscillations 预览
3
作者 Van T.H. Phan Fabrizio Bardelli +5 位作者 Pierre Le Pape Raoul-Marie Couture Alejandro Fernandez-Martinez Delphine Tisserand Rizlan Bernier-Latmani Laurent Charlet 《地学前缘:英文版》 CAS CSCD 2019年第5期1715-1729,共15页
The cumulative effects of periodic redox cycling on the mobility of As,Fe,and S from alluvial sediment to groundwater were investigated in bioreactor experiments.Two particular sediments from the alluvial floodplain o... The cumulative effects of periodic redox cycling on the mobility of As,Fe,and S from alluvial sediment to groundwater were investigated in bioreactor experiments.Two particular sediments from the alluvial floodplain of the Mekong Delta River were investigated: Matrix A (14 m deep) had a higher pyrite concentration than matrix B (7 m deep) sediments.Gypsumwas present in matrix B but absent in matrix A.In the reactors,the sediment suspensions were supplemented with As(III) and SO4^2-,and were subjected to three full-redox cycles entailing phases of nitrogen/CO2,compressed air sparging,and cellobiose addition.Major differences in As concentration and speciation were observed upon redox cycling.Evidences support the fact that initial sediment composition is the main factor controlling arsenic release and its speciation during the redox cycles.Indeed,a high pyrite content associated with a low SO4^2- content resulted in an increase in dissolved As concentrations,mainly in the form of As(III),after anoxic half-cycles;whereas a decrease in As concentrations mainly in the form of As(V),was instead observed after oxic half-cycles.In addition,oxic conditions were found to be responsible for pyrite and arsenian pyrite oxidation,increasing the As pool available for mobilization.The same processes seem to occur in sediment with the presence of gypsum,but,in this case,dissolved As were sequestered by biotic or abiotic redox reactions occurring in the FeeS system,and by specific physico-chemical condition (e.g.pH).The contrasting results obtained for two sediments sampled from the same core show that many complexes and entangled factors are at work,and further refinement is needed to explain the spatial and temporal variability of As release to groundwater of the Mekong River Delta (Vietnam). 展开更多
关键词 Redox oscillation PYRITE oxidation GYPSUM DISSOLUTION ISOTOPE sulfur ISOTOPE oxygen
在线阅读 下载PDF
同位素电磁分离器离子源控制系统的研制 预览
4
作者 米亚静 曾自强 +2 位作者 任秀艳 屠锐 吴灵美 《计算机测量与控制》 2019年第8期85-88,103,共5页
同位素电磁分离器EMIS-170是我国唯一一台大型同位素电磁分离器;同位素电磁分离器计算机控制系统主要利用西门子TIA博途软件进行开发,用于监测同位素电磁分离器整个工艺系统和设备的运行参数和状态;离子源系统是同位素电磁分离器一个重... 同位素电磁分离器EMIS-170是我国唯一一台大型同位素电磁分离器;同位素电磁分离器计算机控制系统主要利用西门子TIA博途软件进行开发,用于监测同位素电磁分离器整个工艺系统和设备的运行参数和状态;离子源系统是同位素电磁分离器一个重要系统,利用计算机控制离子源的分离参数,实现对离子源分离参数的控制,并提供必要的连锁保护功能,防止操作员的误操作,根据模拟信号、开关量监测显示报警状态,提高了分离器重要电参数的调节精度,有效提高了同位素产品的丰度。文章介绍了同位素电磁分离器离子源控制系统的设计与实施,该系统已投入使用,工作稳定可靠。 展开更多
关键词 计算机 控制系统 同位素电磁分离器 博途 PLC
在线阅读 下载PDF
Genetic type and source of natural gas in the southern margin of Junggar Basin, NW China 预览
5
作者 CHEN Jianping WANG Xulong +4 位作者 NI Yunyan XIANG Baoli LIAO Fengrong LIAO Jiande ZHAO Changyi 《石油勘探与开发:英文版》 2019年第3期482-495,共14页
Natural gas has been discovered in many anticlines in the southern margin of the Junggar Basin. However, the geochemical characteristics of natural gas in different anticlines haven’t been compared systematically, pa... Natural gas has been discovered in many anticlines in the southern margin of the Junggar Basin. However, the geochemical characteristics of natural gas in different anticlines haven’t been compared systematically, particularly, the type and source of natural gas discovered recently in Well Gaotan-1 at the Gaoquan anticline remain unclear. The gas composition characteristics and carbon and hydrogen isotope compositions in different anticlines were compared and sorted systematically to identify genetic types and source of the natural gas. The results show that most of the gas samples are wet gas, and a few are dry gas;the gas samples from the western and middle parts have relatively heavier carbon isotope composition and lighter hydrogen isotope composition, while the gas samples from the eastern part of southern basin have lighter carbon and hydrogen isotope compositions. The natural gas in the southern margin is thermogenic gas generated by freshwater-brackish water sedimentary organic matter, which can be divided into three types, coal-derived gas, mixed gas and oil-associated gas, in which coal-derived gas and mixed gas take dominance. The Jurassic coal measures is the main natural gas source rock in the southern margin, and the Permian lacustrine and the Upper Triassic lacustrine-limnetic facies source rocks are also important natural gas source rocks. The natural gas in the western part of the southern margin is derived from the Jurassic coal measures and the Permian lacustrine source rock, while the natural gas in the middle part of the southern margin is mainly derived from the Jurassic coal measures, partly from the Permian and/or the Upper Triassic source rocks, and the natural gas in the eastern part of the southern margin is originated from the Permian lacustrine source rock. The natural gas in the Qingshuihe oil and gas reservoir of Well Gaotan-1 is a mixture of coal-derived gas and oil-associated gas, of which the Jurassic and Permian source rocks contribute about half each. 展开更多
关键词 southern JUNGGAR Basin NATURAL GAS hydrogen ISOTOPE carbon ISOTOPE NATURAL GAS genetic type GAS SOURCE identification JURASSIC coal measures
在线阅读 免费下载
Triple oxygen isotope constraints on the origin of ocean island basalts
6
作者 Xiaobin Cao Huiming Bao +4 位作者 Caihong Gao Yun Liu Fang Huang Yongbo Peng Yining Zhang 《中国地球化学学报:英文版》 EI CAS CSCD 2019年第3期327-334,共8页
Understanding the origin of ocean island basalts(OIB) has important bearings on Earth’s deep mantle.Although it is widely accepted that subducted oceanic crust, as a consequence of plate tectonics, contributes materi... Understanding the origin of ocean island basalts(OIB) has important bearings on Earth’s deep mantle.Although it is widely accepted that subducted oceanic crust, as a consequence of plate tectonics, contributes material to OIB’s formation, its exact fraction in OIB’s mantle source remains ambiguous largely due to uncertainties associated with existing geochemical proxies. Here we show, through theoretical calculation, that unlike many known proxies, triple oxygen isotope compositions(i.e.△^17 O) in olivine samples are not affected by crystallization and partial melting. This unique feature, therefore, allows olivine △^17 O values to identify subducted oceanic crusts in OIB’s mantle source. Furthermore, the fractions of subducted ocean sediments and hydrothermally altered oceanic crust in OIB’s mantle source can be quantified using their characteristic △^17 O values. Based on published △^17 O data, we estimated the fraction of subducted oceanic crust to be as high as 22.3% in certain OIB, but the affected region in the respective mantle plume is likely to be limited. 展开更多
关键词 TRIPLE oxygen ISOTOPE Helium ISOTOPE Ocean island BASALTS MANTLE PLUME MANTLE heterogeneity Crustal recycling
Stable carbon and hydrogen isotopic characteristics of natural gas from Taibei sag, Turpan-Hami Basin, NW China 预览
7
作者 NI Yunyan LIAO Fengrong +3 位作者 GONG Deyu JIAO Lixin GAO Jinliang YAO Limiao 《石油勘探与开发:英文版》 2019年第3期531-542,共12页
Turpan-Hami Basin is a major petroliferous basin in China. To date the natural gas exploration is concentrated in the Taibei sag. The origin and source of natural gas in the Taibei sag has long been controversial. To ... Turpan-Hami Basin is a major petroliferous basin in China. To date the natural gas exploration is concentrated in the Taibei sag. The origin and source of natural gas in the Taibei sag has long been controversial. To further investigate the origin and source of the natural gas in the Taibei sag, combined with previous studies and the local geological backgrounds, this study collected 23 gas samples from the Baka, Qiuling, Shanshan and Wenmi oil fields in the Taibei sag and analyzed the sample composition, stable carbon and hydrogen isotopes of all the gas samples. The results show that, gases from the four oil fields in the Taibei sag are dominated by hydrocarbon gas and belong to wet gas. Methane accounts for 65.84% to 97.94%, the content of heavy hydrocarbon (C2-5) can be up to 34.98%, while the content of nonhydrocarbon (CO2, N2) is trace. The δ13C1 value is –44.9‰ to –40.4‰,δ13C2 is –28.2‰ to –24.9‰,δ13C3 is –27.1‰ to –18.0‰ and δ13C4 is –26.7‰ to –22.1;while the variation of δD1 is not significant from –272‰ to –252‰,δD2 is –236‰ to –200‰ and δD3 is –222‰ to –174‰. Methane and its homologues (C2-5) are characterized by normal stable carbon and hydrogen isotopic distribution pattern, i.e., with the increase of carbon number, methane and its homologues become more and more enriched in 13C or D (δ13C1<δ13C2<δ13C3<δ13C4<δ13C5,δD1<δD2<δD3), which is consistent with the carbon and hydrogen isotopic features of typical thermogenic gas. All these results show that the natural gases in the four oil fields are coal-derived gas with low maturity (Ro averaged at 0.7%), and are sourced from the Middle-Lower Jurassic coal measure. The hydrogen isotopic data of natural gas are affected by both thermal maturity and the water medium of the environment where source rocks are formed. The hydrogen isotopic data indicate that the source rocks are formed in terrestrial limnetic facies with freshwater. Natural gases from Well Ba23 and Well Ke19 experienced biodeg 展开更多
关键词 Turpan-Hami Basin Taibei SAG Jurassic carbon ISOTOPE HYDROGEN ISOTOPE coal-derived GAS low MATURE GAS
在线阅读 免费下载
First-principles investigation of the concentration effect on equilibrium fractionation of Ca isotopes in forsterite
8
作者 Yahui Song Yonghui Li +1 位作者 Wenzhong Wang Zhongqing Wu 《中国地球化学学报:英文版》 EI CAS CSCD 2019年第4期497-507,共11页
Previous theoretical studies have found that the concentration variations within a certain range have a prominent effect on inter-mineral equilibrium isotope fractionation(10^3 lna).Based on the density functional the... Previous theoretical studies have found that the concentration variations within a certain range have a prominent effect on inter-mineral equilibrium isotope fractionation(10^3 lna).Based on the density functional theory,we investigated how the average Ca–O bond length and the reduced partition function ratios(10^3 lnb)and103lna of 44 Ca/40 Ca in forsterite(Fo)are affected by its Ca concentration.Our results show that Ca–O bond length in forsterite ranges from 2.327 to 2.267 A with the Ca/(Ca+Mg)varying between a narrow range limited by an upper limit of 1/8 and a lower limit of 1/64.However,outside this narrow range,i.e.,Ca/(Ca+Mg)is lower than1/64 or higher than 1/8,Ca–O bond length becomes insensitive to Ca concentration and maintains to be a constant.Because the 10^3 lnb is negatively correlated with Ca–O bond length,the 10^3lnb significantly increases with decreasing Ca/(Ca+Mg)when 1/64<Ca/(Ca+Mg)<2/16.As a consequence,the 10^3lna between forsterite and other minerals also strongly depend on the Ca content in forsterite.Combining previous studies with our results,the heavier Ca isotopes enrichment sequence in minerals is:forsterite[orthopyroxene[clinopyroxene[calcite & diopside[dolomite[aragonite.Olivineand pyroxenes are enriched in heavier Ca isotope compared to carbonates.The 10^3lna between forsterite with a Ca/(Ca+Mg)of 1/64 and clinopyroxene(Ca/Mg=1/1,i.e.,diopside)is up to~0.64%at 1200 K.The large 103lnaFodiopsiderelative to the current analytical precision for Ca isotope measurements suggests that the dependence of10^3 lnaFo-diopsideon temperature can be used as a thermometer,similar to the one based on the 103lna of 44 Ca/40 Ca between orthopyroxene and diopside.These two Ca isotope thermometers both have a precision approximate to that of elemental thermometers and provide independent constraints on temperature. 展开更多
关键词 Ca ISOTOPE FIRST-PRINCIPLES CALCULATIONS FORSTERITE Concentration effect EQUILIBRIUM ISOTOPE FRACTIONATION
罗溪温泉水文地球化学特征及热水来源 预览
9
作者 李鹭 孙占学 +1 位作者 陈功新 张智超 《中国矿业》 北大核心 2019年第1期164-169,共6页
本文选取江西省罗溪温泉为研究对象,综合应用地质、水化学和同位素等手段,对其水化学特征及来源进行系统研究,为热水的可持续开发利用提供了科学依据。研究表明:温泉为HCO3·CO3-Na型热水,可作为含F和H 2S的医疗热矿水进行开发,但... 本文选取江西省罗溪温泉为研究对象,综合应用地质、水化学和同位素等手段,对其水化学特征及来源进行系统研究,为热水的可持续开发利用提供了科学依据。研究表明:温泉为HCO3·CO3-Na型热水,可作为含F和H 2S的医疗热矿水进行开发,但不宜作为灌溉用水使用。通过分析温泉的D、18O及87Sr/86Sr同位素资料,可知热水的补给来源为温泉东西方向海拔约950m的山区的大气降水,降水与地壳中岩石相互作用形成温泉。利用Person法修正热水的14 C年龄约为19800年。通过计算推测热储温度约为82℃,循环深度为1900m左右。温泉为花岗岩中地下水获得大气降水补给入渗后,经深循环加热上升出露而成。 展开更多
关键词 温泉 水化学 水源 同位素
在线阅读 下载PDF
Sedimentary geochemical proxies for methane seepage at Site C14 in the Qiongdongnan Basin in the northern South China Sea 预览
10
作者 Tiantian Sun Daidai Wu +3 位作者 Fei Yang Lihua Liu Xuegang Chen Ying Ye 《海洋学报:英文版》 SCIE CAS CSCD 2019年第7期84-95,共12页
Recent studies have shown that specific geochemical characteristics of sediments can be used to reconstruct past methane seepage events.In this work,the correlation between the Sr/Ca and Mg/Ca ratios of sediment sampl... Recent studies have shown that specific geochemical characteristics of sediments can be used to reconstruct past methane seepage events.In this work,the correlation between the Sr/Ca and Mg/Ca ratios of sediment samples is analyzed and the sulfate concentration profile in Site C14 from cold-seep sediments in the Qiongdongnan Basin in northern South China Sea is obtained.The results confirmed that,sulfate at 0–247 cm below sea floor(Unit I)is mainly consumed by organic matter sulfate reduction(OSR),while sulfate at 247–655 cm(UnitⅡ)is consumed by both the OSR and the anaerobic oxidation of methane(AOM).In addition,the bottom sediment layer is affected by weak methane seepage.The Mo and U enrichment factors also exhibit similar trends in their respective depth profiles.The responses of trace elements,including Co/Al,Ni/Al,Cr/Al and Zn/Al ratios to methane seepage allowed the study of depositional conditions and methane seepage events.Based on the results,it is speculated that the depositional conditions of UnitⅡchanged with depth from moderate conditions of sulfidic and oxic conditions to locally anoxic conditions,and finally to suboxic conditions due to methane fluid leakage.The stable isotope values of chromium-reducible sulfide produced by AOM and those of sulfide formed by OSR in the early diagenetic environment suffered serious depletion of 34S.This was probably due to weak methane leakage,which caused the slower upward diffusion and the effect of early diagenesis on the samples.It is necessary to consider the effects of depositional environments and diagenesis on these geochemical parameters. 展开更多
关键词 Qiongdongnan Basin trace elements stable ISOTOPE values ANAEROBIC oxidation of METHANE METHANE activity
在线阅读 下载PDF
Petrogenesis of the Payangazu Complex in Southern Mandalay, Central Myanmar and Its Tectonic Implications
11
作者 KaixuanLi Huaying Liang +3 位作者 Zhiwei Bao Wenting Huang Jian Zhang Long Ren 《地球科学学刊:英文版》 SCIE CAS CSCD 2019年第1期20-36,共17页
The Payangazu complex in the central Myanmar is composed mainly of quartz diorite,granodiorite,and some synplutonic mafic dikes.The quartz diorite and granodiorite have zircon U-Pb ages of 130.5±4.0(MSWD=3.5)and ... The Payangazu complex in the central Myanmar is composed mainly of quartz diorite,granodiorite,and some synplutonic mafic dikes.The quartz diorite and granodiorite have zircon U-Pb ages of 130.5±4.0(MSWD=3.5)and 118.4±2.5 Ma(MSWD=2.4),respectively.Rock samples of the quartz diorite and granodiorite are metaluminous,enriched in large-ion lithophile elements like LREE,Rb,Th,and U,and depleted in high field-strength elements such as HREE,Nb,Ta,P,and Ti,indicative of arc-type magmatic affinities.Whole rock samples of the quartz diorite haveεHf(t)value of+0.6,initial^87Sr/^86Sr ratios of 0.708 6 to 0.710 0,andεNd(t)values of-4.8 to-4.9;whereas rocks of the granodiorite are relatively isotopically enriched,withεHf(t)values of-5.1 to-7.2,initial ^87Sr/^86Sr ratios of 0.711 7 to 0.711 8,andεNd(t)values of-8.7 to-8.8.The isotopic data together with the high Mg#(both the quartz diorite and granodiorite have Mg#values of>40)suggest a strong involvement of mantle materials in the genesis of the parent magmas.The possible petrogenetic process may be that the ascending of melts from partial melting of metasomatized mantle wedge triggered by dehydration of subducted slab resulted in partial melting of the lower crust and mixed with the latter.These Early Cretaceous intrusions from the complex are older than those found in the eastern Wuntho-Popa arc in western Myanmar,eastern Himalaya,and western Yunnan which are interpreted to be related to the Neo-Tethyan subduction,and haveεNd(t),εHf(t)values lower than the latter.On the contrary,the ages and geochemical characteristics of the Payangazu complex are consistent with some of the intrusions in the northern magmatic belt in Tibet,eastern Himalaya,and western Yunnan which are believed to be associated with the subduction of the Bangong-Nujiang Ocean crust.Thus,we propose that the Early Cretaceous intrusions in the central Myanmar are most likely related to the southward subduction of an ocean slab that was possibly an extension of the Bangong-Nujiang Ocean. 展开更多
关键词 CENTRAL Myanmar ZIRCON U-PB age isotope Early CRETACEOUS SUBDUCTION
Geochronology and Petrochemistry of Volcanic Rocks in the Xaignabouli Area, NW Laos
12
作者 Meifeng Shi Zhenbo Wu +4 位作者 Shusheng Liu Zhimin Peng Linnan Guo Fei Nie Siwei Xu 《地球科学学刊:英文版》 SCIE CAS CSCD 2019年第1期37-51,共15页
An integrated study of zircon U-Pb geochronology and petrochemistry, together with zircon Lu-Hf isotopes, has been carried out on the basaltic-andesitic tuff and volcanic breccia from the Nam Hang Formation and andesi... An integrated study of zircon U-Pb geochronology and petrochemistry, together with zircon Lu-Hf isotopes, has been carried out on the basaltic-andesitic tuff and volcanic breccia from the Nam Hang Formation and andesitic tuff from the Muang-Nan Formation in the Xaignabouli area, which had been mapped as the Permian–Early Triassic on the 1 : 1 000 000 geological map or Late Carboniferous on the 1 : 200 000 geological maps. Zircon U-Pb dating of three samples yielded weighted mean ages of 235±2.6, 232±1.4 and 278±2.8 Ma, respectively, suggesting a Late Triassic origin for the Nam Hang Formation and an Early Permian origin for the Muang-Nan Formation. Geochemically, they are characterized by depletions in HFSEs(e.g., Nb, Ta, Ti) and high LILE/HFSE ratios, and they have positive zircon εHf(t) values of 8.7–15.9, which exhibits the continental arc volcanic affinity and partial melting of subducting oceanic slab in the magma source. Combined with spatial occurrence of the volcanic rock and existing geochronological and geochemical data, we suggest that the Xaignabouli-Luang Prabang volcanic belt can be linked to the Loei-Phetchabun belt. The Permian–Triassic volcanic rocks in this belt might be a product of the Nan back-arc basin eastward subduction. 展开更多
关键词 VOLCANIC rock ZIRCON U-Pb GEOCHRONOLOGY geochemistry ZIRCON LU-HF isotope Xaignabouli Laos
Piaoac Granites Related W-Sn Mineralization, Northern Vietnam: Evidences from Geochemistry, Zircon Geochronology and Hf Isotopes
13
作者 Tuan Anh Nguyen Xiaoyong Yang +2 位作者 Hien Vu Thi Lei Liu Insung Lee 《地球科学学刊:英文版》 SCIE CAS CSCD 2019年第1期52-69,共18页
Piaoac granites exposed in the Cao Bang region, northern Vietnam, are S-type granite, which are associated with W-Sn-Mo-Be-F mineralization. Zircon U-Pb ages, major and trace elements, mineral chemical and Hf isotopic... Piaoac granites exposed in the Cao Bang region, northern Vietnam, are S-type granite, which are associated with W-Sn-Mo-Be-F mineralization. Zircon U-Pb ages, major and trace elements, mineral chemical and Hf isotopic compositions of the W-Sn-bearing granites from the Piaoac District have been investigated in detail. LA-ICP-MS U-Pb dating of zircon grains from these granites yielded ages of 82.5±2.3 and 82±1.8 Ma, representing an episode of Late Cretaceous magmatic event. These granites are characterized by high peraluminous and have typical S-type geochemical signatures with high SiO2(72.37 wt.%–73.07 wt.%), high A/CNK values(1.61–1.65) and Al2O3(14.4 wt.%–15 wt.%). They are enriched in Rb, U, K, Th, Ta and Pb and display pronounced negative Ba, Sr, Nb, Ti and Eu(Eu/Eu*=0.19–0.24) anomalies. The high degree of fractional crystallization is characterized by low Rb, Sr, Ba and Eu concentrations with high ratios of La/Sm and Eu/Eu*. Zircon grains show εHf(t) values from-9.69 to-0.9 and the corresponding TDM2 range from 1.2 to 1.7 Ga, indicating that these granites could be derived from the Proterozoic basement rocks with minor input from mantle-derived magmas. The calculation of Fe3+ and Fe2+ of biotites indicates a low oxygen fugacity condition(log fO2 ranging from 10-17 to 10-18 bars, below MH), which is favorable for the W-Sn mineralization. Tungsten and tin have been enriched in granitic magmas through fractionation, and low oxygen fugacity conditions have promoted the accumulation and transportation of W-Sn in the hydrothermal fluids, leading to deposition of mineral phases. The geochemical data suggest that Piaoac granites formed in an extensional setting related with the Late Cretaceous magmatism occurring large-scale lithospheric extensional in South China Block. 展开更多
关键词 GEOCHEMISTRY ZIRCON U-PB age Hf isotope Piaoac GRANITE W-Sn mineralization Northern Vietnam
Isotope analysis of nitrate pollution sources in groundwater of Dong'e geohydrological unit 预览
14
作者 LI Yang KANG Feng-Xin ZOU An-de 《地下水科学与工程:英文版》 2019年第2期145-154,共10页
As nitrate pollution in groundwater has become increasingly serious in recent years, nitrogen isotope was adopted in this paper to define its sources in a typical agricultural area of Dong5e hydrogeological unit. The ... As nitrate pollution in groundwater has become increasingly serious in recent years, nitrogen isotope was adopted in this paper to define its sources in a typical agricultural area of Dong5e hydrogeological unit. The results show that: Higher content of NO3^- detected in shallow groundwater is 27.77 mg/L on average and δ^15N content ranges from 7.8‰ to 12 ‰, indicating that shallow groundwater is mainly contaminated by sewage or feces. In contrast, less NO3^- in deep groundwater (karst water) has an average value of 12.81 mg/L and δ^15N content is between 7.2‰ and 14.3‰, which is closely related to human disturbance as mentioned above. In addition, considering relatively low groundwater quality at some monitoring sites, reasonable fertilization is a better choice in the study area to reduce nitrate source in groundwater. 展开更多
关键词 NITROGEN ISOTOPE GROUNDWATER NITROGEN POLLUTION source AGRICULTURAL area
在线阅读 下载PDF
Terrestrial dissolved organic carbon consumption by heterotrophic bacterioplankton in the Huanghe River estuary during water and sediment regulation 预览
15
作者 ZHANG Mingliang YU Guanglei +4 位作者 WANG Fei LI Bin HAN Huizong QI Zhanhui WANG Tengteng 《海洋湖沼学报(英文)》 SCIE CAS CSCD 2019年第3期1062-1070,共9页
Nearly 20%–50% of the annual terrestrial dissolved organic carbon(DOC)from the Huanghe(Yellow)River was transported to the estuary during the 5-14d of water and sediment regulation.The concentration of DOC increased ... Nearly 20%–50% of the annual terrestrial dissolved organic carbon(DOC)from the Huanghe(Yellow)River was transported to the estuary during the 5-14d of water and sediment regulation.The concentration of DOC increased sharply during the period of water and sediment regulation,which may promote the terrestrial DOC consumption by heterotrophic bacterioplankton.Water and sediment regulation provides an ideal condition for the study of terrestrial DOC consumption by heterotrophic bacterioplankton when terrestrial DOC increases sharply in rainy season,which may help to seek the fates of terrestrial DOC in the estuaries and coasts.In this study,the concentration and stable isotope of DOC,the biomass,growth,and respiration of heterotrophic bacterioplankton were determined.By the study,we found both average percent contribution of terrestrial DOC to the DOC pool and Contribution of terrestrial DOC to the carbon composition of heterotrophic bacterioplankton decreased as distance from the river mouth increased off shore,which was deceased from(39.2±4.0)%,(37.5±4.3)%to(30.3±3.9)%,(28.2±3.9)%respectively.255-484μg C/(L·d)terrestrial DOC was consumed by heterotrophic bacterioplankton.And 29%-45%terrestrial DOC consumed by heterotrophic bacterioplankton releasing as CO2 by respiration.Comparing with tropical estuary,terrestrial DOC consumed by heterotrophic bacterioplankton was lower in temperate estuary(this study).Temperature may limit the consumption of terrestrial DOC by heterotrophic bacterioplankton. 展开更多
关键词 TERRESTRIAL dissolved organic CARBON HETEROTROPHIC BACTERIOPLANKTON CARBON stable ISOTOPE BIOGEOCHEMICAL cycles
在线阅读 下载PDF
青海省基础地学数据库的建设成果及建议 预览
16
作者 石海岩 严玲琴 +3 位作者 于小亮 代岩 王振东 张学德 《黄金》 CAS 2019年第5期47-50,56共5页
随着"358地质勘查工程"和"找矿突破战略行动"的深入实施,青海省在基础地学数据库建设方面取得了一些优良的建设成果。介绍了"青海省矿产资源潜力评价数据库""青海省矿产资源数据库""青海... 随着"358地质勘查工程"和"找矿突破战略行动"的深入实施,青海省在基础地学数据库建设方面取得了一些优良的建设成果。介绍了"青海省矿产资源潜力评价数据库""青海省矿产资源数据库""青海省地质钻孔数据库""青海省同位素数据库"及"青海省地质工作项目管理信息系统"等多种地学基础数据库和项目管理信息系统的建设成果,并给出了建设基础地学数据库的评价和建议。基础地学数据库的建设成果和信息管理系统为青海省地质工作的开展提供了丰富的基础地质资料,规范了地学项目数据和成果资料的管理体系,整合了计算资源,提高了应用研究水平。 展开更多
关键词 基础地学 数据库 矿产资源 地质工作项目管理 地质钻孔 同位素
在线阅读 下载PDF
Impact of municipal solid waste incineration on heavy metals in the surrounding soils by multivariate analysis and lead isotope analysis
17
作者 Yang Li Hua Zhang +2 位作者 Liming Shao Xiaoli Zhou Pinjing He 《环境科学学报:英文版》 SCIE EI CAS CSCD 2019年第8期47-56,共10页
Municipal solid waste(MSW) incineration has become an important anthropogenic source of heavy metals(HMs) to the environment. However, assessing the impact of MSW incineration on HMs in the environment, especially soi... Municipal solid waste(MSW) incineration has become an important anthropogenic source of heavy metals(HMs) to the environment. However, assessing the impact of MSW incineration on HMs in the environment, especially soils, can be a challenging task because of various HM sources. To investigate the effect of MSW incineration on HMs in soils, soil samples collected at different distances from four MSW incinerators in Shanghai, China were analyzed for their contents of eight HMs(antimony, cadmium, chromium, copper,lead, mercury, nickel, and zinc) and lead(Pb) isotope ratios. Source identification and apportionment of HMs were accomplished using principal component analysis and Pb isotope analysis. Results indicated that the relatively high contents of cadmium, lead,antimony, and zinc in the soils at 250 m and 750–1250 m away from the MSW incinerators were related to MSW incineration, while the elevated contents of the other four HMs were associated with other anthropogenic activities. Based on Pb isotope analysis, the contribution ratio of MSW incineration(which had been operated for more than 14 years)to the accumulation of Pb in soil was approximately 10% on average, which was lower than coal combustion only. Incinerator emissions of Pb could have a measurable effect on the soil contamination within a limited area(≤1500 m). 展开更多
关键词 MUNICIPAL solid waste INCINERATION SOILS HEAVY metals Source identification Pb ISOTOPE ratios
汶川地震断层带中碳酸盐岩碳氧同位素分异对断层愈合机制的启示 预览
18
作者 郭瑾 闫小兵 +2 位作者 李自红 陈慧 扈桂让 《地质通报》 CAS CSCD 北大核心 2019年第6期959-966,共8页
汶川地震断层带北川擂鼓镇赵家沟剖面的露头及显微结构均发现多期次脉体纵横交错,角砾岩被胶结。通过对断层岩相关的碳酸盐矿物同位素分析得知,断层岩角砾和脉体中大量的白云石来源应是断层带内富Mg离子的流体,且碳氧同位素显著分异,角... 汶川地震断层带北川擂鼓镇赵家沟剖面的露头及显微结构均发现多期次脉体纵横交错,角砾岩被胶结。通过对断层岩相关的碳酸盐矿物同位素分析得知,断层岩角砾和脉体中大量的白云石来源应是断层带内富Mg离子的流体,且碳氧同位素显著分异,角砾的δ18O值和δ13C值与灰岩围岩更接近,脉体和基质显示重同位素亏损。通过“同震热分解”和“水-岩相互作用”2种可能模型的研究分析,同震热分解模型δ13C值明显高于实际,而水-岩相互作用则可形成这种分异结果。故震后深部流体上涌所导致的表层大气水再循环可能是导致震后断层快速愈合的重要原因,同震破裂和间震期愈合则形成完整的断层系统。 展开更多
关键词 汶川地震 断层带 碳酸盐岩 同位素 断层愈合
在线阅读 下载PDF
准噶尔盆地南缘霍玛吐背斜带油气源对比研究 预览
19
作者 杨见 何寅 王振齐 《粘接》 CAS 2019年第9期20-25,共6页
所谓油气源对比,是从成因关系出发,将含油气盆地油气与烃源岩之间进行对比,从而分析已聚集油气的来源,将油气和烃源岩一一对应。其原理是根据有机化学的知识,确定对比参数,从而分析油、气及与源岩之间的配置关系。文章是对比原油(天然气... 所谓油气源对比,是从成因关系出发,将含油气盆地油气与烃源岩之间进行对比,从而分析已聚集油气的来源,将油气和烃源岩一一对应。其原理是根据有机化学的知识,确定对比参数,从而分析油、气及与源岩之间的配置关系。文章是对比原油(天然气)和烃源岩之间相同馏分中某种成分的含量,确定了原油A、B、C三大类及其地球化学特征和标志性特征。结果可对分析油气朝哪个方向运移、运移距离和油气的次生变化,寻找油气聚集带,确定有利的勘探区域,为油气开发提供指导。 展开更多
关键词 参数比值 油气 有机质 同位素
在线阅读 下载PDF
长江口盐度梯度下不同形态碳的分布、来源与混合行为 预览
20
作者 叶君 姚鹏 +2 位作者 徐亚宏 王金鹏 赵彬 《海洋学报》 CAS CSCD 北大核心 2019年第4期15-26,共12页
河口碳的生物地球化学过程是全球碳循环的重要组成。通过测定溶解无机碳(DIC)及其稳定同位素丰度(δ13CDIC),溶解有机碳(DOC),有色溶解有机物(CDOM),颗粒有机碳(POC)及其稳定同位素丰度(δ13CPOC)与元素比值(N/C)及相关指标,研究了2014... 河口碳的生物地球化学过程是全球碳循环的重要组成。通过测定溶解无机碳(DIC)及其稳定同位素丰度(δ13CDIC),溶解有机碳(DOC),有色溶解有机物(CDOM),颗粒有机碳(POC)及其稳定同位素丰度(δ13CPOC)与元素比值(N/C)及相关指标,研究了2014年7月长江口盐度梯度下不同形态碳的分布、来源和混合行为。结果表明,DIC浓度、DOC浓度、POC含量分别为1 583.2~1 739.6μmol/L,128.4~369.4μmol/L和51.2~530.8μmol/L,这些不同形态碳及CDOM的荧光组分的分布模式相似,均是从口内到口外,整体呈现先增大后减小的趋势,并与盐度呈现非保守混合行为。添加作用主要发生在在口门处最大浑浊带附近。与含量相反,从口内到口外,δ13CDIC和δ13CPOC均呈现逐渐减小再增大的趋势,在口门附近达到最低值,分别为-9.7‰和-26.7‰。在口门附近不同形态碳含量上升及δ13CDIC、δ13CPOC的降低可能主要与沉积物再悬浮及微生物作用有关。基于蒙特卡洛模拟的三端元混合模型的结果显示,河口内外POC来源变化明显,口内POC以陆源有机碳贡献为主,平均为62.3%,口外海源贡献逐渐增加。CDOM相关参数结果表明长江口CDOM主要来自陆源输入,海源及人类活动等也对其产生影响。 展开更多
关键词 长江口 最大浑浊带 无机碳 有机碳 同位素 有色溶解有机物
在线阅读 下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部 意见反馈