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Maastrichtian–Danian strata of the Cauvery basin as well as selected sections of NE-Mexico, Guatemala and Israel record Ba anomalies, away from the Cretaceous/Tertiary boundary (KTB) in addition to common occurrences of geochemical and stable isotopic anomalies across the KTB. Ba anomalies were recorded in monotonous shallow marine sandstones of the Cauvery basin (south India) which contain minor amounts of Ba-orthoclase. Barium anomalies were observed also in shallow marine carbonates in sections of Israel, NE-Mexico and Guatemala. Calculation of excess Ba with reference to PAAS (Post-Archaen Average Australian Shale), comparison of coeval geochemical anomalies, depositional pattern and associated petrographic and mineralogical features of the Cauvery basin revealed that while a first Ba peak was related to detrital influx, the second Ba peak was coincident with sea level fall which in turn may have been influenced by emission of volatile hydrocarbons and resultant climatic changes. In view of intrinsic involvement of Ba in various geochemical processes and occurrence of Ba anomalies in K/T sites distributed around the world (NE-Mexico, Guatemala and Israel), it is suggested that probable causes of such widespread Ba-anomalies should be taken into consideration while analyzing end Cretaceous events. These observations support the views espoused by many workers who have stated that the K/T boundary was also accompanied by many non-catastrophic events that might have contributed to environmental stress on marine fauna, as a result of which selective multi-stage extinctions occurred. 相似文献
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渤海湾百年来沉积物Li/Ba 和Rb/Sr 协同变化的地球化学特征与环境指示作用 总被引:1,自引:0,他引:1
通过对渤海湾两根柱状沉积物中Li、Rb、Sr、Ba以及Li/Ba和Rb/Sr的系统研究,阐明了百年来沉积物中Li、Rb、Sr、Ba的垂直变化特征,发现了在不同年代沉积物中Li/Ba和Rb/Sr具有的协同变化规律,揭示了沉积物Li/Ba和Rb/Sr作为近海区域性环境演变可能的指示作用。结果表明,在0~20 cm沉积层间,Li、Rb在A2和A6柱中均有随深度增加而增加的趋势,Sr和Ba随着深度的增加而降低;近百年来,渤海湾沉积物A2和A6柱中Li/Ba和Rb/Sr垂直变化表现出惊人的协同变化特征,Li/Ba和Rb/Sr在近河口的A2柱中,基本呈现随深度的增加而增加的趋势,而在远离河口区域的A6柱中,其结果是0~15 cm段(1963~2008年),Li/Ba和Rb/Sr随深度的增加而增加,15 cm以下(1900~1963年)则基本稳定,在海洋过程作用下该区域沉积物Li/Ba和Rb/Sr变化发生在45 a时间段内;沉积物中Li/Ba反映沉积物从河流进入海湾沉积过程中的变化,Rb/Sr反映来源沉积物的化学风化历史并指示来源区的气候环境变迁过程。A2沉积柱的20~22 cm(20世纪30年代)和10~12 cm(20世纪60年代),Li/Ba出现极小值,与1939年和1963年的海河流域大洪水相契合,在0~12 cm段,两柱样Rb/Sr随着深度的降低有明显减小的趋势,对应20世纪70年代初至2008年这一区域百年来气温升高并持续高温的时段。 相似文献
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南极阿德雷岛湖泊沉积物Sr/Ba与B/Ga比值特征 总被引:6,自引:0,他引:6
测试了南极企鹅聚集区阿德雷岛湖泊沉积物Sr、Ba、B、Ga的垂向含量变化,阿德雷岛湖泊沉积物元素平均含量为:Sr为1 069.36±422.10 mg/kg,Ba为213.84±39.48 mg/kg,B为6.89±3.79 mg/kg,Ga为16.65±3.91 mg/kg,阿德雷岛湖泊沉积物Sr/Ba比值为4.92±1.53,B/Ga比值为0.43±0.26,Sr/Ba比值远大于1.0,而B/Ga比值小于3.3,这表明在特殊的生态环境下Sr/Ba比值不能用来判别沉积物的沉积相,南极阿德雷岛湖泊沉积的Sr/Ba比值异常是通过企鹅生物地球化学过程沉积改造而引起的,受到企鹅粪沉积影响. 相似文献
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浙江八面山萤石矿床稀土元素地球化学特征及成因探讨 总被引:2,自引:2,他引:2
对浙江八面山萤石矿床中不同类型萤石矿石和围岩样品的稀土元素的系统分析表明,细粒萤石矿石的ΣREE〈39×10-6,LREE为14.36×10-6~34.24×10-6,HREE0.96×10-6~2.04×10-6,Y〈3×10-6;巨晶萤石矿石中的ΣREE3.62×10-6~20.81×10-6,LREE2.71×10-6~17.67×10-6,HREE0.24×10-6~1.49×10-6;而围岩花岗岩的ΣREE460.29×10-6,LREE225.97×10-6,HREE91.32×10-6,Y>140×10-6;沉积岩中的ΣREE20.22×10-6、LREE16.11×10-6、HREE1.61×10-6。矿石与围岩中沉积岩的稀土总量、轻稀土、重稀土和Y的含量接近,与花岗岩的稀土总量、轻稀土、重稀土和Y元素含量相差悬殊。萤石矿石的稀土分布型式主要为轻稀土富集型,(La/Yb)N通常多数大于8,在8.07~17.26间,δEu值在0.45~1.30,δCe在0.89~1.14间,Ce、Eu基本不显异常。矿石与围岩的稀土地球化学研究显示,八面山萤石矿床为受地层、岩体与断裂共同控制"三位一体"的低温热液型矿床。 相似文献
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Kirsten van Zuilen Thomas F. Nägler Thomas D. Bullen 《Geostandards and Geoanalytical Research》2016,40(4):543-558
The interest in variations of barium (Ba) stable isotope amount ratios in low and high temperature environments has increased over the past several years. Characterisation of Ba isotope ratios of widely available reference materials is now required to validate analytical procedures and to allow comparison of data obtained by different laboratories. We present new Ba isotope amount ratio data for twelve geological reference materials with silicate (AGV‐1, G‐2, BHVO‐1, QLO‐1, BIR‐1, JG‐1a, JB‐1a, JR‐1 and JA‐1), carbonate (IAEA‐CO‐9) and sulfate matrices (IAEA‐SO‐5 and IAEA‐SO‐6) relative to NIST SRM 3104a. In addition, two artificially fractionated in‐house reference materials BaBe12 and BaBe27 (δ137/134Ba = ?1.161 ± 0.049‰ and ?0.616 ± 0.050‰, respectively) are used as quality control solutions for the negative δ‐range. Accuracy of our data was assessed by interlaboratory comparison between the University of Bern and the United States Geological Survey (USGS). Data were measured by MC‐ICP‐MS (Bern) and TIMS (USGS) using two different double spikes for mass bias correction (130Ba–135Ba and 132Ba–136Ba, respectively). MC‐ICP‐MS measurements were further tested for isobaric and non‐spectral matrix effects by a number of common matrix elements. The results are in excellent agreement and suggest data accuracy. 相似文献
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The lack of self consistency in the current wind accretion models is pointed out. Taking account of δr ≠ 0, the modification equations of orbital parameters are re-deduced. Combined with wind accretion scenarios, calculations of nucleosynthesis for intrinsic AGB stars are first used to calculate s-process enrichments of Ba stars. Comparisons are also made between the predictions of calculations and the observations. It is found that predictions from the model for the standard case are an upper limit to the observations. Better agreements are obtained either by increasing the wind velocity or reducing the accretion rate. 相似文献
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Frequent sampling during an annual cycle of dissolved(<0.45 m) and suspended (>0.45 m) elementshas been conducted in the Kafue River at Raglan'sFarm, upstream from the mining activities within theCopperbelt Province, Zambia. Additional sampling ofsediment and interstitial pore water was conductedduring low water discharge. The presence of carbonateswithin the drainage basin naturally gives rise to highelement concentrations in the dissolved phase(Ca = 626, Mg = 494, Na = 360 and K = 24 mmol l-1).During the rainy season the relative composition ofthe dissolved elements indicated a wash out ofaccumulated weathering products and mineralisedorganic material from the unsaturated zone of the soilprofile. High concentrations of dissolved Al, Fe andMn were measured during high water discharge. At lowwater discharge the sediment was a major source of Fe,Mn and associated Co and Cu to the water column.Enhanced concentrations of dissolved and suspended S,Co and Cu during the rainy season indicated thatatmospheric deposited particles from the mining areawere washed out into the river. Autochthonousformation of particles rich in Si indicated diatomproduction during low water discharge. 相似文献