Constraints of authigenic carbonates on trace elements (Sr, Mg) of lacustrine ostracod shells in paleoenvironment reconstruction and its mechanism

Molar ratios of Mg/Ca and Sr/Ca were measured in two species of ostracod shells preserved in the upper core (15-55 m) of the Heqing Basin in Yunnan Province, southwest China. By correlating the molar ratios between Mg/Ca and Sr/Ca and comparing them with Sr concentrations of the sediments, we suggested that: (1) the molar Mg/Ca and Sr/Ca ratio variations in respective ostracod primo re- flected the changes in its ambient water composition and ecology; (2) the molar Sr/Ca ratios responded better to the salinity change linearly than Mg/Ca without aragonite precipitation in the system, and otherwise there was no linear relation between them; and (3) the molar Sr/Ca ratios were mainly con- trolled by salinity and authigenic carbonate precipitation, whereas the molar Mg/Ca ratios were related to both salinity and temperature. In fact, the rate of ostracod growth owing to temperature controls the fluctuation of Mg/Ca in shells. Here, more attentions should be paid to the constraint of authigenic mineral precipitation processes on the trace elements in ostracod shells and to the correlation between these trace elements in biogenic carbonates and compositions of the sediments in systems and in fu- ture in vitro experiments.     

菲尔德斯半岛新生代火山岩中Sr,Ba,Ca元素的相关变化及其对岩浆演化的启示

菲尔德斯半岛新生代火山岩岩石组合为高铝玄武岩-玄武安山岩-安山岩-英安岩,是一套低钾高铝的钙碱性岩系。以岩石中Sr/Ca,Ba/Ca比值作为讨论岩浆演化的一个指标,确认高铝玄武岩为本区岩浆作用的初始岩浆,经过岩浆房中斜长石和单斜辉石为主的分离结晶作用,依次演化出玄武安山岩、安山岩和英安岩岩浆。     

海水中Ca2, Mg2的含量及Mg2/Ca2对日本鳗鲡受精卵孵化率的影响

日本鳗鲡 Ａｎｇｕｉｌｌａｊａｐｏｎｉｃａ)为降海洄游产卵鱼类 ,它生于江河等淡水水域,性成熟后要洄游到海洋中产卵 ,幼体在海洋中发育变态成柳叶鳗随海水漂游到河口近岸,并逐渐变态为白鳗苗进入江河生长［３］。虽然王义强等１９８０年就对鳗鲡的人工繁殖有过报道 ,但到目前,日本鳗鲡人工繁殖尚未成功［１ ,５］在日本鳗鲡人工繁殖过程中 ,常用近海区的海水作为实验用水。谢刚等１９９５年对日本鳗鲡幼体发育所需海水的温度、盐度作了报道。但近海区由于受河流淡水的影响,不仅盐度会有变化 ,而且海水中一些主要离子含量也很不恒定,从而…     

海水中Ca2+,Mg2+, K+含量对黑鲷胚胎及早期仔鱼发育的影响

１９９２￣１９９３年，用不同Ｃａ＾２＋，Ｍｇ＾２＋和Ｋ＋含量的人工配制海水，孵化黑鲷（Ｓｐａｒｕｓ ｍａｃｒｏｅｐｈａｌｕｓ Ｂａｓｉｌｅｗｓｋｙ）受精卵，培育前期仔鱼。实验揭示了：在没有Ｃａ＾２＋的海水中不能孵出仔鱼，在没有Ｍｇ＾２＋的海水中能孵出少量畸形仔鱼；低Ｋ＾＋对黑鲷受精卵孵化无明显影响，但对早期仔鱼的影响明显。针对咸淡水域海水鱼类育苗的特点，提出了调配海水中适宜的Ｍｇ＾２＋／Ｃａ＾２＋     

盐度和Ca2+浓度对中国明对虾稚虾耗氧率的影响

设计双因子实验研究了水温25.0℃±0.5℃下,盐度(5,15,30)和Ca2 质量浓度(175,350,700,1 400,2 800 mg/L)对中国明对虾(Fenneropenaeus chinensis)稚虾耗氧率的影响,实验对虾的湿体质量为0.301 g±0.041 g。实验结果表明:(1)不同盐度下,中国明对虾稚虾耗氧率的大小顺序为R5>R30>R15。其中,盐度15下对虾的耗氧率显著低于盐度5和30下的耗氧率(P<0.05);(2)不同Ca2 质量浓度下,中国明对虾稚虾耗氧率的大小顺序为R2 800>R175>R700>R1 400>R350。其中,Ca2 质量浓度为350 mg/L组对虾的耗氧率显著低于其它处理组,Ca2 质量浓度为2 800 mg/L组对虾的耗氧率显著高于其它处理组(P<0.05),而Ca2 质量浓度为175,700和1 400 mg/L组间对虾的耗氧率差异不显著(P>0.05);(3)盐度和Ca2 质量浓度的交互作用显著影响中国明对虾稚虾的耗氧率(P<0.05)。     

Proposal for International Agreement on Ca Notation Resulting from Discussions at Workshops on Stable Isotope Measurements Held in Davos (Goldschmidt 2002) and Nice (EGS-AGU-EUG 2003)

A proposal is made to standardise the reporting of Ca isotope data to the δ⁴⁴Ca/⁴⁰Ca notation (or δ⁴⁴Ca/42Ca) and to adopt NIST SRM 915a as the reference standard.     

珊瑚中微量铀的ID-ICP-MS高精度测定及其在珊瑚U/Ca温度计研究中的应用

建立了同位素稀释技术与ICP-MS相结合的ID-ICP-MS分析方法,成功测量了取自南海北部的滨珊瑚样品中的微量铀,获得0．5％左右的精度。并以此建立南海北部近岸海域的珊瑚U／Ca温度计,其温度精度可达±0．5℃。     

南海神狐海域Site 4B沉积物地球化学特征及其对甲烷渗漏的指示意义

前人对Site 4B站位海底浅表层沉积物的研究显示该站位历史上可能存在甲烷渗漏事件。为研究该站位的甲烷渗漏历史,分析了Site 4B站位柱状沉积物的元素地球化学特征,及沉积物中Mg/Ca和Sr/Ca比随深度的变化规律以及自生碳酸盐矿物的分布特征。元素相关性分析表明:研究区Ca、Sr等碳酸盐相关的元素极有可能来自于与甲烷渗漏有关的自生碳酸盐。结合沉积物的粒度特征,认为Site 4B站位在15.78 ka B.P.之前泥火山活动造成甲烷渗漏,且甲烷渗漏速率具有增大—减小的周期性变化特点。研究站位在24.15 ka B.P.、27.47 ka B.P.、31.05 ka B.P.具有相对较高的甲烷渗漏速率,且在31.05 ka B.P.达到最大值。研究结果对探明南海北部的甲烷渗漏历史具有重要的意义。     

Calcium Isotope Ratio (δ44/40Ca) Measurements of Ca‐Dominated Minerals and Rocks without Column Chemistry Using the Double‐Spike Technique and Thermal Ionisation Mass Spectrometry

In this study, to evaluate whether bias free Ca isotope ratios can be properly achieved by thermal ionisation mass spectrometry (TIMS) using the ⁴²Ca–⁴³Ca double‐spike technique without chemical purification, a series of comparable experiments (with or without column chemistry) were made on Ca‐dominated minerals and rocks. Minerals, including fluorite, calcite, titanite and apatite, displayed similar Ca isotope ratios with Δ^44/40Ca_{with‐without} ranging from ?0.02 to +0.07‰. For Ca‐rich rocks, we mainly focused on the carbonates since they are the main repositories of Ca at the surface of the Earth. Coral, stalagmite, carbonatite, dolomite, marble and limestone are studied here. Interestingly, δ^44/40Ca_{SRM 915a} of these minerals and rocks without chemical purification displayed little drift compared with that of rocks with chemical purification, with Δ^44/40Ca_{with‐without} merely spanning from ?0.04 to +0.04‰. This implies that Ca isotope ratios can be achieved without column chemistry, possibly due to a property of TIMS in which Ca ions are only ionised at a target temperature and with a specific activator without ionising other ions. Therefore, for Ca‐dominated minerals or rocks, we suggest that column chemistry is unnecessary if they are totally dissolved and mixed in proper proportion with the ⁴²Ca–⁴³Ca double spike for TIMS measurement.     

Controls on shell Mg/Ca and Sr/Ca in cultured planktonic foraminiferan, Globigerinoides ruber (white)

Mg/Ca and Sr/Ca ratios were determined on a single species of planktonic foraminiferan, Globigerinoides ruber (white), collected from the Gulf of Eilat and cultured in seawater at five different salinities (32 to 44), five temperatures (18 to 30 °C) and four pH values (7.9 to 8.4). The Mg/Ca-temperature calibration of cultured G. ruber (with an exponential slope of 8 ± 3%/°C) agrees well with previously published calibrations from core-tops and sediment traps. However, the dependence of Mg/Ca on salinity (with an exponential slope of 5 ± 3%/psu) is also significant and should be included in the calibration equation. With this purpose, we calculated a calibration equation for G. ruber dependent on both temperature and salinity within the 95% confidence limits:

Mg/Ca(mmol/mol)=exp[0.06(±0.02)*S(psu)+0.08(±0.02)*T(°C)−2.8(±1.0)],R²=0.95