The fine structure of check rings in the otolith of the New Zealand orange roughy (Hoplostethus atlanticus)

Heating otoliths of the orange roughy (Hoplostethus atlanticus; Trachichthyidae) by the break‐and‐burn method causes a crystal transformation from aragonite to calcite. However, the change does not affect the legibility of the check rings. Orange roughy otolith check rings fall into two classes: a diffuse deposit (that is not visible in the break‐and‐burn method, but may have an annual periodicity) and structural check rings (which appear as fine lines on the surface, but as dark bands in the body of the otolith). Structural check ring deposition is irregular, but fortuitous aggregations of structural check rings might be mistaken for conventional annual check rings.     

生物胺对赤潮藻生长的影响作用初探

选取东海赤潮高发区常见的两种甲藻[东海原甲藻(Prorocentrum donghaiense)、塔玛亚历山大藻(Alexandrium tamarense)]和两种硅藻[中肋骨条藻(Skeletonema costatum)、海链藻(Thalassiosirasp.)],以2-苯基乙胺、腐胺、亚精胺、精胺四种赤潮水体中常见的生物胺为因素,设置0、5、25、100nmol/L四个浓度水平,进行L16(45)正交添加培养实验。根据Logistic生长模型进行曲线拟合,分析得到的生长参数。结果显示,不同的生物胺对各赤潮藻生长影响的大小、趋势均存在差异。其中,2-苯基乙胺对四种赤潮藻的生长影响最显著。高浓度的2-苯基乙胺对中肋骨条藻的生长具有明显的抑制作用,对塔玛亚历山大藻的生长具有明显的促进作用。多胺物质(腐胺、亚精胺和精胺)对甲藻(东海原甲藻和塔玛亚历山大藻)生长的促进作用大于硅藻(海链藻和中肋骨条藻)。多胺中的亚精胺对塔玛亚历山大藻和海链藻的生长影响最大,精胺对东海原甲藻和中肋骨条藻的生长影响最大。多胺可能是2010年东海赤潮由中肋骨条藻向东海原甲藻演替的一个诱导因素,其中精胺可能发挥的作用较大。     

Quantitative aspects of Mn-activated cathodoluminescence of natural and synthetic aragonite

The cathodoluminescence analyses of the trigonal carbonates calcite and dolomite have been applied intensively in sedimentary petrology for a long time and the properties of these minerals are well-known, but much less attention has been paid to aragonite. In this study, the cathodoluminescence behaviour and the trace element composition of natural and synthetic aragonite have been studied employing trace element analyses (proton induced X-ray emission) and luminescence spectroscopy. Aragonite doped with Mn²⁺ has been synthesized in a NH₄⁺–Mg²⁺–Ca²⁺–Cl⁻ solution in contact with a CO₂–H₂O–NH₃ atmosphere. The low effective distribution coefficients indicate a rapid growth of the crystals of millimetre size which occurred within hours or days. The natural aragonite samples contain Mn, Fe and Sr in different concentrations. The Mn-bearing aragonites exhibit a bright green luminescence which is caused by a strong emission band at 575 nm with a half-width of about 84 nm. The luminescence intensity shows a strong positive correlation with Mn in aragonite when Fe and Mn do not exceed 2000 p.p.m. The intensity is depressed if the concentration of these elements exceeds the critical values. In the shell of a recent Unio sp., the luminescence intensity deviates from the linear correlation, although the trace element contents are not too high; this is probably an effect of quenching by organic material between the crystallites of the biogenic aragonite.     

南非巴伯顿绿岩带条带状铁建造岩石磁学及磁性矿物的组成特征

条带状铁建造(BIFs)中含有大量的亚铁磁性矿物,其组成及来源是认识BIF成因的重要依据。本文研究了南非巴伯顿绿岩带无花果树群(距今约32亿年)恩圭尼亚组的BIFs样品的磁学和矿物学特征。通过测量富铁层与富硅层的磁滞回线、等温剩磁获得曲线与退磁曲线、矫顽力谱分析、一阶反转曲线(FORC)、低温(20～300K)有场/无场冷却曲线以及k-T曲线、Lowrie三轴热退磁曲线,结合扫描电镜观测,揭示出研究样品中磁性矿物主要为赤铁矿和磁铁矿。基于矫顽力谱分析,富铁层中磁铁矿主要是多畴及假单畴颗粒,相对含量平均为2. 1%;赤铁矿的相对含量平均为97. 9%。富硅层中磁铁矿主要为假单畴及超顺磁性颗粒,相对含量平均为4. 6%;赤铁矿相对含量平均为95. 4%。测试样品具有Morin转变特征,转变温度介于250～260K,说明BIFs中主要为赤铁矿(0. 5～6mm)。富硅层样品出现～107K、～125K两个Verwey转变温度,表明其中可能存在生物成因和非生物成因两种类型磁铁矿。     

黔中沉积磷灰石的硫碳同位素及其地质意义

本文研究了黔中磷块岩中磷灰石的结构硫同位素组成。磷灰石的δ３４Ｓ值为３４．２‰～４２．４‰，它高于同期海水的δ３４Ｓ（约３４．２‰），也高于共生的成岩黄铁矿的δ３４Ｓ（１５．４‰～１９．８‰），表明磷灰石形成于富有机质沉积物早期成岩作用硫酸盐还原带的最上部，其间同时伴有大量硫酸盐细菌的还原过程。磷灰石的碳同位素组成（δ１３Ｃ＝－３．６３‰～１．０‰），表明它含有微生物有机质分解演化而来的ＣＯ２－３，而磷灰石比胶结白云石更富集轻同位素则反映出沉积阶段生物作用的影响比成岩阶段更为明显     

木兰山蓝片岩中两种文石的产出特征及其动力学意义

微米－纳米尺度显微超显微研究表明，木兰山蓝片岩中存在微米级粒间文石和亚微米级文石包裹体，它们是木兰山蓝片岩快速折返动力学机制的证据。并指出木兰山蓝片岩区硬柱石和绿纤石等Ca-Al硅酸盐矿物的缺失与本区变质流体中CO2浓度较高和（或）岩石中含方解石／文石有关。     

Measurement of biogenic sulfur emissions from soils and vegetation using dynamic enclosure methods: Total sulfur gas emissions via MFC/FD/FPD determinations

Metal foil collection/flash desorption/flame photometric detection (MFC/FD/FPD) was one of the analytical methods used to measure emissions of gaseous, sulfur-containing compounds from several terrestrial natural sources during a cooperative field program in the summer of 1985. Nonspeciated, total sulfur gas emissions were determined by using the MFC/FD/FPD technique in combination with a Nafion Perma-Pure drying device to sample air from three designs of dynamic enclosure chambers. These enclosures were placed over various soil orders and vegetation in the vicinity of field sites in Iowa and Ohio previously examined during the 1977–80 SURE study of biogenic sulfur fluxes. Because of the sensitivity and detection characteristics of the MFC/FD/FPD technique, it was possible to obtain measurements on enclosure air samples that were collected for relatively short time periods,. e.g., 1 to 5 min. The magnitudes of these time-resolved, total sulfur gas emissions are correlated exponentially with internal enclosure air temperatures. Potential errors and uncertainties associated with this application of the MFC/FD/FPD methodology are assessed.The total sulfur gas flux values obtained from this study and the SURE program are compared. Unquantified sources of error in the current two parameter extrapolation model used to calculate regional and global terrestrial source strengths of biogenic sulfur emissions are also summarized and are shown to prevent a reliable estimate of overall uncertainty limits in the resultant inventory.     

In situ impedance spectroscopy on pyrophyllite and CaCO<Subscript>3</Subscript> at high pressure and temperature: phase transformations and kinetics of atomistic transport

In situ impedance spectroscopy in laboratory experiments at high pressure and temperature can provide crucial quantitative information on properties of rock materials at depth as well as on physical and chemical processes occurring in the deep Earth. We developed an experimental setup for in situ electrical impedance measurements in a piston-cylinder apparatus and applied it to study the kinetics of charge carriers and phase transformations in pyrophyllite and CaCO₃ aggregates. From comparison with previous studies, we found that absolute values of electrical conductivity and pressure–temperature conditions for dehydration reactions in pyrophyllite and phase transformations in CaCO₃ can be accurately determined using our setup. Dehydration of pyrophyllite significantly enhances the transport kinetics and the effect is more pronounced under undrained conditions than under drained conditions. When dehydroxylation and decomposition temperatures for pyrophyllite under undrained and drained conditions are combined, they appear independent of pressure rather than increasing with pressure as previously suggested. Electrical conductivity of CaCO₃ varies with impurity content and grain size, and is most likely controlled by diffusion of oxygen along wet grain boundaries. When applied to the Earth, the results on pyrophyllite suggest that the increase in electrical conductivity in rocks that undergo dehydration should be taken into account in interpreting magnetotelluric surveys of regions with anomalously high conductivity found above subducting plates. The results on CaCO₃ indicate that grain boundary transport controls the electrical conductivity in fine-grained calcite rocks; hence calcite mylonites may be detected using magnetotelluric methods. Order–disorder transformations, such as occurring in calcite, possibly affect the physical properties of rocks (e.g., rheology) by changing the kinetics of atomistic transport processes.     

Anaerobic microbial activity affects earliest diagenetic pathways of bivalve shells

The earliest diagenetic post‐mortem exposure of biogenic carbonates at the sea floor and in the uppermost sediment column results in the colonization of hard‐part surfaces by bacterial communities. Some of the metabolic redox processes related to these communities have the potential to alter carbonate shell properties, and hence affect earliest diagenetic pathways with significant consequences for archive data. During a three‐month in vitro study, shell subsamples of the ocean quahog Arctica islandica (Linnaeus, 1767) were incubated in natural anoxic sediment slurries and bacterial culture medium of the heterotrophic Shewanella sediminis HAW ‐EB 3. Bulk analyses of the liquid media from the Shewanella sediminis incubation revealed an over ten‐fold increase in total alkalinity, dissolved inorganic carbon and Ω_Aragonite, and the alteration of the Mg/Ca, Mg/Sr and Sr/Ca ratios relative to control incubations without cultures. Ion ratios were most affected in the incubation with anoxic sediment, depicting a 25% decrease in Mg/Ca relative to the control. Shell sample surfaces that were exposed to both incubations displayed visible surface dissolution features, and an 8 wt% loss in calcium content. No such alteration features were detected in control shells. Apparently, alteration of shell carbonate properties was induced by microbially driven decomposition of shell intercrystalline organic constituents and subsequent opening of pathways for pore fluid–crystal exchange. This study illustrates the potential influence of benthic bacterial metabolism on biogenic carbonate archives during the initial stages of diagenetic alteration within a relatively short experimental duration of only three months. These results suggest that foremost the biological effect of bacterial cation adsorption on divalent cation ratios has the potential to complicate proxy interpretation. Results shown here highlight the necessity to consider bacterial metabolic activities in marine sediments for the interpretation of palaeo‐environmental proxies from shell carbonate archives.