On the Origin of Petroleum Hydrocarbon Gases

The compositional variation of oil-soluble gaseous hydrocarbons in high-pressure in-place oil from more than 40 oil wells in the Northern Jiangsu oil field, China, was studied. Samples in which the effects of the factors of pressure and biodegradation had been got rid of were chosen as the representatives that could really reflect the original composition of hydrocarbon gases. Such samples were compared compositionally with their corresponding hydrocarbons formed by decarboxylation of volatile low-molecular fatty acids. Thus highly correlative regularities were found to exist between them. The numerical values of both are graphically expressed. The two curves on the diagram are very similar. These two sets of values have a simple correlation coefficient of 0.9935, which presents their genetic relation.Based on the study of the formation of gaseous hydrocarbons from decarboxylation of volatile fatty acids, the following regularities of the isomers are revealed:1) n-butyric acid + isobutyric acid = propane:2) 1 2 isopentanoic acid(2-methyl-butyric acid) + n-pentanoic acid = n-butane; and3) 1 2 isopentanoic acid(3-methyl-butyric acid) = isobutane.The thermodynamics of decarboxylation was analysed and the enthalpy change △H, entropy change △S and Gibbs free energy change △G in the following reaction were calculated:CH_3COOH(1)--CH_4(g) + CO_2(g).Thus the author considers that the reaction for the formation of hydrocarbons due to the decarboxylation of fatty acids is an exothermic one with increased entropy and decreased free energy as well as a spontaneous one. According to the CRC rule, the resultant Gibbs free energy change △G is approximately-41.84 kJ/mol, which is well within the range of the energy levels of biophysiological changes.According to the changes in odd-carbon preference in n-alkanes of petroleum and sediments and the analysis of fatty acids and amino acids, it is considered that hydrocarbon gases do not originate from pyrolysis or thermal degradation but from decarboxylation of organisms. But this biological reaction is not ordinary biochemical reaction in the artificial fermentation for generating marsh gas. On the basis of the change tendency of the fatty acid content in the fermentation liquor for marsh gas generation and the change tendency of the carbon isotopes in methane and carbon dioxide in the marsh gas, it can be judged that the biochemical reaction for forming hydrocarbon gases is a special biological one occurring after the fermentation.     

Ions of Organic Carboxylic Acids (Formic,Acetic, and Oxalic) in the Snow Cover of Permafrost Landscapes of Boreal Eastern Siberia

The distribution of ions of organic carboxylic acids (formic, acetic, and oxalic) was investigated in the snowpack of permafrost landscapes of the boreal zone of Eastern Siberia. The contents of formate-, acetate-, and oxalate-ions were determined in permafrost landscapes of different zones of latitudinal and mountain- belt types. The maximum contents of organic carboxylic acid ions were observed in the snow cover of middle-taiga landscapes. The input rate of the ions into the snow cover of middle-taiga and mountain landscapes is controlled by altitudinal zonation and correlates with the total mass of plant organisms, which are the main source of organic carboxylic acids in the atmosphere. The obtained data suggest that organic carboxyl acid ions were supplied mainly by the atmosphere (74–90%), whereas the contribution of soil respiration was minor. The upward migration of organic carboxylic acid ions from the substrate to the snow cover depends on soil and snow temperature. Cooling of the soil surface below–5°C results in a considerable decrease in the migration of organic carboxylic acid ions from soil to snow.     

碳酸盐倒退溶解模式的化学热力学基础——与H_2S有关的溶解介质及其与CO_2的对比

以化学热力学中的吉布斯自由能增量为基础,计算了与H2S(g)/ H2S(aq) /HS-/ H+/S2-系统有关反应在不同温度下的平衡常数,同时根据方解石和白云石在酸性条件下的溶解过程,获得了这两种碳酸盐矿物溶解过程中地层中流体pH值与PCO2、地层压力和埋藏深度的关系。在此基础上,对比了从地表到深埋藏的温度和压力条件下,与CO2和H2S有关的酸性介质对流体\[H+\]贡献的差异性,以及对于碳酸盐溶解作用的差异性。计算结果表明:1）无论以CO2还是以H2S作为溶解介质,温度增加和（或）PCO2增加,都会造成方解石和白云石溶解所需要的\[H+\]增加,在深埋藏相对高温和高压条件下,高PCO2条件会使得碳酸盐矿物的溶解更加困难,如果\[H+\]受到缓冲,CO2的增加不仅不能造成碳酸盐矿物的溶解,反而会造成碳酸盐矿物的沉淀;2）无论在何种酸性介质中,碳酸盐矿物的倒退溶解模式在化学上都是成立的,低温的成岩环境,深部地层中高温流体的向上运移、构造抬升所造成的温度降低（-ΔT）都会提高H2S和（或）CO2流体（也包括其它酸性介质）对碳酸盐矿物溶解能力;3）在地表和近地表条件下（几百米深度范围内）,在同时存在CO2和H2S的环境中,CO2对应酸的电离提供的\[H+\]略多于H2S对应酸的电离,与CO2有关的酸性流体对碳酸盐矿物溶解相对重要,而在深埋藏条件下、尤其是深度大于4 000 m的深埋藏地层中,H2S对应酸的电离提供的\[H+\]显著大于CO2,其对碳酸盐矿物的溶解更为重要,在存在硫酸盐还原作用的深埋藏地层中,碳酸盐的深部溶解作用会更为发育,这可能是川东北地区深埋藏条件下次生孔隙发育的重要原因之一。     

Assaying the catalytic potential of transition metal sulfides for abiotic carbon fixation

A suite of nickel, cobalt, iron, copper, and zinc containing sulfides are assayed for the promotion of a model carbon fixation reaction with relevance to local reducing environments of the early Earth. The assay tests the promotion of hydrocarboxylation (the Koch reaction) wherein a carboxylic acid is synthesized via carbonyl insertion at a metal-sulfide-bound alkyl group. The experimental conditions are chosen for optimal assay, i.e., high reactant concentrations and pressures (200 MPa) to enhance chemisorption, and high temperature (250°C) to enhance reaction kinetics. All of the metal sulfides studied, with the exception CuS, promote hydrocarboxylation. Two other significant reactions involve the catalytic reduction of CO to form a surface-bound methyl group, detected after nucleophilic attack by nonane thiol to form methyl nonyl sulfide, and the formation of dinonyl sulfide via a similar reaction. Estimation of the catalytic turnover frequencies for each of the metal sulfides with respect to each of the primary reactions reveals that NiS, Ni₃S₂, and CoS perform comparably to commonly employed industrial catalysts. A positive correlation between the yield of primary product to NiS and Ni₃S₂ surface areas provides strong evidence that the reactions are surface catalytic in these cases. The sulfides FeS and Fe_(1−x)S are unique in that they exhibit evidence of extensive dissolution, thus, complicating interpretation regarding heterogeneous vs. homogeneous catalysis. With the exception of CuS, each of the metal sulfides promotes reactions that mimic key intermediate steps manifest in the mechanistic details of an important autotrophic enzyme, acetyl-CoA synthase. The relatively high temperatures chosen for assaying purposes, however, are incompatible with the accumulation of thioesters. The results of this study support the hypothesis that transition metal sulfides may have provided useful catalytic functionality for geochemical carbon fixation in a prebiotic world (at least intially) devoid of peptide-based enzymes.     

深层温压条件下有机酸热稳定性模拟研究

深层、超深层中有机酸的分布特征及其热稳定性对储层物性有着重要影响。采用高温高压水—岩模拟装置对储层中典型一元和二元有机酸（乙酸和乙二酸）的分解反应进行了模拟,对动力学参数进行了计算,并分析其影响因素。结果显示:乙二酸比乙酸更容易分解,且分解反应的速率更高;乙酸和乙二酸分解反应的起始温度分别为230 ℃和180 ℃,其反应速率随着温度的升高而急剧增加。反应体系中高pH值和钾长石的存在明显提高了乙酸和乙二酸分解反应的反应速率,但对起始温度影响较小。高流体压力和静岩压力均会抑制乙酸和乙二酸的分解,在提高有机酸分解反应起始温度的同时降低分解反应速率。从地质意义上来讲,相对高压、低地温的地层环境更有利于有机酸的保存,因此具有低地温梯度的沉积盆地形成深层—超深层优质储层的可能性更高。     

Use of molecular ratios to identify changes in fatty acid composition of Miscanthus × giganteus (Greef et Deu.) plant tissue,rhizosphere and root-free soil during a laboratory experiment

Fatty acids (FAs) are abundant lipids in plants, microorganisms and soil. Depending on chain length they provide potential for evaluating different sources of C in soil: shoots, roots and microorganisms. This, together with their fast turnover and transformation in living and decaying plant tissues, suggests the use of FA molecular ratios as source indicators in soil. To evaluate the applicability of FAs as source indicators, their dynamics in plant tissue and soil were traced during a laboratory experiment using the highly productive perennial C₄ energy grass Miscanthus x giganteus (Greef et Deu.). For the comprehensive use of FAs as source indicators various ratios were calculated: fatty acid ratio (originally defined as carboxylic acid ratio: CAR), carbon preference index (CPI), average chain length (ACL) and unsaturated vs. saturated C₁₈ acids. The FA composition was specific for individual plant tissues as indicated by the CAR, with high values in roots and lower ones in the above ground plant tissue. Based on ACL values of rhizosphere, soil and roots, an enrichment in root derived FAs vs. root-free soil could be estimated. The rhizosphere contained 35–70% more plant derived FAs than root-free soil. The ACL showed potential for estimating root derived carbon in the rhizosphere. The study documents for the first time very fast spatial processes in soil related to plant growth, thereby strongly influencing the FA composition of soil.     

通过第一性原理预测内地核的成分与结构

内地核成分与结构的确定一直是地球深部研究的重要课题。目前地核的公认成分是铁和少量的镍。但由于地核密度低于纯粹的铁镍合金(固态内核2%～3%,液态外核6%～7%),其中必定掺杂有一定量的轻元素,其种类与浓度有待确定。除成分外,地核条件下铁的晶体结构也存在争议。根据地震学观测,声波沿地轴方向的传播速度比赤道平面方向快大约3%～4%。这意味着内地核是各向异性的;但在极端高压下,晶体结构中的原子应该按致密的密排六方结构(h.c.p)排列,而h.c.p结构对声波传输是高度各向同性的,这就需要确定地核条件下铁的晶体结构。根据第一性原理计算得到的高压下体系能量以及爱因斯坦谐振子模型,本项研究估算了给定结构的自由能以及掺杂轻元素后的影响。根据计算结果可以定性的分析得出,在高压OK下致密的h.c.p结构显然比疏松的体心立方(b.c.c)更稳定;而随着温度的升高,原子核的振动造成b.c.c结构的自由能比h.c.p结构下降得更快,因此在高温下b.c.c结构更稳定;掺杂轻元素后,这种优势变得更加明显,而3.6at.%的Si则恰好同时解释了2%～3%的密度缺失和b.c.c结构在内地核条件下的稳定性。因此我们建议内地核的基本结构与成分应为以体心立方结构存在的铁,掺杂约3.6at.%的硅元素,内地核温度至少在5500K以上。这一结论与其它更复杂的方法得到的结果一致。     

Antimony(III) complexing with O-bearing organic ligands in aqueous solution: An X-ray absorption fine structure spectroscopy and solubility study

The stability and structure of aqueous complexes formed by trivalent antimony (Sb^III) with carboxylic acids (acetic, adipic, malonic, lactic, oxalic, tartaric, and citric acid), phenols (catechol), and amino acids (glycine) having O- and N-functional groups (carboxyl, alcoholic hydroxyl, phenolic hydroxyl and amine) typical of natural organic matter, were determined at 20 and 60 °C from solubility and X-ray absorption fine structure (XAFS) spectroscopy measurements. In organic-free aqueous solutions and in the presence of acetic, adipic, malonic acids and glycine, both spectroscopic and solubility data are consistent with the dominant formation of Sb^III hydroxide species, , at strongly acid, acid-to-neutral and basic pH, respectively, demonstrating negligible complexing with mono-functional organic ligands (acetic) or those having non adjacent carboxylic groups (adipic, malonic). In contrast, in the presence of poly-functional carboxylic and hydroxy-carboxylic acids and catechol, Sb^III forms stable 1:1 and 1:2 complexes with the studied organic ligands over a wide pH range typical of natural waters (3 < pH < 9). XAFS spectroscopy measurements show that in these species the central Sb^III atom has a distorted pseudo-trigonal pyramidal geometry composed of the lone pair of 5s² electrons of Sb and four oxygen atoms from two adjacent functional groups of the ligand (OC-OH and/or COH), forming a five-membered bidendate chelate cycle. Stability constants for these species, generated from Sb₂O₃ (rhomb.) solubility experiments, were used to model Sb complexing with natural humic acids possessing the same functional groups as those investigated in this study. Our predictions show that in an aqueous solution of pH between 2 and 10, containing 1 μg/L of Sb and 5 mg/L of dissolved organic carbon (DOC), up to 35% of total dissolved Sb binds to aqueous organic matter via carboxylic and hydroxy-carboxylic groups. This amount of complexed Sb for typical natural DOC concentrations is in agreement with that estimated from dialysis experiments performed with commercial humic acid in our work and those available in the literature for a range of standardized IHSS humic acids. Our results imply that a significant part of Sb is likely to be bound with humic acids via hydroxy-carboxylic moieties, in the form of bidendate complexes. However, following the strong chemical affinity of Sb^III for reduced sulfur, some undefined fraction of Sb^III might also be bound to the minor thiol-bearing moieties of humic acids; further studies are required to check this hypothesis.     

东海表层沉积物黏土粒级中多态脂肪酸组成与地球化学特征

对东海陆架泥质沉积区两个代表性站位表层沉积物开展了黏土粒级分离提取,并对其依次进行溶剂萃取、碱解和酸解处理,得到结合程度不同的三种脂肪酸组分：有机溶剂抽提的游离态脂肪酸、碱解得到的碱解酸和酸解得到的酸解酸。三种赋存态酸的存在表明它们所联结的宏观分子的结构不同或所吸附黏土矿物的保护作用不同。不同赋存态酸的数量、组成和分布有一定差异,两站位相同赋存态酸的数量与组成也存在明显差异。组成与分布特征表明东海陆架泥质区超细颗粒物中脂肪酸以海洋内源藻类来源为主（〉70％）,陆源高等植物贡献相对较低,并有少量的细菌源贡献。各赋存态酸的降解程度为碱解酸高于酸解酸高于游离酸,可能与其在黏土中的赋存状态和吸附过程有关。靠近长江河口的表层沉积物样品（24站）海洋内源藻类贡献略低于远离河口的站位（30站）,陆源高等植物的输入稍高于后者,是受两泥质区沉积环境综合影响的结果。     

Albite dissolution kinetics as a function of distance from equilibrium: Implications for natural feldspar weathering

Determining the kinetics of many geologic and engineering processes involving solid/fluid interactions requires a fundamental understanding of the Gibbs free energy dependency of the system. Currently, significant discrepancies seem to exist between kinetic datasets measured to determine the relationship between dissolution rate and Gibbs free energy. To identify the causes of these discrepancies, we have combined vertical scanning interferometry, atomic force microscopy, and scanning electron microscopy techniques to identify dissolution mechanisms and quantify dissolution rates of albite single crystals over a range of Gibbs free energy (−61.1 < ΔG < −10.2 kJ/mol). During our experiments, both a previously dissolved albite surface exhibiting etch pits and a pristine surface lacking dissolution features were dissolved simultaneously within a hydrothermal, flow-through reactor. Experimental results document an up to 2 orders of magnitude difference in dissolution rate between the differently pretreated surfaces, which are dominated by different dissolution mechanisms. The rate difference, which persists over a range of solution saturation state, indicates that the dissolution mechanisms obey different Gibbs free energy dependencies. We propose that this difference in rates is the direct consequence of a kinetic change in dissolution mechanism with deviation from equilibrium conditions. The existence of this kinetic “switch” indicates that a single, continuous function describing the relationship between dissolution rate and Gibbs free energy may be insufficient. Finally, we discuss some of the potential consequences of our findings on albite’s weathering rates with a particular focus on the sample’s history.     

土地利用对岩溶作用碳汇的影响研究综述

耦合水生光合作用的岩溶作用碳汇新模式的提出使得碳酸盐岩的风化过程成为寻找“陆地剩余碳汇”(residual land sink) 的新方向。传统意义上,碳酸盐岩风化在全球碳循环模型中被认为是未快速响应地表环境变化的地质过程,然而最新一系列研究表明人类土地利用显著改变了这一地质循环过程。文章总结了岩溶作用碳汇对不同土地利用/覆被变化的具体响应,并对其机理进行了系统分析。发现土地利用与覆被变化影响岩溶作用碳循环过程主要源自土壤CO2浓度和径流量变化以及外源酸（硝酸和硫酸）的介入。证据显示在土地利用对岩溶作用碳汇的调控中土壤CO2浓度与径流量是复杂且相互制约的两个机制,人类活动产生的外源酸干扰在不同层面上的影响也不同。由于地表水生生态系统所产生的内源有机碳（AOC）的巨大稳碳能力(水生碳泵效应)在以往的研究中并没有与碳酸盐岩风化过程相联系,因而其对土地利用变化的响应过程和机理是岩溶碳循环研究的最新方向。基于土地利用调控碳酸盐岩风化过程的复杂性和多样性特点,综合考虑岩溶作用产生的DIC(溶解无机碳)与AOC在不同土地利用情况下的相互关系以及定量分析各环境因素的具体效应成为了合理制定人为土地利用调控策略的必要前提,也是岩溶作用碳汇研究的未来发展方向。      

超纯水中甲酸、乙酸污染的实验研究及其对雪冰有机酸测定的意义

塑料容器是降水中生物有机酸研究的常用样品储集器,极地冰芯和粒雪样品钻取中也常用聚乙烯塑料袋盛装,且常常采用双封口方式保存。这种样品保存方式和样品暴露于大气一样,都会造成样品中有机酸含量的污染。定量研究一述污染是准确分析降水中有机酸含量的前提和基础。以超水为主要实验样品,对聚乙烯塑料顺和空气的甲酸,乙酸污染的研究表明,甲酸、乙酸的污染主要来自聚乙烯塑料代的热塑封口过程,而聚乙烯塑料桶的影响不明显。塑     

An integrated thermodynamic mixing model for sphalerite geobarometry from 300 to 850°C and up to 1 GPa

An asymmetric, Margules-type, solid solution model was used to model the mixing behavior of Fe-Zn sphalerites. The model is based on an analysis of experimental results from fifteen independent data sources. After a careful, stepwise, analysis of the available runs, the solid solution model was constrained using a refined experimental database of 279 experiments which were simultaneously regressed to obtain the excess parameters and a general geobarometric equation. The model indicates that, when pressures are low, the value of γ_FeS^Sph, which is always greater than one, is higher at low FeS contents and an increase in temperature causes it to decline. However, for certain compositions γ_FeS^Sph values might be slightly less at low T than at high T. This behavior is corrected when pressure increases, regardless of the composition. The excess Gibbs free energy has positive values at any P&T while it is asymmetric. Pressure increases the value of the excess free energy. On the other hand, the Gibbs free energy of mixing is always negative, with a single minimum that tends to move towards Fe-poorer compositions as the pressure goes up. An increase in temperature leads to a more negative Gibbs free energy mixing function suggesting that increasingly Fe-poorer sphalerite would be expected at high temperatures and pressures. The application of the solid solution model to a selection of case-studies provided results which are consistent with independent pressure estimates. However, the pressure determinations for sphalerite + pyrite + pyrrhotite and sphalerite + pyrrhotite assemblages are very sensitive to uncertainties in the composition of the phases involved and, to a lesser extent, to temperature. The results of the application of the model to a field case (scheelite-mineralized Hercynian veins from the Central Pyrenees) were also consistent when compared with independent pressure-constraining silicate assemblages. Thus, the solid solution model described in this paper provides a workable framework with which to compute the pressures of the formation of rocks over a wide range of geological conditions.     

Occurrence Forms of Carbon,Sulfur, and Noble Metals in Deposits of the Black-Shale Formation by the Example of the Degdekan Gold-Ore Deposit (Northeastern Russia)

Pyrite crystals and ore-bearing shales of the Degdekan deposit were studied by means of XPS, SEM–EDX, EPMA, and AAS. Five peaks of carbon organic forms were identified, conforming to polymer compounds containing either double bonds of carbon or alkyne groups and compounds containing C–OH and C=O bonds, as well as, probably, small amounts of S-containing compounds and those with functional groups of carboxylic acids. Sulfate prevails over sulfite in pyrites; among the surface sulfide forms, disulfide prevails over monosulfide; the presence of polysulfide is registered. The occurrence of various chemical forms of sulfur on the surface might provide for concentrating of microelements including the noble metals (NMs) in their surface-bound forms. The regular behavior of NMs (Au, Pt, Pd, and Ru) depending on the grain sizes (specific surfaces) of pyrite crystals along with the narrow range of the ratios of structural and surface components of the concentrations of different NMs points to NM coprecipitation with pyrite during the same productive stage. No capture of NM-containing carbonaceous phases took place, which should violate the regularity of Au distribution in pyrites of the Sukhoi Log deposit.     

ATR-FTIR spectroscopic study of the adsorption of desferrioxamine B and aerobactin to the surface of lepidocrocite (γ-FeOOH)

The adsorption of two model siderophores, desferrioxamine B (DFOB) and aerobactin, to lepidocrocite (γ-FeOOH) was investigated by attenuated total reflection infrared spectroscopy (ATR-FTIR). The adsorption of DFOB was investigated between pH 4.0 and 10.6. The spectra of adsorbed DFOB indicated that two to three hydroxamic acid groups of adsorbed DFOB were deprotonated in the pH range 4.0-8.2. Deprotonation of hydroxamic acid groups of adsorbed DFOB at pH values well below the first acid dissociation constant of solution DFOB species (pK_a = 8.3) and well below the point of zero charge of lepidocrocite (pH_PZC = 7.4) suggested that the surface speciation at the lower end of this pH range (pH 4) is dominated by a surface DFOB species with inner-sphere coordination of two to three hydroxamic acids groups to the surface. Maximum adsorption of DFOB occurred at approximately pH 8.6, close to the first pK_a value of the hydroxamic acid groups, and decreased at lower and higher pH values.The spectra of adsorbed aerobactin in the pH range 3-9 indicated at least three different surface species. Due to the small spectral contributions of the hydroxamic acid groups of aerobactin, the interactions of these functional groups with the surface could not be resolved. At high pH, the spectral similarity of adsorbed aerobactin with free aerobactin deprotonated at the carboxylic acid groups indicated outer-sphere complexation of the carboxylate groups. With decreasing pH, a significant peak shift of the asymmetric carboxylate stretch vibration was observed. This finding suggested that the (lateral) carboxylic acid groups are coordinated to the surface either as inner-sphere complexes or as outer-sphere complexes that are strongly stabilized at the surface by hydrogen bonding at low pH.     

Fictive component model of pyroxenes and multicomponent phase equilibria

Pyroxenes are considered as ideal solid solutions of some real components (e.g. diopside or orthoenstatite) and some fictive or hypothetical components (e.g. orthodiopside or orthohedenbergite). Using the reversed experimental data in the CaO-MgO-SiO₂ system, the Gibbs free energy of formation of fictive orthodiopside and of fictive clinoenstatite have been determined in the temperature range of 1,000 to 1,600 °K. The data on free energies of components in the binary system can be used to extend the fictive component model to the ternary CaSiO₃-MgSiO₃-FeSiO₃ system. Using published phase diagrams on the pyroxene quadrilateral, Gibbs free energy of formation of fictive orthohedenbergite has been calculated. Application of the ideally mixing fictive component model to computation of phase equilibria leads to the determination of compositions of coexisting Fe-Mg-Ca pyroxenes at different temperatures.Abbreviations and symbols G _f ⁰ Gibbs free energy of formation from the elements at 1 bar and temperature - G ^Ex excess free energy of mixing in a solution - G molar Gibbs free energy - R gas constant - H enthalpy - S entropy - T absolute temperature - P pressure - KJ/M kilojoules per mole - j joules - Opx orthopyroxene - Cpx clinopyroxene - H hedenbergite - D diopside - E enstatite - F ferrosilite - X mole fraction - K equilibrium constant     

Geochemistry of amino acids in some Florida peat accumulations—I. Analytical approach and total amino acid concentrations

Amino acids have been isolated from peats and fractions thereof at two sites in different environments in the Florida Everglades. For comparison, amino acids were also obtained by hydrolysis of organs of the plants now providing the surface cover at the sites and of discarded plant parts in surface litter. The amino acids, including a number of non-protein acids, were analyzed by GLC of volatile derivatives. There is a marked tendency for the total amino acid concentrations to increase in the order plant material < surface litter < peat, and for the ratio of non-protein to protein acids to increase in the same sense. It appears that the nature of the ecosystem is such that a comparatively small proportion of the carbon in the macroflora accumulates as peat while nitrogen is extensively re-worked but largely conserved. The greatest proportion both of the organic matter and of the amino acids were found in the humin fractions of the peat. The amount of free acids (i.e. extractable by cold acid) was very small, but the ratio, non-protein/protein, was greatest in this fraction.     

The Gibbs free energy of mixing of natural silicate liquids; an expanded regular solution approximation for the calculation of magmatic intensive variables

The compositions of liquids coexisting with experimentally grown crystals of olivine, plagioclase, clinopyroxene, orthopyroxene, leucite, spinel, rhombohedral oxide, melilite and potassium feldspar are used to define, through mass action expressions of liquid/solid equilibrium, compositional derivatives of the Gibbs free energy of mixing of naturally occuring silicate liquids as a function of temperature, pressure and the fugacity of oxygen. The available experimental data describe these derivatives over a range of compositions which includes basic magmas. Therefore, for silicate liquids in this composition range, the topology of the Gibbs free energy of mixing can be approximated from experimental determinations of its derivatives. The majority of the existing thermodynamic data on the liquid phase is consistent with the application of regular solution theory to model the free energy of mixing. Strictly symmetric, temperature and pressure independent, regular solution interaction parameters are calibrated from this phase equilibrium data using regression techniques which have their basis in inverse theory. These techniques generate numerically stable interaction parameters which incorporate inter-variable correlation and account for experimental uncertainty. The regular solution model fits the available data on anhydrous silicate liquids to within the accuracy of the thermodynamic database +/?550 cals). Extensions to regular solution theory allow water solubility in more silica rich liquids to be modelled somewhat less accurately (+/?750 cals). The topology of the excess free energy of mixing surface is strongly asymmetric, possessing a single multicomponent saddle point which defines a spinodal locus. Given this prediction of a multicomponent spinode, a mathematical procedure based upon minimisation of the Gibbs free energy of mixing is developed for the calculation of the compositions of coexisting immiscible liquids. Predicted binodal compositions substantially agree with elemental liquid/liquid partitioning trends observed in lavas. Calculations suggest that an immiscible dome, in temperature-composition space, intersects the liquidus field of the magma type tholeiite. Immiscible phenomena are predicted at sub-liquidus temperatures for the bulk compositions of more basic or alkalic lavas, but are absent in more siliceous rock types for temperatures of the metastable liquid down to 900 K. The regular solution model is used in four petrological applications. The first concerns a prediction of the binary olivine-liquid phase diagram. The calculated geometry exhibits a minimum near Fa₇₅, which, though not in accord with experimental results on the pseudobinary system, compares quite favorably with olivine-liquid phase equilibria interpreted from rhyolites, namely that the olivine phenocrysts of rhyolites are more iron rich than their coexisting liquids. The second petrological example concerns estimating the depth of the source regions of several basic lavas whose compositions cover a range from ugandite to basaltic andesite. The third application is a calculation of the saturation temperatures and compositions of plagioclase and olivine in four experimental basaltic liquids and a prediction of the liquidus temperatures and first phenocryst compositions of the Thingmuli lava series of Eastern Iceland. Lastly, enthalpies of fusion are computed for a variety of stoichiometric compounds of geologic interest. These demonstrate good agreement with calorimetrically measured quantities     

Catabolic and anabolic energy for chemolithoautotrophs in deep-sea hydrothermal systems hosted in different rock types

Active deep-sea hydrothermal vents are hosted by a range of different rock types, including basalt, peridotite, and felsic rocks. The associated hydrothermal fluids exhibit substantial chemical variability, which is largely attributable to compositional differences among the underlying host rocks. Numerical models were used to evaluate the energetics of seven inorganic redox reactions (potential catabolisms of chemolithoautotrophs) and numerous biomolecule synthesis reactions (anabolism) in a representative sampling of these systems, where chemical gradients are established by mixing hydrothermal fluid with seawater. The wide ranging fluid compositions dictate demonstrable differences in Gibbs energies (ΔG_r) of these catabolic and anabolic reactions in three peridotite-hosted, six basalt-hosted, one troctolite-basalt hybrid, and two felsic rock-hosted systems. In peridotite-hosted systems at low to moderate temperatures (<∼45 °C) and high seawater:hydrothermal fluid (SW:HF) mixing ratios (>10), hydrogen oxidation yields the most catabolic energy, but the oxidation of methane, ferrous iron, and sulfide can also be moderately exergonic. At higher temperatures, and consequent SW:HF mixing ratios <10, anaerobic processes dominate the energy landscape; sulfate reduction and methanogenesis are more exergonic than any of the aerobic respiration reactions. By comparison, in the basalt-hosted and felsic rock-hosted systems, sulfide oxidation was the predominant catabolic energy source at all temperatures (and SW:HF ratios) considered. The energetics of catabolism at the troctolite-basalt hybrid system were intermediate to these extremes. Reaction energetics for anabolism in chemolithoautotrophs—represented here by the synthesis of amino acids, nucleotides, fatty acids, saccharides, and amines—were generally most favorable at moderate temperatures (22-32 °C) and corresponding SW:HF mixing ratios (∼15). In peridotite-hosted and the troctolite-basalt hybrid systems, ΔG_r for primary biomass synthesis yielded up to ∼900 J per g dry cell mass. The energetics of anabolism in basalt- and felsic rock-hosted systems were far less favorable. The results suggest that in peridotite-hosted (and troctolite-basalt hybrid) systems, compared with their basalt (and felsic rock) counterparts, microbial catabolic strategies—and consequently variations in microbial phylotypes—may be far more diverse and some biomass synthesis may yield energy rather than imposing a high energetic cost.