A combined pyrolysis mass spectrometric and light microscopic study of peatified Calluna wood isolated from raised bog peat deposits     

Edwin van der Heijden  Jaap J. Boon 《Organic Geochemistry》1994,22(6)

Stem wood of the Angiosperm Calluna vulgaris (Scotch heather), isolated at different depths from a selection of raised bog peat deposits, was chemically characterized using in-source pyrolysis mass spectrometry (Py-MS) and Curie-point pyrolysis gas chromatography mass spectrometry (Py-GC-MS). Light microscopy was performed to relate mass spectrometric characteristics with anatomical features. Peatified wood samples, isolated from increasing depth show a gradual decrease in carbohydrate content. This decrease in anatomically reflected in a selective removal of secondary cell wall material from the fibre-tracheids and wood parenchyma. During prolonged peatification a selective removal of hemicellulose sugars is observed, while a part of the cellulose fraction is preserved. This highly resistant cellulose is mainly located in the secondary cell walls of the vessels. The lignin macromolecule is preserved, but a gradual decrease in syringyl to guaiacyl ratio (S/G) is observed during peatification. Because no increase in catechol and phenolic compounds is observed, we conclude that S/G shifts are due to removal the of syringyl-rich secondary cell wall material and the retention of guaiacyl-rich compound middle lamella. Small chemical changes in the lignin macromolecule involve shifts in oxygen substitutions on the aliphatic side chains of the methoxyphenolics and the occurrence of aromatic acids.  相似文献   

造盆作用及成矿盆地的历史──动力综合分类   总被引：5，自引：4，他引：5  

陈国达 《大地构造与成矿学》1994,18(1):1-23

关于盆地的分类，不少学者提出过有意义的方案。它们主要是从某个单一角度进行：或者是从历史角度分析，或者是从动力角度分析，为了更较全面地认识它们，以求得更有效地指导找矿勘探，作者把两种分析方法结合起来，提出一个综合分类方案。按历史－动力综合分类，造盆作用及盆地可划分为三大类：大洋壳型、雏陆壳（过渡壳）型及大陆壳型。大洋壳型中可细分为活动区型（主要为拉张式）和稳定区型。雏陆壳型包括前地槽型（其中可分出多种活动区型及稳定区型，有待详究；活动区型中拉张式多见）及地槽前期型（主为拉张式）．大陆壳型中计有地槽后期（褶皱带）型（挤压式或拉张式）、地台型（主为陷落式，偶为张陷式－－断拉谷Ｑｕｌａｃｏｇｅｎ）和地洼型（挤压式、拉张式或压张式）。  相似文献   

钇易解石族的端员—钛钇易解石的发现     

陈德潜  尹道玲 《地质论评》1994,40(1):82-86

本矿物为新发现的钇易解石族的端员矿物－钛钇易解石，产于江西省龙南县足洞燕山期中粒白云母花岗岩及其风化壳中。矿物属斜方晶系，常呈板状或短柱状，为天然晶质体，浅黄色，粒度为０．０７５ｍｍ，硬度４．７，比重４．７３，二轴正晶，Ｎｇ＝２．２４８，Ｎｍ＝２．２１２，Ｎｐ＝２．１９４，Ｎｇ－Ｎｐ＝０．０５４，２Ｖ＝７０°。空间群为Ｄ＾１６２ｈ－Ｐｍｎｂ，ａ０＝０．７５０ｎｍ，ｂ０＝１．０９２ｎｍ，Ｃ０＝０．５  相似文献   

位于导电介质中三维导体的电磁响应          下载免费PDF全文

靳职理  许洪海 《地球物理学报》1989,32(4):423-432

本文给出一种用积分方程法配合有限差分法计算位于导电介质中三维导体的电磁响应的新途径,在二层大地条件下给出了具体计算方法和结果。详细讨论了围岩介质的导电性对导体异常的影响。这对于开展低阻覆盖层地区的电磁法工作具有一定的指导意义。  相似文献   

Transient electromagnetic response due to a pair of horizontal conducting sheets in a loop field     

R. Nagendra  I. B. Ramaprasada Rao  Satyanarayan Kabra 《Journal of Earth System Science》1985,94(3):269-277

The transient electromagnetic response due to a pair of horizontal conducting sheets induced by a loop field is obtained. The response characteristics in the three different regions (above the upper sheet, between the two sheets and below the lower sheet) are briefly discussed. In the first and second regions the composite response is characterised by an overburden response asymptote during early times and a target response asymptote during late times. The transition zones are characterised by shoulder-like bends. In the third region, the composite response increases in direct proportion to the induction number, eventually merging with the target response for large values of the induction number.  相似文献   

Gas chromatographic determination of peroxyacetyl nitrate: Two convenient calibration techniques     

Horst Meyrahn  Günter Helas  Peter Warneck 《Journal of Atmospheric Chemistry》1987,5(4):405-415

Two procedures for the calibration of an electron capture detector (ECD) for peroxyacetyl nitrate (PAN) are discussed. One is based on the first-order decay rate of the the PAN mixing ratio in conditioned glass storage vessels. The other method makes use of the photochemical generation of PAN in mixtures of acetone and NO₂ in air. For this purpose a Penray Hg lamp was inserted into a glass vessel filled with 1 atmosphere of air containing 10 ppm NO₂ and 1% acetone. After 3 min of irradiation, the average PAN mixing ratio formed was 8.87±0.25 ppmv as determined in six separate runs.  相似文献   

黄铁矿与沥青铀矿的共生条件及在沥青铀矿形成过程中所起作用的实验研究   总被引：5，自引：0，他引：5  

赵凤民  沈才卿 《铀矿地质》1986,(4)

高价铁与高价铀混合溶液在还原场中形成了共生的黄铁矿与沥青铀矿,该过程必须在弱酸性-中性-碱性介质中进行,其中在弱酸性至中性介质中易形成大的黄铁矿单晶。高价铀溶液流经黄铁矿矿区时,若在高温高压条件下,有新生的黄铁矿或白铁矿与沥青铀矿共生。黄铁矿还原六价铀形成沥青铀矿时,起还原作用的是二价硫。赤铁矿常与沥青铀矿共生,但它们是热液演化过程中不同阶段的产物,赤铁矿形成于体系氧逸度高的氧化环境,沥青铀矿形成于体系氧逸度低的还原环境,赤铁矿形成于沥青铀矿之前。  相似文献   

Pyrolysis of immature Torbanite and of the resistant biopolymer (PRB A) isolated from extant alga Botryococcus braunii. Mechanism of formation and structure of torbanite     

C. Largeau  S. Derenne  E. Casadevall  A. Kadouri  N. Sellier 《Organic Geochemistry》1986,10(4-6)

Immature Torbanite and the resistant biopolymer (PRB A) isolated from extant B. braunii were previously compared using bulk spectroscopic methods. In the present work, analysis of 400°C pyrolysis products and pyrolysis residues provided further information on their structure and possible relationships. It appears that such polymers are based upon unbranched, saturated, cross-linked hydrocarbon chains up to C₃₁. In addition to these bridging structures, a substantial part of the alkyl chains is singly bound, as esters of unbranched, saturated or cis unsaturated, even fatty acids. These esters are sterically protected, against chemical degradations, by the network of the bioand geopolymer.Quantitative and qualitative observations derived from 400°C pyrolysis confirm that the chemical structure of PRB A and immature Torbanite are closely related. The pyrolysis residues show a similar evolution and numerous common features are noted, with respect to the nature and the distribution of the major constituents of the pyrolysates (hydrocarbons and fatty acids). Accordingly, Botryococcus provides what seems to be the first example of a close structural relationship between a biopolymer produced in large amounts by an extant alga and the geopolymer of an immature kerogen. The essential role of PRB A in Torbanite formation is ascertained. Moreover, it is found that the resistant biopolymer does not undergo important structural changes during the first stages of diagenesis. Thus, owing to steric protection, the esters of immature Torbanite show a distribution quite close to the one of PRB A esters, with exclusively even constituents and a large contribution of unsaturated acids.Recent observations pointed to the possible genesis of some algal kerogens principally by selective preservation of resistant macromolecules. Such a type of formation is clearly predominant in Torbanite, where the bulk of the fossil organic matter corresponds to a selectively preserved and weakly altered, resistant biopolymer, while incorporation of lipids into the kerogen structure during diagenesis seems to play a minor role.  相似文献   

Ra法找矿及其在异常评价中的应用     

龚新喜  胡敏知 《华东地质学院学报》1986,(2)

本文介绍带电收集片测定土等粉末样品的 Ra 含量来找 U 矿的方法,称为 Ra 法。此法灵敏度高,操作简便,成本低,可以使用~(210)Po 法曲仪器和铜片,便于推广使用。文中介绍了测 Ra 流程,测定误差和灵敏度.Ra 法在详查和区调阶段的用途。总结了深部盲矿、地表矿化和非矿异常地段上地表的 Ra、Po 和γ异常的特征,指明 Ra 法和 Po 法结合可用于评价异常,提高找深部铀矿的能力。  相似文献   

均质土坡的安全系数     

徐金明  陈文才 《上海国土资源》1995,(3):43-48

本文用变分法的基本理论的方法，推导出了均质土坡稳定性在平面应变情况下的基本方程，将简单边坡无粘性土（Ｃ＝０）与纯粘性土ψ＝０）的情况作为特例导出了相应的计算方法与计算公式，并对传统的条分法与土坡临界高度计算方法进行了讨论。  相似文献