Rocky coast processes: with special reference to the recession of soft rock cliffs

Substantial progress in research on the recession of coastal cliffs composed of soft materials has been made in recent years and data with higher accuracy have been accumulated. This paper provides the state of the art review in the recession studies and highlights two new findings obtained from the reanalysis of existing data. The review topics are: episodic and localized nature of cliff recession; the development of cliffline; the relationship between cliff height and recession rate; mechanisms of cliff toe erosion by waves; a fundamental equation for wave-induced toe erosion; factors controlling toe erosion; and slope instabilities and mass movements. The findings are presented on (1) the temporal change in cliffline recession mode and (2) the effect of beach sediment at the cliff base on the cliff erosion.     

乌江流域沉积岩风化过程中稀土元素的富集与释放

以乌江流域石灰岩、白云质灰岩、白云岩、硅质岩、页岩和砂岩等沉积岩的13条风化剖面为对象，运用R型分层聚类分析和质量平衡计算方法，研究了这些岩石风化过程中稀土元素（REE）的富集与释放及其对植物生长和河水REE分布的影响，目的是为河水物质来源研究和为农业生产提供依据。结果表明：（1）乌江流域石灰土中REE的富集程度显著高于各自母岩、黄壤、上陆壳（UCC）、中国土壤（CS）和世界土壤（WS）；（2）沉积岩风化过程中REE的富集特征和机制可能与母岩中REE分布特征以及风化剖面中有机质、铁（氢）氧化物和粘土矿物的吸附有关；（3）沉积岩风化过程中释放的REE可为植物吸收利用；（4）石灰岩等沉积岩风化过程中REE和F。等元素的释放对河水溶解态REE的分布有重要影响。     

Implication of fractal geometry for fluid flow properties of sedimentary rocks

It is demonstrated that a certain amount of order can be extracted from an apparently random distribution of pores in sedimentary rocks by exploiting the scaling characteristics of the geometry of the porespace with the help of fractal statistics. A simple fractal model of a sedimentary rock is built, and is tested against both the Archie law for conductivity and the Carman-Kozeny equation for permeability. We demonstrate how multifractal scaling of pore-volume can be used as a tool for rock characterization by computing its experimentalf() spectrum, which can be modelled by a simple two-scale Cantor set.     

Über die Isotopenzusammensetzung des Schwefels in seinem natürlichen Kreislauf

Es wird ein Modell des globalen Kreislaufs der Isotope des Schwefels erarbeitet, auf dessen Grundlage die säkularen Veränderungen der Isotopenzusammensetzung des Schwefels in sedimentären Sulfiden, in organisch gebundenem Schwefel und in sedimentären Sulfaten verstanden werden können. Das Modell berücksichtigt die Venwitterung von Magmatiten und sedimentärem Schwefel unter Oxydation von Sulfid zu Sulfat, die Verwitterung sedimentärer Sulfate, die Bildung sedimentärer Sulfide und organisch gebundenen Schwefels, die Bildung sedimentärer Sulfate, die Metamorphose der Sedimente und die Überführung sedimentären Schwefels in die Ozeane durch vulkanische Prozesse. Es wird gezeigt, daß nur die Isotopieeffekte bei der mikrobiellen Reduktion von Sulfat zu Sulfid, bei der Assimilation von Sulfaten durch die Pflanze und bei der Verwitterung sedimentärer Sulfide und organisch gebundenem Schwefel unter Oxydation von Sulfid zu Sulfat Einfluß auf die globale Isotopenzusammensetzung des Schwefels in den Sedimenten haben können. Im Wechselspiel dieser Prozesse kommen die säkularen Verānderungen der δ³⁴S-Werte, insbesondere die charakteristischen Schwankungen der δ³⁴S-Werte zustande. Dabei begünstigen starke Meeresbedeckungen der Erdoberfläche und warmes Klima die mikrobielle Reduktion von Sulfat zu Sulfid in den Ozeanen und führen zum Sinken bzw. Steigen der δ³⁴S-Werte in den sedimentären Sulfiden und im organisch gebundenen Schwefel bzw. in den sedimentären Sulfaten. Regressionen der Ozeane und kaltes Klima, insbesondere Vereisungen begünstigen die Verwitterung und Oxydation von Sulfiden zu Sulfaten und führen zu einem Steigen bzw. Sinken der δ³⁴S-Werte in den sedimentären Sulfiden und im organisch gebundenen Schwefel bzw. in den sedimentären Sulfaten.     

论地震发生机制

地震发生的物理机理和过程是还没有认识清楚的问题. 此前人们将浅源地震归因于弹性回跳,根据这一观点和岩石实验结果计算得到的地震能量与实际观测结果有很大矛盾,被称之为“热流佯谬”. 中源和深源地震发生在地幔区域,其成因也没有合理的解释. 考虑到地壳和地幔是离散集合态物质体系及其慢动力学运动行为的基本特点,本文根据物理学原理,特别是近年凝聚态物理发展出来的相关新观念,并依据已有观测事实,从新的视角探究地震发生的物理机制. 1) 关于地壳岩石层中的应力分布:在不考虑构造力时,依据万物皆流的流变学原理,原始地壳岩石在自重压强长时间作用下,纵向和横向应力相同,没有差应力. 大地构造力推动岩块滞滑移动挤压断层泥,施加于其他岩块,逐渐传递和积累. 这种附加的横向构造力与原始岩石中应力叠加,形成地壳岩石层中的实时应力. 由于断层泥属于颗粒物质体系,具有与岩石不同的力学特征,其弹性模量比岩石小得多,且随压强而增大,导致构造作用力随深度非线性增大. 给出了地壳中构造应力分布及其变化规律. 2) 关于地壳岩石层强度:地壳岩石的自重会使岩石发生弹性–塑性转变. 通过对弹性–塑性转变深度的计算,并根据实际情况分析,给出了地壳岩石弹性、部分塑性和完全塑性三个区域的典型深度范围. 在部分塑性区,塑性体比例达到约10%以上时,发生塑性连通,这时岩石剪切强度由塑性特征决定. 塑性滑移的等效摩擦系数比脆性破裂小一个数量级以上,致使塑性滑移时岩石剪切强度比脆性破裂小得多. 同时,随深度增大,有多种因素使得岩石剪切屈服强度减小. 另一方面,地震是大范围岩石破坏,破坏必然沿薄弱路径发生. 因此,浅源地震岩石的实际破坏强度必定比通常观测到的岩石剪切强度值低. 给出了地壳岩石平均强度和实际破坏强度典型值随深度的分布规律. 3) 关于地震发生的条件和机制:地震发生必定产生体积膨胀,只有突破阻挡才可膨胀. 地震发生的条件是:大地构造力超过岩石破坏强度、断层边界摩擦力以及所受阻挡力之和. 因此,浅源地震是岩石突破阻挡发生的塑性滑移. 在此基础上提出了浅源地震发生的四种可能模式. 深源地震是冲破阻挡发生的大范围岩块流. 浅源地震和深源地震都是堵塞–解堵塞转变,是解堵塞后岩石层块滑移或流动造成的能量释放. 4) 关于地震能量和临震前兆信息:地震能量即为堵塞–解堵塞转变过程释放的动能. 以实例估算表明,地震岩石滑移动能与使岩块剪切破坏和克服周围摩擦阻力所需做的功相一致,不会出现热流佯谬. 同时指出,通过观测地震发生前构造力的积累过程、局域地区地质变迁以及岩石状态变化等所产生的效应,均可能获得有价值的地震前兆信息. 关键词： 地震发生机制 热流佯谬 地壳岩石应力和强度 堵塞–解堵塞转变     

低本底伽马能谱测量在沉积岩分类判别中的应用及其影响因素探讨

沉积岩中放射性元素铀、钍、钾的含量主要取决于岩石中泥质的含量,而泥质含量的高低是判别沉积岩类别的主要依据,因此,可以将铀、钍、钾的比活度或含量值作为判别沉积岩岩类的量化指标。利用低本底伽马能谱法测量岩石样品中铀、钍、钾的比活度或含量,可以快速、准确地进行岩类判别。由于放射性测量受样品几何形状、样品质量及其所含水分含量变化的影响,因此岩类判别的准确性会受到影响。通过理论探讨和实验验证,发现各待测核素特征峰计数率值与样品质量成线性关系, 且不同的能量区域、不同的岩性,线性关系系数与趋势拟合程度都是不同的;当样品的水分含量不超过10%(取样时,岩屑水分不超过10%)时,对测量结果的影响很小(变化值均在一倍均方差以内),因此,水分含量对低本底伽马能谱法判别沉积岩岩类的准确性不产生显著的影响,一般可以不予考虑。对陕西定边某油气勘查区钻孔岩屑样品进行判别试验,对实测数据进行质量校正后,利用铀、钍、钾道的“归一化”计数率值(即单位质量的计数率)只能粗略地划分不同沉积岩的大类,再以铀、钍、钾特征峰的合峰计数率建立综合判别模式,能够对岩类进行进一步细分,且判别准确度达到75%以上。     

A statistical measure of association and a series expansion of chain conformations

A simple, easily calculated, nonparametric statistic is described that can detect the presence of a functional relationship in bivariate data. Given a sample of data points (x,y), the statistic's value is nearly 1 if y is a linear function of x with little noise; it is greater than 1 if y is a nonlinear function of x; and it is close to 2 if x and y are uniformly and independently distributed. The statistic can be used to rapidly screen through large data sets to identify the most functionally related variable pairs. As an illustration, the statistic is used to detect relations between polypeptide conformational energy and functions of a series expansion for chain conformations.     

Chemical analyses of martian soil and rocks obtained by the Pathfinder Alpha Proton X-ray spectrometer

The US Mars Pathfinder spacecraft, which landed on the red planet on the 4th of July 1997, carried an Alpha Proton X-ray Spectrometer (APXS) that obtained the chemical composition of martian soil and rocks. The principles of the APXS operation are based on three interactions of alpha particles with matter: Rutherford alpha backscattering; (, p) nuclear reactions; and X-ray generation by charged particles and X-ray excitation. The APXS, as was implemented on the Pathfinder mission, uses for all three modes of operation a monoenergetic beam of alpha particles from about 40 mCi of ²⁴⁴Cm radioisotope. It employs Si charged particle detectors for alpha and proton modes and a specially designed silicon PIN detector for its X-ray mode that does not require cooling for its operation. The APXS can detect all of the elements (except H and He) present above a few tenths of a percent for all major elements and several hundred ppm for many minor and trace elements.

The APXS on Pathfinder was transported to various locations on the martian surface by the Sojourner rover which enabled it to analyze multiple soil and rock samples selected by the science team from the lander camera images. The APXS performed excellently under the adverse martian environment conditions and provided important information about the chemical composition of the martian soil and rocks. All of the analyzed rocks at the Pathfinder site were found to have high concentrations of silica, sulfur and iron, and low in magnesium, similar to those of the terrestrial basaltic andesites and definitely different from the SNC meteorites that are believed to have originated from Mars. All of the soil samples analyzed by the APXS have similar composition and are very close to the soil analyses obtained by the two Viking missions. The information derived from the Pathfinder APXS has significant implications about the origin and evolution of planet Mars.     

Probenchemische Methode zur Bestimmung von 15N an in Gesteinen fixiertem Stickstoff

Zur Klärung geologischer Prozesse werden in zunchmendem Maße die Isotopenvariationen des Stickstoffs herangezogen. Da der größte Teil des Stickstoffs der Gesteine in gebundener Form als Ammoniumstickstoff [1–6] vorliegt, kommt der Untersuchung der Isotopenvariationen desselben eine große Bedeutung zu.     

Extractive Spectrophotometric Determination of Titanium in Silicate Rocks, Soils and Columbite–Tantalite Minerals

2,3-Dihydroxynaphthalene forms a strong chelate with titanium over the pH range 4 to 9. At pH 4–5, titanium is extracted into ethyl acetate along with iron, leaving behind V, Nb, Mo, and a host of elements present in complex matrices of rock samples. In the extract, titanium is easily separated from iron after raising the pH of the medium and re-extracting. The method is free from any interference. The sensitivity of the method is 3.2×10⁴ L·mol^–1cm^–1. The method has been applied to a number of diverse samples including rocks and minerals. The precision of the Ti method is excellent. This method has been compared with tiron, chromotropic acid, diantipyrilmethane (DAM) and other existing spectrophotometric methods used in the analysis of rocks, ores and minerals. The proposed method has definite advantages over most spectrophotometric methods in terms of sensitivity, selectivity, reproducibility and simplicity.