二叠纪海相碳酸盐的锶同位素演化及其意义

本文从沫阳和熊家场剖面二叠纪海相碳酸盐和玄武岩的锶同位素变化出发,讨论了碳酸盐的锶同位素组成与峨嵋山玄武岩喷发之间的关系,以及玄武岩中海相碳酸盐的锶同位素贫化原因,指出海相碳酸盐的锶同位素组成可作为了解地球构造演化的工具。     

西藏日土县拉热拉新花岗岩体特征及构造环境

拉热拉新花岗岩体属于唐古拉-东达山花岗岩带西段羌塘花岗岩区的组成部分,岩石类型主要为黑云角闪闪长岩、黑云角闪石英闪长岩、黑云角闪石英二长岩、黑云花岗闪长岩、黑云二长花岗岩、黑云花岗岩。其地球化学特征表现为：富Si,K,贫Ti,Mg,Fe,Ca,铝饱和指数ACNK〈1．1,稀土元素球粒陨石标准化图式呈右倾斜的“V”字型,LREE富集,HREE相对亏损,铕亏损。其形成时代为早白垩世,为多期次同碰撞的同熔型花岗岩。     

The northern Ossa-Morena Cadomian batholith (Iberian Massif): magmatic arc origin and early evolution

Diorites and related rocks in the Mérida area of northern Ossa-Morena (SW Iberia) are intrusive into Precambrian metavolcanic and metasedimentary sequences. Cumulate products from the H₂O-rich magmas are amphibole-rich gabbros to hornblendites. Major and trace element compositions, including Sr and Nd isotope data, allow the definition of a calc-alkaline series likely formed in relation to an immature arc setting. Crystallization of the intrusives has been established between ca. 570 and 580 Ma by U-Pb dating of constituent zircons. Garnet growth in dioritic rocks reflects a tectono–thermal overprint dated by Sm-Nd internal isochrons at around 555 Ma. Older Sm-Nd and Lu-Hf results between ca. 593 and 637 Ma on the same rocks suggest an earlier stage of regional metamorphism within the arc environment. The northern Ossa-Morena composite batholith and related metamorphic units have been tectonized and dismembered in the course of subsequent low-grade events during final stages of the Cadomian orogeny and the Variscan cycle. The units studied represent a well preserved segment of the arc region that evolved in Neoproterozoic times along the western border of Gondwana to conform the Cadomian–Avalonian basement of the Hercynian realm.This revised version was published in October 2004 with corrections to the names and order of the authors.     

台湾西南海域似海底反射分析

台湾西南海域弧陆碰撞及俯冲作用形成增生楔,在增生楔部位地震调查原始炮集数据上可清楚地识别BSR极性及波形特征。通过对该区域地震调查数据处理,获得了常规地震偏移、瞬时振幅及瞬时相位3种属性剖面,三者可清楚地反映BSR特征及分布,瞬时相位剖面还反映了BSR之上弱反射层的结构特征。研究表明,增生楔部位构造沉积明显控制BSR的形成与分布,该区天然气水合物成矿前景良好。     

南海西南次海盆声呐浮标地震测深资料研究

利用声纳浮标资料，得到了南海西南次海盆地壳的速度结构。确定海盆中沉积物的速度为1．6～3．9km／s，基底顶面速度为4．2～6．8km／s。确定海盆中存在洋壳。海盆中基底起伏较大，埋深为4400～5700m，很多地方的基底上只有一层300～500m厚的低速沉积层，而缺少其它上第三系的沉积物。海盆中沉积物的厚度为300～1500m，时代为晚渐新世～第四纪，由此推测西南次海盆的扩张开始时间应该为早渐新世。     

测绘数据处理中MATLAB的优越性及应用

MATLAB应用于复杂的测绘数据处理,具有提高测绘数据处理的速度和保证精确性的特点。本文从测量平差、变形监测数据分析、坐标换算、线性方程组的解算、MATLAB工具箱以及编程等方面出发研究MATLAB在数据处理工作中的优越性和应用。     

The response of Oneirophanta mutabilis (Holothuroidea) to the seasonal deposition of phytopigments at the Porcupine Abyssal Plain in the Northeast Atlantic

The impact of seasonal pulses of phytodetritus on the grazing behaviour of Oneirophanta mutabilis was assessed on the Porcupine Abyssal Plain (PAP) in the NE Atlantic. Sediment and sediment trap samples were analysed by HPLC to estimate the quantity and quality of the organic material in terms of phytopigments and nucleic acids. Food selection by Oneirophanta was estimated by analysing these constituents in the gut contents.The study area is characterised by large interannual variations in the deposition of fresh organic material. The mass fluxes at 10 m above bottom (mab) varied from 0.25 g DW m⁻² d⁻¹ in September 1996 to <0.1 g DW m⁻² d⁻¹ in March 1997. The material caught in the sediment trap in September 1996 had a relative fresh signature with a chlorophyll-a:phaeophorbide ratio of 1.33. During the other seasons (March 1997, July 1997 and October 1997) the chlorophyll-a:phaeophorbide ratio remained low. In sediment cores this ratio showed a similar seasonal and inter-annual pattern, and again September 1996 was the period of maximum abundance of fresh organic material in the surficial sediment. The analyses of the gut contents of Oneirophanta mirrored exactly the seasonal variation of the phytopigments in both the sediment and the sediment trap material. Concentrations of pigments in the fore-gut were 5 to 15 times higher than in the sediment and the nucleic acid concentrations were up to 80 times higher. This discrepancy between pigments and nucleic acids concentrations suggests that the latter are “indigenous” to the gut of Oneirophanta, either because the gut contains high numbers of actively-dividing bacteria or as a result of cell lysis of the gut epithelium. The seasonal differences in the pigment concentration factor suggest that Oneirophanta does not actively search for hotspots where pigment concentrations are enriched. By using the degradation rate of chlorophyll-a in the PAP sediments, the minimum residence time of chlorophyll in the sediment within the gut of Oneirophanta was calculated. In combination with gut volume and density data it was estimated that each year the Oneirophanta population skims a third of the sediment surface at the PAP site.     

A comparison between the megafauna communities on the N.W. Iberian and Celtic continental margins—effects of coastal upwelling?

Megafauna biomass and feeding guilds were studied on the NW Iberian upwelling Continental Margin in order to determine the presence of enriched zones pointing to enhanced particle input. We compare these findings with similar data obtained from a transect across the Celtic Continental Margin that represents a regime without coastal upwelling. Additionally sediment concentrations of phytopigments (chlorophyll-a, phaeophorbides) representing recent inputs of algal production and of nucleic acids (DNA, RNA) are used as proxies for microbial biomass, to assess if there was a relation between these parameters and the megafauna distribution. The sediment on the upper slope (<1600 m) of the Iberian Margin was found to be inhabited by filter-feeding megafauna (26–73% of total invertebrate density, and 1–35% of biomass), and contained relatively low levels of phytopigments (3–6 ng/cm³ chlorophyll-a) and nucleic acids (12–16 μg⁻¹ DNA, 1.5–3.5 μg⁻¹ RNA). In contrast, on the upper slope of the Celtic Margin the dominant component of the megafauna were deposit-feeders (57–92% of total invertebrate density, and 23–90% of biomass) and the sediments contained higher concentrations of phytopigments and nucleic acid. These observations, supplemented by video records revealing the presence of current ripples on the Iberian upper slope, show that these upper slope regions are non-depositional, high energy environments. Conditions at the lower slope and the abyssal plain on the Iberian transect were more quiescent with large deposit-feeding holothurians dominating the megafauna (72–94% of invertebrate biomass), and with relatively high sediment concentrations of phytopigments (7–9 ng/cm³ chlorophyll-a, 157–170 ng/cm³ phaeophorbides) and nucleic acids (21–38 μg⁻¹ DNA, 2.4–5.5 μg⁻¹ RNA). On the basis of our data we argue that the benthic food for the deepest stations on the Iberian transect does not consist of shelf derived organic matter. More likely, fast sinking offshore blooms, possibly associated with filaments of upwelling water, form the major contribution to the annual food supply of the deep living megafauna.     

南海北部地壳的深地震地质结构探测

１９９３年５月，中国科学院南海海洋研究与日本东京大学地震研究所等单位合作南海北部共同开展了综合地球物理测量实验，本文介绍了其中的海底地震仪海上资料采用，室内资料处理，根据资料的初步处理解释结果，文中分析了测区的地壳地质结构。     

基于随机理论的地下水环境风险评价

针对确定性模型难以描述含水层非均质空间分布的问题,提出基于随机理论的地下水环境风险评价方法。以矩形场地地下水污染风险评价为例,采用蒙特卡罗法生成大量渗透系数随机场,模拟含水层参数各种可能的非均质空间分布,在此基础上建立场地地下水流模型与溶质运移模型,分别计算污染物在地下水中的迁移转化情况。统计大量随机模拟中污染事故发生的频率,当模拟次数足够多时,污染频率收敛于污染概率,污染风险即通过污染概率体现出来。该方法将模型参数设为满足一定分布特征的随机变量,避免了确定性方法得出的武断的评价结果,可为工厂的选址、水源地的选址等工作提供科学指导。