南海IODP 349航次基底玄武岩中碳酸盐岩脉的岩石学特征*

国际大洋发现计划(International Ocean Discovery Program, IODP)349航次在南海东部次海盆和西南次海盆残留扩张脊附近的U1431和U1433站位首次钻取基底玄武岩, 通过对16块基底玄武岩内的碳酸盐岩脉薄片镜下观察以及激光拉曼光谱分析, 揭示碳酸盐矿物为方解石和文石, 为典型的洋壳低温热液蚀变次生矿物。U1431站位碳酸盐岩脉为独立的方解石脉、文石脉交替出现; 而U1433站位则存在方解石脉、文石脉和方解石-文石共生脉三种情况。此外, U1431站位在基底~42.1m处出现了平行的方解石脉和文石脉, 揭示U1431存在不同来源热液的多期活动, 即可能存在多次或多阶段不同的热液注入。U1431和U1433站位的碳酸岩脉中, 文石的矿物集合体形状基本一致, 呈块状、纤维状和放射纤维状; 而方解石存在差异, U1431的方解石以斑块状、块状、粒状和纤维状出现, 而U1433的方解石仅出现块状。U1431站位的碳酸盐岩脉的丰度明显高于U1433站位。这些均揭示U1431站位的低温热液活动强, 而U1433站位则相对弱。两个站位的热液活动不同很可能是由于区域地质环境的差异造成——U1431附近的巨大海山为其提供了热液补给, 而U1433远离热液的补给/渗漏点。     

Terrestrial discharge influences microbioerosion and microbioeroder community structure in coral reefs

Microbioerosion rates and microbioeroder community structure were studied in four Kenyan protected coral-reef lagoons using shell fragments of Tridacna giant clams to determine their response to the influence of terrestrial run-off. Fourteen different microbioeroder traces from seven cyanobacteria, three green algae and four fungi species were identified. The river discharge-impacted reef and ‘pristine’ reef showed similar composition but higher microbioeroder abundance and total cyanobacteria- and chlorophyte-bioeroded areas when compared with the other study reefs. Cyanobacteria dominated during the north-east monsoon (NEM) relative to the south-east monsoon (SEM) season, with algae and cyanobacteria being major microbioeroders in the river-impacted and pristine reefs. The rate of microbioerosion varied between 4.3 g CaCO3 m^?2 y^?1 (SEM) and 134.7 g CaCO₃ m^?2 y^?1 (NEM), and was highest in the river-impacted reef (127.6 g CaCO₃ m^?2 y^?1), which was almost double that in the pristine reef (69.5 g CaCO₃ m^?2 y^?1) and the mangrove-fringed reef (56.2 g CaCO₃ m^?2 y^?1). The microbioerosion rates measured in this study may not be high enough to cause concern with regard to the health and net carbonate production of Kenya’s coral reefs. Nevertheless, predicted increases in the frequency and severity of stresses related to global climate change (e.g. increased sea surface temperature, acidification), as well as interactions with local disturbances and their influence on bioerosion, may be increasingly important in the future.     

颗粒状纳米碳酸钡锶钙的研制

介绍一种气-液相合成技术合成氧化物阴极用三元碳酸盐,研究沉淀温度、浓度及搅拌速率对合成碳酸钡锶钙结晶形貌的影响,分析其结晶过程.通过优化合成溶液温度及合成浓度,控制碳酸盐的成核和生长速率,合成了一种颗粒状纳米三元碳酸盐,并进行直流发射测试.实验表明,这种纳米碳酸盐能明显提高氧化物阴极的发射性能.     

Theoretical analyses of acidization dissolution front instability in fluid‐saturated carbonate rocks

This paper presents an instability theory that can be used to understand the fundamental behavior of an acidization dissolution front when it propagates in fluid‐saturated carbonate rocks. The proposed theory includes two fundamental concepts, namely the intrinsic time and length of an acidization dissolution system, and a theoretical criterion that involves the comparison of the Zhao number and its critical value of the acidization dissolution system. The intrinsic time is used to determine the time scale at which the acidization dissolution front is formed, while the intrinsic length is used to determine the length scale at which the instability of the acidization dissolution front can be initiated. Under the assumption that the acidization dissolution reaction is a fast process, the critical Zhao number, which is used to assess the instability likelihood of an acidization dissolution front propagating in fluid‐saturated carbonate rocks, has been derived in a strictly mathematical manner. Based on the proposed instability theory of a propagating acidization dissolution front, it has been theoretically recognized that: (i) the increase of the mineral dissolution ratio can stabilize the acidization dissolution front in fluid‐saturated carbonate rocks; (ii) the increase of the final porosity of the carbonate rock can destabilize the acidization dissolution front, while the increase of the initial porosity can stabilize the acidization dissolution front in fluid‐saturated carbonate rocks; (iii) the increase of the mineral dissolution ratio can cause an increase in the dimensionless propagation speed of the acidization dissolution front; (iv) the increase of the initial porosity can enable the acidization dissolution front to propagate faster, while the increase of the final porosity can enable the acidization dissolution front to propagate slower in the acidization dissolution system. Copyright © 2012 John Wiley & Sons, Ltd.     

我国首次发现的纤碳铀矿

本文报道的纤碳铀矿产于湖南某花岗岩型铀矿床氧化带中。纤碳铀矿是一种铀酰碳酸盐矿物,在中国是首次发现。本文作了系统的矿物研究并与国外资料作了对比。     

Bauxite development in the North Apuseni mountains, western Romania

The stratigraphic and palaeogeomorphologic conditions of bauxite formation in the North Apuseni mountains are related to the geotectonic evolution of western Romania during the Late Jurassic and Early Cretaceous. Bauxitization, accumulation and preservation of the bauxites were directly associated with karst development in the area under study. The petrographic and mineralogic nature of the bauxite deposits reveal superimposed aliagenetic, catagenic and, locally, metamorphic features. A comparative analysis of the principal chemical components of the different bauxite-bearing zones of the North Apuseni mountains are used to show similar development.     

Organic geochemical studies of a recent Inner Great Barrier Reef sediment—I. Assessment of input sources

The concentration of solvent-extractable (SE) and bound hydrocarbons, ketones, alcohols, sterols, monocarboxylic acids, hydroxyacids and α,ω-dicarboxylic acids of a surface sample (0–2.5 cm) from a recent carbonate tropical sediment taken at 60ft (18m) depth north-west of the Low Isles, North Queensland, are reported in detail. n-Alkanes are a minor constituent in the SE and bound hydrocarbon fractions with the major component being unresolved complex hydrocarbon material which is not an anthropogenic input. 6,10,14-Trimethylpentadecan-2-one derived from chlorophyll, as well as phytol, were identified as major components of the ketone and alcohol constituents. No chlorophyll pigments or pigmented degradation products were present, implying degradation before incorporation into the sediment. This conclusion is consistent with evidence for higher-plant input in which all sensitive lipids have been degraded before incorporation. SE and bound fractions have been studied in detail and show considerable differences probably arising from the importance of viable biomass in the SE fraction. Inputs to the sediment are determined as higher plants, algae, bacteria, fungi and meiofauna in descending order of importance.     

Infrared estimates of aliphatic kerogen carbon in sedimentary rocks

An infrared routine has been developed to estimate the aliphatic portion of kerogen carbon in sedimentary rocks. The procedure does not require isolation of the organic matter and is based on a computer-assisted determination of global band areas in the region of the aliphatic carbon-hydrogen stretching vibrations around 2900cm⁻¹. From these integrated absorptions the amount of aliphatic carbon C_al (mg of aliphatic carbon per gram of solvent-extracted rock) is calculated by means of a calibration with model rocks. Carbonate overtones which interfere in the case of limestones are eliminated by comparison to a CaCO₃ standard.The method has been applied to rocks containing kerogens of different types and maturities at TOC levels of 0.5 to 12%. The aliphatic carbon concentrations range from 0.5 to 60mg·g⁻¹ and correlate reasonably well with the residual genetic potentials of the rocks as measured by S₂ values from Rock-Eval pyrolysis. The ratio S₂/C_al is found to decrease with burial depth reflecting a maturity enhanced conversion of aliphatic carbon to fixed aromatic carbon under Rock-Eval conditions.     

Fossil worm tubes from the presumed cold-seep carbonates of the Miocene Hayama Group, Central Miura Peninsula, Japan

Abstract Fossil worm tubes were collected from the Hayama Group, Miura Peninsula, Japan, together with abundant fossils of Calyptogena-Acharax clams. The fossil worm tubes were well preserved and coated with milky white amorphous silica. Most of the tubes were 1-3 mm in diameter, and up to 10 cm in length. Worm tubes were found in siltstone and limestone, and formed network-like assemblages. Elemental mapping on the tube cross-sections revealed the localization of sulfur, zinc and iron at the worm tubes, which suggests that sulfur-related metabolism and deposition occurred in association with the worm tubes. High resolution analysis revealed the localization of zinc-sulfur (sphalerite, ZnS) on the tubes, while iron-sulfur (pyrite, FeS₂) was localized at the center of the tubes. The spatially separate sphaleritization and pyritization imply that epiphytic and endosymbiotic microorganisms perform different sulfur metabolisms, such as sulfate-reduction and sulfide-oxidation.     

Characteristics and Genetic Analysis of the Deep-buried Weathered-crust Karst Hydrocarbon Reservoirs of the Lower Paleozoic Group in the Tarim Basin

The genetic analysis of the deep-buried reservoirs of the Lower Paleozoic carbonate rocks in the Tarim basin is a difficult task involving many factors. Firstly, the object of study is carbonate rocks, which have undergone a long term of modification. Secondly, the rocks are deeply buried with depths of 3800-7000 m in the Tarim basin. The primary reservoir properties formed in the deposition have been strongly modified during the deep burial process. Concurrently, the different burial depths in different areas result in diversities of burial temperature, pressure, underground water, hydrochemistry and various physicochemical changes, which further lead to differences in the diagenetic type, diagenetic property, diagenetic degree and their impacts on the reservoir properties. The Lower Paleozoic Cambrian and Ordovician carbonate reservoirs in the Tarim basin can be grouped into four types, i.e., paleo-weathered-crust reservoirs, reef reservoirs, buried karst reservoirs and dolomite reservoirs. This paper