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81.
Tracing suspended organic nitrogen from the Yangtze River catchment into the East China Sea 总被引:2,自引:0,他引:2
Ying Wu Thorsten Dittmar Kai-Uwe Ludwichowski Gerhard Kattner Jing Zhang Zhuo Y. Zhu Boris P. Koch 《Marine Chemistry》2007
Total suspended matter was collected along the Yangtze River (Changjiang) and in the East China Sea in April to May and in September 2003, respectively, to study origin and fate of particulate organic nitrogen. Concentrations of particulate organic carbon (POC), nitrogen (PN) and hydrolyzable particulate amino acids (PAA; d- and l-enantiomers) were higher in the Yangtze Estuary than in the river and decreased offshore towards the shelf edge. In the coastal area, higher values of PAA were observed in the surface layer than in the bottom water. Stable carbon isotope ratios (δ13C) of POC increased from − 24.4‰ in the river to values around − 21‰ on the East China Sea Shelf. Dominant amino acids were aspartic acid + aspartine (Asx), glutamic acid + glutamine (Glx), glycine, alanine and serine. The proportions of Asx, Glx and isoleucine were higher in the marine than in the riverine samples contrary to the distributions of glycine, alanine, threonine and arginine. The proportions of d-amino acids were highest in the riverine suspended organic matter (6% of PAA) decreasing towards the shelf edge (1.5% of PAA). d-arginine, not reported in natural aquatic samples so far, was the most abundant d-amino acid in the river. The amino acid composition of the particulate organic matter (POM) in the Yangtze River indicates an advanced stage of degradation of POM. Highly degraded organic matter from soils is probably a main source of POM in the Yangtze River, but the relatively high δ13C values and low C/N ratios (7.7 ± 1.6) also indicate contribution from anthropogenic sources. The degraded riverine material was a dominant organic matter source in the estuary, where aquatic primary production had only a small overall contribution. In the East China Sea, gradual settling of riverine organic matter and the addition of fresher phytoplankton impacted the amino acid composition and δ13C values, and on the outer shelf relatively fresh phytoplankton-derived organic matter dominated. 相似文献
82.
The sedimentary rocks of the Metlaoui Formation in the Gafsa basin (southern Tunisia), which may be grouped in three units: the basal (Thèlja), middle (Chouabine) and upper unit (Kef Eddour), provide a record of preserved sedimentary, authigenic and biological processes. This paper presents the findings of sedimentological investigations of the biosiliceous deposits of the middle unit. This unit contains either well-preserved (Opal-A) or diagenetically altered (Opal-CT, clinoptilolite, quartz and even clays) diatom frustules. Such diagenetic changes are commonly described in marine and lacustrine biosiliceous deposits. The fossil content of theses diatomaceous layers implies shallow-marine conditions.The opal-rich sediments, and the associated facies record the transgressive transitions associated with high organic productivity, probably enhanced by seasonal input of nutrients, and high sea level stands, and a close association with stratified water column conditions. The formation of bedded diatomaceous sediments is known to require either high organic productivity or anoxic conditions in bottom/intermediate water, and eventually both processes. The initial organic content of the biogenic deposits was impoverished in early stages of sedimentation and diagenesis. A large part of the organic matter could have been destroyed during early diagenetic processes and from further oxidation in outcrops. 相似文献
83.
S. Dewaele Ph. Muchez J. Vets M. Fernandez-Alonzo L. Tack 《Journal of African Earth Sciences》2006,46(5):455-469
A multiphase origin of the Cu–Co ores in the western part of the Lufilian fold-and-thrust belt in Central Africa is proposed based on literature, satellite image interpretations and petrographic and fluid inclusion analyses on samples from the stratiform mineralization of Kamoto and Musonoi (DR Congo). The various mineral occurrences in the Katanga Copperbelt can be classified in distinct categories: stratiform, supergene enrichment and vein-type. The stratiform mineralization form the largest group and can be found mainly in Lower Roan (R-2) rocks, which can be identified as ridges on satellite imagery. Ore deposits outside the R-2 occur along lineaments and result often from supergene enrichment.The main phase of the stratiform mineralization in the Katanga Copperbelt occurred during diagenesis preceding the Lufilian orogeny. Petrographic observation identified various mineralizing phases, which played a role in the formation of these stratiform mineralization. Mineralization started during early diagenesis, but mainly occurred during further burial. After the formation of early diagenetic pyrite, the circulation of diagenetic Cu–Co-rich fluids resulted in the formation of the main mineralization. Preliminary microthermometric investigation of primary inclusions in authigenic quartz, associated with the main stage of stratiform mineralization, indicates that an H2O–NaCl fluid with a minimum temperature between 80 and 195 °C and a salinity between 8.4 and 18.4 eq. wt% NaCl circulated during the main phase of mineralization.Numerous faults and fractures formed during the Lufilian orogeny cut the stratiform mineralization. They are, however, at Kamoto and Musonoi only associated with minor sulphides. Supergene alteration along faults and fractures resulted in an enrichment of the mineralization, with the formation of secondary Cu-oxides, -carbonates and -silicates.The importance of the interaction of various processes for the formation of economic Cu–Co ore deposits is confirmed by the straightforward relationship on satellite imagery between the location of economic mineral occurrences and faults, which acted as pathway for descending waters that caused the supergene enrichment and upgrading of the primary mineralization. 相似文献
84.
D. J. Huisman G. T. Klaver A. Veldkamp B. J. H. van Os 《International Journal of Earth Sciences》2000,89(1):154-169
2 O contents, which can be attributed to the Alpine source supplying fresh, sodic plagioclase-rich material instead of the local,
strongly weathered sediments. Increasing K2O/Al2O3 can be attributed to a similar decrease in degree of weathering. However, this trend is disturbed by the loss of K from clay
minerals during weathering in organic-rich layers. Local high TiO2 anomalies, caused by preferential sorting and concentration, are found in most Pliocene sections, but they are absent in
the Upper Pliocene and Lower Pleistocene Alpine-derived deposits. This change is probably due to a change in the energy of
the fluvial system. Finally, (pyrite-) S contents drop (siderite-) Fe contents rise. Micromorphological observations indicate
that the Pliocene pyrite was formed when freshwater deposits were flooded with seawater during short-term events. The decrease
in S, and the increase in siderite-Fe, can be attributed to decreasing marine influence, as a result of the marine regression
at the Pliocene–Pleistocene transition.
Received: 28 August 1999 / Accepted: 2 November 1999 相似文献
85.
86.
87.
Qijia-Gulong Depression Northern Songliao Basin YAN Jianping LIU Li ZHANG Xinrong MA Yanping 《东北亚地学研究》2002,(2)
IntroductionTheorderingofdiageneticeventsisoneofthemostimportantkeystotheultimateinterpretationofthewaysinwhichthegeologicalandgeochemicalhistoryofasandstoneaffecteditscompositionandtexture .Thisarti clegiveadetaildescriptionandoriginexplanationtothea… 相似文献
88.
The saturated and unsaturated hydrocarbons of two samples (HD-19 and HD-21) from the same section of the Middle Eocene lacustrine Huadian oil shale in NE China were identified and shown to be mainly from algal and bacterial sources. Comparison of the two samples provided an opportunity to explore the contribution from telalginite to the hydrocarbon profiles. Cells identified from microscopy as Botryococcus in the telalginite of HD-21 were confirmed as belonging to the L race of B. braunii from the presence of monoaromatic lycopane derivatives and small amounts of several lycopadienes. Lycopane was abundant and was probably derived from biohydrogenation of lycopadienes and related lipids on the basis of δ13C values. Hopane distributions showed a dominance of those with the biological 17β,21β-stereochemistry, as expected for an immature shale, with low amounts of 17β,21α-hopanes (moretanes) and 17α,21β-hopanes. Two hopenes were also abundant and assigned as C29 and C30 neohop-13(18)-enes, which occurred together with the C29 and C30 hop-17(21)-enes. These had depleted carbon isotope values (−43.7‰ to −50.8‰), indicative of production by methane oxidizing bacteria (methanotrophs). The high proportion of hopanoids with carbon numbers < C32 indicates extensive post-depositional diagenetic alteration of bacteriohopanepolyols as well as a direct input of C30 hopanoids. The data clearly indicate that there was active utilization of methane in this lacustrine depositional setting, but isoprenoid hydrocarbon biomarkers for methanogens, such as pentamethylicosane (PMI) and squalane, were in surprisingly low abundance. It is possible that these bacterial contributions were present as polar lipids. The origins of an unusual C38 isoprenoid alkane assigned as bipristane are uncertain, but may be from methanogens. Steranes and sterenes were relatively minor components, but abundant diasterenes and 4-methyldiasterenes were present, reflecting significant conversion of the original lipid composition by way of clay-catalysed diagenesis. The biomarker data suggest that the bottom waters in the original depositional environment had low O2 content, but the sediments were probably neither sulfidic nor strongly reducing. The high content of organic matter in the shale likely reflects both high (but fluctuating) productivity due to eutrophic conditions in the overlying water and good preservation in the sediments. 相似文献
89.
中二叠世茅口组中-下部发育一种特殊的眼球状灰岩, 眼球部分通常为颜色较浅, 富含生屑颗粒的灰岩; 而眼皮部分通常为颜色较暗的泥灰岩。其成因一直存在分歧。本文通过对重庆南川大铺子剖面茅口组底部眼球状灰岩的野外观察和室内研究, 认为陆源输入的改变导致眼球和眼皮部分泥质含量的差异; 在成岩过程中, 碳酸盐沉积物为主的眼球部分因为胶结作用而没有被机械和压实作用破坏, 泥质含量较多的眼皮部分则受到强烈的压实。因此, 该地区眼球状灰岩的形成是沉积和成岩过程相互作用的结果, 为浅海陆棚沉积环境。 相似文献
90.
通过普通薄片、铸体薄片、X射线衍射、扫描电镜等多项测试方法,对鄂尔多斯盆地杏子川油田 W 区块长6储层的岩石学特征、孔隙结构、成岩作用进行分析与研究。结果表明:研究区长6储层岩性主要为细粒长石砂岩,颗粒分选性较好,胶结类型以接触式-孔隙式为主,少量镶嵌式胶结。储集空间类型以原生粒间孔、溶蚀粒间孔隙为主。砂岩储层成岩作用复杂,成岩现象丰富,对储集层物性影响显著。 相似文献