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1.
雷州半岛硅藻土煅烧中的结构变化 总被引：5，自引：4，他引：5
本文应用Ｘ射线衍射、红外光谱、扫描电镜等手段，对广东海康、徐闻的硅藻土在煅烧过程中热结构变化进行了探讨。结构表明，煅烧使硅藻内部矿物的微观结构发生变化而引起形变，主要为ＳｉＯ２从无序含水的蛋白石转变为有序的方石英晶体。形变温度随其硅藻的种类和杂质不同而各异。本研究为这两地硅藻土的开发提供了科学依据。 相似文献
2.
Diatomaceous deposits of Fayium, Egypt; characterization and evaluation for industrial application 总被引：1，自引：0，他引：1
The Holocene lacustrine diatomaceous earth of Fayium,South West of Cairo,has been studied to define its minerals,chemistry,petrography and physical properties.Minerals were processed by way of calcination at 550℃ ,followed by acid leaching to reduce levels of mineral impurities.The diatomite is of biogenic opal A.with calcite as the main ganue mineral,quartz and clay minerals(smectite followed by kaolinite in abundance and a trace amount of illite).Silica in the diatomaceous earth accounts for about 63% on average.Positive correlation between CaO and CO2 indicates that Ca is present mainly as calcite.Al2O3,Fe2O3,MgO and K2O are attributed mainly to clay minerals.However,the physical properties of the diatomaceous earth as filter-aids and filler for paints and plastics are poor because of general high levels of impurities.The technological performances of the diatomaceous earth have been significantly improved owing to upgrading of diatoms through mineral processing trical. 相似文献
3.
通过对四川若尔盖高原玛曲—红原一带20个表土孢粉样的分析,研究了该区域表土孢粉组合与现代植被的关系。结果显示,玛曲—红原一带表土的孢粉组合基本反映了现代植被的整体特征,与现代植被在植被类型、植被带的空间排列、主要建群种属和优势种属等方面基本一致。依据孢粉的百分含量,可以划分为亚高山灌丛植被区,亚高山灌丛、亚高山草甸植被区和高寒草甸、草原植被区3个植被带。表土花粉的代表性因种属的不同而各有差异,松属和菊科花粉具超代表性,云杉属花粉的代表性较好,禾本科和莎草科具低代表性,而桦木属则不具有超代表性,可能与桦木属花粉不易搬运有关。3个植被区中的表土孢粉的种类、比例与现代植被均存在一定的差别,这可能与植被退化有关。 相似文献
4.
Lattice thermal diffusivities of eleven orientated natural and synthetic quartz samples were measured using a laser-flash
apparatus (LFA). For α-quartz, thermal diffusivity (D) decreases with temperature, so that directionally averaged values of D(T) between 20° and 500°C can be fit with D(T) = 1/(0.0017T + A), where A varies from 0.12 to 0.18 among the samples and D is in mm2/s. For β-quartz, D decreases very slightly or is constant with temperature. Values of D measured along [001] exceed those measured along [100] at all temperatures studied. A sharp decrease of D(T) marks the α-β phase transition, consistent with correlation of 1/D with C
P
in the damped harmonic oscillator model. Due to the rapidity of the laser-pulse and the dynamic nature of the measurements,
the raw data show evidence of latent heat being released at the transition temperature over ∼50 ms. D(T) values within 10 K of the transition are affected both by latent heat release and by the phase change. For our suite of samples,
D at all temperatures varies by ±7% from the overall average. This range is outside the 2% experimental uncertainty. To ascertain
causes of D variations, we characterized out samples using infrared absorption spectroscopy, electron microprobe analyses and secondary
ion mass spectrometry. Differences between the samples seem to result from the interplay of different impurity types: cations
that replace Si in the silicate tetrahedra, cations squeezing into the lattice, and OH. Although limitations in quantifying
amounts of trace impurities and poor understanding of where impurities reside in the lattice hamper interpretation, it seems
that samples containing more substitutional impurities (e.g., Al3+) have higher diffusivities along [001], those with more interstitial defects (e.g., Li+) have higher diffusivities along [100], and that OH reduces D. 相似文献
5.
Forty-seven samples from Upper Cretaceous sections penetrated by the Kachi-1 and Inga-1 wells in the South Yellow Sea Basin have been analysed for their spore and pollen content. Thirty-five species of 18 spore genera and 54 species of 28 pollen genera are documented. One new monotypic genus, Diporocolpopollenites, and its type species, D. kachiensis sp. nov., are erected, and Dilwynites Harris, 1965, and its type species, D. granulatus Harris, 1965, are emended. There are also three new combinations: Ephedripites eocaenicus (Selling, 1944), E. praeclarus (Chlonova, 1961), and Retitricolpites anguloluminosus (Anderson, 1960). Two palynological zones are erected: anAquilapollenites attenuatus Assemblage Zone, which encompasses deposits that are considered to be latest Campanian–Early Maastrichtian in age, and an Aquilapollenites eurypteronus Assemblage Zone for sections that have been dated as Late Maastrichtian. The assemblages are typical of the Yenisey-Amur Subprovince of the Aquilapollenites (floral) Province. Lowland floodplain to shallow, commonly mesotrophic, lacustrine environments of deposition are indicated. The climate was probably wet subtropical, with rainfall being somewhat higher during the Late Maastrichtian than through the latest Campanian–Early Maastrichtian. 相似文献
6.
雷州半岛硅藻土中的硅藻及其化学成分 总被引：4，自引：5，他引：4
本文论述雷州半岛各硅藻土矿床中的硅藻形态和种属。九斗洋和田洋钻孔样品中硅藻种属随深度而变化，由直链藻到了冠盘藻，直到小环藻。总结了对不同种属硅藻的硅质硬过峭同部位的Ｘ射线能谱成分分析和研究结果。 相似文献
7.
Three palynological biozones are proposed for the Maastrichtian Stage of South Carolina. In ascending stratigraphic order, the biozones are the Carolinapollis triangularis (Ct) Interval Biozone, the Holkopollenites chemardensis (Hc) Interval Biozone, and the Sparganiaceaepollenites uniformis (Su) Interval Biozone. Integration of the biostratigraphy with lithologic and geophysical log data suggests that within the study area, the upper and lower boundaries of each zone are bounded by regional unconformities, and that a three-fold subdivision of the Maastrichtian Stage is warranted. The biozonation is based on the analysis of 114 samples from 24 subsurface and three outcrop sections from the Coastal Plain of South Carolina; samples from an additional seven subsurface and 18 outcrop sections from North Carolina and Georgia were examined to evaluate the geographic extent of the biozones. One new genus and five new species of pollen are described, and emendations are presented for two genera and one species of pollen. 相似文献
8.
The fresh and saline lakes of Ounianga Kebir and Serir in northeastern Chad are among the very few permanent aquatic ecosystems currently existing in the hyper‐arid core of the Sahara desert. The confirmed modern fauna of aquatic molluscs at Ounianga comprises three widespread species (Melanoides tuberculata, Biomphalaria pfeifferi and Lymnaea natalensis), of which only the first appears to maintain a thriving population. We recovered seven more species of gastropods, among which one is new to science (Gabbiella ouniangaensis), and one bivalve species from early Holocene outcrops of diatomaceous limestone at Ounianga Serir. All species except one are known to be commonly spread between lake and river systems by birds, and in its entirety this species‐rich fossil mollusc fauna of Ounianga Serir resembles that of other Saharan lake sites known to have been hydrologically isolated during the early Holocene. The impoverished modern mollusc fauna, which lacks even the widespread and opportunistic species Bulinus truncatus, may have become established relatively recently through new colonisation events, following eradication of the early Holocene mollusc fauna during a later episode of high salinity or desiccation. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
9.
Luca Pellegrino Francesco Dela Pierre Richard W. Jordan Kenta Abe Yuta Mikami Marcello Natalicchio Rocco Gennari Francesca Lozar Giorgio Carnevale 《Sedimentology》2020,67(7):3389-3421
During the late Miocene the Mediterranean experienced a dramatic intensification of opaline accumulation, recorded by the deposition of diatomaceous sediments. The fine lamination of these deposits potentially records annual to sub-annual palaeoceanographic processes that occurred during a critical phase of the geodynamic evolution of the Mediterranean basin, which eventually led to the Messinian salinity crisis. The diatomaceous facies has been interpreted by previous researchers as the product of intensified upwelling currents and of bottom anoxia formation in the Mediterranean basin. However, until now, no efforts have been made to unravel the sedimentological and micropalaeontological content of these deposits at the lamina-scale. This paper presents the first case study of a systematic scanning electron microscope-based morphological investigation of the diatomaceous sediments deposited during the late Miocene at the northernmost offshoot of the Mediterranean basin (Piedmont Basin, north-west Italy). Using a non-invasive analytical approach, six faciological components (laminae, laminated packets, non-laminated intervals, burrows, opal-rich aggregates and mixed pelletal structures) and their relationships are described and interpreted herein. Following the lamina-scale study of these sediments, an annual sedimentary cycle could be identified and an accumulation rate (ca 50 cm kyr−1) inferred that is atypical for a setting actively influenced by upwelling. The role played by the entanglement of diatom valves in creating a physical barrier to the bioturbation is here emphasized as the main process responsible for the preservation of the laminated fabric of diatomaceous sediments, challenging the supposed role of deep anoxia. These results suggest that the late Miocene diatomaceous deposition in the Piedmont Basin cannot be univocally considered as a by-product of upwelling intensification and seafloor oxygen depletion. 相似文献
10.
The Axymyiidae is one of the small families of the suborder Nematocera within the Diptera.Up to date,three genera and seven species of extant axymyiids have been described from the Holarctic Region,including Canada,China,Hungary,Japan,Russia,and USA,with three genera and three species of fossil taxa described from the Middle Jurassic of Daohugou,northeastern China.A new genus Raraxymyia gen.nov.and two new species,R.parallela and R.proxima gen.et sp.nov.from the Middle Jurassic Jiulongshan Formation of Daohugou Village,Inner Mongolia,China,are herein described based on their well-preserved wings and body characters.A revised key to the genera of axymyiids is provided. 相似文献
11.
A new genus, Cretaproscolia, and three new species of scoliid wasps, Archaeoscolia hispanica, Cretoscolia montsecana and Cretaproscolia josai, are described from the Lower Cretaceous of Spain and Brazil. The species representing the new genus is attributed to the plesiomorphic extant subfamily Proscoliinae, while the two other new species are assigned to two previously described genera in the extinct, archaic subfamily Archaeoscoliinae. The Brazilian species is the first Mesozoic scoliidid to have been described from the New World. 相似文献
12.
I. B. Tsoy 《Stratigraphy and Geological Correlation》2011,19(1):87-101
The most complete characterization of Dictyochophyceae (silicoflagellate) assemblages from sediments of the Kronotskii Bay,
Eastern Kamchatka, which are typical of the Corbisema hexacantha (Middle Eocene) and Naviculopsis foliacea (terminal middle-initial
Late Eocene) zones in the tropical/subtropical zonation by Bukry (1981), is considered for the first time. In total, 43 silicoflagellate
species of 8 genera are identified. The prevalence of species of the genera Corbisema and Dictyocha in the assemblages suggest warm, close to subtropical conditions in a sea basin that existed in the Eastern Kamchatka region
during the Middle-Late Eocene. 相似文献
13.
A new genus and species of fossil elaterid namely Clavelater ningchengensis gen. et sp. nov. assigned to the subfamily Protagrypninae based on one specimen from the Middle Jurassic Jiulongshan Formation near Daohugou Village, Ningcheng County, Inner Mongolia, northeastern China is described and illustrated. This specimen displays a pair of large antennae that easily differs from those of most Mesozoic elaterids. There are around 36 species within 20 genera referred to elateroids described from the Early Jurassic to Miocene of China, with another three species within three genera reviewed, but the taxonomic assignment of at least seven species within three genera is doubted. The systematic position of fossil elateriform beetles reported from China is reviewed and the evolution of Mesozoic elateroids briefly discussed. 相似文献
14.
The abundance and diversity of macrofossils in the Ediacaran have attracted much attention. The upper Doushantuo macrobiotas in South China, including the Miaohe biota from Hubei and the Wenghui biota from Guizhou, are mainly preserved as the carbonaceous compressions and dominated by macroscopic algae and metazoans. Here, we describe 10 genera and 10 species (including 6 new genera and species) of macrofossils from the Wenghui biota. At present, the Wenghui biota yields macrofossils in more than 31 genera and 33 species, excluding those given no image and established on a few unascertained specimens. Based on the occurrence and distribution of macrofossils in both Miaohe and Wenghui areas, the middle-late Ediacaran (back shales of the upper Doushantuo Formation) in South China can be subdivided into two assemblage biozones in biostratigraphy: (i) the Protoconites–Linbotulitaenia–Eoandromeda–Anomalophton assemblage biozone characterized by abundant and diverse macrofossils and by the ranges of Protoconites, Linbotulitaenia and Anomalophton; and (ii) the Baculiphyca–Gesinella–Cucullus–Beltanelliformis assemblage biozone characterized by the acme of the longer macrofossils Baculiphyca and Gesinella, and by few shorter and discoidal macrofossils. 相似文献
15.
Phase transformation and crystal growth in nanoparticles may happen via mechanisms distinct from those in bulk materials. We combine experimental studies of as-synthesized and hydrothermally coarsened
titania (TiO2) and zinc sulfide (ZnS) with thermodynamic analysis, kinetic modeling and molecular dynamics (MD) simulations. The samples
were characterized by transmission electron microscopy, X-ray diffraction, synchrotron X-ray absorption and scattering, and
UV-vis spectroscopy. At low temperatures, phase transformation in titania nanoparticles occurs predominantly via interface nucleation at particle–particle contacts. Coarsening and crystal growth of titania nanoparticles can be described
using the Smoluchowski equation. Oriented attachment-based crystal growth was common in both hydrothermal solutions and under
dry conditions. MD simulations predict large structural perturbations within very fine particles, and are consistent with
experimental results showing that ligand binding and change in aggregation state can cause phase transformation without particle
coarsening. Such phenomena affect surface reactivity, thus may have important roles in geochemical cycling. 相似文献
16.
The release of mercury (Hg) from leaf tissue was compared between two dominant salt marsh macrophytes,Spartina alterniflora andPhragmites australis. Rates of Hg release were measured for individual leaves from late May to late July, along with concentrations of Hg in leaf tissue, rates of sodium (Na) release, and rates of transpiration. Leaves ofS. alterniflora consistently releasd 2–3 times more Hg than leaves ofP. australis. Leaves ofS. alterniflora also contained greater concentrations of Hg during these months. In contrast toP. australis leaves, rates of Na release were high forS. alterniflora and were correlated with rate of Hg release. Transpiration rates averaged 2.2 times greater forPhragmites as compared toS. alterniflora, and were not correlated with the other variables at the leaf level for either species. Leaf Hg concentration was highly correlated with Hg release for both species, but the slope was significantly greater forS. alterniflora. Monthly differences were profound for all climate and physiological variables measured, with high measurements in May, and lower measurements in June and July. For both species, the highest Hg content was found in lower leaves in May, followed by upper leaves in May. Hg accumulation in leaf tissue and release from both species appear to be greatest in the spring, although differences between the species persist throughout these peak months of the growing season. 相似文献
17.
对贺兰山地区上田组的植物化石开展研究,此次鉴定出12属14种,结合前人资料,上田组植物化石共计20属35种。其中,真蕨纲和种子蕨纲9属19种,占54%;苏铁纲4属6种,占17%;楔叶纲1属4种,占11%;松柏纲3属3种,占9%;银杏纲2属2种,占6%;分类位置不明的种子1属1种,占3%。该地区植物化石组合以中国北方型Danaeopsis-Bernoullia植物群的属种占主导地位,同时混生了中国南方型Dictyophyllum-Clathropteris植物群的分子Dictyophyllum,且苏铁类占一定的比例,反映了晚三叠世末期贺兰山为半干旱的亚热带大陆型气候,且正在向湿热发展。 相似文献
18.
Bruce Runnegar 《Australian Journal of Earth Sciences》2013,60(2):227-252
Megadesmus Sowerby 1838 and Astartila Dana 1847 are bivalves from the Australian Permian, which belong to a group that Newell has termed “primitive desmodonts”. Both genera have a single blunt tooth in the right valve and a corresponding socket in the left. The tooth and socket are derived from folds in the valve margin and are not related to the teeth of heterodonts. Differences in shape, size, and pedal musculature separate Astartila from Megadesmus. Cleobis Dana 1847 differs only in having slightly different dentition and a small siphonal gape and is retained as a subgenus of Megadesmus. Astartila (Pleurikodonta) n. subgen. has been proposed for a small Astartila‐like species with well‐developed radial ornament. 相似文献
19.
Abstract: Abundant benthic foraminifera have been identified in thin sections of the siliceous black ore in the Ezuri Kuroko deposit, Hokuroku, Japan. By treating samples with conventional hydrofluoric acid digestion techniques, sponge spicules and radiolaria have also been recognized in the residue. Under microscopic observations, 94 individual foraminiferal specimens have been detected. However, as it is difficult to identify species or genera by means of microscope observations alone, only a small number of genera have been identified based on morphology. The foraminiferal assemblage is composed predominantly of agglutinated species (83%) with subordinate calcareous species (17%), and is assigned to the Cyclammina Assemblage based on the preponderance of Cyclammina (57%). The foraminifera are generally well preserved within micro‐crystalline to cryptocrystalline quartz, and exhibit no obvious features related to compaction or secondary deformation. Textural observations suggest that the siliceous component of this rock was not derived from an allochthonous block but instead constitutes autochthonous proto‐Kuroko sediment. The Cyclammina Assemblage in the ore is different from recently described foraminiferal assemblages in the vicinity of present deep‐sea hydrothermal vents, but is identical to those found in black shales of the Onnagawa to Funakawa stages in the Green Tuff region. The proto‐Kuroko sediment is assumed to have been deposited in an oxygen‐deficient environment within a closed, deep‐seated basin. The existence of siliceous microfossils suggests that the silica in the siliceous ore did not originate from silica sinter deposits produced by submarine hydrothermal activities, but from a biogenic siliceous ooze, probably composed of diatoms. Sulfide mineralization in the interstices of some of the microfossils is inferred to relate primarily to bacterial sulfate reduction associated with the decomposition of organic matter. The later sulfide mineralization associated with larger crystals (which contain fluid inclusions with homogenization temperatures of approximately 250C) cuts across the siliceous masses and foraminiferal septa, and may have been formed after consolidation of the siliceous ooze, accompanying the formation of acidic intrusive rocks during the late Onnagawa stage. 相似文献
20.
Based on data obtained from field investigations, this paper aims to analyze the influence of the river overflow on the desert
riparian vegetation and discuss the function of the river overflow on the vegetation restoration at the lower Tarim River.
The results show that (1) there are only 17 species, 13 genera and 9 families in the study areas before river overflow, while
there are 34 species, 26 genera and 12 families after the overflowing in which 18 species emerged newly; (2) judging by the
biodiversity indices, the species diversity and species richness in the river overflowed area increase more significantly
than those in the un-overflow area; (3) judging by the importance of different species after years of river overflowing, the
annual herbs germinate quickly at first, while the perennial herbs with deep roots or root clones become dominant in the plant
community; (4) after several times of river overflowing, some arbors and shrubs such as Populus euphratica and Tamarix ramosissima germinate easily and can dominate gradually in the plant community. The results indicate that the river overflowing restores
the severely degraded ecosystem in the lower Tarim River and the function is connected with restoration of eco-hydrological
processes in the study areas. The results suggest that experimental overflowing has initiated a process of restoring ecosystem
function within the riparian forest. 相似文献