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单个流体包裹体LA-ICPMS定量分析技术及其应用(英文) 总被引：7，自引：0，他引：7
ThomasULRICH 《地学前缘》2003,10(2):379-393
对于不同类型的地球化学勘查样品 ,运用恰当的分析方法处理 ,是成功地发现矿床的关键。激光熔融电感耦合等离子质谱分析 ,即LA ICPMS ,是功能最强的多元素分析技术之一。该方法获得数据快捷 ,样品制备简单 ,其高灵敏度为很多主元素和微量元素 (包括铂族元素、稀土元素、高场强元素和多种成矿示踪元素 )提供了低检测限 ,正在并将要持续为地球化学应用提供新的信息。仪器由ICPMS(四极 ,多接受或磁扇域 )附加激光器 (紫外或红外波长 )而构成。应用于地球科学研究的标准仪器的激光器为具有 2 6 6nm四倍频率的Nd :YAG激光器 ,或者是具有 193nm波长的ArF激态原子激光器。激光器熔融样品 ,并通过运载气体将熔融的样品物质传送到IP ,而不是将样品溶解后 ,通过雾化器和雾化室将样品传输给ICP。这就使我们能够进行微区分析 ,如矿物环带 ,或者矿物中的微小矿物、融体和流体包裹体等。运用外标校对元素比值 ,并结合内标使用 ,可以获得定量测试结果。对于固体熔融物的分析精度一般为 2 %～ 5 %RSD(相对标准误差 ) ,对于流体包裹体则为 10 %～ 30 %RSD。LA ICPMS的一些复杂系统可能引起成分分馏和质量干扰。对于分馏效应 ,可以通过运用产生小粒子的短波长激光器和运用He作为运载气体来减小 ;对于质量干扰 ,则可以通过? 相似文献
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JUTTA WINSEMANN JAHN J. HORNUNG JANINE MEINSEN ULRICH ASPRION ULRICH POLOM† CHRISTIAN BRANDES MICHAEL BUßMANN CHRISTIAN WEBER 《Sedimentology》2009,56(4):1041-1076
This paper presents a detailed analysis of the high‐resolution facies architecture of the Middle Pleistocene Porta subaqueous ice‐contact fan and delta complex, deposited on the northern margin of glacial Lake Weser (North‐west Germany). A total of 10 sand and gravel pits and more than 100 wells were examined to document the complex facies architecture. The field study was supplemented with a ground‐penetrating radar survey and a shear‐wave seismic survey. All collected sedimentological and geophysical data were integrated into a high‐resolution three‐dimensional geological model for reconstructing the spatial distribution of facies associations. The Porta subaqueous fan and delta complex consist of three fan bodies deposited on a flat lake‐bottom surface at the margin of a retreating ice lobe. The northernmost fan complex is up to 55 m thick, 6·2 km wide and 6·5 km long. The incipient fan deposition is characterized by high‐energy flows of a plane‐wall jet. Very coarse‐grained, highly scoured jet‐efflux deposits with an elongate plan shape indicate a high Froude number, probably >5. These jet‐efflux sediments are deposited in front of a large ～3·2 km long, up to 1·2 km wide, and up to 25 m deep flute‐like scour, indicating the most proximal erosion and bypass area of the jet that widens and deepens with distance downstream to the region of maximum turbulence (approximately five times the conduit diameter). Evidence for subsequent flow splitting is given by the presence of two marginal gravel fan lobes, deposited in front of 1·3 to 2·5 km long flute‐like scours, that are 0·8 to 1 km wide and 7 to 20 m deep. In response to continued aggradation, small jets developed at the periphery of these bar‐like deposits and filled in the low areas adjacent to the original superelevated regions, locally raising the depositional surface and characterized by large‐scale trough cross‐stratified sand and pebbly sand. The incision of an up to 1·2 km wide and up to 35 m deep channel into the evolving fan is attributed to a catastrophic drainage event, probably related to a lake outburst and lake‐level fall in the range of 40 to 60 m. At the mouth of this channel, highly scoured jet‐efflux deposits formed under hydraulic‐jump conditions during flow expansion. Subsequently, Gilbert‐type deltas formed on the truncated fan margin, recording a second lake‐level drop in the range of 30 to 40 m. These catastrophic lake‐level falls were probably caused by rapid ice‐lobe retreat controlled by the convex‐up bottom topography of the ice valley. 相似文献
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MICHAEL ZECH ANDREI ANDREEV ROLAND ZECH STEFANIE MÜLLER ULRICH HAMBACH MANFRED FRECHEN WOLFGANG ZECH 《Boreas: An International Journal of Quaternary Research》2010,39(3):540-550
Zech, M., Andreev, A., Zech, R., Müller, S., Hambach, U., Frechen, M. & Zech, W.: Quaternary vegetation changes derived from a loess‐like permafrost palaeosol sequence in northeast Siberia using alkane biomarker and pollen analyses. Boreas, Vol. 39, pp. 540–550. 10.1111/j.1502‐3885.2009.00132.x. ISSN 0300‐9483 Alkane biomarker and pollen data were obtained from a 15‐m‐high and probably c. 240‐kyr‐old loess‐like permafrost palaeosol sequence (‘Tumara Palaeosol Sequence’, TPS) in northeast Siberia. The alkane results were corrected for degradation effects by applying an end‐member model and were evaluated by comparing them with the palynological results. The two data sets are generally in good agreement and suggest that the lower part of the TPS developed mainly under larch forests, whereas the upper part of the sequence reflects the expansion of mammoth steppes during the Weichselian glaciation and finally reforestation during the Lateglacial and the early Holocene. For the lower part of the TPS, the palaeoclimatic interpretation according to modern analogue methods would indicate warm, interglacial conditions, but this is at odds with the climate chronostratigraphy based on a multi‐proxy palaeopedological approach and numeric dating. Provided that the correlation of the discussed stratigraphic unit with the Late Saalian glaciation and the Marine Oxygen Isotope Stage 6 is correct, our results suggest that temperature was not a limiting factor for tree growth at that time. Furthermore, it seems very likely that it was not mainly temperature changes but rather increasing aridity and continentality during the course of the last glacial that favoured the expansion of the mammoth steppe. 相似文献
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STEFAN HUCK NIELS RAMEIL TVRTKO KORBAR ULRICH HEIMHOFER THOMAS D. WIECZOREK ADRIAN IMMENHAUSER 《Sedimentology》2010,57(7):1585-1614
Ocean‐wide anoxic events represent intensively investigated anomalies in the global carbon cycle. Most previous research has focussed on hemipelagic and pelagic settings and on the relationship between black‐shale deposition and carbon‐isotope excursions. The study of ocean‐wide anoxic events and coeval shallow‐water settings is now increasingly seen as an interesting complementary approach, but one that is not without problems. Whereas platform drowning characterizes the Early Aptian of the northern Tethyan margin, Lithocodium–Bacinella‐rich facies and ongoing shoal‐water sedimentation at the southern Tethyan margin (Oman) bears important information on potential causes of carbon‐cycle perturbations. The present paper seeks to test the supra‐regional relevance of the Oman data by investigating coeval central Tethyan limestones. Three Lower Aptian shoal‐water sections in Istria (Croatia), deposited on the isolated Adriatic Carbonate Platform, are investigated applying chemostratigraphy (carbon and strontium) and detailed sedimentological analysis. The focus is on peritidal to lagoonal facies characterized by mass occurrences of Lithocodium–Bacinella, an enigmatic microencruster community. Lithocodium–Bacinella facies occurs predominantly in layers ranging from one to several centimetres in stratigraphic thickness, with several layers merging to metre‐thick packages. Growth fabrics within the layers include oncoidal morphotypes, lumps, interconnected patches and columns, layers and rare nodular to massive bindstone facies. These growth patterns show a remarkable regional extent and consistency over study sites distributed several kilometres apart. This widespread distribution suggests that specific Lithocodium–Bacinella morphotypes might serve as regional stratigraphic markers. The high‐resolution carbon‐isotope chemostratigraphy presented here is based on pristine rudist shells and matrix micrite samples and calibrated against strontium‐isotope data obtained from screened rudist low‐Mg calcite. The chemostratigraphic data are consistent with existing biostratigraphic data and place the studied strata at the onset of Early Aptian oceanic anoxic event 1a. Moreover, results indicate the near‐coeval nature of Lithocodium–Bacinella bloom facies in Istria and Oman. The outcomes of this study point to latitudinally different responses of Tethyan shoal‐water carbonate systems (platform drowning versus Lithocodium–Bacinella blooms) to the ocean‐wide anoxic event 1a. 相似文献
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During the Aptian, some carbonate platforms of the sub‐tropical realm (for example, on the northern Tethys margin or in the Gulf of Mexico) were affected repeatedly by severe perturbations in the carbonate production factory and drowning, preferentially during global warming events such as the Early Aptian Oceanic Anoxic Event 1a and a prominent mid‐Late Aptian warming interval. These platform growth crises have been explained mainly by strongly increased coastal runoff (for example, siliciclastics and nutrients) in combination with pronounced eustatic sea‐level rises. In the last few years, increasing evidence suggests that carbonate platforms of lower latitudes were generally less or even not affected by environmental perturbations during these events. This raises the question as to the responsible factors that promoted platform growth or decline in different latitudinal areas. In this study, Upper Aptian (Middle Gargasian to Uppermost Clansayesian) inner‐tropical carbonate ramp deposits of the Serdj Formation at Djebel Serdj, north‐central Tunisia are studied in detail with regard to microfacies, lithology, biostratigraphy and chemostratigraphy. These data allow reconstruction of the palaeoenvironmental evolution of the Tunisian carbonate platform margin and investigation of its response to the prominent mid‐Late Aptian warming interval. The unusually expanded, 600 m thick Serdj Formation consists of limestones, marlstones and siltstones, suggesting deposition within mid‐ramp to inner‐ramp palaeoenvironments. Deposits of the mid‐Late Aptian are represented by quartz‐rich platform carbonates and siltstones, probably resulting from increased coastal runoff on the Tunisian shelf as a response to global warming and accelerated water cycling. The siliciclastic input was accompanied by elevated nutrient levels as indicated by a partial decline in the abundance of oligotrophic biota and mass occurrences of orbitolines and green algae. Carbonate platform drowning during the mid‐Late Aptian, as reported from the sub‐tropical realm, has not been identified. A comparison with other tropical river‐influenced platforms suggests that none of them drowned during the mid‐Late Aptian. One important reason might be widespread arid to semi‐arid climatic conditions within lower latitudes during that time, promoting platform growth due to comparably low nutrient runoff. 相似文献
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P. ŠTÍPSKÁ K. SCHULMANN J. LEHMANN M. CORSINI O. LEXA D. TOMURHUU 《Journal of Metamorphic Geology》2010,28(9):915-933
Newly discovered eclogites, Early Cambrian carbonates and chloritoid‐bearing metapelites form the Tsakhir Uul accretionary wedge, which was thrust during the Early Cambrian over the Mesoproterozoic Dzabkhan‐Baydrag continent. The rock association of the wedge forms a tectonic window emerging through the hangingwall Khantaishir ophiolite unit, which preserves a typical Tethyan‐type ophiolitic sequence. The eclogites correspond geochemically to T‐MORB modified by fluid circulation. They are composed of garnet, omphacite, amphibole, rutile ±muscovite ±quartz ±epidote and exhibit well‐equilibrated matrix textures. Jadeite content of the omphacite reaches up to 45 mol.%, the Si content of muscovite is between 3.40 and 3.45 p.f.u., amphibole is winchite to barroisite, but reaches tschermakitic composition at some rims, and garnet composition is grs0.24–0.36, alm0.43–0.56, py0.05–0.18, sps0.00–0.18, . The peak assemblage, together with the composition of garnet rims, omphacite, amphibole and muscovite, correspond in a pseudosection to 20?22.5 kbar and 590?610 °C. The tschermakitic rim of amphibole is interpreted as partial reequilibration on decompression below 16 kbar and ～600?630 °C. Two muscovite separates from the eclogite yielded an Ar–Ar plateau age of 543.1 ± 3.9 Ma (1σ) and a mean age of 547.9 ± 2.6 Ma (1σ), whereas muscovite from an interbedded garnet‐chloritoid micaschist yielded an Ar–Ar plateau age of 536.9 ± 2.7 Ma (1σ); these ages are interpreted as cooling ages. The P–T data, geochemistry of eclogites and cooling ages suggest an affinity between the Tsakhir Uul wedge and the Gorny Altai and the north Mongolian blueschist belt, which are believed typical for subduction of warm oceanic lithosphere and closure of small oceanic basins. Thus, the discovery of the Tsakhir Uul eclogites represents an important finding suggesting extension of the Early Cambrian subduction system of the Central Asian Orogenic Belt far to the east in a region where it was not expected. 相似文献
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JUTTA WINSEMANN ULRICH ASPRION THOMAS MEYER HARM SCHULTZ PIA VICTOR 《Boreas: An International Journal of Quaternary Research》2003,32(2):386-398
The Coppenbrügge subaqueous ice‐contact fan complex of early Saalian age is about 10 km long and up to 10 km wide and is composed of offset‐stacked fan clinothems that are transgressive‐regressive sequences formed during an overall lake level rise. The individual fan bodies consist of coarse gravel in the ice‐proximal part, passing distally into sandy facies and showing large‐scale foreset bedding. The iceberg scour recognized in an open‐pit outcrop is up to 1.5m deep, up to 2m wide and cut in undisturbed mid‐fan deposits. The scour‐fill can be traced laterally for about 15m and consists of sheared sand and, in the frontal zone, of downbent overlying strata surrounded by a zone of deformed sediments. The deformed sediment produced by the iceberg keel's shearing of the trough walls is a sand mass containing angular soft‐sediment clasts that show internal folds and fractures. The basal surface of the deformed sediment is a nearly horizontal shear plane, steepening up laterally as a discrete thrust and showing a flat‐ramp‐flat geometry. The scour was formed by the iceberg keel's ploughing the substrate and pushing the sediment sideways and frontally, forming a ridge of deformed sediments at the trough end. This ridge was concurrently eroded by an accompanying meltwater underflow which apparently developed a horseshoe system of scouring vortices around the grounded iceberg. The current's scour was filled with massive, non‐stratified sand deposited rapidly from turbulent suspension. The iceberg eventually broke up and its keel part was buried. As these ice fragments gradually melted, the space was closed by normal faulting and downbending of overlying strata. The collapsing scour‐fill became partly liquified, and the resulting water‐escape structures cut the normal faults and the overlying deposits. Though produced chiefly by tangential shear strain, iceberg‐ploughing features are readily distinguishable from other glaciotectonic deformations. They can serve as a diagnostic criterion for glaciolacustrine or glaciomarine environments and the distinguishing of ice‐contact subaqueous fans from ice‐contact deltas in the stratigraphic record. 相似文献
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