南极北维多利亚地难言岛闪长质岩石年代学、地球化学及地质意义SCIEI北大核心CSCD     

高鹏  唐立梅  陈灵  田原  方银霞 《岩石学报》2022,38(3):923-941

东南极北维多利亚地沿威尔逊、鲍尔斯地体边缘发育广泛的花岗质岩浆作用。本文选取了罗斯造山带北维多利亚地难言岛古生代闪长质岩石开展了锆石U-Pb年代学、Sr-Nd-Hf同位素地质学及全岩地球化学研究,分析探讨其岩浆的源区特征和岩石成因。锆石U-Pb同位素定年结果显示,难言岛闪长质岩石形成于约500Ma,属于晚寒武世罗斯造山后岩浆活动产物。岩石地球化学特征显示的SiO_(2)含量变化范围为54.03%~60.10%,总碱值为5.92%~6.91%,里特曼指数σ为2.67~3.68,A/CNK值为0.77~0.85,属于高钾钙碱性、准铝质岩石。在正常洋中脊玄武岩标准化蛛网图中,样品富集大离子亲石元素(LILE),亏损Nb、Ta、Ti;在球粒陨石标准化稀土元素配分图中,难言岛闪长质岩石显示轻稀土相对富集,(La/Yb)N=12.99~14.60,Eu弱负异常(0.62~0.71)。样品的锆石εHf(t)值为-10.7~-6.3;(87 Sr/86 Sr)i范围0.7095~0.7097,(143 Nd/144 Nd)i范围0.511502~0.511629,εNd(t)范围-7.1~-10.3。结合前人资料,显示难言岛闪长质岩石来自于先前富集的陆下岩石圈地幔部分熔融,在罗斯汇聚的过程中被俯冲组分进一步交代。晚寒武世罗斯造山带处于后碰撞环境,熔融可能与后碰撞伸展环境下俯冲板块回卷、撕裂过程中软流圈上涌或其他减薄机制有关。  相似文献   

Quaternary ice thinning of David Glacier in the Terra Nova Bay region,Antarctica     

《Quaternary Geochronology》2022

Understanding the history of Antarctic glaciation is important for interpreting paleoclimatic changes and estimating the changes in climate, sea level, and ice volume in the future. Ice core studies of the East Antarctic Ice Sheet (EAIS) and marine sediment cores from the entire Ross Sea have employed numerous proxies to reconstruct the glacial history of the Antarctic region. However, the ice and marine core records can be biased because of their specific locations, such as the uppermost accumulation zone or the terminus of the ablation zone, thereby introducing significant uncertainties in ice modeling. In this study, we analyzed 34 new ¹⁰Be and ²⁶Al samples from four benches that were glaciated in the past by David glacier and incorporate the present ice-free flat surfaces. We suggest that the David glacier experienced monotonic and stepwise vertical lowering along the flanks of Mt. Priestley since the early Pleistocene. The uppermost bedrock benches on Mt. Priestley were exposed at 1.77 ± 0.32 Ma, with no evidence of subsequent overriding by readvancing ice. At Mt. Priestley, the David glacier has been characterized by a cold-based regime since 1.77 Ma, with a denudation rate of only ∼16 cm/Ma, corresponding to the regional transition from warm to cold-based glaciation at 3.5 Ma. Simple exposure ages from two lower benches date to Marine Isotope Stage (MIS) 7 (234.1 ± 13.1 ka; 545 m asl) and MIS 4 (64.8 ± 13.7 ka; 222 m asl), suggesting that, since MIS 8, the overall lowering of glaciers has remained monotonic. The upper bench marks the lower limit of the MIS 8 glacial period and the upper limit of Penultimate Glacial Maximum (MIS 6), while the lower landform defines the upper limit of the last glacial period (MIS 4–2). The magnitude of Quaternary ice thinning at the David glacier was the highest (∼990 m) in the present terminal area (i.e., the most sensitive ablation zone), in contrast to the other outlet glaciers draining into the Terra Nova Bay, which experienced less ice lowering. The combination of the terrestrial (in situ ¹⁰Be and ²⁶Al) and previous marine (authigenic ¹⁰Be) cosmogenic data used in our study document the history of lowering of the David glacier driven by climatic changes during the Pleistocene. Both deglaciation and glaciation were limited during the mid-Pleistocene transition (MPT) and prior to the mid-Bruhnes event (MBE), due to the prevailing cold and arid climate, whereas deglaciation was dominant during other warm periods.  相似文献   

The refraction seismic experiment GRANU95 in the Saxothuringian belt, southeastern Germany   总被引：1，自引：0，他引：1  

Enderle  Schuster  Prodehl  Schulze  & Bribach 《Geophysical Journal International》1998,133(2):245-259

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Settling fluxes of diatoms to the interior of the Antarctic circumpolar current along 170 °W     

《Deep Sea Research Part I: Oceanographic Research Papers》2014

An array of four sediment trap moorings recorded the particulate flux across the Antarctic Circumpolar Current (ACC) at 170 °W, between November 1996 and January 1998, as part of the US JGOFS-Antarctic Environment and Southern Ocean Process Study (AESOPS) program. The trap locations represent sampling within the Polar Frontal Zone, the Antarctic Polar Front, the Antarctic Zone and the Southern Antarctic Zone. Here we report observations from 1000 m below the sea-surface compared to seafloor and surface water distributions. Sub-sample splits from each trap were obtained and total diatom flux and species composition were determined. The diatom fluxes were quantified using both a dilution and a ‘spike’ method to allow for the rapid repeatability of measurements. Diatom flux was found to be highly seasonal across the ACC particularly at higher latitudes. Marine snow aggregates of intact diatom cells and chains were the major components of the biogenic flux. Siliceous particle size was noted to decrease with increasing latitude, which could be aligned with a shift of the diatom assemblage to small-size species/sea-ice affiliated species. A ‘double-structured’ diatom flux was recorded at the location of the Antarctic Polar Front trap, with a shift in the diatom assemblage from larger to smaller diatoms in the second flux episode. The sediment trap assemblage shows deviations from the surface water assemblage, while surface sediment samples indicate that significant dissolution occurs after 1000 m and at the sediment–water interface. Estimation of diatom biovolumes across the ACC shows that large diatoms have the potential to greatly impact biogenic fluxes to the ocean interior despite their low fluxes. Small species of the genus Fragilariopsis could potentially export as much C_org as Fragilariopsis kerguelensis near the retreating ice edge. However, their low abundance in the surface sediments also suggests that these diatoms are a shallow export species.  相似文献   

A tale of two synclines: Rifting,inversion and transpressional popouts at Lake Julius,northwestern Mt Isa terrane,Queensland     

G. S. Lister  M. G. O'Dea  I. Somaia 《Australian Journal of Earth Sciences》2013,60(2):233-250

This study reviews the origin of two approximately east‐west‐trending synclines in the Lake Julius area at the eastern edge of the Leichhardt Rift. The genesis of one of these structures can be found in a north‐south shortening event (D₁) that occurred at the beginning of the compressional Isan Orogeny (at ca 1600 Ma). Metasediments in a cross‐rift were rammed against a competent buttress defined by the pre‐existing rift architecture, producing the approximately east‐west‐trending Somaia Syncline and its associated axial‐plane slaty cleavage. In contrast, the Lake Julius Syncline was produced by reorientation of an originally approximately north‐south‐trending (D₂) fold, in a transpressional zone adjacent to a strike‐slip fault, at the end of the Isan orogeny. The effects of late fault movement can be partially reconstructed, based on correlations assuming that regionally developed trains of upright folds formed during the peak of the Isan Orogeny (D₂). These folds have been offset, as well as having been tightened and disrupted at the same time as fault movements took place. The overall pattern of movement in the Lake Julius region can be explained as the result of an ‘indentor’ ramming into the ancient edge of the Leichhardt Rift, which acted as a buttress.  相似文献   

Palaeozoic suturing of eastern and western Tasmania in the west Tamar region: Implications for the tectonic evolution of southeast Australia     

A. R. Reed  C. Calver  R. S. Bottrill 《Australian Journal of Earth Sciences》2013,60(5):809-830

A new tectonic model for Tasmania incorporates subduction at the boundary between eastern and western Tasmania. This model integrates thin‐ and thick‐skinned tectonics, providing a mechanism for emplacement of allochthonous elements on to both eastern and western Tasmania as well as rapid burial, metamorphism and exhumation of high‐pressure metamorphic rocks. The west Tamar region in northern Tasmania lies at the boundary between eastern and western Tasmania. Here, rocks in the Port Sorell Formation were metamorphosed at high pressures (700–1400 MPa) and temperatures (400–500°C), indicating subduction to depths of up to 30 km. The eastern boundary of the Port Sorell Formation with mafic‐ultramafic rocks of the Andersons Creek Ultramafic Complex is hidden beneath allochthonous ?Mesoproterozoic turbidites of the Badger Head Group. At depth, this boundary coincides with the inferred boundary between eastern and western Tasmania, imaged in seismic data as a series of east‐dipping reflections. The Andersons Creek Ultramafic Complex was previously thought of as allochthonous, based mainly on associations with other mafic‐ultramafic complexes in western Tasmania. However, the base of the Andersons Creek Ultramafic Complex is not exposed and, given its position east of the boundary with western Tasmania, it is equally likely that it represents the exposed western edge of autochthonous eastern Tasmanian basement. A thin sliver of faulted and metamorphosed rock, including amphibolites, partially separates the Badger Head Group from the Andersons Creek Ultramafic Complex. Mafic rocks in this package match geochemically mafic rocks in the Port Sorell Formation. This match is consistent with two structural events in the Badger Head Group showing tectonic transport of the group from the west during Cambrian Delamerian orogenesis. Rather than being subducted, emplacement of the Badger Head Group onto the Andersons Creek Ultramafic Complex indicates accretion of the Badger Head Group onto eastern Tasmania. Subsequent folding and thrusting in the west Tamar region also accompanied Devonian Tabberabberan orogenesis. Reversal from northeast to southwest tectonic vergence saw imbricate thrusting of Proterozoic and Palaeozoic strata, possibly coinciding with reactivation of the suture separating eastern and western Tasmania.  相似文献   

Financial statement as at 31 December 1969     

N. G. Direen  A. J. Crawford 《Australian Journal of Earth Sciences》2013,60(4):491-502

The Tasman Line, a much‐discussed concept in the geology and tectonics of eastern Australia, has a long and chequered history of interpretation. This extends to current debates regarding the age and position of the Tasman Line in Gondwana‐Rodinia reconstructions. We present constraints, from mapping, geochemistry and geophysics, on the interpretation of gravity and magnetic lineaments attributed to the Tasman Line in New South Wales, South Australia, Victoria and Tasmania. These pieces of evidence suggest a protracted and complex latest Neoproterozoic to Carboniferous geological history that produces a variety of geophysical responses, rather than a simple ‘Line’. We also find no evidence of Rodinian breakup age activity responsible for any of the anomalies. In light of these findings, our preference is that the Tasman Line concept be abandoned as misleading, especially with regard to models of Rodinia‐Gondwana breakup, which must have occurred elsewhere, possibly well to the east. Instead, the rocks preserved in the westernmost part of the Tasmanides are consistent with previously proposed ‘Southwest Pacific’‐style models for Neoproterozoic continental breakup, margin formation and reaccretion of continental fragments in the Early Palaeozoic.  相似文献   

In situ cosmogenic exposure ages from the Isle of Skye,northwest Scotland: implications for the timing of deglaciation and readvance from 15 to 11 ka     

David Small  Vincent Rinterknecht  William Austin  Derek Fabel  Maria Miguens‐Rodriguez  Sheng xu 《第四纪科学杂志》2012,27(2):150-158

We present 10 in situ cosmogenic exposure ages from two moraines on the Isle of Skye. The Strollamus medial moraine was deposited during deglaciation of the Devensian ice sheet and yields a mean exposure age from five samples of 14.3 ± 0.9 ka. The moraine age indicates that a significant ice mass existed on Skye at the time of a regional readvance recorded in Wester Ross, northwest Scotland. Taken at face value the ages suggest that deglaciation did not occur until well into Greenland Interstade 1. The Slapin moraine represents the local limit of the Loch Lomond Readvance (LLR) and yields a mean exposure age from five samples of 11.5 ± 0.7 ka, which is consistent with deposition relating to the LLR. These ages suggest that the maximum extent may have been reached late in the stadial and that some glaciers may have remained active until after the climatic amelioration that marks its end. This scenario is considered unlikely given the nature of the climate during this period, which leads us to call for a locally calibrated production rate. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

利用脂肪酸标记法对南极罗斯海桡足类优势物种的食性研究     

王延清  张晔  牟文秀  庞志鹏  陈晓丽 《海洋科学》2021,45(12):31-38

脂肪酸标记法是浮游动物食性研究的一种重要方法.将提取的脂质区分为中性脂和极性脂,可以进一步查明不同脂质在浮游动物食性研究中的作用.本研究通过分析不同脂质的脂肪酸构成,对2013年1月中国第29次南极考察期间在罗斯海采集的5种优势种桡足类的食性进行了研究.结果显示:5种桡足类的极性脂脂肪酸具有相似的组成,无法给出桡足类食性差异信息,食性信息主要体现于中性脂脂肪酸组成的差异.通过分析中性脂脂肪酸的组成信息,将5种桡足类的食性分为三类:Cala-noides acutus和Calanus propinquus主要摄食浮游植物,Metridia gerlachei及小型桡足类Oncaea curvata为杂食性种,Paraeuchaeta antarctica为肉食性种.本文的结果说明,在应用脂肪酸作为浮游动物食性标记的研究中,应尽量区分不同脂质种类的脂肪酸信息,从而得到更为精确的浮游动物食性信息.  相似文献   

南岭花山和姑婆山花岗岩基属印支期侵位:来自花岗岩熔体冷却-结晶和放射成因热计算的依据     

章邦桐  吴俊奇  凌洪飞  陈培荣 《地质学报》2012,86(7):1031-1046

通过对南岭西段花山和姑婆山花岗岩基地质-岩石地球化学特征研究,判明它们的侵位深度(5.5km)、围岩温度(196℃)及岩浆初始温度(950℃),建立起花山和姑婆山岩基的数学计算模型,计算得出:花山-姑婆山花岗岩熔体侵位后,其初始温度降低至结晶温度所需的时间(△tco1)分别为4.14 Ma(花山)和4.36Ma(姑婆山...  相似文献