柴达木盆地北缘晚中生代—新生代构造应力场——来自构造节理分析的证据

柴达木盆地的构造演化,尤其是中、新生代的构造演化历史及其影响程度一直存在争议。在冷湖0号、冷湖4号、鄂博梁、结绿素等剖面开展了野外构造节理测量,应用地层恢复技术,分析了柴北缘晚中生代—新生代构造应力场的演化过程。结果表明：晚侏罗世之后,柴北缘主要受东西方向的挤压,这与区域上的研究结果一致;早白垩世北西—南东向的挤压应力可能再次影响了侏罗系;晚白垩世受南北挤压应力的影响,地层隆升遭受剥蚀;始新世下干柴沟期至上新世狮子沟期,柴北缘处于弱活动时期,接受稳定沉积;上新统狮子沟组沉积之后,由于阿尔金山的隆升,盆地北缘主体受北西—南东向应力的影响,涉及地层包括上干柴沟组、下油砂山组和上油砂山组;早、中更新世七个泉期之后,受南北向构造应力场的强烈影响,在狮子沟组、上油砂山组和下油砂山组中都有其分量,较老地层的地表露头中也有记录,这期构造运动对柴北缘油气运聚具有破坏和二次成藏的作用。因此,围绕柴北缘其他地质剖面开展更进一步的构造节理测量和分析工作,对油气资源勘探具有指导意义。     

Estimating trends of Atlantic meridional overturning circulation from long-term hydrographic data and model simulations

The ocean meridional overturning circulation (MOC) plays a central role for the climate in the Atlantic realm. Since scenarios for future climate change indicate a significant reduction of the MOC under global warming, an assessment of variations and trends of the real MOC is important. Using observations at ocean weather ship (OWS) stations and along oceanic sections, we examine the hydrographic information that can be used to determine MOC trends via its signature in water mass properties obtained from model simulations with the climate model ECHAM5/MPI-OM. We show that temperature trends at mid-latitudes provide useful indirect measure of large-scale changes of deep circulation: A mid-depth warming is related to MOC weakening and a cooling to MOC strengthening. Based on our model experiments, we argue that a continuation of measurements at key OWS sites may contribute to a timely detection of a possible future MOC slowdown and to separate the signal from interannual-to-multidecadal MOC variability. The simulations suggest that the subsurface hydrographic information related to MOC has a lower variability than the MOC trend measured directly. Based on our model and the available long-term hydrographic data, we estimate non-significant MOC trends for the last 80 years. For the twenty-first century, however, the model simulations predict a significant MOC decline and accompanied mid-depth warming trend.     

An ocean observation system for monitoring the affects of climate change on the ecology and sustainability of pelagic fisheries in the Pacific Ocean

Climate change presents an emerging challenge to the sustainable management of tuna fisheries, and robust information is essential to ensure future sustainability. Climate and harvest affect tuna stocks, populations of non-target, dependent species and the ecosystem. To provide relevant advice we need an improved understanding of oceanic ecosystems and better data to parameterise the models that forecast the impacts of climate change. Currently ocean-wide data collection in the Pacific Ocean is primarily restricted to oceanographic data. However, the fisheries observer programs that operate in the region offer an opportunity to collect the additional information on the mid and upper trophic levels of the ecosystem that is necessary to complement this physical data, including time-series of distribution, abundance, size, composition and biological information on target and non-target species and mid trophic level organisms. These observer programs are in their infancy, with limited temporal and spatial distribution but recent international and national policy decisions have been made to expand their coverage. We identify a number of actions to initiate this monitoring including: consolidating collaborations to ensure the use of best quality data; developing consistency between sub-regional observer programmes to ensure that they meet the objectives of ecosystem monitoring; interrogating of existing time series to determine the most appropriate spatial template for monitoring; and exploring existing ecosystem models to identify suitable indicators of ecosystem status and change. The information obtained should improve capacity to develop fisheries management policies that are resilient and can be adapted to climate change.     

从多岛弧盆系构造看西特提斯造山系构造演化

本文通过综述近年西特提斯带主要缝合带的研究进展及所代表洋盆的发育特征,提出了古特提斯缝合带可能的位置和俯冲消亡方式.结合区域资料探讨了西特提斯带古生代末—中生代洋陆构造格局,认为东、西古特提斯洋完全可以类比,自晚古生代末西特提斯带主要受古特提斯大洋双向俯冲制约,在俯冲带后缘以二叠纪裂谷带为基础逐渐发展成中生代多岛弧盆系...     

Tourmaline rocks associated with Stratabound Scheelite Mineralization in the Austroalpine Crystalline Complex,Austria

Summary This contribution demonstrates, for the first time, the close genetic relationship of concordant tourmaline rocks (tourmalinites) to stratabound tungsten mineralization and their wide regional distribution within the polymetamorphic Austroalpine Crystalline Complex of the Eastern Alps. The occurrences investigated are located in parts of the Austroalpine Crystalline Complex consisting of metavolcanoclastic and metacalcareous sequences of probable Lower Paleozoic age. Tourmalinites composed of tourmaline, quartz, plagioclase, ± almandine-rich garnet, ± muscovite, ± biotite, and minor ilmenite, rutile, graphite,- ± pyrite and, rarely, scheelite are of pre- to synmetamorphic origin. Tourmalines from the tourmalinites have been identified as intermediate members of the dravite-schorl solid solution series with minor amounts of other tourmaline end members. They can be compared to tourmalines from massive sulphide and stratabound tungsten deposits. Tourmalines from pegmatoids, on the contrary, plot close to the schorl end member. Tourmalinites are interpreted as metamorphosed products of elastic sedimentary material which has reacted with boronrich solutions of probable exhalative-hydrothermal origin. These exhalative processes are genetically connected to the transport of B and W and to the formation of syngenetic/syndiagenetic tungsten mineralization. Metamorphic mobilization of these primary concentrations led, during the Variscan and the Alpine metamorphic events, to the formation of scheelite-bearing quartz-tourmaline-, quartz-plagioclase-tourmaline mobilizates and pegmatoids.

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Turmalingesteine und schichtgebundene Scheelitvererzungen im polymetamorphen Kristallin der Ostalpen, österreich

Zusammenfassung Erstmals konnte auch in den Ostalpen die enge genetische Beziehung und weite Verbreitung schichtiger Turmalingesteine (Turmalinite) zu schichtgebundenen Wolframvererzungen gezeigt werden. Die bearbeiteten Vorkommen liegen in Teilen des polymetamorphen ostalpinen Kristallins, eingeschaltet in eine bunte metavulkanoklastisch-, metakarbonatisehe Abfolge, wahrscheinlich altpaläozoischen Alters. Turmalinite setzen sich mineralogisch aus Turmalin, Quarz, Plagioklas, t almandinreichem Granat, ±Muskowit, ± Biotit, untergeordnet Ilmenit, Rutil, Graphit, ± Pyrit und selten Scheelit zusammen und sind prä- bis synmetamorph gebildet worden. Die Turmaline aus den Turmaliniten sind als intermediäre Glieder der Dravit-Schörl-Mischkristallreihe mit untergeordneter Beteiligung anderer Turmalinendglieder bestimmt worden, sie sind in ihrem Mineralchemismus vergleichbar mit Turmalinen aus massiven Sulfid-, und schichtgebundenen Wolframlagerstätten. Turmalin aus Pegmatoiden steht hingegen dem Schörlendglied nahe. Die Turmalinite werden als metamorphe Produkte klastischer Sedimente, die mit borreichen Lösungen, wahrscheinlich exhalativ-hydrothermaler Herkunft, reagiert haben, gedeutet. Diese exhalativen Prozesse stehen mit der Zufuhr von Bor und Wolfram und der Bildung syngenetischer/syndiagenetischer Wolframverer zungen in enger Verbindung. Im Zuge der variszischen und alpinen Orogenesen wurdendiese Ausgangsgesteine mehreren Metamorphosen unterworfen, während der es zur Bildung von scheelitführenden Quarz-Turmalin-, Quarz-Plagioklas-Turmalin-Mobilisaten und Pegmatoiden kam.

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With 6 Figures     

Über einen eruptiven Veränderlichen in Hercules

On plates of the 60/90 cm Schmidt-telescope of the Jena University Observatory taken 1967 June 29 up to August 2 an eruptive variable with a maximum magnitude B = 15^m5 and an amplitude of at least 6 mag was found. There are indications that the object is a U Geminorum star of the subtype SW Ursae maioris.     

Stepwise palaeoclimate change across the Eocene–Oligocene transition recorded in continental NW Europe by mineralogical assemblages and δ15Norg (Rennes Basin,France)

The Eocene–Oligocene transition (EOT, ~34 Ma) is the largest global cooling of the Cenozoic Era and led the Earth's climatic system to change from a greenhouse to an icehouse mode. Although it is well documented in marine settings, the few studies focusing on continental environments have demonstrated regional heterogeneities. The study core CDB1, located in the Rennes Basin (Western France), is a unique terrestrial (lacustrine–palustrine) record comprising well‐preserved and terrestrial‐derived organic‐rich sediments encompassing the EOT. Clay minerals and the first organic nitrogen isotope record (δ¹⁵N_org) of terrestrial origin for this period are used to reconstruct palaeoclimate changes across this key interval. As suggested in worldwide marine and a few continental records, a stepwise transition from warm/humid conditions in the Late Eocene to cooler/drier conditions in the Early Oligocene is confirmed in the area. In addition, an episode of drier conditions in the Late Eocene and humid/dry cycles in the Early Oligocene are suggested.     

Reasons for Spatial Microdistributions of Foraminifers in an Intertidal Pool (Northern Adriatic Sea)

Abstract. The spatial microdistribution of foraminifers was tested by the method of quadratic samplings on 2 sample grids in an intertidal pool of the northernmost Adriatic sea. Abundant species of foraminifers exhibit patchy distributions throughout; the distribution-patterns of some species correspond nearly completely. Using statistical methods (regression- and correlation-analyses) correlations to abiotic and biotic factors (water depth, exposure rate, seagrass, benthonic algae) were ascertained. The significant correlations of the foraminiferal frequencies to blue-green algae and/or diatoms enable an interpretation of these connexions as food dependences. Several foraminiferal species seem to have specific diets.     

Kimberlite-hosted diamond deposits of southern Africa: A review

Following the discovery of diamonds in river deposits in central South Africa in the mid nineteenth century, it was at Kimberley where the volcanic origin of diamonds was first recognized. These volcanic rocks, that were named “kimberlite”, were to become the corner stone of the economic and industrial development of southern Africa. Following the discoveries at Kimberley, even more valuable deposits were discovered in South Africa and Botswana in particular, but also in Lesotho, Swaziland and Zimbabwe.A century of study of kimberlites, and the diamonds and other mantle-derived rocks they contain, has furthered the understanding of the processes that occurred within the sub-continental lithosphere and in particular the formation of diamonds. The formation of kimberlite-hosted diamond deposits is a long-lived and complex series of processes that first involved the growth of diamonds in the mantle, and later their removal and transport to the earth's surface by kimberlite magmas. Dating of inclusions in diamonds showed that diamond growth occurred several times over geological time. Many diamonds are of Archaean age and many of these are peridotitic in character, but suites of younger Proterozoic diamonds have also been recognized in various southern African mines. These younger ages correspond with ages of major tectono-thermal events that are recognized in crustal rocks of the sub-continent. Most of these diamonds had eclogitic, websteritic or lherzolitic protoliths.In southern Africa, kimberlite eruptions occurred as discrete events several times during the geological record, including the Early and Middle Proterozoic, the Cambrian, the Permian, the Jurassic and the Cretaceous. Apart from the Early Proterozoic (Kuruman) kimberlites, all of the other events have produced deposits that have been mined. It should however be noted that only about 1% of the kimberlites that have been discovered have been successfully exploited.In this paper, 34 kimberlite mines are reviewed with regard to their geology, mantle xenolith, xenocryst and diamond characteristics and production statistics. These mines vary greatly in size, grade and diamond-value, as well as in the proportions and types of mantle mineral suites that they contain. They include some of the world's richest mines, such as Jwaneng in Botswana, to mines that are both small and marginal, such as the Frank Smith Mine in South Africa. They include large diatremes such as Orapa and small dykes such as those mined at Bellsbank, Swartruggens and near Theunissen. These mines are all located on the Archaean Kalahari Craton, and it is apparent that the craton and its associated sub-continental lithosphere played an important role in providing the right environment for diamond growth and for the formation of the kimberlite magmas that were to transport them to the surface.