Latest precambrian (Cadomian) zircon ages, Nd isotopic systematics and P-T evolution of granitoid orthogneisses of the Erzgebirge, Saxony and Czech Republic

Single zircons from two orthogneiss complexes, the Grey Gneiss and Red Gneiss, the lowermost tectonic units in the Erzgebirge, were dated. The grey Freiberg Gneiss is of igneous origin and has a ²⁰⁷Pb/²⁰⁶Pb emplacement age of 550±7 Ma. A quartz monzonite from Lauenstein contains idiomorphic zircons with a mean ²⁰⁷Pb/²⁰⁶Pb age of 555±7 Ma as well as xenocrysts ranging in age between 850 and 1910 Ma. Red gneisses from the central Erzgebirge contain complex zircon populations, including numerous xenocrysts up to 2464 Ma in age. The youngest, idiomorphic, zircons in all samples yielded uniform ²⁰⁷Pb/²⁰⁶Pb ages between 550±9 and 554±10 Ma. Nd isotopic data support the interpretation of crustal anatexis for the origin of both units. _Nd(t) values for the grey gneisses are –7.5 and –6.0 respectively, (mean crustal residence ages of 1.7–1.8 Ga). The red gneisses have a wider range in _Nd(t) values from –7.7 to –2.8 (T _DM ages of 1.4–1.8 Ga). The zircon ages document a distinct late Proterozoic phase of granitoid magmatism, similar in age to granitoids in the Lusatian block farther north-east. However, Palaeozoic deformation as well as medium pressure metamorphism ( 8 kbar/600–650° C) are identical in both gneiss units and distinguish these rocks from the Lusatian granitoids. The grey and red gneisses were overthrust by units with abundant high-pressure relicts and a contrasting P-T evolution. Zircon xenocryst and Nd model ages in the range 1000–1700 Ma are similar to those in granitoid rocks of Lusatia and the West-Sudetes, and document a pre-Cadomian basement in parts of east-central Europe that, chronologically, has similarities with the Sveconorwegian domain in the Baltic Shield.     

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Naturwissenschaften Aktuell

Großforschung mit anderen Namen     

The ladybird<Emphasis Type="Italic"> Thalassa saginata</Emphasis>, an obligatory myrmecophile of<Emphasis Type="Italic"> Dolichoderus bidens</Emphasis> ant colonies

The larvae and pupae of the ladybird Thalassa saginata develop inside colonies of the dolichoderine ant Dolichoderus bidens. This association is the first specific and obligatory relationship recorded between ants and ladybirds. The ants provide shelter and protection to the larvae but the diet of the latter remains unclear. The integration of T. saginata larvae into the ant colonies is achieved by mimicking the cuticular patterns of the ants brood. Moreover, the larvae secrete substances from their hairs and anal gland that are likely to enhance their attractiveness.     

Biomineralization in plants as a long-term carbon sink

Carbon sequestration in the global carbon cycle is almost always attributed to organic carbon storage alone, while soil mineral carbon is generally neglected. However, due to the longer residence time of mineral carbon in soils (10²–10⁶ years), if stored in large quantities it represents a potentially more efficient sink. The aim of this study is to estimate the mineral carbon accumulation due to the tropical iroko tree (Milicia excelsa) in Ivory Coast. The iroko tree has the ability to accumulate mineral carbon as calcium carbonate (CaCO₃) in ferralitic soils, where CaCO₃ is not expected to precipitate. An estimate of this accumulation was made by titrating carbonate from two characteristic soil profiles in the iroko environment and by identifying calcium (Ca) sources. The system is considered as a net carbon sink because carbonate accumulation involves only atmospheric CO₂ and Ca from Ca-carbonate-free sources. Around one ton of mineral carbon was found in and around an 80-year-old iroko stump, proving the existence of a mineral carbon sink related to the iroko ecosystem. Conservation of iroko trees and the many other biomineralizing plant species is crucial to the maintenance of this mineral carbon sink.     

敖汉旗生态示范区调查研究对固阳县生态建设的启迪

通过参观学习提高自身认识，拓思路，产生构想，为做好本职工作奠定了基础，增强了信心。     

黑龙江省生物多样性保护重要性评价

根据黑龙江省生物多样性现状和国家规定的评价方法与指标对黑龙江省的生态系统进行生物多样性保护重要性评价,评价结果将黑龙江省生物多样性保护重要地区分为4级,即极重要、中等重要、比较重要和一般重要四个级别,并确定了它们的分布区域.这一成果为黑龙江省生态功能区划奠定了基础,提供了科学依据.     

昆明的水资源及其开发

昆明地区地面水紧缺，地下水资源虽然丰富，但部分富水地段过量开采，已形成严重后果。目前除从流域内水库开发外，规划从牛栏江、普渡河引水，满足近、中期需要。至２０１０年，昆明供水预计出现２８０×１０６ｍ３／ａ的缺口，必须制订相应政策，采取控制和治理滇池污染等措施，才能缓解矛盾，保证经济的可持续发展。     

芬兰城市和工业污水处理现状及发展趋势

介绍了芬兰在城市和工业废水治理方面的情况，芬兰在废水处理技术与管理目标方面取得的成就。最新进展及未来规划为我们提供了可供借鉴的资料和信息。     

临街建筑群中交通噪声的计算机模拟

给出了临街建筑群中纵深方向的交通噪声计算机模拟预测方法。交通干道上车流采用泊松分布和等车距车流相结合模型，考虑多种车型的不同声功率级。每辆车作为一个点声源，以几何声学方法考虑直达声和有限次反射声对测点的影响。在计算程序中只要输入车流量，车流成份，建筑群中有关巷道宽度，测点在巷子纵深方向距离及背景噪声等数据，计算机便能输出Ｌ１０，Ｌ５０，Ｌ９８，Ｌｅｑ等声级值。模拟结果和实测值基本一致。