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971.
972.
安徽月山岩体的40Ar/39Ar年龄及与其有关的成矿时代估计 总被引:13,自引:0,他引:13
安徽月山岩体是长江中下游钢铁成矿带中的一个重要含矿岩体.我们对该岩体的角闪石和黑云母进行了40Ar/39Ar年龄测定.角闪石的未扰动年龄谱给出岩体侵位年龄为136Ma.根据黑云母的扰动年龄谱,估计岩体从浸位到矿化(晚期热液作用)的时间间隔不少于9Ma.月山岩体的年龄测定结果以及前人对长江中下游其它含铜岩体的年龄测定结果表明,该区所有铜矿化岩体均形成于136Ma前,且产出于沿江构造单元内.此外,月山岩体的研究还表明,对中酸性岩的年龄测定,封闭温度高的角闪石是较理想的样品,在解释与矿化有关或热液作用发育的岩体的黑云母K-Ar结果时,必须持慎重态度. 相似文献
973.
The estimation of residual displacements in a structure due to an anticipated earthquake event has increasingly become an important component of performance-based earthquake engineering because controlling these displacements plays an important role in ensuring cost-feasible or cost-effective repairs in a damaged structure after the event. An attempt is made in this study to obtain statistical estimates of constant-ductility residual displacement spectra for bilinear and pinching oscillators wit... 相似文献
974.
预测世界石油资源不仅确定了局部区域的能源潜力 ,还有其战略意义。20世纪最为现实的工作是多次计算了石油的潜在资源 ,而且 ,最新计算的油气资源量通常超过以前的计算 ,并总是因发现以石油、凝析气等不同相态存在的新油田而得到证实。如在20世纪初 ,П.Уикс确定世界石油资源总量为95亿t,但到1958年已增至2070亿t,而到世纪末估计有5400亿t。在石油资源评价上有如此大的进展与烃类普查方法的完善 ,在油气生成领域内理论工作的成功 ,地球物理和地球化学研究的应用以及在成因基础上对含油气性前景论证的充分有关。… 相似文献
975.
最近观测到的异常地震事件——深部低频地震和颤动、甚低频地震及慢滑动事件——形成了慢震群,而这个慢震群受控于不同于普通地震的标定律。根据这个标定律,我们在日本西部的纪伊半岛下方观测到了之前未知的事件,其震源持续时间约20-200s,矩震级为3~4级。这些地震在2~8Hz的频带范围内辐射能量,直接与其地震矩率成比例,但这个比例常数比一般地震小4~5个数量级。这个地区的慢地震可能是由大量的剪切滑动事件组成的,从地震方法上看,总体上会呈现为颤动或长达200s持续时间的较长独立事件,从大地测量方法上看,是慢滑动事件。 相似文献
976.
2004年的苏门答腊—安达曼M9级地震将俯冲的印度—澳大利亚板块和仰冲的缅甸板块分裂开。这次地震的形变属于三维问题,为此我们构建了有限元模型进行模拟,以说明俯冲板块、弧前、火山弧及弧后的物性分布。同震形变的模拟使用一种基于协议的方法。该方法考虑俯冲带的地质复杂性,使用有限元模型反演估计断层滑动分布。结果表明不考虑俯冲带中物性差异的形变预测的灵敏度比近场GPS的测量误差可大一个数量级还多。本文介绍的基于有限元模型的技术可用于地质上相符的形变模型,提高同震与震后形变、应力耦合及海啸发生的基于模拟技术的评估可靠性。 相似文献
977.
A numerical modeling and simulation experiment is carried out to assess the sediment dynamics of Arklow Bank, Ireland. To meet a requirement for favorable site selection to establish windmills on the bank, the long-term morphological changes of the coast are studied using the CAMS (Coastal Area Morphological Shell) model of the Mike-21 suite of programs. The morphological modeling of the bank was accomplished by pursuing a probabilistic approach for the observed tide and wave characteristics that contribute significantly to the sediment transport processes over the bank. A series of simulations are performed using Mike-21 NSW (Nearshore Spectral Wind-Wave), HD (Hydrodynamic), and ST (Sand Transport) models to establish the coastal hydraulics parameters. The results of the morphological modeling showed that generally the bank is dynamically stable with most areas of the bank having average bed level changes on the order of ±8 cm/day. 相似文献
978.
S.Selvam P.Muthukumar Sruthy Sajeev S.Venkatramanan S.Y.Chung K.Brindha D.S.Suresh Babu R.Murugan 《地学前缘(英文版)》2021,12(1):29-38
The present study focused on the estimation of submarine groundwater discharge(SGD)and the effects of nutrient fluxes due to the SGD process.The parameters of SGD such as magnitude,character,and nutrient flux in Punnakayal region of South East coast of India were evaluated using multiple tracers of groundwater inputs in 2019.It was found that the elevated values for the tracers in the study area,displayed a gradational change in the values as move from estuarine part to the offshore.Simultaneous occurrence of fresh and saline SGD is observed on the study sites.Also,indicated that the SGD fluxes ranged from 0.04 to 0.12 m^3 m^-2d^-1 at the estuary and0.03-0.15 m^3 m^-2d^-1at the groundwater site.A substantially increased value for 222 Rn activities is distinguished in the estuary to values over 312 dpm L^-1.Nutrient embellishments were generally greatest at locations with substantial meteoric elements in groundwater;however,the recirculation of saltwater through the geological formation could provide a way of transferring terrestrially-derived nutrients to the coastal zone at many places. 相似文献
979.
980.
Carney MW Erwin K Hardman R Yuen B Volz DC Hinton DE Kullman SW 《Marine pollution bulletin》2008,57(6-12):255-266
Polycyclic aromatic hydrocarbons (PAHs) are widespread persistent pollutants that readily undergo biotic and abiotic conversion to numerous transformation products in rivers, lakes and estuarine sediments. Here we characterize the developmental toxicity of four PAH transformation products each structural isomers of hydroxynaphthoic acid: 1H2NA, 2H1NA, 2H3NA, and 6H2NA. Medaka fish (Oryzias latipes) embryos and eleutheroembryos were used to determine toxicity. A 96-well micro-plate format was used to establish a robust, statistically significant platform for assessment of early life stages. Individual naphthoic acid isomers demonstrated a rank order of toxicity with 1H2NA>2H1NA>2H3NA>6H2NA being more toxic. Abnormalities of circulatory system were most pronounced including pericardial edema and tube heart. To determine if HNA isomers were AhR ligands, spatial-temporal expression and activity of CYP1A was measured via in vivo EROD assessments. qPCR measurement of CYP1A induction proved different between isomers dosed at respective concentrations affecting 50% of exposed individuals (EC50s). In vitro, all ANH isomers transactivated mouse AhR using a medaka CYP1A promoter specific reporter assay. Circulatory abnormalities followed P450 induction and response was consistent with PAH toxicity. A 96-well micro-plates proved suitable as exposure chambers and provided statistically sound evaluations as well as efficient toxicity screens. Our results demonstrate the use of medaka embryos for toxicity analysis thereby achieving REACH objectives for the reduction of adult animal testing in toxicity evaluations. 相似文献