神农架大九湖15.753kaB.P.以来的孢粉记录和环境演变*

根据对大九湖297cm厚的泥炭地层10个AMS ¹⁴ C年龄的测定以及148块孢粉样品的分析,发现每块样品的孢粉(浓度)含量都很高,植物种类繁多,分属于137(科)属,可划分为6个孢粉组合带,植被类型演替大体为:含少量常绿树种的针阔叶混交林—含常绿阔叶树种的落叶阔叶林—常绿落叶阔叶林—含常绿阔叶树种的落叶阔叶林—含少量常绿树种的针阔叶混交林。孢粉带Ⅰ(15.753~11.280kaB.P.)记录了该区域晚冰期及其向全新世过渡时期冷暖波动频繁的气候条件,其中亚带Ⅰ -1(15.753~15.549kaB.P.),Ⅰ -3(14.936~14.505kaB.P.)和Ⅰ -5(12.655~11.280kaB.P.)可能分别对应最老仙女木期、老仙女木和新仙女木冷期,而亚带Ⅰ -2(15.549~14.936kaB.P.)和Ⅰ -4(14.505~12.655kaB.P.)分别对应博令和阿勒罗德暖期。孢粉带Ⅱ(11.280~9.218kaB.P.)代表了由晚冰期冷湿气候向全新世温暖气候转换的早全新世缓慢升温的过渡时期。孢粉带Ⅲ(9.218~7.530kaB.P.)代表中全新世前期的气温波动上升期,7.7kaB.P.前后达到最高温。孢粉带Ⅳ(7.530~4.051kaB.P.)代表中全新世适宜期,水热配置条件最佳。孢粉带Ⅴ(4.051~0.911kaB.P.)体现晚全新世温干的气候。孢粉带Ⅵ(0.911~0kaB.P)反映了大九湖温凉稍湿的气候。     

利用非线性方法反演琉球-台湾-吕宋地区的岩石层P波速度结构

根据中国地震台网和ISC台站提供的P波走时资料,使用差异演化全局优化算法(DE算法)和移动窗方法反演了琉球-台湾-吕宋地区岩石层尺度的P波速度结构.在台站和地震分布较为密集的地区,反演窗口为2°×2°,移动步长为1°;在台站和地震较少的地区,反演窗口为4°×4°左右,移动步长为2°.反演结果揭示出琉球-台湾-吕宋地区壳幔结构的横向差异:琉球岛弧西侧受冲绳海槽地幔热扰动的地壳减薄,东侧由于菲律宾海板决的俯冲挤压地壳略有增厚;欧亚大陆与菲律宾海板块的相互碰撞导致台湾地区地壳及岩石层明显增厚;吕宋及菲律宾北部岩石层受岛弧火山下方热流影响较大.结果表明,非线性全局优化算法和移动窗方法能够用于反演较大尺度速度结构的横向变化.     

中国云南易门式铜矿床的主要类型及成因

系统地概括了易门铜矿田的成矿地质背景及2种矿床类型的地质特征,在此基础上论证了火山热水沉积作用、构造改造作用、岩浆叠加作用、地下热水再造作用与成矿密切相关。易门式铜矿床为"裂谷成矿背景-火山热水沉积-构造改造富集-深源岩浆叠加-地下热水再造"型多因复成矿床,建立了新的成矿模式,为该类矿床深部及外围的找矿预测指明了方向。     

参数调整对气象预测的B-P网络模型性能的影响

为了探索ＢＰ网络的参数调整特性,进行了参数α、β的选取对ＢＰ算法的收敛速度和模型的稳定性的影响研究。通过ＢＰ网络用于气象预测建模的参数调整个例分析表明：参数α、β的取值对ＢＰ模型的稳定性无显著影响,但参数值的调整尤其是β值的调整对建模的收敛速度有明显的影响。     

统一分布下的LP估计抗差测度

本文根据定位参数Ｍ估计理论,导出了ＬＰ估计的影响函数,分析了ＬＰ估计的抗差能力,同时还推导了ＬＰ估计的渐近效率,综合抗差能力和效率,分析了ＬＰ估计的优劣性,明确指出,用现测数据中含有粗差扰动的数据和Ｐ为（１,１．２５）的ＬＰ估计进行处理,结果较优,效率较高。     

Teleseismic delay-time tomography of the upper mantle beneath southeastern India: imprint of Indo–Antarctica rifting

A 3-D P -velocity map of the crust and upper mantle beneath the southeastern part of India has been reconstructed through the inversion of teleseismic traveltimes. Salient geological features in the study region include the Archean Dharwar Craton and Eastern Ghat metamorphic belt (EGMB), and the Proterozoic Cuddapah and Godavari basins. The Krishna–Godavari basin, on the eastern coastal margin, evolved in response to the Indo–Antarctica breakup. A 24-station temporary network provided 1161 traveltimes, which were used to model 3-D P -velocity variation. The velocity model accounts of 80 per cent of the observed data variance. The velocity picture to a depth of 120 km shows two patterns: a high velocity beneath the interior domain (Dharwar craton and Cuddapah basin), and a lower velocity beneath the eastern margin region (EGMB and coastal basin). Across the array velocity variations of 7–10 per cent in the crust (0–40 km) and 3–5 per cent in the uppermost mantle (40–120 km) are observed. At deeper levels (120–210 km) the upper-mantle velocity differences are insignificant among different geological units. The presence of such a low velocity along the eastern margin suggests significantly thin lithosphere (<100 km) beneath it compared to a thick lithosphere (>200 km) beneath the eastern Dharwar craton. Such lithospheric thinning could be a consequence of Indo–Antarctica break-up.     

根据含超压气体裂隙震源模式讨论P波初动符号的分布

利用含超压气体裂隙震源模式［１］分析研究了Ｐ波初动符号的分布．根据理论推导,不同倾角含超压气体裂隙可分别形成Ｐ波初动符号的四象限分布图象和圆、椭圆、抛物线、双曲线等圆锥曲线形Ｐ波节线．按节线形状和失稳方式进行了地震分类．所推论的初动Ｐ波、Ｓ波振幅分布规律和地形变特征都与实际相符     

Meteor observations in Japan: new implications for a Taurid meteoroid swarm

Observational evidence is sought that the long-term (10⁴ yr) action of a mean motion resonance with Jupiter can produce structure in a meteoroid stream, concentrating meteoroids in a dense swarm. More specifically, predictions tabulated by Asher & Clube of enhanced meteor and fireball activity from a Taurid Complex swarm in the 7:2 resonance are compared with observational data collected in Japan over several decades. The swarm model was proposed for reasons independent of the observations analysed here, and these newly considered data are shown to be consistent with it. This allows increased confidence in the Taurid swarm theory, and more generally could mean that resonant trapping is a dynamical mechanism affecting a significant amount of meteoroidal material in the inner Solar system.     

Unpairing metamorphic belts: P–T paths and a tectonic model for the Ryoke Belt, southwest Japan

Southwest Japan is divided into Outer and Inner Zones by the Median Tectonic Line (MTL), a major transcurrent fault. The Outer Zone is composed of the Sambagawa (high-pressure intermediate or high P/T type metamorphism), Chichibu and Shimanto Belts. In the Inner Zone, the Ryoke Belt (andalusite– sillimanite or low P/T type metamorphism) was developed mainly within a Jurassic accretionary complex. This spatial relationship between high P/T type and low P/T type metamorphic belts led Miyashiro to the idea that metamorphic belts were developed as ‘paired’ systems. Textural relationships and petrogenetically significant mineral assemblages in pelites from the Ryoke Belt imply peak P–T conditions of ≈5 kbar and up to 850 °C in migmatitic garnet–cordierite rocks from the highest-grade metamorphic zone. It is likely that the thermal anomaly responsible for metamorphism of the Ryoke Belt was related to a segment of the Farallon–Izanagi Ridge as it subducted under the eastern margin of the Asian continent during the Cretaceous. The sequence of mineral assemblages developed in pelites implies a metamorphic field gradient with shallow dP/dT slope, inferred to have been generated by a nested set of hairpin-like ‘clockwise’P–T paths. These P–T paths are characterized by limited prograde thickening, minor decompression at peak-T , and near-isobaric cooling, features that may be typical of P–T paths in low P/T type metamorphic belts caused by ridge subduction. A ridge subduction model for the Ryoke Belt implies that juxtaposition of the high-P/T metamorphic rocks of the Sambagawa Belt against it was a result of terrane amalgamation. Belt-parallel ductile stretching, recorded as syn-metamorphic, predominantly constrictional strain in both Ryoke and Sambagawa Belt rocks, and substantial sinistral displacement on the MTL are consistent with left-lateral oblique convergence. Diachroneity in fast cooling of the Ryoke Belt is implied by extant thermochronological data, and is inferred to relate to progressive SW to NE docking of the Sambagawa Belt. Thus, an alternative interpretation of ‘paired’ metamorphic belts in Japan is that they represent laterally contemporaneous terranes, rather than outboard and inboard components of a trench/arc ‘paired’ system. Amalgamation of laterally contemporaneous terranes during large translations of forearcs along continental margins may explain other examples of ‘paired’ metamorphic belts in the geological record.