SHRIMP U–Pb zircon dating of a metagabbro and eclogites from western Dabieshan (Hong''an Block), China, and its tectonic implications

The Tyrrhenian Sea is a Neogene back-arc basin formed by continental extension at the rear of the eastward migrating Apennine subduction system. Its central part, generated from Tortonian to Pliocene, includes the Sardinia rifted margin to the west, an area with large volcanoes in the deep central sector, and the Campania rifted margin to the east. A reprocessing of some 2000 km of MCS lines, a new swath bathymetric map, and a review of previous geological and geophysical data allow to analyse the nature and distribution of continental vs. oceanic crust in this area, which evolved in a short time span.The central portion of the southern Tyrrhenian Sea is characterized by MOHO at about 10 km depth. North of Magnghi and Vavilov Smts, this thinned crustal domain include a wide continent–ocean transition, with the occurrence of extensional allochthons and of serpenitinzed sub-continental mantle, recalling other well known rifted margins, as the Iberia one. Sectors floored by oceanic crust should occur, mainly in the southern part of the study area, but they do not appear related to discrete spreading ridges. The continent–ocean boundary cannot be drawn unequivocally in the area, due also to the occurrence of widespread and huge magmatic manifestations not related to oceanic spreading. These portions of the southern Tyrrhenian Sea represents therefore a complex oceanic back-arc basin surrounded by magma-rich rifted continental margins.The abundant igneous manifestations and the very high stretching rates observed in the area may be related to the fact that the present Tyrrhenian area was occupied by an orogenic domain affected by shortening until middle Miocene times, which is just before the Late Miocene onset of back-arc extension. The lithosphere in the region had then to be rheologically weak. Abundant generation and ascent of magmas, mostly of Ocean Island Basalt type, was favoured by the large lithospheric permeability induced by strong extensional deformations.     

裂谷盆地下的壳-幔结构及其成因机制讨论——以由近垂直反射地震剖面揭示的松辽盆地下的壳-幔结构为例

详细研究了七段、约130km长的近垂直反射地震剖面所揭示的松辽盆地下的壳幔结构。松辽盆地之下壳幔之间为相对厚的Moho过渡带。可分为薄Moho和透镜状Moho以及过渡型Moho,与之对应的壳幔结构也有差异。松辽盆地的发育阶段明显地可分为断陷期、拗陷期以及夭折期,不同的壳幔结构可能与松辽盆地不同的发育期存在密切联系。此外,通过对比,认为裂谷盆地区具有类似的特殊壳幔结构。在裂谷区,壳幔之间强烈相互作用,不同的地壳组成和裂谷形成的不同阶段是形成不同壳幔结构的主要原因,而且它们之间具有成因上的联系,并与裂谷的形成阶段相一致。     

热带海表温度持续异常对东亚初夏大气环流的影响

利用NCEP/NCAR月平均海表温度及北半球大气环流分析资料,系统研究了热带海洋表面温度持续异常状况下东亚初夏（5、6月份）大气环流的异常特征.研究发现,暖海温年,南亚高压、西太平洋副热带高压明显偏强,冷海温年明显偏弱;暖海温年,欧亚大陆南支西风急流明显减弱北移,东亚大陆对流层低层温度偏高或接近常年,青藏高原近地面温度偏高,而冷海温年,东亚大陆对流层低层温度偏低,5月份青藏高原近地面温度偏低.研究表明,海表温度的持续异常对东亚初夏大气环流的季节转换有重要影响.     

CASS测图软件中DTM的建立与应用

本文探讨了CASS测图软件中DTM的建立及其在工程中的应用,并提出了在建立过程中应该注意的一些实际问题,供有关人员参考应用.     

旱,涝年与海气相互作用

利用１９５１￣１９９１年５００ｈＰａ高度场和海温场以及１９８０￣１９９１年ＴＢＢ资料，采用合成分析方法研究了东亚季风区季节转换在旱、涝年的不同特征。发现旱、涝年海温场分布型的不同及其形成的海气相互作用的差异使得西太平洋副热带高压在涝年季节北进较平缓，其脊线位置稳定在２５°Ｎ左右，强度较强，从而导致夏季风雨带在江淮流域停滞，形成江淮洪涝。中还讨论了中南半岛对流和赤道干旱带的变化对江淮流域旱、涝的先     

Implementation schemes for avoiding artifact discontinuities in simulated annealing

The simulated annealing algorithm has been applied successfully to conditional simulation of categorical variables (e.g., rock or facies units) with the objective of improving the match between measured and modeled spatial variability. In some implementation schemes, however, spurious features termed “artifact discontinuities” may occur near conditioning data, especially during the “zero- temperature” case referred to as simulated quenching. This paper shows that artifact discontinuities can be avoided by considering the anisotropy of the spatial variability model, reducing the number of lag vectors used in the objective function, and providing a rudimentary initial configuration. Results from several test cases suggest that the artifact discontinuities might be caused by overly precise fitting of measured to modeled spatial variability.     

Modeling Spatial Variability with One and Multidimensional Continuous-Lag Markov Chains

The continuous-lag Markov chain provides a conceptually simple, mathematically compact, and theoretically powerful model of spatial variability for categorical variables. Markov chains have a long-standing record of applicability to one-dimensional (1-D) geologic data, but 2- and 3-D applications are rare. Theoretically, a multidimensional Markov chain may assume that 1-D Markov chains characterize spatial variability in all directions. Given that a 1-D continuous Markov chain can be described concisely by a transition rate matrix, this paper develops 3-D continuous-lag Markov chain models by interpolating transition rate matrices established for three principal directions, say strike, dip, and vertical. The transition rate matrix for each principal direction can be developed directly from data or indirectly by conceptual approaches. Application of Sylvester's theorem facilitates establishment of the transition rate matrix, as well as calculation of transition probabilities. The resulting 3-D continuous-lag Markov chain models then can be applied to geo-statistical estimation and simulation techniques, such as indicator cokriging, disjunctive kriging, sequential indicator simulation, and simulated annealing.     

CaTiO3－钙钛矿的晶体结构相变、高温流变及其下地幔地球动力学意义

利用高精度的ＭＴＳ材料实验系统，在１４７３－１６７３Ｋ的温度区间和可控热力学环境条件下，对［１００］ｐｃ和［１１０］ｐｃ两个方位的ＣａＴｉＯ₃－钙钛矿单晶体进行了高温蠕变试验，着重观测了晶体结构相变和高温流变的相关性．研究表明，钙钛矿的晶体结构相变对其高温流变性质有明显影响，斜方晶系钙钛矿蠕变强度大大高于四方和立方晶系钙钛矿，后两者具有很强的高温塑性各向异性．在分析相变过程晶体结构变化特征和观测到的高温流变数据基础上，认为钙钛矿晶体结构相变中发生的位错结构的变化是导致其高温流变性变化的主要物理机制．