寿昌—临浦火山岩带赋矿流纹岩特征及归属雏议

本文介绍的火山岩带,有层状流纹岩及穹丘状、岩颈状等非层状流纹岩,分别属溢流相、侵出相及火山管道相,三种流纹岩均受火山岩带核中断裂及晚期火山构造控制,复盖或穿发寿昌组一段地层,又被寿昌组一段之后的次火山岩及隐爆岩所穿切,局部被横山组不整合复盖。该类流纺岩同位素年龄值较小,多数在１３０Ｍａ左右,处于晚侏罗世与早白垩世过渡期。根据其层序、穿切关系及同位素年龄等,认为三种流纹岩均属火山岩带晚期不同岩相的产     

火山活动与沉积盆地的形成和演化

我国大陆地壳进入中生代以来,发生了较其他陆壳更为强烈的构造运动,印支,燕山,喜马拉雅运动都是发生在我国大陆地壳以裂陷作用为主的典型运动,在中生代板块构造的特定时代和以裂陷作用主主的构造运动作用下,岩浆活动沿断穿骨石圈和地壳的深断裂发生,上涌至地壳地面形成火山岩带和地层格架中的火山岩层,上涌至地壳内部形成壳内流体相央浆房而成为高导层,火山活动是由中生代生成的太平洋板块和我国大陆地壳俯冲,使大陆地壳深     

华北克拉通基性火山岩高场强元素对Ar-Pt界限及新生代地幔源区特征的示踪

华北克拉通不同时代基性火山岩存在向富集方向演化的趋势,并出现明显的Ａｒ－Ｐｔ界限和新生代异常．元古宙基性火山岩比太古宙富集大部分高场强元素（ＨＦＳＥ）和轻稀土元素（ＬＲＥＥ）,ＲＥＥ分异程度显著增加,而且相容性接近的不相容元素（如Ｎｂ,Ｔａ）的相对不相容性发生了改变．新生代玄武岩ＨＦＳＥ及Ｎｉ高度富集,ＲＥＥ强烈分异,δ（Ｅｕ）值最高．Ａｒ－Ｐｔ界限可能与地幔熔融时物理条件（如氧逸度）的改变和地幔富集作用有关．新生代玄武岩独特的地球化学特征可能主要反映了地幔源区的特殊性———“似ＯＩＢ型”富集地幔,其形成既可能有携带远洋沉积物的俯冲古老玄武岩洋壳部分熔融残余的贡献,也可能有直接循环（如通过拆沉作用）的陆壳物质的贡献,同时还可能涉及了地幔柱活动的影响．     

内蒙古中部下二叠统火山岩特征及构造环境意义

内蒙古中部下二叠统火山岩的研究多年来存在争议,从岩石学,岩石地球化学等多方面对其进行研究分析,并探讨了形成环境及构造意义。     

Model of a strong volcanic blast and a method of estimating the mass ejected

A hydrodynamic model of a strong volcanic blast associated with large (caldera-forming) ash–gas-flow eruptions is presented. We show that the mass erupted from a vent influences considerably the damping of the shock wave. If the ejected mass flux is constant, the shock amplitude as a function of distance will decrease slower (in accordance with the inverse 4/3 power law) than that of an atomic explosion (the inverse cube power law). From the modelling, we extract a relation connecting the effective energy of a blast with the mass ejected during the blast phase. The mass released during the largest explosion of the 1883 eruption of Krakatau, and the lateral blast energy at Mount St. Helens on 1980 May 18 are estimated on the basis of the equation obtained.     

新疆火山岩分区及其地质意义

新疆火山活动强烈 ,火山岩类型多 ,出露广泛。依据火山岩特征和时空分布规律 ,新疆火山岩分布区域可以划分两个较大级别的火山岩分区单元 :第一级为火山岩区 ,第二级为火山岩带。全区共划分出 6个火山岩区和 30个火山岩带。火山岩分区的划分对火山岩、地质构造和矿产的研究具有重要的意义和实用价值     

Tertiary compressional structures on the Faroe–Rockall Plateau in relation to northeast Atlantic ridge-push and Alpine foreland stresses

A number of compressional anticlinal structures are identified in the western and northern part of the Faroe–Rockall Plateau. These structures occur on that part of the Faroe–Rockall Plateau which was above sea level during the latest phase of Paleocene plateau basalt extrusion. Three post-basalt compressional phases have affected the plateau. Most of the compressional structures in the northern part of the plateau are related to NE–SW- to ENE–WSW-oriented stress which we date to Late Paleocene–Early Eocene. The Oligocene phase is interpreted as resulting from N–S-directed compressional stress which also mainly affected the compressional structures on the northern part of the plateau. Compressional stress from the northwest seemed to affect the whole of the Faroe–Rockall Plateau and we suggest it to be of Miocene age. It is proposed that during the Late Paleocene–Early Eocene phase of compression local structure, and anomalously oriented gravitational ridge-push from the now extinct Aegir Axis contributed to a local NE–SW compressional stress system. The two later deformation phases were apparently connected to the regional northwest European stress system with small local modifications.     

The Effect of Uniform Rotation on Convective Instability of a Mushy Layer During Binary Alloys Solidification

The linear stability analysis of interstitial liquid within the mushy layer relative to a steady basic state is performed in order to incorporate the effect of uniform rotation on the onset of convective instability whose existence was found by Anderson and Worster (1996). The full set of non–dimensional governing equations for the temperature field, the local solid fraction and the fluid velocity are reduced asymptotically. In particular, the limit of small dimensionless mushy layer thickness, the limit of small differences between the initial and eutectic compositions of the liquid and the limit of large Stefan number are considered. The square root of Taylor number is assumed to be of the order unity. These simplifying assumptions involved in our analysis lead to a much simplified model which can essentially be solved analytically.