西藏冈底斯带侏罗纪岩浆作用的时空分布 及构造环境

在新近完成的1：25万区域地质调查资料和相关研究成果的基础上,初步研究了西藏冈底斯带侏罗纪岩浆作用的分布特点及其年代学,并利用已有的地球化学数据重点分析了早期关注程度较低的侏罗纪花岗岩类岩浆作用的性质。目前在冈底斯弧背断隆带未发现侏罗纪火山岩;在冈底斯东部地区,早侏罗世岩浆活动几乎同时发生于南冈底斯（叶巴组火山岩和鸟郁、尼木花岗岩类）、冈底斯弧背断隆带（宁中、金达、布久花岗岩类）和北冈底斯（聂荣花岗岩类）,中晚侏罗世接奴群和拉贡塘组火山岩断续分布于北冈底斯,晚侏罗世岩浆活动零星分布于沙莫勒一麦拉一洛巴堆～米拉山断裂以北。将冈底斯侏罗纪岩浆活动置于时空框架内分析发现,南冈底斯和北冈底斯在侏罗纪时主要受俯冲作用的影响．而冈底斯弧背断隆带和中冈底斯自早侏罗世以来除了受到俯冲作用的影响外,还受到自东向西逐步扩展的碰撞作用的影响。结合古地磁重建资料和其他新发现．认为冈底斯带侏罗纪这种岩浆活动的特点可用班公湖一怒江洋壳向南、新特提斯洋壳向北的双向剪刀式（剪刀口向西张开）俯冲模式来解释。     

Geology of the Heimaey volcanic centre, south Iceland: early evolution of a central volcano in a propagating rift?

Heimaey is the southernmost and also the youngest of nine volcanic centres in the southward-propagating Eastern Volcanic Zone, Iceland. The island of Heimaey belongs to the Vestmannaeyjar volcanic system (850 km²) and is situated 10 km off the south coast of Iceland. Although Heimaey probably started to form during the Upper Pleistocene all the exposed subaerial volcanics (10 monogenetic vents covering an area of 13.4 km²) are of Holocene age. Heimaey is composed of roughly equal amounts of tuff/tuff-breccias and lavas as most eruptions involve both a phreatomagmatic and an effusive phase. The compositions of the extrusives are predominantly alkali basalts belonging to the sodic series. Repeated eruptions on Heimaey, and the occurrence of slightly more evolved rocks (i.e. hawaiite approaching mugearite), might indicate that the island is in an early stage of forming a central volcano in the Vestmannaeyjar system. This is further substantiated by the development of a magma chamber at 10–20 km depth during the most recent eruption in 1973 and by the fact that the average volume of material produced in a single eruption on Heimaey is 0.32 km³ (dense rock equivalent), which is twice the value reported for the Vestmannaeyjar system as a whole. We find no support for the previously postulated episodic behaviour of the volcanism in the Vestmannaeyjar system. However, the oldest units exposed above sea level, i.e. the Norðurklettar ridge, probably formed over a 500-year interval during the deglaciation of southern Iceland. The absence of equilibrium phenocryst assemblages in the Heimaey lavas suggests that magma rose quickly from depth, without long-time ponding in shallow-seated crustal magma chambers. Eruptions on Heimaey have occurred along two main lineaments (N45°E and N65°E), which indicate that it is seismic events associated with the southward propagation of the Eastern Volcanic Zone that open pathways for the magma to reach the surface. Continuing southward propagation of the Eastern Volcanic Zone suggests that the frequency of volcanic eruptions in the Vestmannaeyjar system might increase with time, and that Heimaey may develop into a central volcano like the mature volcanic centres situated on the Icelandic mainland.     

二维TIM中的传播矩阵与面波相速度

本文利用横向各向同性介质（ＴＩＭ）中的传播矩阵和面波形成条件，导出了面波波慢度方程。对瑞利波给出了各向同性及横向各向同性弹性介质中其相速度的解析解；对于勒夫波，给出了横向各向同性介质中的波慢度方程。     

Episodic granite accumulation and extraction from the mid‐crust

The processes of long‐range granitic magma transfer from mid‐ and lower crustal anatectic zones to upper crustal pluton emplacement sites remain controversial in the literature. This is partly because feeder networks that could have accommodated this large‐scale magma transport remain elusive in the field. Existing granite ascent models are based largely on numerical and theoretical studies that seek to demonstrate the viability of fracture‐controlled magma transport through dykes or self‐propagating hydrofractures. In most cases, the models present very little supporting field evidence, such as sufficiently voluminous near‐ or within‐source magma accumulations, to support their basic premises. We document large (deca‐ to hectometre‐scale), steeply dipping and largely homogeneous granite lenses in suprasolidus (~5 kbar, ~750 °C) mid‐crustal rocks in the Damara Belt in Namibia. The lenses are surrounded by and connected to shallowly dipping networks of stromatic leucogranites in the well‐layered gneisses of the deeply incised Husab Gorge. The outcrops define a four‐stage process from (i) the initial formation and growth of large, subvertical magma‐filled lenses as extension fractures developed at high angles to the subhorizontal regional extension in relatively competent wall‐rock layers. This stage is followed by (ii) the simultaneous lateral inflation and (iii) subcritical vertical growth of the lenses to a critical length that (iv) promotes fracture destabilization, buoyancy‐driven upward fracture mobilization and, consequently, vertical magma transport. These field observations are compared with existing numerical models and are used to constrain, by referring to the dimensions of the largest preserved inflated leucogranite lens, an estimate of the minimum fracture length (~100 m) and volume (~2.4 × 10⁵ m³) required to initiate buoyancy‐driven brittle fracture propagation in this particular mid‐crustal section. The critical values and field relationships compare favourably with theoretical models of magma ascent along vertical self‐propagating hydrofractures which close at their tails during propagation. This process leaves behind subtle wake‐like structures and thin leucogranite trails that mark the path of magma ascent. Reutilization of such conduits by repeated inflation and drainage is consistent with the episodic accumulation and removal of magma from the mid‐crust and is reflected in the sheeted nature of many upper crustal granitoid plutons.     

青藏高原云团东传过程及其中中尺度对流系统的统计特征

利用逐小时风云卫星TBB资料、逐小时中国自动站与CMORPH降水产品融合数据以及国家级地面观测站24小时累积降水量,统计分析2010～2016年夏季,伴随下游地区（104°E以东）降水的青藏高原云团东传过程以及东传过程中镶嵌于云团中的中尺度对流系统（Mesoscale Convective System,简称MCS）特征。结果表明,共出现120次伴随下游降水的高原云团东传过程,6月出现最频繁,但持续时间较长的过程多出现在7月。云团向东传播的主要三条路径是平直东传、沿长江折向东传和复合东传。其中路径二——沿长江折向东传中的过程是高影响过程,因为过程次数较多（46次）,过程平均持续时间较长（62小时）,在下游地区引发的降水日数和暴雨日数最多。属于东传过程的MCS在7月形成最多,集中分布在青藏高原东坡、云贵高原东部、长江沿岸及其以南地区。高原MCS影响长江中下游地区降水主要是通过向东传播的形式实现,因为即使生命史更长的中α尺度对流系统（Meso-α Convective System,简称MαCS）也鲜少直接移动至110°E以东地区。不同区域的中α尺度持续性拉长形对流系统（Permanent Elongated Convective System,简称PECS）的日变化特征显示,东传过程MCS更容易在夜间从高原东坡向东传播至下游地区。在三条路径中,路径二中的东传过程MCS数量最多、在下游地区发展最旺盛并与降水日数和覆盖范围存在更好的对应关系。     

粘弹性介质中的地震波

给出了三元件的标准线性粘弹性固体在半平面内传播的地震波的解析解，它是由已知的弹性半平面内的解析解迭粘滞性解而得，从而克服了视地壳为二元件粘弹性体的Voigt模型或Maxell模型的缺点。     

潜水含水层水压力传递的时效性

传统的渗流模型研究中，忽略了渗流场中水压力传递的时效性。本文针对潜水含水层井流问题，分析了井流场的特征。在前人研究的基础上，作者详尽地推导了上部入渗补给为常量情况下的降落漏斗半径和水压力传递速度与时间的关系式，并对某电厂水源地进行了计算。     

目标相似性的矢量数据联动更新方法

针对地理空间矢量数据更新和相似性在地理信息领域应用的研究现状,文章分析了不同几何类型目标之间的几何相似性,结合属性相似度,提出了针对数据联动更新的目标相似性的计算模型以及目标匹配方法;在此基础上,提出了数据变化发现和提取方法,并依据数据之间的映射关系实现多重表达矢量数据的联动更新。最后以某省矢量数据的水系要素之间联动更新为实例,证明了本数据联动更新方法能够完成多重表达地理空间矢量数据的更新,同时保证数据之间的一致性。     

时-空二维波传播分解方法及其在季节内振荡分析中的应用

大气季节内振荡最显著的特征之一就是其复杂多变的传播特征。为了进一步分析大气季节内振荡的传播特征及其不同传播方向分量的不同作用,基于波的传播理论,对时-空谱分析进行了发展,提出了时-空二维波传播分解方法,并用理想函数验证了其正确性和可行性。结果表明:对任一时-空二维序列,采用此方法均可正确地分解得到空间上具有不同传播方向的3部分分量:前进波、后退波和驻波分量。之后,对向外长波辐射(OLR)、200和850hPa纬向风的东传、西传分量以及驻波分量分别进行联合经验正交函数(CEOF)分析。结果表明,在东传分量上,热带大气季节内振荡主要表现为纬向1波的向东传播,与对流层高、低层纬向风呈现反位相的斜压结构,和未分解的情况相比,前两个主要模态重要性的排序出现了颠倒,说明通过时-空二维波传播分解,避开了各分量之间的相互影响,进一步揭示了前两个模态的物理意义及其在季节内振荡中的重要性;在西传分量上,热带大气季节内振荡主要表现为纬向2—3波的向西传播;驻波分量主要表现出印度洋和太平洋的反位相结构。对热带地区大气季节内振荡的东、西分量的分析,深化了对热带大气季节内振荡东传、西传特征的了解,这对于热带大气季节内振荡更加准确预报及其...     

Morphology of the Blanco Transform Fault Zone-NE Pacific: Implications for its tectonic evolution

The right-lateral Blanco Transform Fault Zone (BTFZ) offsets the Gorda and the Juan de Fuca Ridges along a 350 km long complex zone of ridges and right-stepping depressions. The overall geometry of the BTFZ is similar to several other oceanic transform fault zones located along the East Pacific Rise (e.g., Siquieros) and to divergent wrench faults on continents; i.e., long strike-slip master faults offset by extensional basins. These depressions have formed over the past 5 Ma as the result of continual reorientation of the BTFZ in response to changes in plate motion. The central depression (Cascadia Depression) is flanked by symmetrically distributed, inward-facing back-tilted fault blocks. It is probably a short seafloor spreading center that has been operating since about 5 Ma, when a southward propagating rift failed to kill the last remnant of a ridge segment. The Gorda Depression on the eastern end of the BTFZ may have initially formed as the result of a similar occurrence involving a northward propagating rift on the Gorda ridge system. Several of the smaller basins (East Blanco, Surveyor and Gorda) morphologically appear to be oceanic analogues of continental pull-apart basins. This would imply diffuse extension rather than the discrete neovolcanic zone associated with a typical seafloor spreading center. The basins along the western half of the BTFZ have probably formed within the last few hundred thousands years, possibly as the result of a minor change in the Juan de Fuca/Pacific relative motion.