P-T path development derived from shearband boudin microstructure

This work focuses on the development of a regional P-T-path from the Malpica-Lamego Ductile Shear Zone, NW Portugal, based on the microstructures of shearband boudins evolved during progressive simple shear. The combination of microstructural analysis, fluid inclusion studies, crystallographic preffered orientation and fractal geometry analyses, allows to link several stages in the internal evolution of the boudin to regional P-T conditions. The boudinage process is initiated under differential stress after the original layer achieved sufficient viscosity contrast relative to the surrounding matrix. Two main transformations occur simultaneously: i) change in the external shape with continuous evolution from tabular rigid body to sigmoidal asymmetric morphology (shearband boudin) and ii) localized dynamic recrystallization in the sharp-tips of the structure (acute edge of shearband boudin), and along the boudin's margin and grain boundaries. Smaller recrystallized grains, particularly in the sharp-tip domains, accommodate most of the external strain, and larger relict grains are preserved in the centre. Dynamic recrystallization under constant strain rates and strain partitioning inside the boudins is indicated by fractal geometry based on grain boundary and grain area analysis. Progressive deformation leads to the generation of structural and textural heterogeneous domains inside the boudins, and is recorded by quartz c-axis orientation analysis and fluid inclusion studies. The last deformation episode shows the final formation of the blunt-tip domain and internal secondary shear planes. The regional P-T path begins with the crystallization of andalusite after an internal shearband boudin dilation event and ends with quartz dynamic recrystallization on boudin tips. The main deformation stage (310/315 Ma) led to reactivation of internal secondary shear zones with sillimanite crystallization.     

复杂断块油田高分辨率层序地层学及砂体几何学特征——以海塔盆地贝尔凹陷呼和诺仁油田贝301区块南屯组二段为例

准确刻画扇三角洲单期扇体几何形态是破解海塔油田开发的关键地质技术,以高分辨率层序地层学和现代沉积学理论为指导,在海塔盆地贝尔凹陷呼和诺仁油田贝301区块南屯组二段识别出3个长期（LSC）、4个中期（MSC）、6个短期（SSC）、53个超短期（相当于单砂体）基准面旋回,首次建立了海塔盆地已加密开发区块单砂体级高分辨率层序地层格架。沉积微相研究表明,优势砂体发育的水下分流河道、河口坝微相主要发育于可容纳空间较小的SSC3、SSC4及SSC5与SSC6的转换面附近。单期水下分流河道宽厚比为50∶1～200∶1,平均为85∶1;随着基准面的下降,水下分流河道的宽度增大、厚度增厚、宽厚比增大,随着基准面的上升,水下分流河道的宽度变窄、厚度减小、宽厚比减小。河口坝展布面积与其厚度有一定正相关性,一般半径与厚度的比值为60∶1～120∶1,平均为90∶1。本次研究首次实现海塔盆地单砂体级沉积微相工业化制图,精细刻画了主要砂体几何学特征,为综合挖潜提供了一定的地质依据。     

大别造山带西段南部构造几何学和运动学初步分析

根据红安—大悟地区构造填图的结果,结合室内显微镜分析,给出了研究区的构造演化序列、变形几何学特征和运动学方向。本地区经历了两期构造变形,早期变形(D1)是发生在地壳中部层次向北的韧性剪切推覆,形成了区域性、透入性的面理和线理构造,第二期变形(D2)是向较浅层次的向北东方向的逆冲推覆,形成了控制地层分布的区域性褶皱和各种露头尺度的小褶皱。结合已有的构造年代学结果,西大别南部的变形历史可分两个阶段:第一阶段为240Ma到225～210Ma的韧性剪切变形;第二阶段为早于195Ma的褶皱变形,二者均表现为总体由南向北的运动学特征,揭示出大别造山带折返过程的动力学背景。     

Modelling Compositional Change: The Example of Chemical Weathering of Granitoid Rocks

Perturbation on the simplex is an operation which can be used to numerically describe changes in the composition of, for example, soils, sediments, or rocks. The combination of perturbation and power transformation provides a strong tool for analyzing compositional linear processes in the simplex. When the process is constrained in the sense of a well-known starting (or final) composition, noncentred principal component analysis can be used to estimate the leading perturbation vector of the process. Applying these mathematical tools to chemical major element data from a weathering profile developed on granitoid rocks allows us to model the compositional changes associated with the process of chemical weathering. The comparison of these results with the compositional linear trend defined by erosional products of several of the world's major drainage systems yields close similarities. The latter observation allows for a mathematical formulation of a global mean weathering trend within the system Al₂O₃–CaO– Na₂O– K₂O. We further demonstrate the usefulness of the approach for validating processes behind individual trends and for combining the effects of different processes which modify the composition of soils, sediments, and rocks. Alternatives to the Chemical Index of Alteration (CIA) are discussed to obtain a translation-invariant scale for the process of chemical weathering.     

Use of Space-Filling Curves in Generating a National Rural Sampling Frame for HIV/AIDS Research*

The classical geographic research problem of regionalization and resource allocation is most commonly tackled by means of location-allocation methods. This paper introduces the spatial-order method as an alternative for creating regions or clusters. The spatial-order method utilizes space-filling curves, also known as Peano curves, to determine the nearness or spatial order of areal units, such as counties. Given a capacity constraint, the areal units are grouped consecutively according to their spatial order values. We applied the method to create clusters of rural counties for a national sampling survey of HIV/AIDS patients in the United States. Using the criteria that each cluster had approximately 50 new AIDS cases in 1991–1993 and that contiguity of areal units was maximized, 226 clusters were created from the 1,853 rural counties or health districts. The rural clusters generated by this method have been adopted as the national rural sampling frame in the HIV Cost and Services Utilization Study (HCSUS) being undertaken by RAND. In addition to its simplicity and fast computational speed, the spatial-order method produces satisfactory results. With minor modifications, this method can be an efficient alternative to the location-allocation method for solving a wide variety of locational problems, such as routing, political districting, and facilities location and allocation. This paper also demonstrates how a classical geographic research methodology, with the enhancement of GIS, can contribute to the multidisciplinary study of a pressing societal problem in our nation.     

储层地质模型建立步骤

本文系统介绍了单砂体模型、单井模型、二维模型和三维模型的建立步骤，是目前较为普及和实用的一种建模过程。文章对每种模型的关键点、参数选取和方法都作了概要的叙述，这一方法和步骤特别是对油田开发早期的模型建立具有很好的实用性。     

Fractal trees and Horton''s laws

Fractal trees as a model for drainage systems are described in its generalized non-homogeneous form from the viewpoint of fractal geometry. Box covering techniques are used to show the numerical equivalence between the Hausdorff-Besicovitch dimension and the similarity dimension of the fractally-dominant dust formed by the sources. In this way, the similarity relationD=log (N)/log (1/r) is reinterpreted in terms of bifurcation and length ratio (r _B andr _L ) asD=log (r _B )/log (r _L ). We test this relation for non-homogeneous exact fractal trees and two natural drainage systems. The fact thatr _B andr _L are common parameters in quantitative geomorphology allows a trivial stimation of the fractal dimension of well-known drainage basins.     

A Critical Approach to Probability Laws in Geochemistry

Probability laws in geochemistry have been a major issue of concern over the last decades. The lognormal on the positive real line or the additive logistic normal on the simplex are two classical laws of probability to model geochemical data sets due to their association with a relative measure of difference. This fact is not fully exploited in the classical approach when viewing both the positive real line and the simplex as subsets of real space with the induced geometry. But it can be taken into account considering them as real linear vector spaces with their own structure. This approach implies using a particular geometry and a measure different from the usual ones. Therefore, we can work with the coordinates with respect to an orthonormal basis. It could be shown that the two mentioned laws are associated with a normal distribution on the coordinates. In this contribution both approaches are compared, and a real data set is used to illustrate similarities and differences.     

汤加王国洪加火山的前世今生

洪加（Hunga）火山位于新西兰—克马德克—斐济俯冲带,该火山于2021年末又开始活动,并在2022年1月14、15日发生了千年一遇的世纪大喷发。喷发柱穿进平流层,形成了一个最高30 km、最宽800 km的蘑菇云,后期的气体火山灰云团几乎环绕南半球一周。喷发所引起的海啸在太平洋沿岸多地造成了灾害。根据现有的资料分析,洪加火山岩浆成分以安山岩为主,岩浆可能是沿着破火山口边缘由富气岩浆团块的“渗漏”驱动喷发的。这次洪加火山大喷发的一个最重要特征是喷发时产生了极为强烈的大气冲击波,这代表了岩浆内火山气体的极大富集。正是这种“超级富气岩浆”的喷发在喷火口位置形成了远超0.1 MPa(1 标准大气压）的出口压强,引发了向全球辐射的冲击波和数千千米以外都能听到的喷发声响。本次火山喷发引发海啸的机制,其一是爆炸冲击波,向外扩张的冲击波推动了海面表层海水的向外扩张;其二是苏特塞式（Surtseyan）喷发本身就有向外排走海水的能力。未来洪加火山喷发形式,很可能是沿着破火山口周边断裂或靠近破火山口中央谷地的熔岩穹丘或熔岩流。苏特塞式喷发会比较常见,但喷发规模不会太大。     

EVIDENCE OF A RESPONSE-BIAS EXPLANATION OF NONEUCLIDEAN COGNITIVE MAPS*

Two groups of subjects with varying amounts of experience with the city in which they lived judged from memory distances between familiar locations. The distance judgments were processed by a multidimensional scaling algorithm (MULTISCALE) that estimates the parameters of a power function transformation of the response scale and the coordinates of the locations in k-dimensional euclidean space. The results for both subject groups suggested that inaccuracies of distance cognition do not reflect the noneuclidean nature of urban cognitive maps but are caused by response bias.