Deformation localization in orogens: Spatiotemporal expression and thermodynamic constraint

Orogens are spatiotemporal expressions of instabilities in materials under load, constrained by thermodynamics, and preserved in the cold outer shell of the planet. Their pressure–temperature–time histories are consistent with the predictions of differential grade-2 (DG-2) materials in pure shear. We place the statistically invariant shear localization mechanism of these materials in a coherent thermodynamic context using an analysis of strained elastic materials. This prototype system exhibits non-classical thermodynamic symmetry-breaking, where the potentials are all functions of a single variable and the distinction between heat and work fades from view. Consequently, internal energy must be described by a monotonically decreasing function of the entropy in order for heat capacity and absolute temperature to be positive. The entropy itself exhibits an inverse dependence on length. These constraints are satisfied by the overall shape and slope of the distributed deformation threshold ψ^D for DG-2 materials, and its noted 1/length correlation with naturally observed folds as a function of thermomechanical competence κ/χ. We predict that temperature in this non-linear elastic material will vary in proportion to the slope of ψ^D, being high at low competence, and low at high competence. Similar constraints apply to a self-gravitating body, where the energy function varies inversely with radius. Assigning zero pressure at the surface of the body, we also predict that pressure, the tensor trace of its stress–energy density, will vary inversely with radius. Thus, the body force of gravity will be expressed in this elastic self-gravitating system through the interplay of elastic and thermal lengths. Deformation localization in DG-2 materials arises due to the dynamic rescaling of lengths in response to a spike in the intrinsic energy ψ^I at κ/χ = ½. While the intrinsic ψ^I and localization ψ^L thresholds are monotonically decreasing for κ/χ > ½, they exhibit positive slopes at lower competence, signaling a return to classical thermodynamics and Joule heating in this transitional domain. Numerous structural and tectonic observations can be correlated using this remarkably simple model, beginning with the thickness and mechanical character of the brittle crust and oceanic lithosphere. In effect, this model projects the kinematic theory of plate tectonics into four-dimensional spacetime.     

"中新生代陆内变形与活动构造"专辑特邀主编寄语

传统的板块构造学说认为, 地壳缩短变形往往集中在大陆边缘的狭长的俯冲带或碰撞造山带.随着研究的深入, 地质学家发现, 陆缘板块俯冲或碰撞的远程应力可以传播很远, 到大陆内部, 并在大陆内部形成宽广的变形带.     

Energy:Preface

Energy is a vital commodity that sustains human lives,as well as eco-nomic processes.The challenges towards energy generation,demand and supply are plenty owing to the use of fossil fuels leading to climate change and environmental problems like water and air pollution.With the increasing awareness over climate change,post Paris Agreement,the role of energy plays a key role towards achieving the proposed tar-get.The contributions in this Special Issue of Geoscience Frontiers on En-ergy includes 8 papers from esteemed research groups worldwide which explores,highlights and provide new insights towards the vari-ous aspects of energy.     

Deformation mechanism of strain localization in 2D numerical interface tests

Heterogeneity arises in soil subjected to interface shearing, with the strain gradually localizing into a band area. How the strain localization accumulates and develops to form the structure is crucial in explaining some significant constitutive behaviors of the soil–structural interface during shearing, for example, stress hardening, softening, and shear-dilatancy. Using DEM simulation, interface shear tests with a periodic boundary condition are performed to investigate the strain localization process in densely and loosely packed granular soils. Based on the velocity field given by grains’ translational and rotational velocities, several kinematic quantities are analyzed during the loading history to demonstrate the evolution of strain localization. Results suggest that tiny concentrations in the shear deformation have already been observed in the very early stage of the shear test. The degree of the strain localization, quantified by a proposed new indicator, α, steadily ascends during the stress-hardening regime, dramatically jumps prior to the stress peak, and stabilizes at the stress steady state. Loose specimen does not develop a steady pattern at the large strain, as the deformation pattern transforms between localized and diffused failure modes. During the stress steady state of both specimens, remarkable correlations are observed between α and the shear stress, as well as between α and the volumetric strain rate.     

Himalayan Tectonics:Preface

The Himalayan-Tibetan orogen system serves as the modern paradigm for understanding convergence-related processes in orogenic belts. The advancements made studying the region have been applied to other ancient orogenic belts leading not only to a better understanding of their development, but also of secular changes in collisional processes. As more advanced methodologies are introduced and utilized in geological research, the type, scale, and quality of data available enable quantification of geological processes not previously possible. These complex and robust datasets now form the core of many of the research projects undertaken across the Himalaya and continue to provide unprecedented insight into the myriad different aspects of the evolution of the collisional system.     

High pressure geochemistry:Preface

The origin and history of the Earth are manifested as the evolutionary processes of chemistry and physics of its interiors,which can be recognized by deciphering the geochemical signals recorded in minerals and rocks.Deep interiors of the Earth and other rocky planets are under both extreme pressure and temperature,i.e.,approximately 360 gigapascals(GPa)and as high as 7000 K at the center of the Earth.     

忆吾师望未来(代序)

今年是黄汲清和李春昱二老诞辰100周年纪念，为追怀这两位地学界泰斗、良师，国土资源部和中国地质学会等均组织了有关纪念活动。我虽从师黄汲清先生较早，但二位老师对我的教诲以及相互间的交流却从无别样。二老的经历和性格有所异同，但他们对地质事业恪尽职责、治学严谨、报国育人的高尚品质，永远是我一生学习的榜样。     

Preface

正Trans-Eurasian exchange along the Ancient Silk Road The Ancient Silk Road was the major passageway for linking China, Central and West Asia, and Europe between the second century BCE(Before Common Era) and the sixteenth CE, which is identified as the center of civilizations in the Old World during that period(Frankopan, 2015). While archaeological evidences indicate the transcontinental exchange across the Eurasia emerged during the third Millennium BCE at least     

序

贺邢裕盛先生八十华诞和从事地质工作五十七周年邢裕盛教授是我国著名前寒武纪地层古生物学家,是我国前寒武纪微古植物和古藻类学研究的奠基人之一.他治学严谨、才思敏捷、辛勤耕耘,成果卓著.多年来,他注重野外调查和科学实践,踏遍祖国的大江南北,走过世界的四海五洲.不仅为我国地层古生物学的发展做出了重大贡献,而且为我国培养了大批前寒武纪微古植物研究和各断代古生物学研究的专门人才.