板块构造图的制图理论与方法探讨

通过编制区域性1:300万“青藏高原板块构造图”和1:50万“柴达木北缘板块构造地质图”的体会,并结合国内学者对这两份图件的审查意见及建议,重点讨论有关区域性板块构造图编制的理论与方法,供区域地质工作者参考。     

汶川─理县志留系茂县群无根钩状褶皱构造初步解析

钩状褶皱又称无根钩状褶皱，是区域变质岩中广泛发育的特有构造形态之一，与面状构造置换密切相关。对它的研究，有助于恢复大型褶皱形态和变质岩原岩产状。本文初步探讨了四川汶川─理县志留系茂县群中广泛发育的无根钩状褶皱的形态、产状、成因和与大型褶皱构造的关系。     

Late Paleozoic and Mesozoic deformations in the southwestern Primorye region

Two types of tectonic deformations indicating different geodynamic settings are defined in the southwestern Primorye region. Near-latitudinal compression forces were responsible for the oldest, Late Paleozoic deformations. The Permian stratified complexes host a near-meridional system of folds and zones of dynamothermal metamorphism, cleavage, and foliation oriented orthogonally relative to the compression. Late Proterozoic (?) mafic-ultramafic rocks are characterized by similar deformations. In the Late Permian, the deformations were accompanied by granitoid magmatism controlled by fold and cleavage structures. The younger, Mesozoic deformations produced by near-meridional compression are represented by NE-trending sinistral strike-slip faults and their structural parageneses: an ENE-trending system of folds and downdip-thrusts both superimposed on Paleozoic protostructures and manifested in Mesozoic and Cenozoic sequences. It is inferred that, at the Paleozoic-Mesozoic boundary, near-latitudinal compression was replaced by near-meridional compression, probably, in response to the corresponding change in direction of the lateral displacement of the interacting Asian continent and (or) Pacific Plate.     

Multistage Landform Development, with Particular Reference to a Cratonic Bornhardt

The multistage concept is explained and illustrated, with particular reference to a bornhardt from the southern Yilgarn Block of southwestern Western Australia. Hyden Rock is a complex inselberg developed on Archaean granite. It probably developed through fracture-controlled differential subsurface weathering in the Cretaceous, followed in the Eocene by erosion of the lateritic regolith and exposure of the massive compartment as an inselberg. But the variations in fracture density to which Hyden Rock owes its origin developed long before the Cretaceous, probably in the latest Archaean or earliest Proterozoic. The relief amplitude of the residual has increased through the Cainozoic.
A rich assemblage of minor forms (basins, runnels, tafoni, pitting, displaced slabs, A-tents) is developed on the bornhardt and, though their mode of development varies, the origin of many can be traced back to magmatic and tectonic events of Late Archaean and earliest Proterozoic times. Others were initiated at the weathering front during the later Mesozoic, and many have developed since exposure, beginning in the Eocene. A few are related to tectonism during the later Quaternary.
The residual is a multistage form. Its development as a major landform can be traced back some 120 million years, and the structures to which the outlines of the bornhardt, and those related to several minor features, originated in later Archaean times. The geomorphological evolution of landforms of the shield lands and cratons extends over vast ages and cannot be regarded as a geologically recent phenomenon.     

Appreciation of Contributions by Georges Matheron and John Tukey to a Mineral-Resources Research Project

Georges Matheron (1930–2000) and John Tukey (1915–2000) were among the most prominent mathematical statisticians of the 20th century. Both men produced numerous important new theoretical and practical results. This personal appreciation of their work concentrates on contributions to mineral-resources research and describes their influence on my work in mineral-resource evaluation studies at the Geological Survey of Canada (1966–1983).     

The evolution of brittle and ductile structures at the surface of a partly debris-covered,rapidly thinning and slowly moving glacier in 1998–2012 (Pasterze Glacier,Austria)

Many glaciers in alpine regions are currently rapidly receding and thinning at historically unobserved rates causing changes in the velocity field and in normal and shear stresses affecting the surface expression of structures within the ice. We studied the distribution of brittle and ductile structures at the surface of Pasterze Glacier during a 14-year period by analysing orthophotos and digital elevation models of five stages (1998, 2003, 2006, 2009 and 2012). A structural glaciological mapping key was applied. Normal faults, strike-slip faults, en échelon structures (systematic stepping of fractures), thrust faults, and band ogives were distinguished. Results indicate substantial deceleration and glacier thinning in 1998–2012. Glacier thinning was not homogenous over time related to the uneven distribution of supraglacial debris causing differential ablation or the selective ablation effects of subglacial water channels. Peculiar supraglacial features observed are circular collapse structures with concentric crevasses which form when the ice between the surface and the roof of water channels decreases. The total length of brittle structures increased from 38.4 km to 56.9 km whereas the extent of the glacier tongue decreased by 25%. The fracture density doubled from 0.009 to 0.018 m/m². Areas of the glacier tongue which were up to 100 m away from the nearest brittle structure increased by 16%. The visual appearance of thrust faults shifted upglacier due to decreasing glacier velocity causing horizontal shortening or due to exhumation of faults that did not previously extend to the surface. A large number of brittle structures are progressively independent from glacier motion. Our study suggests that glacier tongues which are in a state of rapid decay and thinning are prone to fracturing due to normal fault formation and glacier disintegration. Water further increases ablation rates substantially if rather large amounts drain through supra-, en- or subglacial water channels. © 2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.     

北黄海海域复杂构造区三维地震精细解释技术

研究工区位于北黄海海域陆相断陷沉积盆地内,该区多期构造运动叠加,断裂发育,地震资料品质差。中生代为其主要勘探目的层,为一已证实的含油气区域。结合本区地质特点,对该区进行三维地震解释时所采用的综合解释技术进行了总结,主要包括三维地震资料品质分级评价技术、无VSP井区空间层位标定技术、层位自动追踪技术、三维可视化解释、多属性体断裂解释技术和变速成图技术等实用的解释技术。多种解释手段的联合应用高质高速地完成了本复杂构造区的构造精细解释,完善了该区的解释方案,理顺了复杂断层的切割关系,识别了活动较弱的小断层。特别是对高精度三维速度场的建立,实现了变速成图,消除了高陡构造区速度陷阱所带来的构造假象,为对该复杂区的地震解释和圈闭形态的落实以及进一步的井位部署与地质评价提供了依据。     

Impact cratering - a review,with special reference to the economic importance of impact structures and the Southern African impact crater record

Only since several decades has impact cratering been recognized as an important surface process on all planetary bodies in the Solar System. However, as the process has not yet been effectively introduced into geological curricula, it is necessary to inform a wider public about its importance for (i) planetary formation and (ii) evolution, (iii) the understanding of this process as a geological process, (iv) the terrestrial impact crater record and its limitations, and (v) the recognition criteria for terrestrial impact structures, as well as (vi) the need of improvement of the impact cratering record in the light of the potential danger of an impact catastrophe on this planet. It is, particularly for developing countries, of interest to examine the economic and educational-environmental potential of impact structures. That it is possible to carry out an effective, low-budget geological investigation of impact structures within a Second World environment is demonstrated by the discussion of the progress that has been made in recent years with regard to the Southern African impact crater record. Several recommendations on how to improve, on the one hand, the terrestrial impact crater record and, on the other, their general working situation by activation of workers in Developing Countries are discussed.