第七代国际地磁参考场的检验与评价

本文对国际地磁和高空物理学会推荐的第七代国际地磁参考场进行了检验和评价。评价工作是通过１９６０～１９９５年（５年间隔）中国地磁台的观测数据;对中国地区复测点的测量数据;中国地区三阶泰乐多项式模型与第七代国际地磁参考场模型进行了比较,求得了平均差和标准偏差。并以１９９０年代为例,做出了１９９０年代各个地磁要素两个模型计算值之间的差值图,图上显示出这些差值的异常分布,这结异常是来自地壳源,比较结果,可     

山西省塔儿山—二峰山地区破碎带型金矿地质特征及找矿标志

通过找工作的实践,证实塔儿山－二峰山财区金矿体产于破碎带内,并认为破碎带构造复杂,硅化,黄铁矿,褐铁矿化,蚀度强裂地段是找金矿的重要标志。     

METAMORPHISM IN THE LESSER HIMALAYAN CRYSTALLINES AND MAIN CENTRAL THRUST ZONE IN THE ARUN VALLEY AND AMA DRIME RANGE (EASTERN HIMALAYA)

METAMORPHISM IN THE LESSER HIMALAYAN CRYSTALLINES AND MAIN CENTRAL THRUST ZONE IN THE ARUN VALLEY AND AMA DRIME RANGE (EASTERN HIMALAYA)1　BrunelM ,KienastJR . tudep啨ｔｒｏ structuraledeschevauchementsductileshimalayenssurlatrans versaledel’Everest Makalu (N啨ｐａｌｏｒｉｅｎｔａｌ) [J].CanadianJ .EarthSciences,1986 ,2 3:1117～ 1137. 2　LombardoB ,RolfoF .TwocontrastingeclogitetypesintheHimalayas :implicationsfortheHimalayanorogeny…     

成渝产业带主要城市空间关系研究

城市空间关系是指城市与城市空间相互作用关系,它的复杂程度是区域城市群体集聚效益的重要标志之一。通过对成渝产业带主要城市空间相互作用强度进行测算,分析了产业带内主要城市空间关系,提出了产业带内主要城市空间关系协调发展的思路。     

脆性材料强破裂前兆的初步研究

本文依据现有的实验结果初步研究脆性材料在破坏孕育过程中发生的强破裂的前兆特征.以应变(形变)突变、破裂弹性波限幅等物理变化特征确定强破裂;研究总结了不同试样、两种加载方式的破坏试验中的多个强破裂的前兆特征变化:一类为包括定点和场的应变变化特征,另一类为包括声发射率(破裂频度)、b值、波谱及微破裂时空分布等的声发射变化....     

Geology and hydrothermal resources in the northern Lake Abaya area (Ethiopia)

The northern Lake Abaya area located in the southern part of the Main Ethiopian Rift (MER) evidently contains an advective hydrothermal system. Regional extensional tectonics and subsidence that began in Late Miocene was followed by rift margin rhyolitic volcanism which produced extensive ignimbrite succession and rift shoulder trachytic volcanism in Pliocene. The extensional axis of the MER became the locus of volcanic activity in the Quaternary with bimodal basalt – rhyolitic volcanic products in the rift floor. Shallow crustal magma chambers feeding the axial volcanic complexes provide heat for the hydrothermal system which reside in Tertiary volcanic succession and is capped by lacustrine and volcanoclastic graben infill sediments. Duguna Fango rhyolitic volcanic complex which has extruded as much volume of volcanic products as all the other felsic centers put together is the most important heat source for the hydrothermal system and related manifestations. The closed drainage basin centered at Lake Abaya with adjacent plateau receiving over 1500 mm annual precipitation maintains a stable recharge for the prevailing hydrothermal system. Regional ground water flow direction is to the southwest following Bilate River which is the major river draining into the lake flowing parallel to the major NNE-SSW structural pattern of MER.Analyses of remote sensing data provided some insight into how the structural fabric had a control on the distribution of the groups of hydrothermal manifestations identified as hydrothermal fields. Thermal infrared image showed distinct thermal signature over the rift floor where hydrothermal fields are situated as compared to the plateau and areas covered by the cap-rock. A hydrothermal field around Duguna Fango volcanic complex has volcanological favorable setting despite lower inferred reservoir equilibrium geothermometer temperatures on the thermal springs. About 30 km to the south two other hydrothermal fields are located at a latitudinal distance of less than 15 km between each other. The near boiling point spring #6 of Northwest Abaya discharge mature water with highest geothermal fluid – host rock equilibrium geothermometer temperatures which together with a nearby fumarolic activity may be explained as an outflow. Across Chewkare graben the Bolcho and northeast Abaya hydrothermal fields located between Bilate and Gidabo rivers geochemically appear to be from a different high-enthalpy geothermal reservoir probably related to the cluster of felsic volcanic centers such as Chericho, Kilisa, Donga and Werencha. The high temperature springs indicate the existence of at least two geochemically distinct hydrothermal reservoirs in the study area. It remains to be proven weather an up-flow of an advective hydrothermal system centered to the north around Duguna Fango have long distance concealed out flows to the south on the northern shores of Lake Abaya which is the hydrologic depocenter.     

http://www.sciencedirect.com/science/article/pii/S1674987110000393

Wide-open V-shaped conjugate strike-slip faults in Asia are typically related to extrusion tectonics. However, the tectonic model based on the slip-line theory of plasticity has some critical problems associated with it. The conjugate sets of slip-lines in plane deformation, according to the theory of plasticity should be normal to each another but, in reality, the angles between the conjugate strike-slip faults, which are regarded as slip-lines in extrusion tectonics in the eastern Mediterranean, Tibet-middle Asia, China and the Indochina Peninsular regions, are always more than 90° (on average 110°) in the direction of contraction. Another problem is that the slip-line theory fails to explain how, in some cases, e.g., in the Anatolian area in the eastern Mediterranean, the extrusion rate is much higher than the indent rate. The two major problems are easy to solve in terms of the Maximum-Effective-Moment (MEM) Criterion that predicts that orientations of the shear zones are theoretically at an angle of 54.7° and practically at angles of 55°±10° with the σ1- or contractional direction. The orientations of the strike-slip faults that accommodate extrusion tectonics are, therefore, fundamentally controlled by the MEM Criterion. When extrusion is along the MEM-orientations, the extruding rate is normally higher than the indenting rate.     

2022年1月8日青海门源MS6.9地震震前变形特征分析

2022年1月8日1时45分27秒青海海北藏族自治州门源县发生 M_S6.9地震,基于大地测量资料详细分析震源区的构造运动、应变演化以及深部变形特征,对于发震机理及震后危险性分析具有重要的意义。本文利用1991—2016、2017—2020期中国大陆地区GNSS速度场,分析了青藏高原东北缘各断裂带的运动学特征、门源地震震中和周边区域的地壳应变及其动态演化特征;结合剖面投影和非线性拟合算法,定量计算了托莱山、冷龙岭断裂的滑动速率和闭锁深度,得到以下认识:①青藏高原东北缘不同断裂带的运动学特征差异较大,整体以地壳缩短运动为主,局部区域伴随旋转运动; ②震中位于面膨胀率和最大剪应变率高值区的边缘,与前人关于强震地点的认识基本一致; ③区域应变参数的时空演化过程显示,震中附近应变特征整体变化不大,表明断层可能处在孕震晚期阶段; ④托莱山断裂带具有较高的滑动速率和闭锁深度,结合库仑应力的研究结果认为,该断裂未来一段时间的地震危险性仍值得关注。     

Systematic changes in orientation of linear mylonitic fabrics: An example of strain partitioning during transpressional deformation in north Golpaygan,Sanandaj–Sirjan zone,Iran

Kilometer-scale, shallowly dipping, NW-striking top-to-the NE reverse and dextral strike-slip shear zones occur in metamorphic rocks of north Golpaygan. These metamorphic rocks are exposed at the NE margin of the central part of the Sanandaj–Sirjan zone in the hinterland of the Zagros orogen. NW-striking top-to-the NE normal shear zones were also found in a small part of the study area. Structural evidence of three deformation stages were found. Pre-mylonitization metamorphic mineral growth happened during D₁. The main mylonitization event was during the D₂ deformational event, following coaxial refolding, synchronous to retrograde metamorphism of amphibolite to greenschist facies in the Late Cretaceous–Paleocene, and before D₃ folding and related mylonitization. We documented the systematic changes in the orientations of D₂ linear fabrics especially stretching lineations and superimposition relations of structures. It is concluded that the dextral strike-slip and dip-slip shear zones were coeval kinematic domains of partitioned dextral transpression. The shallowly dipping reverse and strike-slip shear zones are compatible with partitioning in a very inclined transpressional model. Fabric relations reflect that the top-to-the NE normal shear zones were not produced during deformation partitioning of inclined dextral transpression. The Late Cretaceous–Paleocene strain partitioning was followed by later N–S shortening and NE-extension in the north Golpaygan area.     

Microstructural evolution during strain localization in dolomite aggregates

Dolomite aggregates deformed by dislocation creep over a wide range of conditions (T = 700–1000 °C, effective pressure of 900 MPa, strain rates of 10⁻⁷ – 10⁻⁴/s) strain weaken by up to 75% of the peak differential stress. Microstructural study of samples shortened to different finite strains beyond the peak differential stress shows that strain becomes highly localized within shear zones by high-temperature creep processes, with no contribution of brittle cracking. At low strains (8%), dolomite deforms homogeneously by recrystallization-accommodated dislocation creep. At progressively higher sample strains, deformation is localized into narrow shear zones made up of very fine (∼3 μm) recrystallized grains and relict porphyroclasts (20–100 μm). Finely-recrystallized dolomite grains in the shear zones are largely dislocation free and localized shear is facilitated by diffusion creep. In contrast, original dolomite grains and porphyroclasts in shear zones have high dislocation densities and do not deform after shear zone formation. Calculated strain rates in the shear zones are two to three orders of magnitude faster than the imposed bulk strain rate of the samples and these strain rates are consistent with predictions of the diffusion creep flow law for fine-grained dolomite.