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41.
阿尔金断裂与祁连山北缘断裂的交汇部位是阿尔金断裂向东扩展的新破裂生长点,两断裂构造与新生的红柳峡断裂构成似三联点构造。破裂生长点附近的最新构造变形表现为:阿尔金断裂的旋转隆升和向北扩展;祁连山北缘断裂的逆冲推覆兼右旋走滑;红柳峡断裂的挤压拖曳弯曲,它们共同受制于青藏高原的强烈隆升和向外扩张作用。推测阿尔金断裂自西而东的破裂扩展就是似三联点构造逐一形成而又被切割贯通的过程。阿尔金断裂以蠕滑活动为主,2002年玉门地震与祁连山北缘逆冲断裂及其伴生的调节断层的活动相关。 相似文献
42.
Analysis of the deformation structures in the West Kunlun-Tarim basin-range junction belt indicates that sediments in the southwestern Tarim depression were mainly derived from the West Kunlun Mountains and that with time the region of sedimentation extended progressivdy toward the north. Three north-underthrusting (subducting), steep-dipping, high-velocity zones (bodies) are recognized at depths, which correspond to the central West Kunlun junction belt (bounded by the Kiida-Kaxtax fault on the north and Bulungkol-Kangxiwar fault on the south), Quanshuigou fault belt (whose eastward extension is the Jinshajiang fault belt) and Bangong Co-Nujiang fault belt. The geodynamic process of the basin-range junction belt generally proceeded as follows: centering around the magma source region (which largely corresponds with the Karatag terrane at the surface), the deep-seated material flowed and extended from below upward and to all sides, resulting in strong deformation (mainly extension) in the overlying lithosphere and even the upper mantle, appearance of extensional stress perpendicular to the strike of the orogenic belt in the thermal uplift region or at the top of the mantle diapir and localized thickening of the sedimentary cover (thermal subsidence in the upper crust). Three stages of the basin- and mountain-forming processes in the West Kunlun-southern Tarim basin margin may be summarized: (1) the stage of Late Jurassic-Early Cretaceous rampingrapid uplift and rapid subsidence, when north-directed thrust propagation and south-directed intracontinental subduction, was the dominant mechanism for basin- and mountain-building processes; (2) the stage of Late Cretaceous-Paleogene deep-level detachment-slow uplift and homogeneous subsidence, when the dominant mechanism for the basin- and mountain-forming processes was detachment (subhorizontal north-directed deep-level ductile shear) and its resulting lateral propagation of deep material; and (3) the stage of Neogene-pre 相似文献
43.
Elimination of Interferences in the Determination of Palladium,Platinum and Rhodium Mass Fractions in Moss Samples using ICP‐MS/MS 下载免费PDF全文
Terhi Suoranta Syed N. H. Bokhari Thomas Meisel Matti Niemelä Paavo Perämäki 《Geostandards and Geoanalytical Research》2016,40(4):559-569
Moss samples (Pleurozium schreberi) exposed to traffic‐related emission of Pd, Pt and Rh were analysed in this study. Successful elimination of interferences was achieved in the determination of Pd, Pt and Rh mass fractions in these samples using inductively coupled plasma‐tandem mass spectrometry (ICP‐MS/MS). Based on the results, a reliable determination of Pd, Pt and Rh mass fractions in microwave‐digested moss samples was obtained using ammonia (10% NH3 in He) in the collision/reaction cell when 103Rh was measured either on‐mass (103→103) or with mass‐shift (103→171) and mass‐shifts for 108Pd (108→159) and 195Pt (195→229) were used. The ICP‐MS/MS procedure was validated using BCR‐723 (road dust) as a reference material. In addition, a good agreement between the ICP‐MS/MS results and the results obtained with cloud point extraction and quadrupole ICP‐MS was observed for the moss samples. 相似文献
44.
为了提高GPS数据预处理过程中基线解算的精度,文章研究利用多项式拟合法得到Kalman滤波的系统状态方程和转移矩阵,提出利用Kalman滤波算法对三差观测值进行粗差及周跳的修复。实验结果证明Kalman滤波可以对含噪信号进行有效的降噪,经降噪后的信号具有更好的分布。 相似文献
45.
Anne Briais 《Marine Geophysical Researches》1995,17(5):431-467
The morphological characteristics of the segmentation of the Central Indian Ridge (CIR) from the Indian Ocean Triple Junction (25°30S) to the Egeria Transform Fault system (20°30S) are analyzed. The compilation of Sea Beam data from R/VSonne cruises SO43 and SO52, and R/VCharcot cruises Rodriguez 1 and 2 provides an almost continuous bathymetric coverage of a 450-km-long section of the ridge axis. The bathymetric data are combined with a GLORIA side-scan sonar swath to visualize the fabric of the ridge and complement the coverage in some areas. This section of the CIR has a full spreading rate of about 50 mm yr–1, increasing slightly from north to south. The morphology of the CIR is generally similar to that of a slow-spreading center, despite an intermediate spreading rate at these latitudes. The axis is marked by an axial valley 5–35 km wide and 500–1800 m deep, sometimes exhibiting a 100–600 m-high neovolcanic ridge. It is offset by only one 40km offset transform fault (at 22°40S), and by nine second-order discontinuities, with offsets varying from 4 to 21 km, separating segments 28 to 85 km long. The bathymetry analysis and an empirical orthogonal function analysis performed on across-axis profiles reveal morphologic variations in the axis and the second-order discontinuities. The ridge axis deepens and the relief across the axial valley increases from north to south. The discontinuities observed south of 22°S all have morphologies similar to those of the slow-spreading Mid-Atlantic Ridge. North of 22°S, two discontinuities have map geometries that have not been observed previously on slow-spreading ridges. The axial valleys overlap, and their tips curve toward the adjacent segment. The overlap distance is 2 to 4 times greater than the offset. Based on these characteristics, these discontinuities resemble overlapping spreading centers (OSCs) described on the fast-spreading EPR. The evolution of one such discontinuity appears to decapitate a nearby segment, as observed for the evolution of some OSCs on the EPR. These morphological variations of the CIR axis may be explained by an increase in the crustal thickness in the north of the study area relative to the Triple Junction area. Variations in crustal thickness could be related to a broad bathymetric anomaly centered at 19°S, 65°E, which probably reflects the effect of the nearby Réunion hotspot, or an anomaly in the composition of the mantle beneath the ridge near 19°S. Other explanations for the morphological variations include the termination of the CIR at the Rodriguez Triple Junction or the kinematic evolution of the triple junction and its resultant lengthening of the CIR. These latter effects are more likely to account for the axial morphology near the Triple Junction than for the long-wavelength morphological variation. 相似文献
46.
The junction between oceanic crust generated, within the Antarctic plate, at the Southeast Indian Ridge and the Southwest Indian Ridge has been studied using a SEABEAM swathe bathymetry mapping system and other geophysical techniques between the Indian Ocean Triple Junction (approximately 25°S, 70° E), and a point some 500 km to the southwest (at 28°25 S, 66°35 E). The morphotectonic boundary which marks this trace of the ridge-ridge-ridge triple junction is complex and varies with age. Recent theories proposing a cyclicity of volcanic and tectonic processes at this mode of triple junctions appear to be supported by a series of regularly spaced, en echelon escarpments facing the slowly spreading (0.6 to 0.8 cm a-1, half rate) Southwest Indian Ridge axis. The en echelon escarpments intersect at approximately right angles with the regularly spaced oceanic spreading fabric formed on the Antarctic plate at the Southeast Indian Ridge and together locally flank uplifted northward-pointing corner sections of ocean floor. The origins for the localised elevations are unclear, but may relate to intermittent and/or alternating rifting and volcanic episodes. Variations of degree of asymmetry and/or obliquity in spreading on the Central Indian Ridge and the Southwest Indian Ridge are suggested to explain detailed structural changes along the triple junction trace. It is suggested that discontinuities of the trace may be related to an intermittent development of new spreading centres beneath the most easterly part of the Southwest Indian Ridge, coupled with a more continuous process beneath the faster spreading Central Indian Ridge (2 to 2.5 cm a-1) and the Southeast Indian Ridge (2.5 to 3 cm a-1). A detailed history of triple junction evolution may be thus inferred from basic morphological and structural mapping along the three triple junction traces. 相似文献
47.
阿尔泰大型-超大型矿床富集区地壳演化 总被引:4,自引:0,他引:4
通过构造、岩浆、变质、成矿等地质作用及其时空演化规律的对比分析,以及物探重力、航磁及遥感信息的综合研究,认为古生代阿尔泰富蕴地幔热柱成因的三联点裂谷形成与演化———“手风琴式”开合,是阿尔泰大型- 超大型矿床富集区形成与演化的根本原因。地幔热柱热地幔物质大规模上涌和横向扩张,产生三联点裂谷系统,导致古大陆解体,形成阿尔泰“洋岛型”蛇绿岩、阿尔泰型花岗岩、花岗岩化、高温低压变质带和主要大型- 超大型矿床;地幔热柱活动停止或间息,导致三联点裂谷系统发生A 型俯冲而封闭造山,形成三叉式陆间造山带和同造山花岗岩、 相似文献
48.
FOCAL MECHANISM SOLUTION AND TECTONIC STRESS FIELD CHARACTERISTICS OF THE MIDDLE TIANSHAN MOUNTAINS,XINJIANG 下载免费PDF全文
ZHANG Zhi-bin ZHAO Xiao-cheng REN Lin 《地震地质》1979,42(3):595-611
The middle part of the Tianshan Mountains in Xinjiang is located in the north-central part of the Tianshan orogenic belt, between the rigid Tarim Basin and Junggar Basin. It is one of the regions with frequent deformation and strong earthquake activities. In this paper, 492 MS>2.5 earthquake events recorded by Xinjiang seismograph network from 2009 to 2018 were collected. The MS3.5 earthquake was taken as the boundary, the focal mechanism solutions of the earthquake events in this region were calculated by CAP method and FOCEMEC method respectively. At the same time the focal mechanism solutions of GCMT recorded historical earthquake events in this region were also collected. According to the global stress map classification standard, the moderate-strong earthquakes in the region are mainly dominated by thrust with a certain slip component, which are distributed near the combined belts of the Tarim Basin, Junggar Basin, Turpan Basin and Yili Basin with Tianshan Mountains. The thrust component decreases from south to north, while the strike-slip component increases. The spatial distribution characteristics of the tectonic stress field in the middle section of the Tianshan Mountains in Xinjiang are obtained by using the damped regional-scale stress field inversion method. The maximum principal compressive stress in axis the study area rotated in a fan shape from west to east, the NW direction in the western section gradually shifted to NE direction, its elevation angle is nearly horizontal, in the state of near horizontal compression. The minimum principal compressive stress axis is nearly EW, and the elevation angle is nearly vertical. Influenced by large fault zones such as Kashi River, Bolhinur, Nalati, Fukang, the southern margin of the Junggar and the north Beiluntai, the local regional stress field presents complex diversity. Under the influence of the northward extrusion of Pamir and Tarim blocks, the whole Tianshan is shortened by compression, but its shortening rate decreases from south to north and from west to east, the stress shape factor increases gradually from west to east, the intermediate principal compressive stress axis exhibits a change in compression to extension. There are some differences in the characteristics of tectonic stress field between the north and south of Tianshan Mountains. The regional maximum principal compressive stress axis is 15° north by east on the south side, while it is nearly NS on the north side. The deformation of the Tianshan Mountains and the two basins on both sides is obviously larger than that in the inside of the mountain. Changes in the crustal shortening rate caused by the rotation of the rigid Tarim block and Junggar block to the relatively soft Tianshan block, as well as the uplifts of Borokonu and Bogda Mountains, the comprehensive influence of the material westward expansion constitute the stress field distribution characteristics of the north and south sides of the middle section of Tianshan Mountains. The recent two MS6.6 earthquakes in the region caused the regional stress field to rotate counterclockwise. The post-earthquake stress field and the main source focal mechanism solution tend to be consistent. The seismic activity in the study area is week in the south and strong in the north. The focal depth is about 20km. Most strike-slip earthquakes occur near the junction belt of the Tianshan and Junggar Basin. 相似文献
49.
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