攀西裂谷构造—岩浆活动及其成因探讨     

沈发奎 《岩石矿物学杂志》1989,(4)

本文主要讨论穹窿-火山型攀西裂谷的成因,岩浆深成作用与火山作用过程;穹窿构造的发生、发展的演化历史;岩浆分异趋势及双峰式岩浆演化系列及其成因。 攀西裂谷曾经历了岩石圈穹窿—陆壳穹窿一次火山穹窿三个发展演化阶段。碱性岩浆作用与地壳隆升、地幔去气、热流汇聚作用有着密切的成因联系,成穹作用最盛,岩浆碱度最高。随着陆壳破裂、开放、挥发分散逸,岩浆性质从强碱质—弱碱质—碱酸性转化。 穹窿构造的发展演化阶段有机地控制了岩浆源和二次岩浆房的深度和岩浆演化特点,随着穹窿构造的发展演化,岩浆活动由深成幔源→中浅成幔源加陆壳轻微混染→超浅成壳幔混合源逐渐演化,因而可以认为:穹窿-火山型裂谷发育的各个阶段,存在有低位→中位→高位的二次岩浆房。 攀西裂谷属不发育的夭折裂谷,以演化时间长为特点,有利于岩浆深源(二次岩浆房内)结晶分异、液体不混容性分离作用和陆壳的同化混染作用等得以彻底进行,最终形成“双峰式”岩浆组合。  相似文献   

龙王(石童)A型花岗岩地质矿化特征   总被引：2，自引：0，他引：2  

卢欣祥 《岩石学报》1989,(1)

东秦岭北侧的华北古陆块南缘,发育一条碱性岩和碱性花岗岩带。龙王碴碱性花岗岩是该带中的一个典型的A型花岗岩体,岩石富含K、Na,缺Mg、Ca,多Fe少Al和水,含有碱性暗色矿物和很高的F及稀土元素,形成于非造山环境,属板内花岗岩。成岩时代为晋宁期(1035Ma,Rb-Sr)。龙王(石童)A型花岗岩的发现和厘定,证明华北地台南缘在中上元古代存在一个拉张的裂谷系。  相似文献   

攀西裂谷构造─岩浆活动及其成因探讨     

沈发奎 《岩石矿物学杂志》1989,8(4):311-320

本文主要讨论弯窿一火山型攀西裂谷的成因，岩浆深成作用与火山作用过程;弩窿梅 造的发生、发展的演化历史，岩浆分异趋势及双峰式岩浆演化系列及其成因。 攀西裂谷曾经历了岩石圈弯窿一除壳弯窿一次火山弯窿三个发展演化阶段。碱性岩浆作用与 地壳隆开、地慢去气、热流汇聚作用有着密切的成因联系，成弯作用最盛，岩浆碱度最高。随着 陆壳破裂、开放、挥发分散逸，岩浆性质从强碱质一弱碱质一碱酸性转化。 弯窿构造的发展演化阶段有机地控制了岩浆源和二次岩浆房的深度和岩浆演化特点，随着弯 窿构造的发展演化，岩浆活动由深成慢源→中浅成慢源加嵌轻微混染→超浅成壳慢混合源逐渐 演化，因而可以认为:弯窿一火山型裂谷发育的各个阶段，存在有低位→中位→高位的二次岩浆 房. 攀西裂谷属不发育的夭折裂谷，以演化时间长为特点，有利于岩浆深源(二次岩浆房内)结 晶分异、液体不混容性分离作用和陆壳的同化混染作用等得以彻底进行，最终形成“双峰式”岩 浆组合。  相似文献   

裂谷盆地的火山热液活动和油气生成   总被引：18，自引：0，他引：18  

金强  翟庆龙 《地质科学》2003,38(3):342-349

我国东部裂谷盆地主力烃源岩中均不同程度地发育有玄武岩和辉长岩等基性火成岩,并且伴有规模不等的热液活动。火山热液活动会给烃源岩带来热量,促使有机质快速生烃和异常成熟。玄武岩活动期间的热液作用为烃源岩提供了大量矿物质和养料,使周围泥质岩富含碳酸盐和有机质,可以形成优质烃源岩;热液活动向烃源岩提供了大量过渡金属元素,作者的实验证明了过渡金属对有机质生烃具有强烈的催化作用,使烃源岩在较低温度下生成较多数量的油气;火成岩周围的烃源岩可以提前进入生烃门限。  相似文献   

Neotectonics and extension direction of the Southern Kenya Rift, Lake Magadi area     

Nassima Atmaoui  Dirk Hollnack   《Tectonophysics》2003,364(1-2):71-83

The Magadi area, located in the southern part of the Kenya Rift, is a seismically active region where rifting is still in progress. The recent tectonic activity has been investigated through a seismological survey and the study of neotectonic joints found in Lake Magadi sediments, which were deposited some 5000 years ago. The structural analysis of these open fractures was combined with a quantitative analysis of the orientation and size characteristics of imagery faults. The gathered data demonstrate (1) that the majority of the systematic joints have straight and parallel trajectories with a common en echelon mode of propagation displayed through a rich variety of patterns, and (2) that there is a self-similarity in fault and joint principal directions recognised at the different telescopic scales. SPOT image (1:125,000), aerial photos (1:76,000), and outcrop fieldwork reveal two important structural orientations which are N015°E and N015°W. The N015°E regional direction is consistent with the orientation of the southern segment of the Kenya Rift. Structural analysis is supported by results of a joint microseismic investigation in the Lake Magadi area. Obtained focal mechanism solutions indicate an E–W to ESE–WNW normal faulting extension direction.  相似文献   

Dynamic causes for the opening of the Baikal Rift Zone: a numerical modelling approach   总被引：1，自引：0，他引：1  

O. P. Polyansky   《Tectonophysics》2002,351(1-2)

Previous dynamic models of the Baikal Rift Zone (BRZ) are mostly two-dimensional on vertical plane. In this study, a numerical model of neotectonics in the region on map view was constructed using the adapted PLATES program. The present work is an attempt to test different mechanisms for opening Baikal Rift by comparing the modelled and observed stress and strain rate fields. The following rifting scenarios were tested: (1) pure northwest–southeast extension, (2) pure northeast–southwest compression, (3) oblique rift opening and (4) combined northwest–southeast extension and northeast–southwest compression. The models are calibrated using geologically and GPS-derived strain rates and stress-tensor determinations from fault-slip data and earthquake focal mechanisms. The most successful model requires a combination of NE–SW compression and orthogonal extension. The model results indicate that the present extensional regime in BRZ can be explained by combining the India plate indentation northward into Eurasia, east–west convergence between the North America and Eurasia plates and southeastward extrusion of the Amur plate in northeastern Asia. Predicted fault-slip rates for the best-fit model are consistent with the observed Holocene fault-slip rates in the Lake Baikal region. The generally accepted rotation of the Amur and Mongolia microplates are used as independent constraints for the choice of the best-fit model. These data correlate well with the predicted direction of rotation in our best model.  相似文献   

Detection of geothermal anomalies using Landsat 8 TIRS data in Tulu Moye geothermal prospect,Main Ethiopian Rift     

《International Journal of Applied Earth Observation and Geoinformation》2019

Despite the high geothermal potential of the Main Ethiopian Rift (MER), risks associated with the industry and the difficulty of identifying possible targets using ground surveys alone continue to impede the development of geothermal power diligence in Ethiopia. In this paper, we investigate the geothermal potential of the Tulu Moye prospect area in the MER using Landsat 8, which is an important and cost-effective method of detecting geothermal anomalies. Data with a path/row of 168/054 were obtained from the Landsat 8 Operational Land Imager (OLI) and Thermal Infrared (TIR) sensors for October 17, 2014. Based on radiometric calibration, atmospheric correction (with the 6S model) and an NDVI-based threshold method for calculating land surface emissivity, a split-window algorithm was applied to retrieve the land surface temperature (LST) of the study area. Results show LST values ranging from 292.2 to 315.8 K, with the highest values found in barren lands. A comparison of LST between the Moderate Resolution Imaging Spectroradiometer (MODIS) and Landsat 8 shows a maximum difference of 1.47 K. Anomalous areas were also discovered, where LST was about 3-9 K higher than the background area. We identified seven of these as areas of high geothermal activity in the Tulu Moye prospective geothermal area. Auxiliary data and overlay analysis tools eliminated any non-geothermal influences. The research reveals that the distribution of highy prospective geothermal areas is consistent with the development and distribution of faults in the study area. Magmatism is the thermal source and faults provide conduits for the heat to flow from earth’s interior to the surface, facilitating the presence of geothermal anomalies. Finally, TIR remote sensing methods prove to be a robust and cost-effective technique for detecting LST anomalies in the geologically active area of MER. Moreover, combining TIR remote sensing with knowledge of the structural geology of the area and geothermal mechanisms is an efficient approach to detecting geothermal areas.  相似文献   

穿越东非大裂谷工程地质与线路比选分析——以内罗毕—马拉巴铁路为例     

宋成辉  李伟  蒋富强  任文峰  李守定 《工程地质学报》2020,28(1):141-148

内罗毕-马拉巴铁路工程是东非"北方走廊"的重要组成部分,是非洲内陆国家发展经济的主干线。铁路线路工程穿越的东非大裂谷,地质复杂、火山地貌、断裂带和拉张裂缝等不良地质极为发育,而东非大裂谷铁路工程建设的研究资料十分匮乏。为了研究穿越东非大裂谷的铁路线路,本文首先介绍了东非大裂谷地形、地貌、裂谷的发育机理、区域断裂分布,然后以铁路沿线经济控制点为主轴,制定了穿越东非大裂谷铁路线路3大通道。分别对线路3大通道穿越的地形、地貌比选,穿越的地层、断裂和地裂缝比选,穿越地震、火山发育比选以及穿越的不良地质灾害比选,最后比选各线路通道的投资以及优、缺点,最终推荐南线通道方案。该线路方案得到肯尼亚政府的肯定和采纳。目前内马铁路正试运营,实践表明内马铁路裂谷段选线是较为成功的,可为同类工程提供借鉴。  相似文献   

Analytic models for orogenic collapse     

Margarete A. Jadamec  Donald L. Turcotte  Peter Howell   《Tectonophysics》2007,435(1-4):1-12

The temporal and spatial distribution of the aftershock sequences of the Ruwenzori (February 5, 1994, Mb (5.8)), Masisi (April 29, 1995, Mb (5.1)) and Kalehe (October 24, 2002, Mb (5.9)) earthquakes have been studied. It has been found that most of the aftershocks of the Ruwenzori earthquake are located on the eastern flank of the main escarpment and those of the Masisi earthquake are confined to the northwest of Lake Kivu margin where earthquake occurrence of swarm-type was normally observed. The Kalehe earthquake occurred in the central part of Lake Kivu and it was the largest earthquake observed in the Lake Kivu basin since 1900. The rate of decrease in aftershock activity with the time has shown that the p-value for Ruwenzori and Masisi earthquake equals 0.6, somehow smaller than that found in other geotectonic zones where p is close to 1. The p-value of the Kalehe earthquake is a normal value equal to 1.From an area delimited by spatial distribution of aftershocks, the linear dimension of the fault was estimated. The fault area determined in this study correlates well with those of previous studies which occurred in the Western Rift Valley of Africa including the Tanganyika and Upemba Rift.  相似文献   

Evolution of the Academician Ridge Accommodation Zone in the central part of the Baikal Rift, from high-resolution reflection seismic profiling and geological field investigations   总被引：4，自引：0，他引：4  

V. D. Mats  O. M. Khlystov  M. De Batist  S. Ceramicola  T. K. Lomonosova  A. Klimansky 《International Journal of Earth Sciences》2000,89(2):229-250

 New high-resolution seismic reflection data from the central part of Lake Baikal provide new insight into the structure and stratigraphy of Academician Ridge, a large intra-rift accommodation zone separating the Central and North Baikal basins. Four seismic packages are distinguished above the basement: a thin top-of-basement unit; seismic-stratigraphic unit X; seismic-stratigraphic unit A; and seismic-stratigraphic unit B. Units A and B were cored on selected key locations. The four packages are correlated with a series of deposits exposed on the nearby western shores: the Ularyar Sequence (Oligocene); the Tagay Sequence (Lower to Middle Miocene); the Sasa Sequence (Upper Miocene to Lower Pliocene); the Kharantsy Sequence (Upper Pliocene); and the Nyurga Sequence (Lower Pleistocene). Based on stratal relationships, sedimentary geometries, distribution patterns and principal morphostructural elements – both onshore and offshore – we propose a new palaeogeographic evolution model for the area. In this model progressive tectonic subsidence of the Baikal basins and successive pulses of uplift of various segments of the rift margins lead to: (a) formation of the ridge as a structural and morphological feature separating the Central and North Baikal basins during the Middle to Late Miocene; (b) gradual flooding of the main parts of the ridge and establishment of a lacustrine connection between the two rift basins during the Late Miocene; and (c) total submergence of the top parts of the crest of the ridge during the latest Pleistocene. This new model helps to better constrain numerous phases in the structural evolution of the Baikal Rift, in which the Academician Ridge as an accommodation zone plays a crucial role. Received: 26 November 1999 / Accepted: 12 March 2000  相似文献