Geology of the High Grade Proterozoic Terrains of Sri Lanka, and the Assembly of Gondwana: an Update on Recent Developments   总被引：1，自引：0，他引：1  

V. Mathavan  W.K.B.N. Prame  P.G. Cooray 《Gondwana Research》1999,2(2):237

Nd model ages determined for the high-grade rocks of Sri Lanka delineate three crustal units, viz., the Highland Complex (HC), the Wanni Complex WC), and the Vijayan Complex (VC). The distribution of these three units differs considerably from the three geological divisions demarcated previously on the basis of geological mapping. The centrally located HC comprises mainly granulite grade charnockitic rocks, and metasediments characterized by older Nd model ages (2.0–3.4 Ga). The Highland sedimentary pile was thickened by intermittent granitoid intrusions, most of which are now charnockitic gneiss, and granulites, and basaltic sills, and dikes. All these metaigneous rocks now occur as conformable bands or layers due to intense polyphase deformation. The HC is bounded on the east by the amphibolite grade VC, composed mainly of granitic gneisses, basic gneisses, and migmatites, and they have ‘younger’ Nd model ages (1.1–1.8 Ga). The isotopic, and geochemical characteristics identify the precursors to the Vijayan rocks as I-type calc-alkaline granitoids originated at an ‘arc’-related tectonic environment. Thus, the earlier interpretation that the Vijayan rocks represent reworked HC was rejected. The granulite inliers within the VC, earlier considered as “resisters” to re-working, are now shown as overthrust klippen or rotated rafts of the HC. The WC, demarcated on the basis of Nd model ages (1.1–1.8 Ga) similar to those of the VC, lies west of the HC. It consists mainly of granitic gneisses, charnockitic gneisses, and migmatites, and the metamorphic grade ranges from amphibolite to granulite.Comprehensive geothermobarometric surveys constrain the P-T evolution of the three crustal units, and indicate that both the HC, and WC underwent near isobaric cooling, followed by a decompression with decreasing temperature. Extensive isotopic studies (U-Pb, Pb-Pb, Sm-Nd, Rb-Sr) have established a new geochronological framework for these high-grade rocks of Sri Lanka. The new framework has bracketed the age of high grade metamorphism in the three crustal units at 550–600 Ma.The recent advances in knowledge of the geology of Sri Lanka favour a strong geological correlation of the HC, and the VC of Sri Lanka, respectively, with the Lutzöw-Holm Complex, and the Yatmato-Belgica Complex in the East Antarctica. The geology of the WC suggests a possible correlation with Madagascar, and East Africa. The amalgamation of the three crustal units of Sri Lanka, is apparently related to the two distinct orogenic events that resulted in the assembly of the Gondwana supercontinent.  相似文献   

火山构造组合研究和地质填图方法 ——以福建闽清测区1∶5万区域地质调查为例   总被引：1，自引：0，他引：1  

马金清李进堂  冯宗帜 《地质通报》2000,19(2):198-204

闽清测区 1∶5万区调在运用火山岩双重填图法过程中 ,进一步改进了工作方法和程序 ,深化了火山地质研究 ,取得了显著成果。本区调工作以遥感地质为先导 ,在填图中从调查单个火山构造扩展到多个、多种火山构造组合叠置关系及火山群体的研究。从而填制出火山构造面貌清楚 ,具有较强立体感的古火山地质图 ,全面反映了不同时期 (阶段 )火山作用特点、演化规律及火山岩相的分布特征 ,合理地建立起火山岩地层格架。  相似文献   

天文辐射空间分布与尺度效应研究     

周文臻  陈楠 《地球信息科学学报》2018,20(2):186-195

天文辐射是地表实际入射太阳辐射的基础背景,也是辐射计算、太阳能资源评估和农业生产潜力估算等方面的重要天文参量。本文基于分辨率为30 m的福建省数字高程模型,使用MATLAB软件提供的并行计算框架模拟了起伏地形下福建省天文辐射空间分布,定量地分析了坡度坡向对天文辐射分布的影响规律,同时探讨数字高程模型对天文辐射产生的空间尺度效应。结果表明：福建省年天文辐射量大部分处于10 000~13 000 MJ/m²,呈现东南沿海向中西部递减的分布特征;不同季节的天文辐射分布受纬度和坡度坡向的影响具有明显的差异性,呈现季节分布的不对称性;不同坡度和坡向对天文辐射的影响与福建省总体上西北高东南低地势特征相吻合,天文辐射量随坡度增大而减小,东、东南和南坡向是天文辐射分布较集中的区域,总体上呈现山脊多、山谷少、阳坡多、阴坡少的地域差异性;数字高程模型的空间尺度效应在起伏较大的福建中西部丘陵地貌表现更加明显,该区域的天文辐射对分辨率的变化更加敏感。  相似文献   

崤山太古宙花岗—绿岩地体的地质特征     

庞振山  梁天佑  肖中军 《河南国土资源》2000,(1)

崤山太古宙花岗—绿岩地体由 15%的绿岩带 (变质表壳岩系 )和 85%的花岗质片麻岩系(变质侵入岩 )组成。呈包体产出的绿岩系分为以变火山岩为主的兰树沟岩组和以变沉积岩为主的杨寺沟岩组。花岗质片麻岩包括早期富钠的TTG质花岗岩和稍后的富钾花岗岩。晚期则有代表大陆地壳裂解的基性岩墙群侵入。文中介绍了各岩石单元的地质、地球化学特征及花岗—绿岩带的变形和变质特征 ,探讨了研究区太古宙的大陆地壳演化  相似文献   

Geophysical structures and tectonic evolution of the southern Guyana shield,Brazil     

《Journal of South American Earth Sciences》2014

Aerogeophysical data of an area located on the southern portion of the Guyana shield in Brazil was processed using a fine interpolating mesh, and a corresponding spatial data integration strategy which included the stacking of different high-resolution images, and interpretation following quality control of these. The selected images were correlated to the local known surface geologic units, and to the spatial distribution of the main geochronological provinces of the Amazonian craton. The interpretation of the results also included the available geophysical information for the region, related to Moho depth values, and previously determined SKS shear-wave splitting direction. The observed magnetic regional trends may be strongly influenced by the Proterozoic crustal structure in the area, while radiometric anomalies correlate with the more detailed geologic features. Based on the parallelism among mapped geochronological provinces of the Amazonian craton, and observed geophysical structures on the study area, a geotectonic model is proposed for southern Guyana shield at Proterozoic age.  相似文献   

厄瓜多尔奥连特盆地斜坡带地震多属性储层预测     

魏春光  谢寅符  何雨丹 《吉林大学学报(地球科学版)》2011,(Z1):374-379

南美安第斯前陆盆地斜坡带主要含油气圈闭为低幅度构造-岩性圈闭,储层预测是厄瓜多尔奥连特盆地低幅度隐蔽圈闭识别和描述的重要环节。为了准确预测储层砂体及油藏空间分布特征,采用高品质3D地震资料,沿层提取包括AVO信息在内的多种地震属性参数,利用地震属性和已知井的地层物性参数建立统计对应关系,并利用这一关系预测了未知点地层的储层物性、砂岩储层空间分布特征和储层含油气性特征预测。结果表明:预测结果与已有钻井吻合程度较高;下一步勘探潜力区位于区块南部和西部。  相似文献   

顾及地形邻域影响的地质灾害风险易发区评估     

徐刚  胡坤霖  温剑峰  徐登财  戴欣宜  陈杰  朱安峰  章豪  苏宗奎 《测绘通报》2021,(7):59-64

地质灾害发生时通常会带来巨大的人力物力损害,而易发区评估是防灾减灾的重要手段。为了尽可能减少灾害带来的经济损失和人员伤亡,本文在GIS的支持下开展地质灾害风险评估研究。具体结合温州市自然地理状况及相关受灾情况历史数据,分析高程因子、坡度因子、坡向因子等地质灾害影响因子,提出了综合邻近环境的地质灾害分析方法,利用层次分析方法计算各因子权重,构建了温州市滑坡灾害易发性评价指标体系,确定了温州市地质灾害易发区;同时还研究了山区、平原不同地形条件下的地质灾害风险规律。  相似文献   

基于多层次模糊综合优选找矿远景区   总被引：1，自引：0，他引：1  

左仁广 《地质与勘探》2009,45(2):85-89

找矿远景区优选是矿产预测评价中的重要研究内容之一.文章利用多层次模糊综合评价的方法优选西藏冈底斯斑岩铜矿找矿远景区.实践结果表明:该方法不仅能够比较全面地考虑各种因素的影响及其相互作用,实现优选找矿远景区的合理、定量分析,并能在一定程度上反映出影响找矿远景区优选的关键因素,减少了人为主观因素,其优选结果具有客观性和科学性.  相似文献   

Distribution patterns of SOC/TN content and their relationship with topography,vegetation and climatic factors in China’s north-south transitional zone     

Zhang  Junhua  Zhu  Lianqi  Li  Guodong  Zhao  Fang  Qin  Jingting 《地理学报(英文版)》2022,32(4):645-662

Journal of Geographical Sciences - The spatial distributions and variation mechanism of key soil indices in the Qinling-Daba Mountains are important indicators for the identification of the...  相似文献   

Groundwater flow in a volcanic–sedimentary coastal aquifer: Telde area, Gran Canaria, Canary Islands, Spain     

M. C. Cabrera  E. Custodio 《Hydrogeology Journal》2004,12(3):305-320

Groundwater conditions in a 75- km² coastal area around the town of Telde in eastern Gran Canaria island have been studied. Pliocene to Recent volcanic materials are found, with an intercalated detrital formation (LPDF), which is a characteristic of the area. Groundwater development has become intensive since the 1950s, mostly for intensive agricultural irrigation and municipal water supply. The LPDF is one order of magnitude more transmissive and permeable than the underlying Phonolitic Formation when median values are compared (150 and 15 m² day^–1; 5 and 0.5 m day^–1, respectively). These two formations are highly heterogeneous and the ranges of expected well productivities partly overlap. The overlying recent basalts constituted a good aquifer several decades ago but now are mostly drained, except in the southern areas. Average values of drainable porosity (specific yield) seem to be about 0.03 to 0.04, or higher. Groundwater development has produced a conspicuous strip where the watertable has been drawn down as much as 40 m in 20 years, although the inland watertable elevation is much less affected. Groundwater reserve depletion contributes only about 5% of abstracted water, and more than 60% of this is transmitted from inland areas. Groundwater discharge into the sea may still be significant, perhaps 30% of total inflow to the area is discharged to the sea although this value is very uncertain.

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Resumen Se ha llevado a cabo un estudio detallado de una zona costera de 75 km² situada en la costa del Municipio de Telde, al Este de la isla de Gran Canaria, en el Archipiélago Canario. En ella se encuentran materiales volcánicos de edad Pliocena a Reciente, con una formación detrítica intercalada (FDLP), que constituye la máxima singularidad del área. La explotación de las aguas subterráneas ha sido intensiva a partir de la década de 1950, fundamentalmente para el riego de cultivos intensivos y para el suministro a la población. Comparando las medianas de los valores de transmisividad y permeabilidad entre la FDLP y la Formación Fonolítica que está debajo (140 a 15 m²/día y 5 a 0,5 m/día respectivamente) se comprueba que la primera es un orden de magnitud más transmisiva y permeable que la segunda, aunque ambas formaciones son muy heterogéneas y los rangos de productividad esperables en los pozos se solapan entre sí. Los Basaltos Recientes que están encima fueron un buen acuífero hace algunas décadas, pero en la actualidad han sido drenados casi en su totalidad, excepto en el sector Sur. Los valores medios de la porosidad drenable (eficaz) parecen estar alrededor de 0,03 a 0,04, o más. La explotación de las aguas subterráneas ha producido una franja con un destacado descenso de los niveles piezométricos, que alcanza los 40 m en 20 años, aunque la superficie piezométrica hacia el centro de la isla está menos afectada. El descenso calculado en la reserva de aguas subterráneas alcanza solamente un 5% del agua extraída y más de un 60% se transmite desde las cumbres de la isla. La descarga al mar puede ser aún significativa, quizás el 30% de las entradas totales, aunque esta cifra es muy incierta.

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Résumé Les conditions de gisement de leau souterraine dune région de 75 km² de la côte Est de lîle de la Grande Canarie (archipel des Canaries), dans le secteur de Telde, ont été étudiées, en utilisant seulement les données fournies par les puits dexploitation existants. Les matériaux volcaniques, dâge Pliocène à sub-actuel, sont séparés par une formation détritique (FDLP), qui constitue la principale singularité de cette région. Lexploitation de leau souterraine est devenue intensive à partir de 1950, principalement pour des besoins dirrigation (agriculture intensive) et dalimentation en eau des zones urbaines. La comparaison des valeurs médianes montre que la FDLP est dun ordre de grandeur plus transmissive et perméable que les formations volcaniques phonolitiques au-dessous (respectivement 150 et 15 m²/jour ; 5 et 0,5 m/jour). Néanmoins, ces deux formations sont très hétérogènes et les deux gammes de valeurs de productivité des puits se recouvrent. Les Basaltes récents au-dessus qui constituaient, il y a encore quelques décades, un bon aquifère, sont presque entièrement desaturés à lheure actuelle, a exception faite de la partie sud. Les valeurs moyennes de porosité drainable (efficace) sont de lordre de 0,03 à 0,04, voire localement plus élevées. Lexploitation des eaux souterraines a induit de forts rebattements au long dune zone littorale (denviron 40 m au cours des 20 dernières années), alors que la surface piézométrique est moins affectée en amont vers le centre de lîle. La diminution de la réserve des eaux souterraines dans la zone étudiée représente seulement 5% des volumes deau extraits. Plus de 60% proviennent du centre de lîle. Les écoulements vers la mer peuvent être significatifs, (environ 30% des entrées totales) bien que cette estimation soit sujeté à une très forte incertitude.

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