Journal of African Earth Sciences (1983)最新文献_第4页

I.G.C.P. 227 Workshop Mesozoic to present-day magmatism of the African plate and its structural setting 非洲板块中生代至现代岩浆活动及其构造背景

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 Epub Date: 2010-07-13 DOI: 10.1016/0899-5362(87)90050-9

引用次数: 0

Petrography of the migmatites from the High Dam Western Quarry, Aswan, South Egypt 埃及南部阿斯旺高坝西部采石场混合岩的岩石学特征

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 Epub Date: 2010-07-13 DOI: 10.1016/0899-5362(87)90084-4

Mostafa M. Soliman, Emad M. Ibrahim

{"title":"Petrography of the migmatites from the High Dam Western Quarry, Aswan, South Egypt","authors":"Mostafa M. Soliman, Emad M. Ibrahim","doi":"10.1016/0899-5362(87)90084-4","DOIUrl":"10.1016/0899-5362(87)90084-4","url":null,"abstract":"<div><p>The migmatites of the High Dam Western Quarry are part of a crystalline massif south of Aswan and comprise granitoid and trondhjemitic varieties. Both comprise leucocratic (leucosome) and melanocratic (melanosome) fractions. The granitoid migmatites are more abundant and their mineralogy is similar to that of biotite gneisses whereas that of the trondhjemitic migmatites is similar to that of the hornblende gneisses of Aswan. The migmatites show stromatic, ptygmatic and phlebitic structures. The plagioclase is normally zoned and usually carries fine inclusions of sphene, apatite and iron oxide that lie in planes parallel to the long axes or the twin planes of these plagioclase crystals. K-feldspar megacrysts show intensive perthitization of exsolution origin and some include xenomorphic quartz crystals between the idiomorphic cores and their outer rims. Porphyritic, myrmekitic, graphic and rapakivi textures are common in the migmatites. These features suggest crystallization of the leucosomes from silicate melts formed by partial melting in small closed systems in water-undersaturated conditions through high grade regional metamorphism up to the K-feldspar-sillimanite-almandine sub-facies.</p></div>","PeriodicalId":100749,"journal":{"name":"Journal of African Earth Sciences (1983)","volume":"6 4","pages":"Pages 407-419"},"PeriodicalIF":0.0,"publicationDate":"1987-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0899-5362(87)90084-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"53877389","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Reduction of equivalence in layer-model interpretation by combination of electrical resistivity soundings and electromagnetic conductivity measurements; some case histories in groundwater survey 电阻率测深与电导率测量相结合的层模型解释等效性降低地下水调查中的一些实例

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 Epub Date: 2010-07-13 DOI: 10.1016/0899-5362(87)90080-7

Ko J.M.J. Van Juijk, A.M. Haak, I.L. Ritsema

{"title":"Reduction of equivalence in layer-model interpretation by combination of electrical resistivity soundings and electromagnetic conductivity measurements; some case histories in groundwater survey","authors":"Ko J.M.J. Van Juijk, A.M. Haak, I.L. Ritsema","doi":"10.1016/0899-5362(87)90080-7","DOIUrl":"10.1016/0899-5362(87)90080-7","url":null,"abstract":"<div><p>An interactive programme for microcomputers has been developed and has been used for rapid interpretation of electrical resistivity soundings (conventional Schlumberger configuration) and frequency domain electromagnetic conductivity measurements at low induction numbers (vertical and horizontal loop configuration; Geonics EM 343).</p><p>Layer model interpretation can be improved by simultaneously calculating the electrical resistivity sounding response and the electromagnetic conductivity response. Whenever discrepancies occur between the measured electromagnetic data and the calculated data the resistivity layer-model interpretation has to be matched, until a model has been found that fits both the electrical and the electromagnetic measurements. In this way, equivalence in interpretation of electrical soundings can be reduced.</p><p>Calculation of ‘imaginary EM 34-3 sounding curves’ makes it possible for the surveyor to predetermine the optimal configuration of the electromagnetic system of measuring variations in thickness or conductivity of a target layer. An example is given.</p><p>Two recent case histories are discussed in which equivalence was eliminated: one concerning the delineation of a pollution plume (The Netherlands), the second concerning the determination of depth to basement (Sudan). For groundwater surveys in basement areas of Africa the combined application of electrical resistivity soundings and an electromagnetic system operating at low induction numbers can be very useful; the survey target in general is shallow and the electrical resistivities of the crystalline bedrock are high.</p></div>","PeriodicalId":100749,"journal":{"name":"Journal of African Earth Sciences (1983)","volume":"6 3","pages":"Pages 379-384"},"PeriodicalIF":0.0,"publicationDate":"1987-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0899-5362(87)90080-7","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"53877336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 3

A paleomagnetic study of the Dokhan volcanic formation and younger granites, eastern desert of Egypt 埃及东部沙漠多汗火山构造和较年轻花岗岩的古地磁研究

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 Epub Date: 2010-07-13 DOI: 10.1016/0899-5362(87)90078-9

A.E.M. Nairn , T.A. Perry , R. Ressetar , S. Rogers

引用次数: 17

Clay mineral burial diagenesis: A case study from the Calabar flank of the Niger Delta 粘土矿物埋藏成岩作用:以尼日尔三角洲卡拉巴尔侧翼为例

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 Epub Date: 2010-07-13 DOI: 10.1016/0899-5362(87)90060-1

Sokari P. Braide

{"title":"Clay mineral burial diagenesis: A case study from the Calabar flank of the Niger Delta","authors":"Sokari P. Braide","doi":"10.1016/0899-5362(87)90060-1","DOIUrl":"10.1016/0899-5362(87)90060-1","url":null,"abstract":"<div><p>Detailed clay mineralogic and chemical analyses of Tertiary subsurface sediments of the Agbada and Akata Formations, from two wells on the Calabar Flank of the Niger Delta, have been systematically studied with a view to understanding clay mineral burial diagenesis. Five principal clay minerals, smectite, illite, kaolinite, chlorite and various proportions of mixed-layer illite/smectite were identified. Seven major oxides (SiO<sub>2</sub>, Al<sub>2</sub>O<sub>3</sub>, MgO, Fe<sub>2</sub>O<sub>3</sub>, CaO, Na<sub>2</sub>O, K<sub>2</sub>O) were analysed for with an atomic absorption spectrophotometer, with a view to ascertain any depth related variations. The geothermal gradient of the two wells (Uruan-1 and Uda-1) was also calculated.</p><p>The results appear to suggest a transformation from smectite to a mixed-layer illite/smectite (I/S) phase. The transformation first goes to a random I/S phase, and then to ordered I/S and back to random I/S, even though postulated conditions for a complete transformation to illite did exist. It would therefore seem, from this case study, that neither temperature nor the availability of potassium is the principal factor controlling the transformation. Kaolinite and chlorite distribution does not exhibit any systematic trend that could be related to burial diagenesis.</p><p>These results provoked an extensive literature review on the subject, and key ideas discerned are summarized here. The prognosis? In the author's opinion, we still have a lot to learn about the factors that control the mechanics and reaction extent of clay mineral burial diagenesis.</p></div>","PeriodicalId":100749,"journal":{"name":"Journal of African Earth Sciences (1983)","volume":"6 2","pages":"Pages 181-196"},"PeriodicalIF":0.0,"publicationDate":"1987-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0899-5362(87)90060-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"53876984","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 3

Le ‘continental terminal’, sa place dans l'évolution géodynamique du bassin sénégalo-mauritanien durant le Cénozoïque “大陆码头”，它在新生代塞内加尔-毛里塔尼亚盆地地球动力学演化中的位置

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 Epub Date: 2010-07-13 DOI: 10.1016/0899-5362(87)90106-0

Georges Conrad, Jean-René Lappartient

{"title":"Le ‘continental terminal’, sa place dans l'évolution géodynamique du bassin sénégalo-mauritanien durant le Cénozoïque","authors":"Georges Conrad, Jean-René Lappartient","doi":"10.1016/0899-5362(87)90106-0","DOIUrl":"10.1016/0899-5362(87)90106-0","url":null,"abstract":"<div><p>The ‘Continental Terminal’ in the Senegalo-Mauritanian basin is a Cenozoic and detrital formation, presenting signs of an intense ferralitic alteration with formation of ferruginous concretions and crustings, neo-formation of kaolinite and significant silica movements.</p><p>Sedimentary structures are generally obliterated by alteration in the formation's summit. However, some fossil layers which have undergone epigenesis by geothite make it possible to establish the sea origin of the eocene and miocene deposits in this ‘Continental Terminal’. A better idea of Cenozoic transgressions and regressions can be achieved by a reconstitution of fossil river beds through alterations on the edge of the African continent.</p><p>The new elements in the ‘Continental Terminal’ and the Senegalo-Mauritanian Cenozoic paleoclimates are: The ‘Continental Terminal’ clearly represents an alteration fringe developed at the expense of marine formations (Tessier <em>et al.</em> 1975 <em>Actes 9ème Congr. Int. Sédim.</em>, Nice, pp. 207–211), but this concept cannot be generalized to all of the coastal Cenozoic or interior Iullemmeden Nigerian basins.</p><p>The ferrallitic alterations mostly occurred in the Pliocene period after the sinking of the basin, as in the Miocene margino-littoral facies, and are still highly dominant. The ferruginous crusting can be seen in this period and also during the lower Pleistocene, because of the latitudinal migration of the basin northwards starting from the upper Cretaceous period.</p></div>","PeriodicalId":100749,"journal":{"name":"Journal of African Earth Sciences (1983)","volume":"6 1","pages":"Pages 45-60"},"PeriodicalIF":0.0,"publicationDate":"1987-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0899-5362(87)90106-0","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"53877676","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 15

Ornamental polymorphism and morphological integration in Brizalina mandoroveensis (Miocene, Cameroun) 喀麦隆中新世Brizalina mandorveensis的观赏多态性和形态整合

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 Epub Date: 2010-07-13 DOI: 10.1016/0899-5362(87)90072-8

Richard A. Reyment

引用次数: 1

Geophysical investigations for groundwater in Precambrian terrains: a case history from Ikare, southwestern Nigeria 前寒武纪地区地下水的地球物理调查:尼日利亚西南部伊卡雷的一个病例史

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 Epub Date: 2010-07-13 DOI: 10.1016/0899-5362(87)90035-2

M.A. Olorunniwo, M.O. Olorunfemi

引用次数: 40

Late glacial soil catena in upper Teleki Valley, Mount Kenya Afroalpine area 肯雅山非洲高山地区上Teleki谷晚冰期土壤链

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 Epub Date: 2010-07-13 DOI: 10.1016/0899-5362(87)90008-X

W.C. Mahaney, M.G. Boyer

引用次数: 3

Acoustic characteristics of the Abu Gharadig Basin sediments, Western Desert, Egypt 埃及西部沙漠Abu Gharadig盆地沉积物声学特征

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 Epub Date: 2010-07-13 DOI: 10.1016/0899-5362(87)90083-2

A.I. Bayoumi , Y.A. Darwish , H.I. Lotfy

{"title":"Acoustic characteristics of the Abu Gharadig Basin sediments, Western Desert, Egypt","authors":"A.I. Bayoumi , Y.A. Darwish , H.I. Lotfy","doi":"10.1016/0899-5362(87)90083-2","DOIUrl":"10.1016/0899-5362(87)90083-2","url":null,"abstract":"<div><p>The present investigation is mainly devoted to the critical analysis of the available exploratory data obtained from more than 35 deep holes, with the aim of delineating the geo-seismic characteristic features of the different rock units existing within the conspicuous Abu Gharadig Cretaceous Basin. Such a study reveals that the base Tertiary, which is separating the strongly deformed Cretaceous reflectors from the undeformed Tertiary ones, has a medium positive reflectivity, whereas the top Alamein ‘dolomites’ (top Aptian) and the top Massajid (top Middle Jurassic) reflectors have strong positive reflectivity of the first order. Moreover, the top Apollonia (top Middle Eocene) and the top Abu Roash (top Coniacian) are found to show up with a medium of strong positive reflectivity of second order. Also, the top Dabaa (top Oligocene), top Bahariya (top Lower Cenomanian) and top Kharita (top Albian) reflectors are considered as weak variable reflectors of the third order. Implications as to the structural setting of the basin are introduced here in view of such acoustic characteristics when applied to some seismic lines in the area studied.</p></div>","PeriodicalId":100749,"journal":{"name":"Journal of African Earth Sciences (1983)","volume":"6 4","pages":"Pages 399-405"},"PeriodicalIF":0.0,"publicationDate":"1987-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0899-5362(87)90083-2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"53877374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 5