Journal of African Earth Sciences (1983)最新文献

Nouvelles données pétrographiques, géochimiques et géochronologiques du massif ‘granitique’ de Bondoukou (Côte d'Ivoire) mise en évidence d'un âge Burkinien, par isochrone Rb/Sr sur roches totales Bondoukou (cote d' ivoire)“花岗岩”地块的新岩石学、地球化学和地球年代学数据，通过Rb/Sr等时线显示了整个岩石的burkinian年龄

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 DOI: 10.1016/0899-5362(87)90068-6

S. Toure , M. Caen-Vachette , P. Tempier

{"title":"Nouvelles données pétrographiques, géochimiques et géochronologiques du massif ‘granitique’ de Bondoukou (Côte d'Ivoire) mise en évidence d'un âge Burkinien, par isochrone Rb/Sr sur roches totales","authors":"S. Toure , M. Caen-Vachette , P. Tempier","doi":"10.1016/0899-5362(87)90068-6","DOIUrl":"10.1016/0899-5362(87)90068-6","url":null,"abstract":"<div><p>The locality of Bondoukou, NE of Ivory Coast, gave its name to a granite type, opposite to the Baoulé-type granite in Bodin's classification (1951, <em>Bull. Dir. Mines AOF</em>, Dakar, N° 12). This classification has been progressively enlarged to the whole of West Africa. The Bondoukou granite is subcircular in form, intrusive and discordant in the tufaceous schists and had not been dated previously.</p><p>Recent age determinations on 15 samples from this massif have been done with the Rb/Sr isochron method on whole rocks. The age obtained is approx. 2170 Ma. Consequently, these new data yield a Burkinian age (ex early Eburnean) which was not expected since a lot of works on Birrimian granites of West Africa assigned a post tectonic character and consequently a later age to the Bondoukou granite, related to the Baoulé-type granites.</p><p>Other age determinations with the same Rb/Sr method were done on granitic massifs which were assigned to the Bondoukou type; they yielded ages slightly younger than 2000 Ma in Senegal and Burkina Faso respectively (Bassot, J. P. and Caen-Vachette, M. 1984. In: 12th <em>coll. Inter. Géol. africaine, Bruxelles, et géol. africaine</em> (Edited by Klerkx, J. et Michot, J.),pp. 191–209. Tervuren, Belgique; and Gamsonre, P. E. and Rossy, M. 1974. Esquisse géologique de la région de Ouahi Gouya (N. W. de la Hte Volta). Chronologie des divers types de granitoîdes, p. 181. 2ème Rast, Nancy).</p><p>So, these few results point out the complex position of the Bondoukou type granites. Their meaning in the main Eburnean orogeny must be considered.</p></div>","PeriodicalId":100749,"journal":{"name":"Journal of African Earth Sciences (1983)","volume":"6 3","pages":"Pages 269-274"},"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)90068-6","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"53877169","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: 8

Geochemical prospecting for gold in the area north of Isanlu, Nigeria 尼日利亚Isanlu北部地区金矿地球化学找矿

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 DOI: 10.1016/0899-5362(87)90070-4

Ibrahim Garba

{"title":"Geochemical prospecting for gold in the area north of Isanlu, Nigeria","authors":"Ibrahim Garba","doi":"10.1016/0899-5362(87)90070-4","DOIUrl":"10.1016/0899-5362(87)90070-4","url":null,"abstract":"<div><p>A combined heavy mineral and stream sediment survey was carried out in the area north of Isanlu to delineate potential areas for a detailed search for gold deposits. The geology of the area is typical of the basement of SW Nigeria with gneisses, schists, amphibolites and granites. Mineralization comprises gold/sulphide-bearing quartz veins and amphibolites.</p><p>Data obtained from the stream sediment survey were subjected to statistical interpretation and it was found that the log-normal pattern appears to be the one most applicable to the element distributions. No indicator for gold has been identified, but the significant correlation that exists between Pb/Cu and Pb/Zn was taken to distinguish vein mineralization from disseminated mineralization in amphibolites.</p><p>The heavy mineral survey, which was intended to simply check for gold occurrences in the field, also proved useful in detecting other anomalies later confirmed by the stream sediment survey. It was found to be a better exploration tool for gold at the reconnaissance stage. The overall high level of gold in the drainage indicates a metallogenic area favourable for gold. The survey succeeded in delineating possible gold targets worthy of follow-up.</p></div>","PeriodicalId":100749,"journal":{"name":"Journal of African Earth Sciences (1983)","volume":"6 3","pages":"Pages 281-286"},"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)90070-4","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"53877214","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: 1

Late Triassic-Early jurassic volcanism along the southern Afar-plateau margin 阿法尔高原南缘晚三叠世—早侏罗世火山作用

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 DOI: 10.1016/0899-5362(87)90076-5

Begashaw Wolde

引用次数: 0

Paleokarst processes in the Eocene limestones of the Pyramids Plateau, Giza, Egypt 埃及吉萨金字塔高原始新世石灰岩中的古岩溶过程

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 DOI: 10.1016/0899-5362(87)90079-0

M.M. El Aref , E. Refai

引用次数: 8

Le complexe volcano-plutonique calco-alcali de la rivière daléma (Est Sénégal): discussion de sa signification géodynamique dans le cadre de l'orogénie eburnéenne (protérozoïque inférieur) dalema河(塞内加尔东部)的钙碱性火山-深成岩复合体:在eburnean造山体(下元古代)背景下讨论其地球动力学意义

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 DOI: 10.1016/0899-5362(87)90091-1

J.P. Bassot

{"title":"Le complexe volcano-plutonique calco-alcali de la rivière daléma (Est Sénégal): discussion de sa signification géodynamique dans le cadre de l'orogénie eburnéenne (protérozoïque inférieur)","authors":"J.P. Bassot","doi":"10.1016/0899-5362(87)90091-1","DOIUrl":"10.1016/0899-5362(87)90091-1","url":null,"abstract":"<div><p>This suite is located in the Kedougou inlier where a Lower Proterozoic sequence is surrounded by unconformable Upper Proterozoic. This suite is a member of the Daléma supergroup which also includes some epicontinental sediments with numerous carbonate layers. In contrast, the Mako supergroup (located further to the west) is characterized by submarine volcanic or plutonic rocks (mainly tholeiitic) intruded by trondhjemites at around 2200 Ma.</p><p>After deposition of carbonate rocks alternating with sandstones or greywackes, the Dalé with some volcanism. The volcanic belt is characterized by dacites or andesites, by a lot of hypovolcanic rocks (accumulative microdiorites) and by its elongation along a N-S trend. This belt was intruded 1990 Ma ago by a plutonic intrusion with petrographic composition ranging from diorite to monzogranite. The two magmatic events are spatially linked but the granitoid develops a strong thermic metamorphism in volcanic and sedimentary rocks which contrasts with the very low grade regional metamorphism. Despite a hydrothermal alteration, petrographic and geochemical studies show that the Dalé,a volcano-plutonic suite is calc-alcaline. Some large amounts of iron ore have been found in skarnoid rocks along the belt near the granitoid.</p><p>The geotectonic significance is discussed; the Daléma suite could result from the subduction of oceanic crust as shown by Mako supergroup. However, it is more probable that the suite has spatial relations with large transcurrent faults according to a geodynamic model proposed for the Stephano-Permian calc-alcaline volcanism of western Europe. The sedimentary and tectonic context, the strongly linear position and the coincidence of a linear positive gravity anomaly with the volcano-plutonic belt are more consistent with the second interpretation.</p></div>","PeriodicalId":100749,"journal":{"name":"Journal of African Earth Sciences (1983)","volume":"6 4","pages":"Pages 505-519"},"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)90091-1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"53877490","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: 65

Lithostratigraphie, sédimentologie et évolution de deux bassins molassiques intramontagneux de la chaine Pan-Africaine: la Série pourprée de l'Ahnet, Nord-Ouest du Hoggar, Algérie 泛非洲山脉两个潮内摩尔盆地的岩石地层学、沉积学和演化:阿尔及利亚Hoggar西北的ahnet pourpree系列

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 DOI: 10.1016/0899-5362(87)90093-5

Ali Ait-Kaci Ahmed , Alexis Moussine-Pouchkine

{"title":"Lithostratigraphie, sédimentologie et évolution de deux bassins molassiques intramontagneux de la chaine Pan-Africaine: la Série pourprée de l'Ahnet, Nord-Ouest du Hoggar, Algérie","authors":"Ali Ait-Kaci Ahmed , Alexis Moussine-Pouchkine","doi":"10.1016/0899-5362(87)90093-5","DOIUrl":"10.1016/0899-5362(87)90093-5","url":null,"abstract":"<div><p>The study of two of the intermontane molassic basins of the ‘Série pourprée de l'Ahnet’ shows that they developed independently both in time and space. The characteristics of their thick sedimentary infillings are quite different. The Ouallen basin is filled by essentially fine-grained sediments which were deposited in continental then marine or lacustrine environments; these sediments thicen from east to west. The In Semmen basin is characterised by coarser sediments which were deposited from south to north, in alluvial fan, fluvial, deltaic and slope environments. This basin is also characterised by an episode of carbonate sedimentation leading to the formation of a remarkable thin layer of carbonate, covering the entire sedimentary area, and perhaps related to a volcanic rhyolitic event. The history of the two basins is also marked by obvious tectonic events simultaneous with the sedimentation and related to the recurrent faulting of major Pan-African faults. These led to the formation of very coarse fanglomerates located near the fault scarps, and are probably responsible for the shape and the evolution of the basins.</p></div>","PeriodicalId":100749,"journal":{"name":"Journal of African Earth Sciences (1983)","volume":"6 4","pages":"Pages 525-535"},"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)90093-5","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"53877512","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: 19

Nouvelles données lithostructurales, pétrographiques, minéralogiques et géochimiques sur le gisement de cuivre d'Akjoujt et son environment géologique (République Islamique de Mauritanie) akjoujt铜矿及其地质环境的新岩石构造、岩石学、矿物学和地球化学数据(毛里塔尼亚伊斯兰共和国)

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 DOI: 10.1016/0899-5362(87)90105-9

André Pouclet, Pierre-Louis Guillot, Ahmedou Ba Gatta

引用次数: 8

Geology, paleoclimatology and laterite genesis in the Gada sector of the Trans-Saharan seaway in northwestern Nigeria 尼日利亚西北部跨撒哈拉海道Gada地区的地质、古气候学和红土成因

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 DOI: 10.1016/0899-5362(87)90003-0

J.R. Adetunji, C.A. Kogbe

引用次数: 2

The younger granites and ring complexes of the Southeastern Desert of Egypt and their relation to mineralization 埃及东南部沙漠年轻花岗岩和环状杂岩及其与成矿作用的关系

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 DOI: 10.1016/0899-5362(87)90010-8

Mostafa M. Soliman

{"title":"The younger granites and ring complexes of the Southeastern Desert of Egypt and their relation to mineralization","authors":"Mostafa M. Soliman","doi":"10.1016/0899-5362(87)90010-8","DOIUrl":"10.1016/0899-5362(87)90010-8","url":null,"abstract":"<div><p>More than 70 small younger granite masses and 10 ring complexes are exposed in the Southeastern Desert of Egypt (about 80,000 km<sup>2</sup>). The granites comprise three main varieties: the Sn mineralized; stanniferous and Sn barren granites. the Sn mineralized granites are usually smaller in size; circular to elliptical in outline and contain higher concentrations of Sn, Nb, Be, Mo, Bi, Y, Cu and Pb and are usually subjected to greisenizaiotn and albitizationn processes which changed their original texture and composition with the development of lode and disseminated cassiterite and beryl mineralization. The stanniferous granties may contain only few accesories of cassiterite. the sn-barren granites are usually larger in size and show hghier Zr values. The granties are calcalkaline, highly aluminous, enriched F with Na<sub>a</sub>O > K<sub>2</sub>O and low CaO and MgO. The ring complexes comprise alkaline rocks mostly of Cretaceous age (although some complexes are older) and range in composition from ultramafic to acidic and from undersaturated to quartz bearing. Disseminated U, Th, Pb, W, ?Nb, Y, Be and Mo are recorded in some ring complexes.</p></div>","PeriodicalId":100749,"journal":{"name":"Journal of African Earth Sciences (1983)","volume":"6 5","pages":"Pages 745-754"},"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)90010-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"53876462","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: 1

Some metallogenetic features of the Nigerian basement 尼日利亚基底的一些成矿特征

Journal of African Earth Sciences (1983) Pub Date : 1987-01-01 DOI: 10.1016/0899-5362(87)90004-2

Michael Woakes , M.A. Rahaman , A.C. Ajibade

{"title":"Some metallogenetic features of the Nigerian basement","authors":"Michael Woakes , M.A. Rahaman , A.C. Ajibade","doi":"10.1016/0899-5362(87)90004-2","DOIUrl":"10.1016/0899-5362(87)90004-2","url":null,"abstract":"<div><p>The Nigerian basement consists of Eburnean granitic and metamorphic rocks into which are folded Upper Proterozoic supra-crustal low grade metasedimentary and metavolcanic rocks forming N-S elongate belts. Pan-African granitoids mark the last major event and they have intrusive and/or tectonic relationships with the earlier units. Structural features are often complex. The Basement can be divided into the Eastern and Western Provinces, where the latter is marked by the occurrence of a variety of metallogenetic types and greater development of the supracrustal N-S belts, while the Eastern province is dominated by Pan-African granitoid rocks and a paucity of metallic mineral occurrences.</p><p>The principle metallogenetic types that are (or have been) exploited are iron deposits, gold vein mineralization and SnTaNb-bearing pegmatites. Small occurrences are known of chromite, asbestos, CuNi sulphides, manganese and a variety of industrial minerals including talc, kyanite and magnesite. Metallogenetic types found in other Pan-African terrains that are markedly absent in Nigeria include basemetal deposits of plate accretion type (e.g. Saudi Arabia) and uranium (e.g. of Rossing type). It is suggested that Nigeria's relatively low metal production from basement deposits is attributable to a regional low metallogenetic inheritance which in turn has discouraged intensive prospecting but there is good potential especially for industrial mineral deposits.</p></div>","PeriodicalId":100749,"journal":{"name":"Journal of African Earth Sciences (1983)","volume":"6 5","pages":"Pages 655-664"},"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)90004-2","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"53876388","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: 126