Mineralogy and Geochemistry of EtekéEburnean Gold Deposit (Gabon)

The Gabon geology offered favorable and natural environments for the formation of various types of mineralization. The Etéké gold district, aim of this study, is located in the Ngounié province (southern Gabon) on the western edge of the Chaillu massif. Geologically, the gold mineralization is associated with the Eburnean orogeny and hosted in the Archean greenstone belts. Also, this deposit is covered by a significant vegetation cover and a very extensive lateritic weathering profile, which hinders the most accurate study. Through this paper, we aim to propose a genesis pattern of this mineralization via a multidisciplinary approach. To do this, a petrographic, metallogenic, and geochemical characterization has been established in the different sectors of the Etéké deposit. The studied deposits display varied facies which are encased in granitoid. They are essentially formed of abundant granitoid, and amphibolite compared to the volcano-sedimentary formations. These rocks display magmatic textures, affected by metamorphism, and not sufficiently preserved. Based on our multidisciplinary approach, the studied samples collected from the core’s boreholes allowed us to decipher a volcanogenic and metamorphosed origin of the gold genesis.

Tele-Analytical Characterization of the Eburnean Tectonic Structures within the Birimian Formations of Mako Area, Eastern Senegal

The tectonic structures of the Mako area in the Kédougou-Kéniéba inlier (KKI) were mapped with tele-analytical investigation which is validated by field data. This study is based on different images processing in particular: 1) the colored combinations (1 to 5) and panchromatic (8) thematic mapping bands of the Landsat-8 (ETM+) satellite;2) Digital Elevation Model (DEM) image of Space Shuttle Radar Topography Mission (SRTM);3) airborne geophysics (aeromagnetic and radiometric) images. In these images, four major directions of lineaments NS, NNE-SSW, NW-SE and EW would be related to the tectonic structures, have been identified and mapped. Field data confirm these four structural directions and show that most of these lineaments are related to faults, shear and/or thrust zones, or even basic rock dykes. N-S to NE-SW oriented lineaments are more frequent followed by those NW-SE oriented. These two directions of lineaments are generally in correlation with trajectories of major sinistral shear zones in the Mako area. They would be associated with the S2a and S2b schistosities relative to the D2 Eburnean major deformation. They often intersect the E-W oriented lineaments which are less frequent and sometimes folded and crenulated. This E-W oriented lineament would be prior and are associated with the S1 schistosity of the D1 Eburnean thrust phase of deformation. At the scale of the studied area, these major linear structures (shear zones) are conjugated and create a partitioning of deformation through an anastomosed network of mylonitic shear zones which surround weakly deformed rock bodies. All these structures would be related to the Eburnean or post-Eburnean orogenic events in this Mako area.

U-Pb Geochronology of the Jebba Granitic Gneiss and Its Implications for the Paleoproterozoic Evolution of Jebba Area, Southwestern Nigeria

Jebba area southwestern Nigeria forms part of the Nigerian basement complex which lies in the Neoproterozoic PanAfrican mobile belt. It is underlain by several lithological units among which is a polydeformed granitic gneiss. This rock has been dated by LA-ICP-MS yielding a concordant U-Pb zircon age of 2207 ± 20 Ma indicating the crystallization age of the granite protolith. This early Rhyacian age and its affinity with within-plate granites indicates emplacement during crustal extension and rifting presceding the main phase of the Eburnean orogeny. The strong, early, shear fabric, S1, in the rock is interpreted to be also of Paleoproterozoic age i.e. imprinted during the Eburnean orogeny. The Jebba granitic gneiss is thus correlatable with the widely abundant Paleoproterozoic granitic magmatism now represented by many orthogneisses and documented in other parts of southwestern Nigeria, the West African craton, the Borborema Province, the Gurupi Belt, Sao Luis craton and Sao Francisco craton in Brazil.

几内亚Siguiri金矿床地质特征与控矿因素

Siguiri金矿床位于几内亚东北部,处在区域性北西西向和近南北向断裂交汇部位。在成矿地质背景和矿床地质特征研究的基础上,分析了控矿因素。矿体呈脉状、板状赋存在浅变质的Birimian岩系内,围岩蚀变主要有硅化、碳酸盐化、绿泥石化和钠长石化等,其中硅化、碳酸盐化与金矿化关系密切。金矿化主要产在Fatoya组粗粒碎屑岩中,岩浆活动可能为成矿提供了热源和部分物源,Eburnean造山运动晚期挤压-伸展转换时期形成的次级断裂控制了矿体的展布,断裂是最重要的控矿因素。

牛耳朵与药用唇柱苣苔叶显微结构观察

利用光学显微镜对牛耳朵和药用唇柱苣苔叶显微结构进行观察.结果显示:叶横切解剖结构,均由表皮、叶肉细胞和叶脉三部分组成.药用唇柱苣苔上、下表皮具有较多的表皮毛,这与牛耳朵有明显的区别.叶上表皮均为多边形,垂周壁平直,不具气孔器;叶下表皮不规则形,垂周壁浅波状至波状,气孔器为不等型.这些特征可为探讨两者的分类学及亲缘关系提供依据.

牛耳朵组培快繁体系的建立及优化

以当年生长良好的牛耳朵叶片为外植体,通过对外植体的消毒、不定芽诱导、增殖及生根培养,筛选高效稳定的无菌芽诱导优化体系。结果表明:外植体最佳消毒方法为用70%酒精浸泡30s,3%Na Cl O消毒2.0 min;不定芽诱导最佳培养基为:WPM+6-BA3.0mg/L+2-ip 1.0mg/L+NAA0.1mg/L,诱导率为83.23%;不定芽增殖最佳培养基为MS+6-BA1.0mg/L+NAA0.1mg/L+GA30.5mg/L,增殖系数为16.0,且不定芽长势良好;生根培养基以1/2MS+IBA0.1mg/L+NAA0.05mg/L为较好,生根率达92.35%。以腐殖土:珍珠岩=3:1为移栽基质的成活率最高达100%。

牛耳朵和黄花牛耳朵的显微和化学鉴别

目的:为苦苣苔科唇柱苣苔属植物牛耳朵和黄花牛耳朵的鉴定和分类提供解剖学和化学依据。方法:采用石蜡制片法和水合氯醛透化法对2种药用植物的根状茎和叶横切面和粉末特征进行研究,应用光学显微镜观察显微结构。采用HPLC-UV法进行化学鉴别。结果:牛耳朵和黄花牛耳朵显微特征无明显区别,但是化学特征有明显的差异。结论:化学诞生特征鉴别方法可以作为2种药用植物的鉴定方法。