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On the origin of the Azzel-Matti circular structure (southern Algeria): Insights from remote sensing, geological and geophysical data 关于 Azzel-Matti 环形结构(阿尔及利亚南部)的起源:遥感、地质和地球物理数据的启示
IF 2.2 4区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2024-10-22 DOI: 10.1016/j.jafrearsci.2024.105457
Mohamed Hassani , Moulley Charaf Chabou , Hamid Haddoum , Mohamed Hamoudi , Saci Kermani , Mohamed Said Guettouche , Sofiane Bellabiod
The Azzel-Matti circular structure (25°51′ N, 0°35’ E) is located on the Tanezrouft plateau at the boundary between the West African Craton and the Bled El Mass compartment. Its morphology exhibits a diameter of about 6.5 km, with a raised rim that stands above the surrounding terrain. This study is based on a combination of remote sensing data (Landsat-8-OLI images and Shuttle Radar Topography Mission (SRTM) images), aeromagnetic and seismic data, and field investigations in and around the Azzel-Matti circular structure to analyze its morphology and ascertain its origin. The investigation of the area surrounding the structure did not reveal any evidence of magmatism, diapirism or impact. However, it did confirm the presence of new faults of a deeper character, as highlighted by remote sensing, aeromagnetic, and seismic analysis. This suggests that tectonic deformation is a probable factor contributing to the formation of this circular structure. The morphology of the structure is explained by the counter-clockwise rotation of the strata, likely resulting from the interplay between movements along the sub-meridian faults marking the eastern and western boundaries and the ESE-WNW oblique reverse fault marking the northern boundary. These faults are coherently arranged to facilitate the counter-clockwise rotation of the strata. The movement of the faults and their depth indicate an NE-SW compressional event corresponding to the Late Paleozoic Variscan (Hercynian) orogeny. This is supported by the presence of horizontal lacustrine carbonate formations, presumably of Jurassic age, which are discordant with the Carboniferous strata, thus providing evidence for the age of the Azzel-Matti circular structure between the Moscovian and the Jurassic.
Azzel-Matti 环形结构(北纬 25°51′,东经 0°35′)位于 Tanezrouft 高原上,地处西非克拉通与布莱德埃尔地块区块的交界处。从形态上看,它的直径约为 6.5 公里,边缘隆起,高出周围地形。本研究综合利用遥感数据(大地遥感卫星-8-OLI 图像和航天飞机雷达地形图任务(SRTM)图像)、航空地磁和地震数据以及对阿泽尔-马蒂圆形结构及其周围地区的实地调查,对其形态进行分析并确定其起源。对该结构周围地区的调查没有发现任何岩浆活动、断裂或撞击的证据。不过,通过遥感、航空磁力和地震分析,确实证实了更深的新断层的存在。这表明构造变形可能是形成这一圆形结构的一个因素。地层的逆时针旋转解释了该结构的形态,这很可能是由于标示东部和西部边界的次经向断层以及标示北部边界的东偏东-西偏西斜向逆断层的运动相互作用造成的。这些断层的连贯排列促进了地层的逆时针旋转。这些断层的移动及其深度表明,在晚古生代瓦里斯坎(海西期)造山运动中发生了东北-西南挤压事件。与石炭纪地层不一致的水平湖相碳酸盐地层(推测为侏罗纪地层)也证明了这一点,从而为阿泽尔-马蒂圆形构造的年代提供了证据,该构造介于 Moscovian 和侏罗纪之间。
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引用次数: 0
Geochronological assessment of the Arabian-Nubian Shield plutonic intrusions in the arc assemblages along the Qift-Quseir transect, Central Eastern Desert of Egypt 埃及中东部沙漠 Qift-Quseir 断面沿线弧形集合体中的阿拉伯-努比亚盾质侵入体的地质年代评估
IF 2.2 4区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2024-10-19 DOI: 10.1016/j.jafrearsci.2024.105456
Sherif Mansour , Noriko Hasebe , Akihiro Tamura , Kamal Abdelrahman , Mohammed S. Fnais , Mohamed A. Gharib , Mohamed Zaki Khedr
The ophiolitic mélange and granitic intrusions along the QiftQuseir transect in the Central Eastern Desert (CED) of Egypt are parts of the Egyptian Nubian Shield (ENS), which is the northern segment of the East African Orogeny (EAO). The Arabian-Nubian Shield (ANS) is the longest Neoproterozoic belt on Earth, and it was formed during the East and West Gondwanaland collisions within the framework of the EAO. The ANS basement rocks were developed during three distinct phases of magmatic activity: the island arc and syn-collisional phases, identifying a compressional tectonic regime, and a post-collisional phase that identifies changing the tectonic regime into an extensional type. The geochronological assessment of these magmatic activities is essential for understanding the regional geology and tectonic development of the ANS. In our study, we dated different rock units along the QiftQuseir transect and revealed ages ranging from the Late Tonian (820 ± 8 Ma) to the Late Ediacaran (563 ± 4 Ma). These ages were associated with three different magmatic pulses: (1) a seafloor spreading and island arc phase (ophiolite and related rocks), represented by sample QQ05, which was dated from 820 ± 8 Ma; (2) a syn-collisional phase, represented by samples QQ08 and QQ10, dated from 733 ± 10 Ma and 729 ± 10 Ma, respectively; and (3) a post-collisional phase, represented by all the other samples, dated from the Ediacaran at 603 ± 9 Ma to 563 ± 5 Ma. These results showed that the post-collisional phase was dominant, especially in terms of the alkali-feldspar granites, relative to ophiolitic rocks, and the syn-collisional granites in the CED. Initiation of the Dokhan Volcanic eruptions at 639 ± 2 Ma gave us the date of the compressional-to-extensional tectonic transition setting, and the post-collisional tensional regime was activated at 603 ± 9 Ma. Additionally, we identified evidence of local magmatic sources by dating 11 grains of Paleo-to Meso-Proterozoic xenocrysts with ages ranging from 1876 ± 18 to 1070 ± 13 Ma (i.e., components of the pre-Arabian-Nubian Shield).
埃及中东部沙漠(CED)Qift-Quseir 断面沿线的蛇绿混杂岩和花岗岩侵入体是埃及努比亚地盾(ENS)的一部分,而埃及努比亚地盾是东非造山带(EAO)的北段。阿拉伯-努比亚地盾(ANS)是地球上最长的新近纪地带,形成于 EAO 框架内的东西冈瓦纳陆碰撞时期。ANS基底岩石是在岩浆活动的三个不同阶段形成的:岛弧和同步碰撞阶段,确定了一种压缩构造体系;后碰撞阶段,确定了构造体系向扩展类型的转变。对这些岩浆活动的地质年代评估对于了解 ANS 的区域地质和构造发展至关重要。在我们的研究中,我们对 Qift-Quseir 断面沿线的不同岩石单元进行了年代测定,结果显示了从晚托尼安(820 ± 8 Ma)到晚埃迪卡拉(563 ± 4 Ma)的不同年代。这些年龄与三个不同的岩浆脉冲有关:(1) 海底扩张和岛弧阶段(蛇绿混杂岩和相关岩石),以样本 QQ05 为代表,年代为 820 ± 8 Ma;(2) 同步碰撞阶段,以样本 QQ08 和 QQ10 为代表,年代分别为 733 ± 10 Ma 和 729 ± 10 Ma;(3) 后碰撞阶段,以所有其他样本为代表,年代从埃迪卡拉纪的 603 ± 9 Ma 到 563 ± 5 Ma。这些结果表明,碰撞后阶段占主导地位,尤其是相对于蛇绿岩的碱长石花岗岩和CED中的同步碰撞花岗岩而言。多汗火山喷发开始于 639 ± 2 Ma,这为我们提供了从压性构造向伸展构造过渡的时间,而碰撞后的张性构造则开始于 603 ± 9 Ma。此外,我们还通过对 11 个年龄在 1876 ± 18 至 1070 ± 13 Ma 之间的古生代至中新生代异长岩(即前阿拉伯-努比亚地盾的组成部分)进行年代测定,确定了当地岩浆源的证据。
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引用次数: 0
Stratigraphy and sedimentology of the uppermost Albian-lower Turonian of the Morsott area (Algero-Tunisian Atlasic Basin) 莫尔索特地区(阿尔及利亚-突尼斯阿特拉斯盆地)最上阿尔卑斯统-下图伦统的地层学和沉积学
IF 2.2 4区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2024-10-19 DOI: 10.1016/j.jafrearsci.2024.105455
Mohamed Amine Zaidi , Marcin Krajewski , Caner Kaya Özer , Mariusz A. Salamon , W. James Kennedy , Madani Benyoucef
The stratigraphical features and palaeoenvironmental conditions of the uppermost Albian-lower Turonian succession of the eastern Algerian Saharan Atlas domain are described for the first time. Two formations have been recognised, called the Ouled Serradj and the Chemla, respectively. Ammonites and calcareous nannofossils enable us to assign the Ouled Serradj Formation to the upper Albian-Cenomanian and the Chemla Formation to the uppermost Cenomanian-lower Turonian. Based on the field data and microfacies studies, the strata of these formations are arranged into eight microfacies types (MT 1 to MT 8) that are described in terms of depositional environments and grouped into three main facies associations (FA-1 to FA-3): FA-1 (MT 1–4), deep-water outer platform marl-dominated facies association 1 with limestone intercalations; FA-2 (MT 5 and 6), mid-platform marl-dominated facies association 2; and FA-3 (MT 7 and 8), mid- and inner platform limestone-marl facies association 3.
该研究首次描述了阿尔及利亚撒哈拉阿特拉斯地区东部最上阿尔卑斯-下都伦演替的地层特征和古环境条件。已确认的两个地层分别称为 Ouled Serradj 和 Chemla。鲑鱼和钙质化石使我们能够将 Ouled Serradj 地层归入上阿尔卑斯-仙人掌纪,将 Chemla 地层归入最上仙人掌-下图伦纪。根据实地数据和微地层研究,这些地层被划分为八种微地层类型(MT 1 至 MT 8),这些微地层类型根据沉积环境进行了描述,并分为三个主要地层组合(FA-1 至 FA-3):FA-1(MT 1-4),深水外平台泥灰岩为主、夹石灰岩的岩相组合 1;FA-2(MT 5 和 6),中平台泥灰岩为主的岩相组合 2;FA-3(MT 7 和 8),中、内平台石灰岩-泥灰岩岩相组合 3。
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引用次数: 0
Stratigraphy and microfacies analysis of the Lower–Middle Jurassic platform carbonate succession in the Yeşilovacık (Mersin) area (Central Taurides, S Turkiye) 叶希洛瓦切克(梅尔辛)地区(土耳其南部,陶里德斯中部)侏罗纪下-中统地台碳酸盐岩层序的地层学和微地层分析
IF 2.2 4区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2024-10-18 DOI: 10.1016/j.jafrearsci.2024.105453
Hayati Koç, Burak Dinçer
This study covers the detailed analyses of stratigraphy, microfacies and depositional environments of the Lower-Middle Jurassic carbonate succession in the southern part of Anatolide-Tauride Carbonate Platform in southern Türkiye (south of Central Taurides, around Yeşilovacık). The carbonate succession is composed of the Dibekli and Tokmar formations, and the Işıklıkızıtepe Member which forms the base of the Tokmar Formation. The Dibekli Formation (Upper Sinemurian-Lower Bajocian) is composed of limestones intercalated with intraformational conglomerates in the lower parts, with dolostones in the lower to middle parts and with oncoidal limestones in middle to upper parts. The Işıklıkızıtepe Member (Upper Bajocian) starts with basal conglomerates containing brown-red- iron nodules and consists of sandstone and sandy-clayey limestone alternations. These are overlain by thin limestone layers passing upward to thick-bedded dolostones of the Tokmar Formation (Upper Bajocian–Bathonian). The middle to upper parts of the formation are composed of sandy, oncoidal limestones rich in bivalve shells and end with dolostones-limestone alternations in the upper part. According to microfacies analyzes and litho-bio content; Late Sinemurian-Plesbachian is a period that low-to moderate-energy, restricted inner platform conditions dominated the depositional environments. The presence of comman intraformational conglomerates shows tectonic activity from time to time in this period. The Toarcian to the earliest Bajocian, low-energy intertidal and shallow lagoon conditions dominated the depositional environments, and in the Early Bajocian, the depositional environment changed to a high-energy sand shoal and above wave base environment. The basal conglomerate consisting of brown-red, iron-noduler and bauxite grains at the base of the earliest Late Bajocian indicates a short-term emersion and continued under low energy shallow lagoonal conditions during the Late Bajocian–Bathonian. Environmental changes during the Toarcian to Early Bajocian, and the earliest Late Bajocian short-term emersion, and the environmental changes during the Late Bajocian-Bathonian are interpreted to short-term sea level changes. Yeşilovacık Lower-Middle Jurassic carbonate sequences are correlated with those in peri-Mediterranean platforms. They show close similarities to the other Tauride carbonate sequences in terms of stratigraphy and facies. Paleontological and sedimentological analyses enable us to reconstruct a detailed dating and paleoenvironmental evolution for the Yeşilovacık carbonate deposits during the Lower-Middle Jurassic period.
本研究详细分析了图尔基耶南部阿纳托利德-陶里德碳酸盐地台南部(陶里德中部以南,叶西罗瓦茨克附近)侏罗系下-中统碳酸盐层序的地层、微地貌和沉积环境。该碳酸盐岩系由迪贝克利层和托克玛层以及构成托克玛层底部的伊谢克勒克兹特佩层组成。Dibekli地层(上新元古代-下巴约乾统)由灰岩组成,下部夹地层内砾岩,中下部为白云石,中上部为鲕粒灰岩。Işıklıkızıtepe岩层(上巴约契期)从含有褐红色铁结核的基底砾岩开始,由砂岩和砂质粘土灰岩交替组成。其上覆盖着薄石灰岩层,并向上延伸至托克玛层(上巴约卡统-巴托纳统)的厚层白云石。该地层的中上部由富含双壳类贝壳的砂质、鲕状石灰岩组成,上部以白云岩-石灰岩交替层结束。根据微观岩相分析和岩石生物含量,晚新元古代-普利斯巴赫期是一个低-中能量、受限内平台条件主导沉积环境的时期。构造内砾岩的出现表明这一时期不时有构造活动。在托阿克纪至最早的巴约克纪,低能量的潮间带和浅泻湖条件占据了沉积环境的主导地位,到了巴约克纪早期,沉积环境转变为高能量的沙洲和高于波基的环境。最早的晚巴约克世底部由棕红色、铁结核和铝土矿粒组成的基底砾岩表明,在晚巴约克世-巴吞纪期间,在低能浅潟湖条件下继续存在短期浸润。托阿尔期至早巴约卡期的环境变化和最早晚巴约卡期的短期浸润,以及晚巴约卡期-巴松期的环境变化被解释为短期的海平面变化。叶西罗瓦茨克下-中侏罗世碳酸盐序列与近地中海平台的碳酸盐序列相关。在地层和地貌方面,它们与其他金牛座碳酸盐序列非常相似。古生物学和沉积学分析使我们能够重建叶西罗瓦茨克碳酸盐沉积在侏罗纪下-中叶时期的详细年代和古环境演变。
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引用次数: 0
Imaging and modelling the subsurface structure of the Rungwe Volcanic Province in SW Tanzania with aeromagnetic data: An improved structural map to support geothermal exploration 利用航磁数据对坦桑尼亚西南部 Rungwe 火山省的地下结构进行成像和建模:支持地热勘探的改进结构图
IF 2.2 4区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2024-10-18 DOI: 10.1016/j.jafrearsci.2024.105454
Makoye M. Didas , Egidio Armadillo , Gylfi Páll Hersir , William Cumming , Daniele Rizzello , Halldór Geirsson
The Rungwe Volcanic Province (RVP) in the East African Rift System, SW Tanzania, provides a unique opportunity to investigate geothermal resources in the context of particularly complex continental rifting processes. To support geothermal resource targeting in the RVP, we present a revised neotectonic structural map based on an interpretation of aeromagnetic data constrained by 2D-forward modelling of magnetic anomalies integrated with the distribution of previously reported faults, seismic epicentre locations, 3D magnetotelluric resistivity models and surface geothermal manifestations. Magnetic anomalies in the RVP, including the nationally prominent Mbeya anomaly, are related to the high magnetic susceptibility or remanent magnetism of Precambrian rocks and Cretaceous carbonatite intrusions buried in the rift under a varying thickness of non-magnetic sediments and volcanic rocks. Magnetic lineaments are related to structures controlling the geometry of the Precambrian rocks and concealed dikes and the thickness of the sediments and volcanics. The recent Ngozi and Rungwe trachyte volcanics have relatively low magnetic susceptibility comparable to the low susceptibility of the sediments in the rift basins. The revised neotectonic structural map shows prominent NW, NE and NS-trending magnetic lineaments that correlate with previously reported faults and alignments of seismic epicentres in the study area and with the regional trend of the rift segments. The NE-trending magnetic lineaments are consistent with interpretations of the current stress field in the RVP. The main volcanoes in the RVP, Ngozi, Rungwe and Kiejo (also known as Kyejo and Kieyo), are aligned with the NW-trending linear magnetic feature joining the Lupa and Livingstone rift border faults. This lineament is intersected and frequently displaced by the NE and NS-trending lineaments, suggesting that the NE to NS-striking structures are younger. The Rungwe and Ngozi volcanoes as well as numerous ‘‘monogenetic’’ eruption centres and the Mwakaleli caldera, which originated ca. 2 Ma ago (Ebinger et al., 1989) following a large explosive eruption emplacing widespread ignimbrite deposits, are located within a zone of low-intermediate magnitude magnetic features forming a basin-like structure surrounded by magnetic high anomalies of the Precambrian basement structures. We interpret the intersections between the NW-trending intra-rift faults and the NS and NE-trending faults as favourable locations for wells to target high permeability within the geothermal resource conceptual models previously constructed using 3D MT resistivity imaging integrated with supporting geoscientific data. The intersections provide a focus area for follow-up ground mapping of subtle features that may be associated with very recent fault movement.
坦桑尼亚西南部东非裂谷系统中的隆圭火山省(RVP)为研究特别复杂的大陆裂谷过程背景下的地热资源提供了一个独特的机会。为了支持 RVP 的地热资源目标定位,我们在对航空磁数据进行解释的基础上,结合之前报告的断层分布、地震震中位置、三维磁测电阻率模型和地表地热表现,提出了经修订的新构造结构图,并对磁异常进行了二维前向建模。RVP 中的磁异常,包括全国著名的姆贝亚异常,与前寒武纪岩石和白垩纪碳酸盐岩侵入体的高磁感应强度或剩磁有关,这些岩石和侵入体埋藏在裂谷中厚度不等的非磁性沉积物和火山岩之下。磁力线条与控制前寒武纪岩石和隐伏岩钉的几何形状以及沉积物和火山岩厚度的结构有关。近期的恩戈齐和隆圭岩屑火山岩的磁感应强度相对较低,与裂谷盆地沉积物的低磁感应强度相当。修订后的新构造结构图显示了突出的西北、东北和北北走向磁力线,这些磁力线与之前报告的研究区域内的断层和地震震中线以及裂谷段的区域走向相关。东北走向的磁力线与对裂谷地段当前应力场的解释一致。该地区的主要火山--恩戈齐火山、隆圭火山和基约火山(又称基耶约火山和基约火山)--与连接卢帕断裂和利文斯通断裂边界的西北走向线性磁力特征相一致。这条线与 NE 和 NS 走向的线相交,并经常发生位移,这表明 NE 至 NS 走向的构造更年轻。Rungwe 火山和 Ngozi 火山以及众多的 "单源 "喷发中心和 Mwakaleli 破火山口(起源于约 2 Ma 前(Ebinger 等人,1989 年)的一次大爆发,形成了广泛的火成岩沉积)都位于中低磁级磁性特征区内,形成了一个盆地状结构,周围环绕着前寒武纪基底结构的磁性高异常区。我们认为,西北走向的断裂内断层与 NS 和 NE 走向的断层之间的交汇处,是先前利用三维 MT 电阻率成像技术和支持性地球科学数据构建的地热资源概念模型中针对高渗透性打井的有利位置。这些交叉点为后续地面测绘可能与近期断层运动有关的细微特征提供了重点区域。
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引用次数: 0
Paucispecific invertebrate associations in the Coniacian (Upper Cretaceous) Essen Formation (Tébessa Mountains, northeast Algeria) 埃森地层(阿尔及利亚东北部泰贝萨山脉)科尼亚期(上白垩世)无脊椎动物的类群关系
IF 2.2 4区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2024-10-16 DOI: 10.1016/j.jafrearsci.2024.105452
Sakina Nemouchi , Sihem Salmi-Laouar , Ahmed A. Abdelhady , Mohamed S. Ahmed , Ali M. Hussain , Bouthaina Ouelaa , Amor Deghaichia
The Coniacian strata of the Tébessa Mountains in northern Algeria are predominantly marly facies that have received few studies. The present study is the first one to be carried out at Djebel Essen (west of Tébessa) to reveal the paleoenvironmental setting. The macrofossil taxa identified herein include fifteen bivalve species, three gastropods, and one cephalopod species, in addition to four irregular echinoid species. Quantitative analysis of these macrofossils indicates the occurrence of three benthic Coniacian macrofaunal associations, which include: 1) Agelasina plenodonta, 2) Cucullaea, and 3) Oscillopha-Plicatula. Both Agelasina plenodonta and Cucullaea associations are dominated by infauna. However, Cucullaea Association contains only suspension-feeders, where deposit-feeders are completely absent, suggesting oligotrophic conditions, that might have resulted in the lowest diversity level. In contrast, epifaunal taxa dominated the Oscillopha-Plicatula association. All the three associations are paucispecific. This low diversity of the Coniacian associations at study area and in other North African countries, can be attributed to the retreat of the sea and the shrinking of shallower habitats’ area. Probably, these associations lived within restricted marginal marine environments. The absence of any potential indicator of the middle-upper Coniacian anoxic event (OAE-3) agrees with the case in nearby sections and confirms a restricted extent of this event. The occurrence of many taxa of either regional or cosmopolitan affinity suggests episodic connection with the Tethyan Ocean.
阿尔及利亚北部泰贝萨山脉的科尼阿克纪地层主要为泥灰岩层,很少有人对其进行研究。本研究是首次在 Djebel Essen(泰贝萨以西)进行的古环境研究。本研究鉴定的大型化石类群包括 15 个双壳类物种、3 个腹足类物种和 1 个头足类物种,以及 4 个不规则的回声类物种。对这些大型化石的定量分析表明,科尼阿克文明出现了三种底栖大型动物群落,包括1)Agelasina plenodonta;2)Cucullaea;3)Oscillopha-Plicatula。Agelasina plenodonta 和 Cucullaea 协会都是以小型动物为主。然而,Cucullaea 协会只包含悬浮取食者,完全不包含沉积取食者,这表明该协会处于低营养状态,可能导致其多样性水平最低。相比之下,附生类群在 Oscillopha-Plicatula 协会中占主导地位。这三个类群都是低营养群。在研究地区和其他北非国家,科尼阿西亚类群的多样性较低,这可能是由于海水退缩和较浅栖息地面积缩小的缘故。也许,这些群落生活在有限的边缘海洋环境中。没有任何潜在的指标表明发生了中上康尼阿克纪缺氧事件(OAE-3),这与附近地段的情况一致,证实了这一事件的范围有限。许多具有区域或世界性亲缘关系的类群的出现表明,它们与哲罗纪大洋存在着偶发性联系。
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引用次数: 0
Mohamed G. Abdelsalam, An obituary by friends and family Mohamed G. Abdelsalam,亲友的讣告
IF 2.2 4区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2024-10-15 DOI: 10.1016/j.jafrearsci.2024.105430
Jean-Paul Liégeois, Robert J. Stern, Mahasin Idris, Hiam Abdelsalam, Francisca Oboh Ikuenobe, Estella A. Atekwana
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引用次数: 0
Palaeoproterozoic Kate granitoid suite provides evidence for slab break-off during the assembly of the Tanzania Craton and Bangweulu Block 古新生代凯特花岗岩套件为坦桑尼亚克拉通和邦圭卢地块组装过程中的板块断裂提供了证据
IF 2.2 4区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2024-10-15 DOI: 10.1016/j.jafrearsci.2024.105448
Xingyuan Wu , Xiaoyang Liu , Kai Sun , Hongwei Sun , Kangkang Xu , Penghui Gong , Shengfei He , Zuomin Zhou , Godfery Machumu
The Archean Tanzania Craton and the Bangweulu Block are separated by the Ubendian-Usagaran Belt, which developed during the Palaeoproterozoic Eburnean orogeny that produced the Congo Craton during the Columbia Supercontinent Cycle. Voluminous 1.80–1.90 Ga metagranitoids and volcanics were intruded both on the edge of the Bangweulu Block and in the Ubendian-Usagaran Belt in response to this geodynamic process. In recent years, research revealed that the extensive 1.90–1.80 Ga plutonic-volcanic suites exposed in the Ubendian- Usagaran Belt (on the Tanzania Craton side) resulted from widespread crustal anatexis caused by a regional thermal anomaly. However, the heating mechanism remains unclear. On the other (Bangweulu Block) side, high-precision chronological and geochemical data for the coeval Kate-Kipili felsic suite which crops out on the boundary of the Western Ubendian Corridor and the Bangweulu Block are scarce. The origin and tectonic setting of this suite are controversial, but crucial to understanding the crustal evolution during the Paleoproterozoic Ubendian orogeny. To address this issue, this paper is focused on the petrogenesis and tectonic setting of the Kate granitoids. New LA-ICPMS zircon U-Pb ages of the Kate granitoids revealed magmatic episodes from 1.87 to 1.90 Ga. Geochemically, the Kate granitoids belong to the magnesian alkalic-calcic rock series. They exhibit distinctive features including high Ga/Al and K2O/Na2O; high concentrations of Nb, Ta, Zr, and Y; and low Eu, Sr, Cr, Co, and Ni. The Kate granitoids could be classified into at least two groups in terms of geochemical characteristics, namely A2-type granites and slab failure plutons, respectively. The Kate-Kipili complex is considered to be related to the process of slab break-off, and the main difference between slab failure magmatism and A-type magmatism is probably the depth of the magma source. Slab break-off is the most likely mechanism for the magmatic intrusions and volcanism that occurred at 1.90–1.80 Ga in SW Tanzania and the Bangweulu Block.
在哥伦比亚超大陆周期产生刚果克拉通的古新生代埃伯恩造山运动期间,形成了乌本迪安-乌萨卡兰带。在这一地球动力学过程中,大量 1.80-1.90 Ga 的元古宙和火山岩侵入了邦圭卢地块边缘和乌本迪安-乌萨卡兰带。近年来的研究表明,乌本迪安-乌萨加兰带(坦桑尼亚克拉通一侧)出露的大面积 1.90-1.80 Ga 热成岩-火山岩套件是由区域热异常引起的大范围地壳膨胀造成的。然而,加热机制仍不清楚。在另一侧(班圭卢地块),在西乌本迪安走廊和班圭卢地块边界上出现的共生凯特-基皮利长英岩组的高精度年代学和地球化学数据十分稀少。该岩组的成因和构造背景颇具争议,但对于了解古近纪乌本底造山运动期间的地壳演化却至关重要。为了解决这个问题,本文重点研究了凯特花岗岩的岩石成因和构造背景。凯特花岗岩新的LA-ICPMS锆石U-Pb年龄显示了1.87至1.90 Ga的岩浆活动。从地球化学角度看,凯特花岗岩属于镁质碱钙岩系列。它们表现出独特的特征,包括高Ga/Al和K2O/Na2O;高浓度的Nb、Ta、Zr和Y;以及低Eu、Sr、Cr、Co和Ni。根据地球化学特征,凯特花岗岩至少可分为两类,即A2型花岗岩和板块崩塌柱状岩。凯特-基皮利复合体被认为与板块断裂过程有关,板块崩塌岩浆活动与 A 型岩浆活动的主要区别可能在于岩浆源的深度。板块断裂是坦桑尼亚西南部和邦圭卢区块在 1.90-1.80 Ga 发生岩浆侵入和火山活动的最可能机制。
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引用次数: 0
Crustal evolution of alternating Paleoproterozoic belts and basins in the Birimian terrane in southeastern West African Craton 西非克拉通东南部 Birimian 地层中古新生代交替带和盆地的地壳演化
IF 2.2 4区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2024-10-15 DOI: 10.1016/j.jafrearsci.2024.105449
Patrick Asamoah Sakyi , Daniel Kwayisi , Samuel Nunoo , Eric Ocran , Ben-Xun Su , Sanjeewa P.K. Malaviarachchi
We present a comprehensive review of available geochemical, geochronological and isotopic data on granitoids from the Paleoproterozoic Birimian terrane of Ghana, aimed at providing an in-depth understanding of the geodynamic evolution of southeastern West African Craton. The focus is on plutonic magmatism, crustal recycling and tectonic setting of the granitoids. The granitoids are mainly TTG suites, calc-alkaline granites, diorites, monzonites, two-mica granites and leucogranites. They are characterized by enrichments in LILE and LREE relative to HREE and HFSE. Their variable positive and negative Eu and Sr anomalies and depletions in Nb-Ta and Ti suggest the presence of residual minerals like hornblende and Fe-Ti oxides (e.g., rutile and ilmenite). The plutons probably formed by partial melting of hydrous basaltic/mafic crust metasomatized by slab-derived melts at different depths. The ɛHf (−14.5 to +7.6) and εNd (−5.3 to +3.5) values and Nd model ages (2.21–2.53 Ga) indicate their crystallization from juvenile magmas derived from a depleted mantle with significant recycling of older crustal material. The older (≥2200 Ma) and younger (<2100 Ma) ages recorded in both belt- and basin-type granitoids indicate that magmatism in both types was contemporaneous. Nonetheless, the basins recorded younger peak emplacement ages compared to adjacent belts. The presence of inherited older zircon grains (Archean zircon cores?), is widespread in southeastern WAC. The granitoids formed in a continental arc setting via subduction–accretion processes. Furthermore, the magmatic time-span is more prolonged in southern Ghana, with the sedimentary basins recording the longest intervals of magma emplacement. The sub-chondritic ɛHf data and Hf model ages strongly suggest the existence of Neoarchean to Mesoarchean crustal material in eastern Ghana during the Birimian crust formation. We propose that the subduction-accretion processes during the Paleoproterozoic Eburnean orogeny in the WAC contributed to the formation of the Columbia supercontinent in the Late Paleoproterozoic-Mesoproterozoic.
我们全面综述了加纳古新生代比里勉岩系花岗岩的地球化学、地质年代和同位素数据,旨在深入了解西非克拉通东南部的地球动力演化。研究重点是花岗岩的构造岩浆作用、地壳再循环和构造背景。花岗岩主要是TTG岩套、钙碱性花岗岩、闪长岩、单斜岩、双云母花岗岩和白花岗岩。相对于 HREE 和 HFSE,它们的特点是 LILE 和 LREE 富集。它们的 Eu 和 Sr 异常值有正有负,Nb-Ta 和 Ti 异常值较低,表明存在角闪石和铁钛氧化物(如金红石和钛铁矿)等残留矿物。这些深成岩可能是由含水玄武岩/闪长岩地壳在不同深度被板块衍生熔体变质部分熔化形成的。ɛHf(-14.5 至 +7.6)和εNd(-5.3 至 +3.5)值以及 Nd 模型年龄(2.21-2.53 Ga)表明,它们是由来自贫化地幔的幼年岩浆结晶而成,其中大量回收了较老的地壳物质。岩带型和岩盆型花岗岩中记录的较老(≥2200Ma)和较年轻(<2100Ma)的年龄表明,这两种类型的岩浆活动是同时发生的。尽管如此,与邻近的岩带相比,盆地记录到的峰值成岩年龄更年轻。在西澳大利亚州东南部,普遍存在继承下来的较古老的锆石颗粒(Archean锆石岩芯?这些花岗岩是在大陆弧环境中通过俯冲-成岩过程形成的。此外,加纳南部的岩浆时间跨度较长,沉积盆地记录的岩浆喷发时间间隔最长。亚软玉ɛHf数据和Hf模型年龄有力地表明,在比里米亚地壳形成期间,加纳东部存在新元古代至中元古代地壳物质。我们认为,西太平洋古生代埃伯恩造山运动期间的俯冲-增生过程促成了晚古生代-中古生代哥伦比亚超大陆的形成。
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引用次数: 0
The source kinematics and slip distribution of the 2023 Mw 6.8 Morocco earthquake 2023 年摩洛哥 6.8 级地震的震源运动学和滑移分布
IF 2.2 4区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2024-10-15 DOI: 10.1016/j.jafrearsci.2024.105451
Wenqiang Wu, Yongzhi Zhang, Xiaoye Hao, Jiaojiao Liu
On September 8, 2023, an Mw 6.8 earthquake struck Haouz province (Morocco), in the central Atlas Mountains, causing many casualties. In this study, we obtain the co-seismic deformation field with the D-InSAR and the Pixel Offset Tracking (POT), and three-dimensional displacement with the strain model-variance component estimation method (SM-VCE). The results indicate that this earthquake belongs to a typical thrust earthquake, and the displacement components in the west-east (W-E) and vertical are quite obvious. Besides, the rupture length from the POT method is about 40 km, and the strike is west-north-west (WNW), consistent with that of the Atlas Mountains. According to the slip inversion, the rupture depth of the fault is about 30 km, and the peak slip is approximately 1.6 m at depths of about 22.75 km. Similarly, the strike is 260°, the dip angle is 70° and the rake angle is 75°, respectively. Moreover, the released energy from this earthquake is approximately a Mw 6.8 earthquake. In addition to the earthquake destruction, the local economic foundation and building structure are crucial reasons for the serious casualties. Therefore, the method in this study could provide references for seismic research and the results could help explore the focal mechanism along the High Atlas in Morocco.
2023 年 9 月 8 日,摩洛哥阿特拉斯山脉中部的豪兹省(Haouz)发生 Mw 6.8 级地震,造成多人伤亡。在本研究中,我们利用 D-InSAR 和像素偏移跟踪(POT)获得了共震变形场,并利用应变模型-方差分量估计法(SM-VCE)获得了三维位移。结果表明,此次地震属于典型的推挤地震,西-东(W-E)和垂直方向的位移分量比较明显。此外,POT 方法得出的断裂长度约为 40 km,走向为西-北-西(WNW),与阿特拉斯山脉的走向一致。根据滑移反演,该断层的断裂深度约为 30 千米,在约 22.75 千米处的滑移峰值约为 1.6 米。同样,断层走向为 260°,倾角为 70°,倾斜角为 75°。此外,这次地震释放的能量约为 Mw 6.8。除了地震破坏之外,当地的经济基础和建筑结构也是造成严重人员伤亡的重要原因。因此,本研究的方法可为地震研究提供参考,其结果有助于探索摩洛哥高阿特拉斯地区的震源机制。
{"title":"The source kinematics and slip distribution of the 2023 Mw 6.8 Morocco earthquake","authors":"Wenqiang Wu,&nbsp;Yongzhi Zhang,&nbsp;Xiaoye Hao,&nbsp;Jiaojiao Liu","doi":"10.1016/j.jafrearsci.2024.105451","DOIUrl":"10.1016/j.jafrearsci.2024.105451","url":null,"abstract":"<div><div>On September 8, 2023, an Mw 6.8 earthquake struck Haouz province (Morocco), in the central Atlas Mountains, causing many casualties. In this study, we obtain the co-seismic deformation field with the D-InSAR and the Pixel Offset Tracking (POT), and three-dimensional displacement with the strain model-variance component estimation method (SM-VCE). The results indicate that this earthquake belongs to a typical thrust earthquake, and the displacement components in the west-east (W-E) and vertical are quite obvious. Besides, the rupture length from the POT method is about 40 km, and the strike is west-north-west (WNW), consistent with that of the Atlas Mountains. According to the slip inversion, the rupture depth of the fault is about 30 km, and the peak slip is approximately 1.6 m at depths of about 22.75 km. Similarly, the strike is 260°, the dip angle is 70° and the rake angle is 75°, respectively. Moreover, the released energy from this earthquake is approximately a Mw 6.8 earthquake. In addition to the earthquake destruction, the local economic foundation and building structure are crucial reasons for the serious casualties. Therefore, the method in this study could provide references for seismic research and the results could help explore the focal mechanism along the High Atlas in Morocco.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"220 ","pages":"Article 105451"},"PeriodicalIF":2.2,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142533129","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
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Journal of African Earth Sciences
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