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Petrology,geochemistry,and zircon U-Pb geochronology of the Zambezi Belt in Zimbabwe:Implications for terrane assembly in southern Africa

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Geoscience Frontiers 2019年第6期10卷 2021-2044页

作者： Yusuke Kuribara Toshiaki Tsunogae Yusuke Takamura Yukiyasu Tsutsumi Graduate School of Life and Environmental Sciences University of TsukubaIbaraki 305-8572Japan Department of Geology University of JohannesburgAuckland Park 2006South Africa Department of Geology and Paleontology National Museum of Nature and ScienceIbaraki 305-0005Japan

The Zambezi Belt in southern Africa has been regarded as a part of the 570-530 Ma Kuunga Orogen formed by a series of collision of Archean cratons and Proterozoic orogenic belts.Here,we report new petrological,geochemical,and zircon U-Pb geochronological data of various metamorphic rocks(felsic to mafic orthogneiss,pelitic schist,and felsic paragneiss)from the Zambezi Belt in northeastern Zimbabwe,and evaluate the timing and P-T conditions of the collisional event as well as protolith formation.Geochemical data of felsic orthogneiss indicate within-plate granite signature,whereas those of mafic orthogneiss suggest MORB,ocean-island,or within-plate affinities.Metamorphic P-Testimates for orthogneisses indicate significant P-T variation within the study area(700-780 C/6.7-7.2 kbar to 800-875 C/10-11 kbar)suggesting that the Zambezi Belt might correspond to a suture zone with several discrete crustal blocks.Zircon cores from felsic orthogneisses yielded two magmatic ages:2655±21 Ma and 813士5 Ma,which suggests Neoarchean and Early Neoproterozoic crustal growth related to within-plate magmatism.Detrital zircons from metasediments display various ages from Neoarchean to Neoproterozoic(ca.2700-750 Ma).The Neoarchean(ca.2700-2630 Ma)and Paleoproterozoic(ca.2200-1700 Ma)zircons could have been derived from the adjacent kalahari Craton and the Magondi Belt in Zimbabwe,respectively.The Choma-Kalomo Block and the Lufilian Belt in Zambia might be proximal sources of the Meso-to Neoproterozoic(ca.1500-950 Ma)and early Neoproterozoic(ca.900-750 Ma)detrital zircons,respectively.Such detrital zircons from adjacent terranes possibly deposited during late Neoproterozoic(744-670 Ma),and subsequently underwent highgrade metamorphism at 557-555 Ma possibly related to the collision of the Congo and kalahari Cratons during the latest Neoproterozoic to Cambrian.In contrast,670-627 Ma metamorphic ages obtained from metasediments are slightly older than previous reports,but consistent with^680-650 Ma metamorphic ages reported from differen

关键词： Geothermobarometry Detrital zircon Neoproterozoic Congo Craton kalahari Craton Gondwana

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Modification of soil properties by <i>Prosopis</i>L. in the kalahari Desert, South-Western Botswana

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Open Journal of Ecology 2013年第2期3卷 145-150页

作者： Samuel Mosweu Christopher Munyati Tibangayuka Kabanda Department of Environmental Science University of Botswana Gaborone Botswana Department of Geography and Environmental Science North-West University Mafikeng Campus Mafikeng South Africa

The aim of this research was to investigate the interactions between Prosopis plants and soils in the kalahari area, south west of Botswana. The underlying assumptions of the research were that Prosopis plants significantly enhanced the nutrient content and improved the condition of soils in the study area, and that the height and canopy size of Prosopis plants affected the interactions between Prosopis plants and the soils. Firstly, soil samples were collected under 42 randomly selected Prosopis plant canopies and in the spaces between Prosopis plant canopies at the depth of 0 -20 cmand 60 –80 cm. Secondly, soil samples were collected under 45 randomly selected Prosopis plant canopies of three different categories of height and canopy size at the depth of 0 -10 cm. The soil samples were analysed for soil organic carbon, pH, total nitrogen (N), electrical conductivity (EC), calcium (Ca), sodium (Na), potassium (K), and magnesium (Mg). Soil collected under Prosopis plant canopies and in the spaces between Prosopis plant canopies showed statistically significant difference in the soil organic carbon content (F = 2.68, P = 0.05, α = 0.05), pH (F = 44.81, P α = 0.05) and electrical conductivity (EC) (F = 3.75, P = 0.01, α = 0.05). Statistically significant difference was also observed in the comparison of soils existing under Classes 1, 2 and 3 Prosopis plant canopies in relation to pH and EC (F = 6.56, P = 0.01 and F = 4.77, P = 0.01 respectively at α = 0.05). Therefore, it was concluded that the fundamental assumptions of the study were valid.

关键词： Prosopis Species Soil Properties kalahari Desert Botswana

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南非kalahari锰矿田地质特征及找矿方法

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矿产勘查 2021年第1期12卷 98-106页

作者：谭康雨曾瑞垠詹勇岳鹏军北京中资环钻探有限公司北京100012 中色地科矿产勘查股份有限公司北京100012

南非kalahari锰矿田内发育众多大小规模的锰矿床,其形成与早期海底热液喷气及后期沉积变质作用密切相关。通过对比研究,区内矿体分布广泛、厚度不均,以层状、似层状、透镜状近平行产出,具有明显的层状分带特征。根据矿石类型可将其划分... 详细信息

南非kalahari锰矿田内发育众多大小规模的锰矿床,其形成与早期海底热液喷气及后期沉积变质作用密切相关。通过对比研究,区内矿体分布广泛、厚度不均,以层状、似层状、透镜状近平行产出,具有明显的层状分带特征。根据矿石类型可将其划分为Wessels型和Mamatwan型,矿石主要矿物成分以黑锰矿、铁锰矿、褐锰矿为主,样品数据表明Fe、Mn总体含量较为稳定,存在较为明显的负相关性,与古元古代的沉积环境和Fe、Mn物理性质关系密切。结合区域以往地质勘探资料,对区内锰矿地质特征、矿床成因及找矿方向进行了探讨,认为其成因类型为沉积变质型铁锰矿床,成矿后期的逆冲推覆构造和正断层破坏了矿体的连续性和完整性,白云岩溶蚀构造是铁锰物质的赋存空间,Hotazel组条带状含铁锰建造是区内找矿的重点部位。

关键词：锰矿田地质特征矿床成因找矿方法 kalahari 南非

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Subcanopy genetics —The relationship between canopy tree size and genetic variation of the savanna species <i>Pollichia campestris</i>Aiton (Illecebraceae)

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Open Journal of Ecology 2014年第2期4卷 60-65页

作者： Josef Simmel Peter Poschlod Christoph Reisch Institute of Botany University of Regensburg Regensburg Germany

In savanna vegetation, trees and their canopies provide an important, but scattered habitat. Seeds of plants growing under these nurse trees often are dispersed by animals, especially birds. In the present study, we investigated the influence of tree size and frugivore dispersal on the genetic variation of the subcanopy species Pollichia campestris, using amplified fragment length polymorphisms (AFLP). Considering the individuals under each nurse tree as subpopulations, we found the genetic variation within subpopulations to be positively correlated with the size of the respective canopy tree. Genetic variation was very low among, but high within subpopulations (ΦPT = 0.026, P = 0.18). We conclude that the low genetic variation among subpopulations is due to effective and directed dispersal (dispersal from one canopy to another) by legitimate and frugivorous dispersal agents.

关键词： Acacia AFLP Directed Dispersal Frugivore kalahari Nurse Tree

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