Pyroclastic Rocks as Natural Fertilizer: Case Study of Volcanic Ashes from Tombel Graben (Cameroon Volcanic Line, Central Africa)

Geotherapy ◽  
2014 ◽  
pp. 455-464 ◽  
Keyword(s):  
Central Africa ◽  
Pyroclastic Rocks ◽  
Cameroon Volcanic Line ◽  
Volcanic Ashes

Fracture network mapping using remote sensing in three crater lakes environments of the Cameroon volcanic line (central Africa)

2021 ◽  
Vol 14 (6) ◽  
Author(s):  
Marthe Mbond Ariane Gweth ◽  
Jorelle Larissa Meli’i ◽  
Valentin Oyoa ◽  
Diab Ahmad Diab ◽  
Daniel Herve Gouet ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Central Africa ◽  
Fracture Network ◽  
Crater Lakes ◽  
Cameroon Volcanic Line ◽  
Network Mapping

scholarly journals Lithospheric mantle refertilization by DMM-derived melts beneath the Cameroon Volcanic Line—a case study of the Befang xenolith suite (Oku Volcanic Group, Cameroon)

2021 ◽  
Vol 176 (5) ◽  
Author(s):  
Sylvin S. T. Tedonkenfack ◽  
Jacek Puziewicz ◽  
Sonja Aulbach ◽  
Theodoros Ntaflos ◽  
Mary-Alix Kaczmarek ◽  
...  
Keyword(s):  
Lithospheric Mantle ◽  
Size Variation ◽  
African Plate ◽  
Cameroon Volcanic Line ◽  
Origin And Evolution ◽  
Volcanic Group ◽  
Cenozoic Volcanism ◽  
Composition Of Minerals ◽  
Ree Patterns

AbstractThe origin and evolution of subcontinental lithospheric mantle (SCLM) are important issues of Earth’s chemical and physical evolution. Here, we report detailed textural and chemical analyses on a mantle xenolith suite from Befang (Oku Volcanic Group, Cameroon Volcanic Line), which represents a major tectono-magmatic structure of the African plate. The samples are sourced from spinel-facies mantle and are dominated by lherzolites. Their texture is cataclastic to porphyroclastic, and foliation defined by grain-size variation and alignment of spinel occurs in part of peridotites. Spinel is interstitial and has amoeboidal shape. Clinopyroxene REE patterns are similar to those of Depleted MORB Mantle (DMM) except LREEs, which vary from depleted to enriched. The A-type olivine fabric occurs in the subset of one harzburgite and 7 lherzolites studied by EBSD. Orthopyroxene shows deformation consistent with olivine. The fabric of LREE-enriched clinopyroxene is equivalent to those of orthopyroxene and olivine, whereas spinel and LREE-depleted clinopyroxene are oriented independently of host rock fabric. The textural, chemical and thermobarometric constraints indicate that the Befang mantle section was refertilised by MORB-like melt at pressures of 1.0–1.4 GPa and temperatures slightly above 1200–1275 °C. The olivine-orthopyroxene framework and LREE-enriched clinopyroxene preserve the protolith fabric. In contrast, the LREE-depleted clinopyroxene, showing discordant deformation relative to the olivine-orthopyroxene protolith framework, and amoeboidal spinel crystallized from the infiltrating melt. The major element and REEs composition of minerals forming the Befang peridotites indicate subsequent reequilibration at temperatures 930–1000 °C. This was followed by the formation of websterite veins in the lithospheric mantle, which can be linked to Cenozoic volcanism in the Cameroon Volcanic Line that also brought the xenoliths to the surface. This study therefore supports the origin of fertile SCLM via refertilization rather than by extraction of small melt fractions, and further emphasizes the involvement of depleted melts in this process.

THE ‘NATIVE’ UNDEFINED: COLONIAL CATEGORIES, ANGLO-AFRICAN STATUS AND THE POLITICS OF KINSHIP IN BRITISH CENTRAL AFRICA, 1929–38

2005 ◽  
Vol 46 (3) ◽  
pp. 455-478 ◽  
Author(s):  
CHRISTOPHER JOON-HAI LEE
Keyword(s):  
Southern Africa ◽  
Central Africa ◽  
Mixed Race ◽  
Court Case ◽  
Colonial State ◽  
Colonial Policy ◽  
Ultimate Failure ◽  
Definition Of ◽  
Determining Factor

This article examines the categorical problem that persons of ‘mixed-race’ background presented to British administrations in eastern, central and southern Africa during the late 1920s and 1930s. Tracing a discussion regarding the terms ‘native’ and ‘non-native’ from an obscure court case in Nyasaland (contemporary Malawi) in 1929, to the Colonial Office in London, to colonial governments in eastern, central and southern Africa, this article demonstrates a lack of consensus on how the term ‘native’ was to be defined, despite its ubiquitous use. This complication arrived at a particularly crucial period when indirect rule was being implemented throughout the continent. Debate centered largely around the issue of racial descent versus culture as the determining factor. The ultimate failure of British officials to arrive at a clear definition of the term ‘native’, one of the most fundamental terms in the colonial lexicon, is consequently suggestive of both the potential weaknesses of colonial state formation and the abstraction of colonial policy vis-à-vis local empirical conditions. Furthermore, this case study compels a rethinking of contemporary categories of analysis and their historical origins.

Beach-Bar Sandstone Reservoir Prediction: A Case Study from Central Africa

2020 ◽  
Author(s):  
W. He ◽  
B. Chen ◽  
J. Li ◽  
L. Xue ◽  
L. Ma ◽  
...  
Keyword(s):  
Central Africa ◽  
Reservoir Prediction ◽  
Sandstone Reservoir ◽  
Beach Bar

Chemistry and origin of the Mayo Kila sapphires, NW region Cameroon (Central Africa): Their possible relationship with the Cameroon volcanic line

2016 ◽  
Vol 118 ◽  
pp. 263-273 ◽  
Author(s):  
Kemeng Paul Mbih ◽  
Sebastien Meffre ◽  
Rose Fouateu Yongue ◽  
Nguo Sylvestre Kanouo ◽  
Thomson Jay
Keyword(s):  
Central Africa ◽  
Cameroon Volcanic Line

Texture discrimination of volcanic ashes from different fragmentation mechanisms: A case study, Mount Nemrut stratovolcano, eastern Turkey

2006 ◽  
Vol 32 (7) ◽  
pp. 936-946 ◽  
Author(s):  
Orkun Ersoy ◽  
Gary Chinga ◽  
Erkan Aydar ◽  
Alain Gourgaud ◽  
H. Evren Cubukcu ◽  
...  
Keyword(s):  
Texture Discrimination ◽  
Eastern Turkey ◽  
Fragmentation Mechanisms ◽  
Volcanic Ashes

scholarly journals Better Word Representation Vectors Using Syllabic Alphabet: A Case Study of Swahili

2019 ◽  
Vol 9 (18) ◽  
pp. 3648
Author(s):  
Casper S. Shikali ◽  
Zhou Sijie ◽  
Liu Qihe ◽  
Refuoe Mokhosi
Keyword(s):  
Language Processing ◽  
Critical Role ◽  
Language Model ◽  
Central Africa ◽  
Spoken Language ◽  
Language Models ◽  
Word Embeddings ◽  
Word Representation

Deep learning has extensively been used in natural language processing with sub-word representation vectors playing a critical role. However, this cannot be said of Swahili, which is a low resource and widely spoken language in East and Central Africa. This study proposed novel word embeddings from syllable embeddings (WEFSE) for Swahili to address the concern of word representation for agglutinative and syllabic-based languages. Inspired by the learning methodology of Swahili in beginner classes, we encoded respective syllables instead of characters, character n-grams or morphemes of words and generated quality word embeddings using a convolutional neural network. The quality of WEFSE was demonstrated by the state-of-art results in the syllable-aware language model on both the small dataset (31.229 perplexity value) and the medium dataset (45.859 perplexity value), outperforming character-aware language models. We further evaluated the word embeddings using word analogy task. To the best of our knowledge, syllabic alphabets have not been used to compose the word representation vectors. Therefore, the main contributions of the study are a syllabic alphabet, WEFSE, a syllabic-aware language model and a word analogy dataset for Swahili.

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