Petrogenesis of the Sabongari alkaline complex, cameroon line (central Africa): Preliminary petrological and geochemical constraints

Njonfang, Emmanuel; Tchoneng, Gilbert Tchuenté; Cozzupoli, Domenico; Lucci, Federico

doi:10.1016/j.jafrearsci.2013.03.004

Cited by 22 publications

(11 citation statements)

References 57 publications

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“…Validation of mineral chemistry results was also achieved through opportune comparisons with the existing literature for (i) Mg-olivine (e.g., Hirano et al, 2004;White et al, 2009;Giordano et al, 2012;Melluso et al, 2014); (ii) Feolivine (e.g., Aldanmaz, 2006;White et al, 2009;Melluso et al, 2010;Giordano et al, 2012); (iii) aegirine-augite clinopyroxene (Cpx5 group; e.g., Piilonen et al, 1998;White et al, 2009;Njonfang et al, 2013); (iv) augite-diopside clinopyroxene (Cpx1-4 groups; e.g., Dawson and Hill, 1998;Aldanmaz, 2006;Melluso et al, 2010Melluso et al, , 2014; (v) orthopyroxene (e.g., Papike et al, 1995;Aldanmaz, 2006;Carvalho and de Assis Janasi, 2012;Hu et al, 2018); (vi) feldspar (e.g., Keil et al, 1972;Giordano et al, 2012;Innocenti et al, 2013;Njonfang et al, 2013); and (vii) spinel and opaque minerals (e.g., Melluso et al, 2014). Back-scattered electron (BSE) imaging was obtained by using the same electron microprobe with operating conditions of 15 kV and 50 nA.…”

Section: A3 Mineral Chemistrymentioning

confidence: 99%

Anatomy of the magmatic plumbing system of Los Humeros Caldera (Mexico): implications for geothermal systems

et al. 2020

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Abstract. Understanding the anatomy of magma plumbing systems of active volcanoes is essential not only for unraveling magma dynamics and eruptive behaviors but also to define the geometry, depth, and temperature of the heat sources for geothermal exploration. The Pleistocene–Holocene Los Humeros volcanic complex is part of the eastern Trans-Mexican Volcanic Belt (central Mexico), and it constitutes one of the most important exploited geothermal fields in Mexico with ca. 90 MW of produced electricity. With the aim to decipher the anatomy (geometry and structure) of the magmatic plumbing system feeding the geothermal field at Los Humeros, we carried out a field-based petrological and thermobarometric study of the exposed Holocene lavas. Textural analysis, whole-rock major-element data, and mineral chemistry are integrated with a suite of mineral-liquid thermobarometric models. Our results support a scenario characterized by a heterogeneous multilayered system, comprising a deep (depth of ca. 30 km) basaltic reservoir feeding progressively shallower and smaller discrete magma stagnation layers and batches, up to shallow-crust conditions (depth of ca. 3 km). The evolution of melts in the feeding system is mainly controlled by differentiation processes through fractional crystallization (plagioclase + clinopyroxene + olivine + spinel). We demonstrate the inadequacy of the existing conceptual models, where a single voluminous melt-controlled magma chamber (or “Standard Model”) at shallow depths was proposed for the magmatic plumbing system at Los Humeros. We instead propose a magmatic plumbing system made of multiple, more or less interconnected, magma transport and storage layers within the crust, feeding small (ephemeral) magma chambers at shallow-crustal conditions. This revised scenario provides a new configuration of the heat source feeding the geothermal reservoir at Los Humeros, and it should be taken into account to drive future exploration and exploitation strategies.

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Section: A3 Mineral Chemistrymentioning

confidence: 99%

Anatomy of the magmatic plumbing system of Los Humeros Caldera (Mexico): implications for geothermal systems

et al. 2020

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“…2). Plutonic complexes are usually of small size (mostly 5-10 km in diameter) and mainly composed of granites or syenites, sometimes associated to intermediate and basic rocks [9]- [32]. The Mboutou, Kokoumi and Nigo complexes, in the Northern part of the CL comprise basic rocks [33]- [36].…”

Section: B Ring Complexes Along the Cameroon Linementioning

confidence: 99%

Emplacement and Evolution of The Nlonako Ring Complex in The Southern Domain of The Cameroon Line

Agathe

Jules

Armand

et al. 2020

EJGEO

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The Cameroon Line (CL) appears as a SW-NE straight line characterized by an intense volcanic activity of basaltic composition with alkaline plutonic complexes, including the Nlonako ring complex (NRC) emplaced in the southern part of the CL. Many hypotheses have been proposed to explain the origin and petrogenetic evolution of these complexes but very few of these works focus or attempt to propose their structural emplacement model, though structural data recorded by them can permit such studies. Using petrographic, structural data and space images, we propose an emplacement model of the NRC and other ring complexes along the CL. The NRC is a ring complex of 10 km diameter slightly elongated in the NNE-SSW direction mainly composed of plutonites among which syenites, gabbros, diorites and biotite-amphibole granites, and a few volcanites made up of rhyolites and basalts occurring as veins or boulders in syenites. This complex was emplaced as sill intrusive body within Pan-African k-feldspars megacrysts granites and gneiss host rocks under fractures control. These fractures developed as result of stress release consecutive to the readjustment of the crust during and after the late Cretaceous general extension, therefore facilitating the upwelling of the mantle plume and the generation of magma that vertically uplift. The progressive magmatic pressure decreases after the NRC emplacement in addition to conjugated fractures networks developed at superficial crust level finally lead to the cauldron subsidence of the NRC summit. This subsidence was facilitated by the downward sliding of rocks along the WNW-ESE fault, finally leading to the formation of a caldera at the summit of the NRC. The NRC and other anorogenic complexes aligned along the CL are located in a tension gash form by the Cretaceous sinistral activation of the N70E Adamawa fault. This left lateral wrench movements developed a tension gash, overprinted on pre-existing transcurrent mega-faults with as result, the development of "en-echelon" fractures. Stress release during the late Cretaceous general extensional phase probably accelerated the uplift of magmas and emplacement of ring complexes along the "en-echelon" regional fractures in an extensional setting during the Tertiary (60 - 30 Ma). This therefore explained the alignment of anorogenic complexes along the N30E CL corridor that are highly correlated to lineament networks and Pan-African megafaults

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“…Greenland (Marks & Markl 2001, Riishuus et al 2008 and Messum, Namibia (Harris et al 1999); ■ Massifs with quartz-bearing rocks only in their central portions, shielded from contact with country rocks (at least at surface level) by silica-undersaturated rocks, e.g., Itatiaia, in Brazil (Penalva 1967, Ribeiro Filho 1967, Brotzu et al 1997, Wadi Dib, in Egypt (Frisch & Abdel-Rahman 1999), Hekanzi, in China (Yang et al 2012) and Pilanesberg, in South Africa (Cawthorn 2015); ■ Massifs composed exclusively, or predominantly, of quartz-bearing rocks associated with other silica-undersaturated massifs in the same magmatic province, e.g., Cerro Pedreira and Morro Distante, Alto Paraguay Province, Paraguay (Comin-Chiaramonti et al 2015), Paresis, Damaraland Province, Namibia (Mingram et al 2000) and Sabongari, Cameroon Line, Cameroon (Njonfang et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Nepheline syenites to syenites and granitic rocks of the Itatiaia Alkaline Massif, Southeastern Brazil: new geological insights into a migratory ring Complex

Rosa

Ruberti

2018

Braz. J. Geol.

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The Itatiaia Alkaline Massif comprises some of the largest meso-cenozoic alkaline igneous occurrences in Brazil, covering over 215 km 2 between the states of Minas Gerais and Rio de Janeiro. It appears as an elongated, 30-km long and 4.5-11.5-km wide SE-NW-trending body emplaced along accommodation zones of the Continental Rift of Southern Brazil, intruding metapelites, orthogneiss and granites of the Brasília and Ribeira fold belts. New data and geological mapping suggest that the massif evolved from a migratory magmatic center manifested as ring structures and successive moon-shaped intrusions from SE to NW in three sectors of distinct lithological and geomorphological characteristics: Southeastern, Central and Northwestern. The lithological variants in the three sectors present themselves as discrete intrusive bodies, comprising feldspathoid-bearing and quartz-bearing syenites, porphyritic to breccioid trachytes, granite, monzonite, gabbro and trachybasalt, which can be grouped into 21 units. These rocks occur in five petrographical sets: plagioclase-free nepheline syenites, plagioclase-bearing nepheline syenite and pulaskites, nordmarkite-granite series, anti-rapakivi associations and basic rocks. Sin-to tardi-plutonic dykes of nephelinites, phonolites, trachytes and rhyolites are also present.

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Petrogenesis of the Sabongari alkaline complex, cameroon line (central Africa): Preliminary petrological and geochemical constraints

Cited by 22 publications

References 57 publications

Anatomy of the magmatic plumbing system of Los Humeros Caldera (Mexico): implications for geothermal systems

Anatomy of the magmatic plumbing system of Los Humeros Caldera (Mexico): implications for geothermal systems

Emplacement and Evolution of The Nlonako Ring Complex in The Southern Domain of The Cameroon Line

Nepheline syenites to syenites and granitic rocks of the Itatiaia Alkaline Massif, Southeastern Brazil: new geological insights into a migratory ring Complex

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