Ignimbrite vents in the Sabaloka cauldron, Sudan

Almond, D.C.

doi:10.1017/s0016756800051190

Cited by 43 publications

(27 citation statements)

References 13 publications

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“…Bouguer anomaly map, strongly, is surmising that the weird reversible steep gradient is due to rotational strike slip movement with NE-SW, crossed by another faulted-steep gradient with NW-SE at Awataib and continuing beyond the valley with the same trend NE-SW above Awataib valley. The last steep gradient is trending nearly W-E direction, fairly occurred at El-ban Gadeed village and probably related to a fault that have been discussed earlier by Almond and Ahmed [18]. (Figure 2), but it ends at lat.…”

Section: Discussionmentioning

confidence: 61%

“…These structures are located southeast the Central African Fault Zone (CAFZ) [23]. The occurrence of obsidian bodies in close association with the felsite dykes put doubts about their age, and aged from K-Ar the obsidian 69 ± 2 Ma [18], but it is clear that at least some felsites predate the Nubian Sandstone Formation as they are seen overlain by Nubian Sandstone Formation in Sabaloka. The dominant dyke's trend is those in NNE, ENE, and NE, which are coinciding with some regional trends.…”

Section: Discussionmentioning

confidence: 99%

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Gravity-Based Structural Modelling of Awataib Area, River Nile, State, Central Sudan

Ah¹,

Aag²

2017

J Earth Sci Clim Change

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In this paper the authors are discussing the structural setting of Awataib valley area through Gravity-based variation measurements, which have been obtained by Simple Bouguer Anomaly formula that uses the relative difference in the vertical component of the earth gravitational field between Base station and other observational points. The study objective at using Regional gravity survey is to reveal the subsurface structural geology of Awataib valley and adjacent areas. Land Sat image aided by collected field data were used in this study. Surfer software version 8.02 used to produce contoured-base map of gravity data set. Grav Modeler Program in the Geological Research Authority of Sudan (G. R. A. S.) has been just used to perform 2-D Density-Depth modeling. Free-hand graphical technique has been used to perform geological sections from derived gravity models. The NW-SE lineament has been considered as fault coincides with valley of Awataib, thus faults map has been suggested from the calibration of Bouguer anomaly steep gradients and field observations. Some of the geology faults are considered to be a rejuvenation of pre-Nubian fractures; so far, this study suggests an extension of Umm Marahik strike slip fault with general trend of NE-SW ending at Awataib valley. The depth of sediments less than 450 meters and the average effective thickness is about 275 meters which's making up basinal features that probably considered as water-bearing formations ready to be drilled.

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Section: Discussionmentioning

confidence: 61%

Section: Discussionmentioning

confidence: 99%

Gravity-Based Structural Modelling of Awataib Area, River Nile, State, Central Sudan

Ah¹,

Aag²

2017

J Earth Sci Clim Change

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“…Such features have been observed in intrusive rocks from other parts of the world where they reflect high level and explosive emplacement processes associated with eruptive activity at surface (Almond 1971). A body of porphyritic quartz microdiorite which is exposed in only a small area south of the summit of Mt.…”

Section: Geological Settingmentioning

confidence: 93%

Geology, alteration and mesothermal Au-Ag-mineralization associated with a volcanic-intrusive complex at Mt. Shamrock-Mt. Ophir, SE Queensland

Williams

1991

Mineral. Deposita

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Abstract. Au-Ag mineralization in the Mt-ShamrockMt. Ophir area of SE Queensland is related to a geographically-isolated calc-alkaline igneous centre consisting of high level plutonic and minor intrusions emplaced into the eroded remains of a silicic volcanic ediface and its basement. Mineralization occurs in both the igneous rocks and in the Permian siltstone country rocks and is controlled by a NE-trending structure parallel to Late Triassic lineaments. This structure is unrelated to, and younger than the exposed intrusions. Au-Ag-As-rich, Cu-Mo-poor mineralization occurs in breccias and veinlet networks within pervasively altered rocks characterized by silicification and H (sericite), CO2 (calcite-ankerite), Na (albite), B (tourmaline), and S (pyrite) metasomatism. Secondary mineral compositions suggest that most of this alteration occurred at temperatures between 350 ~ and 400 ~ The alteration was complex in detail and characterized by multiple hydrothermal events and space and/or time variations of physico-chemical conditions.

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“…For example, dikes feeding lava flows and spatter cones are common in many basaltic settings and, unless they show some particular features, do not normally deserve detailed studies (Atkinson and Lambert 1990;Gudmundsson et al 2008). In contrast, explosive felsic deposits physically connected to their conduits are rather unusual and in a few cases are well described (Almond 1971;Koronovsky 1971;Ekren and The processes of bubble nucleation, vesiculation and deformation have been widely studied in magmas containing small bubbles, and vesicles are also commonly used as magma-flow indicators (Coward 1980;Manga et al 1998;Philpotts and Philpotts 2007;Rust et al 2003). Vesicles and gas bubbles up to decimetre scale are common in volcanic rocks of any composition in the geological record.…”

Section: Introductionmentioning

confidence: 99%

Giant gas bubbles in a rheomorphic vent fill at the Las Cañadas caldera, Tenerife (Canary Islands)

et al. 2009

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During rheomorphism subsequent to fallout deposition, a portion of the densely welded fallout of the La Grieta Member flowed back into the vent from where it was erupted, while the rest of it flowed down the outer slopes of the Las Cañadas caldera in Tenerife. The welded fallout and conduit-vent structure are physically connected and constitute a rare example of this type of deposits rooted to its feeder conduit and exposed in the caldera wall. The lower part of the vent-filling rheomorphic rocks shows gas bubbles and cavities that increase in size (up to 4 m) down vent. Bubbles are deformed against other bubbles, against the steep vent walls, flattened parallel to the flow foliation planes, and elongated parallel to the flow lineation and flow fold axes. The preservation of such giant bubbles, rather than their formation, seems to be a pretty unique feature of the phonolitic products investigated here and it is likely the result of the combination of factors that acted to preserve, in the surrounding of the glass transition interval, the sealing and the late stage cooling of a pressurized system. In addition, strain drop at the base of the vent-filling rheomorphic flow caused by flow stopping against vertical vent walls may have promoted rapid gas exsolution and the formation of large bubbles.

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Ignimbrite vents in the Sabaloka cauldron, Sudan

Cited by 43 publications

References 13 publications

Gravity-Based Structural Modelling of Awataib Area, River Nile, State, Central Sudan

Gravity-Based Structural Modelling of Awataib Area, River Nile, State, Central Sudan

Geology, alteration and mesothermal Au-Ag-mineralization associated with a volcanic-intrusive complex at Mt. Shamrock-Mt. Ophir, SE Queensland

Giant gas bubbles in a rheomorphic vent fill at the Las Cañadas caldera, Tenerife (Canary Islands)

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