| Tahalra volcanic field | |
|---|---|
  Tahalra volcanic field | |
| Highest point | |
| Elevation | 1,467 m (4,813 ft) [1] |
| Coordinates | 22°40′N 5°00′E / 22.67°N 5°E [1] |
Tahalra volcanic field is a volcanic field in Algeria. It consists of a Miocene lava plateau and a number of Pliocene to Holocene age individual vents, including cinder cones.
Geography and geomorphology
Tamanrasset lies east-northeast from the field. Cinder cones, lava domes, lava flows and maars form the field, which covers a surface of 1,800 square kilometres (690 sq mi) [1] elongated west to east. [2] There are about 132 individual vents [1] in the area measuring 30 by 80 kilometres (19 mi × 50 mi). [3]
Geology
Tahalra is part of a province of volcanic fields in the Hoggar, which has been active since the Mesozoic. [3] Seismic tomography has shown the existence of low-velocity mantle beneath the Tahalra and Atakor volcanic fields, sign of the presence of recent volcanism. [4]
The basement beneath the field consists of rocks of Precambrian age, mostly metamorphic rocks and plutons [1] which are part of a mobile belt at the margin of the West African Craton. Parts of the basement are covered with Paleozoic rocks. [3]
The field has erupted basalt, basanite, rhyolite and trachyte. [1] They contain amphibole, clinopyroxene, magnetite and olivine phenocrysts. [3] Patterns in trace element composition and isotope ratios imply that the magmas either developed from variable starting material or from metasomatized mantle. [5]
Eruptive history
Volcanic activity started in the Miocene and led to the development of a lava plateau up to 100 metres (330 ft) thick. [3] Eruptions continued in the Pliocene and the Pleistocene, [1] forming many individual vents. [3] Maars and cones in the northern part of the field are of Pleistocene and Holocene age ( Paleolithic to Neolithic [3]). [1]
References
- ^ a b c d e f g h "Tahalra Volcanic Field". Global Volcanism Program. Smithsonian Institution.
- ^ Dautria et al. 1988, p. 19.
- ^ a b c d e f g Dautria et al. 1988, p. 18.
- ^ Ayadi, A; Dorbath, C; Lesquer, A; Bezzeghoud, M (February 2000). "Crustal and upper mantle velocity structure of the Hoggar swell (Central Sahara, Algeria)". Physics of the Earth and Planetary Interiors. 118 (1–2): 120. Bibcode: 2000PEPI..118..111A. doi: 10.1016/S0031-9201(99)00134-X. ISSN 0031-9201.
- ^ Dautria et al. 1988, p. 33.
Sources
- Dautria, J.M.; Dostal, J.; Dupuy, C.; Liotard, J.M. (June 1988). "Geochemistry and petrogenesis of alkali basalts from Tahalra (Hoggar, Northwest Africa)". Chemical Geology. 69 (1–2): 17–35. Bibcode: 1988ChGeo..69...17D. doi: 10.1016/0009-2541(88)90155-6. ISSN 0009-2541.