| Tahalra volcanic field | |
|---|---|
  Tahalra volcanic field | |
| Highest point | |
| Elevation | 1,467 m (4,813 ft) [1] |
| Coordinates | 22°40′N5°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.
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]
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]
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]