Maar-diatreme volcanoes, their formation and relevance
Like caldera volcanoes the smaller maar-diatreme volcanoes have craters cut into the pre-eruptive surface. Today, it is generally assumed that maar-diatreme volcanoes form when magma of any chemistry - rises in a dyke and, near the surface, interacts explosively with groundwater, thus they are considered to form and erupt phreatomagmatically. They seem to form when only relatively little groundwater is available. Thus, as long as magma interacts with groundwater the deeper a cone of depression forms allowing diatreme and maar crater to grow in size and the tephra ring to get thicker. If magma stops rising a lake usually forms within the crater. However, when groundwater is not available any more but magma still rises it intrudes the diatreme and may erupt to form a scoria cone, lava lake, or a dome. For kimberlite and carbonatite diatremes the phreatomagmatic emplacement model is not generally accepted,. Similar to cauldrons underlying calderas, many diatremes contain valuable ore deposits. The most important diatremes are the diamondiferous kimberlite pipes. Other diatremes may contain: Au, Cu, Pb, Zn, Ag, Fe, As, Sb, F, Ba, V, Te, Bi, Hg, U, REE (Google: maar-diatreme ore deposits). Additional relevance exists for: road metal, groundwater, CO2, research for understanding phreatomagmatic processes and maar hazards, and for education and tourism.
https://www.munich-geocenter.org/events/seminars/frontiers-in-earth-sciences-20/maar-diatreme-volcanoes-their-formation-and-relevance
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Maar-diatreme volcanoes, their formation and relevance
Abstract
Like caldera volcanoes the smaller maar-diatreme volcanoes have craters cut into the pre-eruptive surface. Today, it is generally assumed that maar-diatreme volcanoes form when magma of any chemistry - rises in a dyke and, near the surface, interacts explosively with groundwater, thus they are considered to form and erupt phreatomagmatically. They seem to form when only relatively little groundwater is available. Thus, as long as magma interacts with groundwater the deeper a cone of depression forms allowing diatreme and maar crater to grow in size and the tephra ring to get thicker. If magma stops rising a lake usually forms within the crater. However, when groundwater is not available any more but magma still rises it intrudes the diatreme and may erupt to form a scoria cone, lava lake, or a dome. For kimberlite and carbonatite diatremes the phreatomagmatic emplacement model is not generally accepted,. Similar to cauldrons underlying calderas, many diatremes contain valuable ore deposits. The most important diatremes are the diamondiferous kimberlite pipes. Other diatremes may contain: Au, Cu, Pb, Zn, Ag, Fe, As, Sb, F, Ba, V, Te, Bi, Hg, U, REE (Google: maar-diatreme ore deposits). Additional relevance exists for: road metal, groundwater, CO2, research for understanding phreatomagmatic processes and maar hazards, and for education and tourism.
