ash-flow tuff

ash-flow tuff

[′ash‚flō ‚təf]
(petrology)
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1988) Epithermal gold-silver mineralization, wall-rock alteration, and geochemical evolution of hydrothermal fluids in the ash-flow tuff at Round Mountain, Nevada.
These rocks are overlain by Oligocene to Miocene-age rhyolitic ash-flow tuffs.
The site is in the Leslie Gulch Ash-Flow Tuff Member of the Sucker Creek (also Succor Creek) Formation (Kittleman et al.
The Shin Pond volcanic rocks extend into the adjacent Island Falls quadrangle where they are as much as 300 m thick and consist of slaty felsite, coarse-grained calcareous tuffaceous sandstone and ash-flow tuff (Ekren and Frischknecht 1967).
The aerial extent and continuity of highly-anomalous metal values from the Archibarcacat prospect is suggestive of a more extensive mineralized system at depth covered by a single ash-flow tuff.
A Strathcona Minerals 43- 101 report (July 2003) states that " A serpentinized ultramafic sill or flow in the ash-flow tuff traces a fold structure which is cut by a shear zone (Northwest Arm Shear Zone) under the Northwest Arm".
1970, Ash-flow tuffs of Precambrian age in Southeast Missouri, Missouri Division of Geology and Land Survey Report of Investigations 46.
1984, Chemical signatures of hydrothermally altered Precambrian ash-flow tuffs, St.
The area's geology is fairly typical of the northern Sierra Madre Occidental with structurally disrupted andesite volcanics of the Lower Volcanic Complex (LVC) exposed in the more deeply eroded parts of the district and gently tilted tuffaceous rhyolite ash-flow tuffs of the Upper Volcanic Supergroup (UVS) occupying the higher areas.
The mineralized system consists of one major and several minor northwesterly striking, steeply dipping, sulphide-rich silver-lead-zinc-antimony-gold veins that are hosted in dacitic ash-flow tuffs, agglomerates, and lava flows.