... of the plain.) (D) Vitric lapilli of various sizes in the less-welded central lapilli-tuff of the McMullen Creek Member. ...

... contains sev- eral welded flows, 2.2-70 m in thickness, with well- defined erosional bases (Figs 2 & 3). Between Dinas and Newport (Area 4, Fig. 7), slight to moderately- welded vitric tuffs/lapilli-tuffs occur as beds which vary from < 1 to 5 m and are well exposed as prominent crags at Carn Fron, Carn...

...HANS-ULRICH SCHMINCKE Abstract The Pomona Basalt, an extensive tholeiitic lava flow of the Columbia River Basalt, overlies an airfall vitric tuff in south-central Washington. In many places, this tuff was welded at the contact from the heat and pressure of the overlying basalt. Textures...

... of the Cretaceous are the oil migration pathways. Vitric and crystal-vitric tuffs constitute the main rock types of the tuffaceous tight reservoir. Matrix-related pores in the tuffs mainly comprise interparticle pores between minerals and dissolution intraparticle pores formed by devitrification. The adsorption...

..., boundaries between clasts are marked by sharp changes in dip and dip azimuth of the welding fabric. Elsewhere, breccias are matrix-supported, with well-developed eutaxitic lapilli-tuff blocks set in a matrix similar in lithology but without strong welding fabrics. These fused breccias were probably formed...

.... (A) Photomicrograph of eutaxitic (S 0 ) welded tuff of zone A, showing flattened bubble-wall ash shards. (B) Fiamme in vitric zone A. (C) δ-object (rotated plagioclase crystal) in zone B indicates dextral shear. (D) Plunging, surfboard-shaped vesicles (elongation lineation L 1 ) in zone B (loose block...

... tuff units contain zeolite (heulandite–clinoptilolite) minerals in most occurrences. Vitric tuffs of rhyolitic and rhyodacitic composition are massive and beige, white, yellowish beige and greenish in colour. The phenocrysts are of quartz, alkali feldspar (sanidine), plagioclase (albite–oligoclase...

... to an anticline to the west and that the overall facing direction of the unit is to the east. The Powderhouse formation consists of massive crystal tuff, crystal–vitric tuff, and lapilli tuff that are intercalated with coarse heterolithic breccia. It ranges in thickness, from ∼40 to 320 m ( Fig. 6...

...) were also found in some altered tuffs and clay-marl layers as accessory minerals. The zeolite and other authigenic minerals showed weak stratigraphic zonation. Some vitric tuff layers contained no zeolite minerals and others were found to consist of almost pure Hul/Cpt and chabazite layers...

... low dilution Li-tetraborate fused bead . Advances in X-ray Analysis , 41 , 843 – 867 . Korringa , M.K. ( 1973 ) Linear vent area of the Soldier Meadow Tuff, an ash-flow sheet in northwestern Nevada . Geological Society of America Bulletin , 84 , 3849 – 3866 . Korringa , M.K...

... crystal-vitric Plinian fallout ash) and eutaxitic ignimbrites formed from pyroclastic density currents; one tuff contains extraordinary numbers of lithophysae. Ridges of rhyolitic tuff breccias with pervasive secondary silicification and ferruginization represent pyroclastic eruptive fissures. The area...

...Liberto De Pablo Galan; Mercedes Doval; Angel La Iglesia; Jesus Soriano; Lourdes Chavez Abstract Cristobalite-tridymite blade nanocrystals cemented by SiO 2 -glass and tridymite nanocrystals fill separately SiO 2 -glass spherules released by explosive volcanism, in rhyolitic tuffs from the Province...

... London 1979 136 627 62 Richardson J. L. Zinderen Barker Sr. Van E. M. Palaeolimnological records from rift valley lakes in Central Africa Palaeoecology of Africa, the Surrounding Islands and Antarctica 1972 6 Cape Town Balkema 131 6 Schmincke H. U. Fused tuff...

... of vitric (glassy) shards, crystal and lithic particles, and rarer coarse grained (sand to gravel grade) pumice. Tuffs ( sensu strictu ) are primary pyroclastic fall deposits, often preserved in volcanic settings as the earliest event in an eruption sequence, although ash can also be dispersed over...

... and few Pl, Bt) + volcanic ash 25° 41′ 31.91″ N; 118° 9′ 17.35″ E 001-09 Grey-green Rhyolitic crystal-vitric tuff Crystal (30 % Qz and few Pl) + vitric pyroclasts (5 %) + volcanic ash ZK001 372–205 m 001-08 Grey-green Rhyolitic crystal tuff Crystal (20 % Qz and few Pl) + volcanic ash ZK001...

... of Stoer village, 8 km NW of Lochinver ( Fig. 1a ). It has been described variously as a lahar ( Lawson 1972 ), a peperite ( Sanders & Johnston 1989 ), a vitric tuff ( Stewart 1990 ) and a volcanic debris flow ( Young 2002 ). Its distinctive appearance in the field has made it a useful correlating...

... deposited in a lacustrine environment, altered to clinoptilolite-rich tuffs and cross-cut by several transform faults along which hydrothermal fluids circulated. Petrography and quantitative phase analysis by X-ray diffraction show that the Karacaderbent tuff consists mainly of the diagenetic products...

... metamorphism of silicic vitric tuffs which altered first to analcite-rich tuffs, then to albite-rich tuffs. A serendipitous discovery by ASR of a ‘brown bed’ (sample GH/RB/112) with a grey core in the Birnam Grit Formation (Dalradian Supergroup), Glen Shee, Methven, Perthshire, [NN 9755 3495] led...

... technique mainly on single crystals of alkali feldspar separated from pumice clasts collected from tuffs in the Omo Group. However, where crystals were small (<0.5 mm), multiple crystals (2–6) were fused in a single analysis to have sufficient gas for precise measurement. Where glass from pumice clasts...