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Sample Y-Tsp
NavDat sample number 2911 · TUFF
Sample
| Sample ID | Y-Tsp |
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| Rock name | TUFF |
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| Rock type | VOLCANIC |
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| Composition | FELSIC |
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| Material | IGNEOUS |
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| Collected by | Charles J. Vitaliano |
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| Comment | Actually a welded ash flow tuff, not a rhyolite flow forming vertical cliffs 10 to 12 ft high, particularly where overlain by the resistant Malpais Basalt. It is a brown to gray-brown porphyroclastic rock, with quartz and feldspar grains up to 2 mm long in an aphanitic matrix. Fragments of volcanic rock up to 1.25 cm square are scattered sparsely throughout, along with lenticular streaks of gray devitrified pumice and dark brown glassy fiamme. Parallelism of the pumice and fiamme gives the rock a streaky appearance which is further enhanced by flattened vesicles up to 5 cm long. In thin section, fragmented quartz and sanidine constitute up to 95% of the crystals, clinopyroxene the remainder. The matrix consists predominantly of flattened glass shards with a few grains of accessory apatite and magnetite. Eutaxitic texture is common throughout the rock. See Y-58N264. |
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Location
| Latitude | 37.6944 |
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| Longitude | -117.239 |
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| Location | Esmeralda County, NV |
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| State / province | Nevada |
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| Volcanic field | Goldfield-Tonopah region, West-Central Nevada |
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| Location comment | Spearhead Rhyolite, from type locality; quarry near Rabbit Spring at the foot of Malpais Mesa, just S of Spearhead Point |
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Age
| Age (Ma) | Error | Min | Max | Geologic age | Dated by |
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| 6.9 |
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6.8 |
7 |
|
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Analyses
No chemical analyses are stored for this sample.
