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Sample 3
NavDat sample number 4365 · TUFF
Sample
| Sample ID | 3 |
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| Alternate ID | 774F |
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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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| Comment | Intracauldron tuff, possibly the same cooling unit as that which directly underlies vent tuff outside of the cauldron. Tuff that appears to lap onto cauldron wall is composed of pre-Tertiary sedimentary rocks. Outcrop sampled is about 2.4 km north of fissure vent and about 100 m above base of cooling unit. Lithic-rich altered former glassy tuff; 20 percent phenocrysts comprising the following percentages of minerals: quartz, 25; alkali feldspar, 38; plagioclase, 31; biotite, 1; altered mafic minerals, 4. Plagioclase is altered to nearly opaque clay and alkali feldspar. |
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Location
| Latitude | 38.916 |
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| Longitude | -118.183 |
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| Location | Gabbs Valley, northeastern Mineral County, NV |
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| State / province | Nevada |
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Age
| Age (Ma) | Error | Min | Max | Geologic age | Dated by |
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| 25 |
|
22.5 |
27.5 |
|
|
Analyses
Whole rock
| Item | Value | Std. dev. | Unit | Method |
|---|
| SIO2 | 76.82 | | WT% | XRF |
| AL2O3 | 13.5 | | WT% | XRF |
| FEO | 1.31 | | WT% | XRF |
| MGO | 0.3 | | WT% | AAS |
| CAO | 1.12 | | WT% | AAS |
| NA2O | 1.82 | | WT% | AAS |
| K2O | 4.96 | | WT% | AAS |
| TIO2 | 0.16 | | WT% | XRF |
| MNO | 0.02 | | WT% | XRF |
