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Sample: 87-WAD-13

Sample ID: 87-WAD-13 [1]
Station ID: 87-WAD-13
AT Num:
Volcano:
Possible source:
Eruption:
Collector: Duffield, W. A.
Date sampled: 1987-00-00
Sample type 1: Other
Color:
Final unit:
Text Description: Unassigned rocks, older dacite intrusive rocks (Pleistocene). Light-olive-gray to greenish-gray, porphyritic dacitic intrusions and dikes that contain phenocrysts of plagioclase (5-20%, as large as 4 mm), hornblende (1-5%, as long as 2 mm; generally altered to carbonate, chlorite, and actinolite), fresh biotite (trace to 10%, as large as 5 mm), and traces of quartz and opaque minerals, in cryptocrystalline groundmass that is locally flooded by calcite. * * *K-Ar age on biotite from one sample is 1.35+/- 0.05 Ma.
Sample Location:

References Cited

[1] Geologic map of the Gulkana A-1 Quadrangle, south-central Alaska, 1994

Richter, D. H., Duffield, W. A., Sawyer, D. A., Schmoll, H. R., and Ratte, J. C., 1994, Geologic map of the Gulkana A-1 Quadrangle, south-central Alaska: U.S. Geological Survey Geological Quadrangle Map GQ 1728, unpaged, 1 sheet, scale 1:63,360.