Lone basalt


Facts


  • Official Name: Lone Hill
  • Type: vent
  • Seismically Monitored: No
  • Color Code: UNASSIGNED
  • Alert Level: UNASSIGNED
  • Elevation: 105m (344ft)
  • Latitude: 57.63482
  • Longitude: -156.99332
  • Smithsonian VNum:
  • Nearby Towns:
    • Ugashik 17 mi (28 km) SW
    • Pilot Point 22 mi (36 km) SW
    • Kanatak 36 mi (58 km) SE
    • Egegik 43 mi (68 km) NW
    • King Salmon 74 mi (119 km) NE

    Distance from Anchorage: 351 mi (565 km)

Description

From Hildreth and others (2007) [1] : "About 10 km southwest of Blue Mountain, an isolated 0.38-km-square-area exposure of olivine-basaltic lava (50 weight percent SiO2, 7 weight percent MgO) forms a subdued, glacially scoured ridge (Lone basalt) that rises 80 m above the surrounding muskeg. The rock contains 5 to 8 volume percent olivine phenocrysts (0.5-2 mm diam) and sparse oxide microphenocrysts in a holocrystalline groundmass of intergrown plagioclase laths and equant grains of olivine, oxides, and rare clinopyroxene. This subalkaline basalt is similar to, but not quite as primitive as, the basalt of Ukinrek Maars. It differs compositionally, however, from the mafic rocks of nearby Mount Peulik [2] and from those of the other arc-front centers nearby, and is not demonstrably related to Blue Mountain dacite. Nonetheless, the composition of the Lone basalt is not far from that of the mafic enclaves in Blue Mountain dacite, nor from that of the 500-ka subalkaline basaltic cone at Gertrude Creek northeast of Becharof Lake. Wilson and Shew (1992) [3] determined a whole-rock K-Ar age of 593+/-73 ka for the Lone basalt.

Name Origin

Lone Hill was named by the U.S. Geological Survey in 1956 (Orth, 1971).


References Cited

[1] Blue Mountain and The Gas Rocks: rear-arc dome clusters on the Alaska Peninsula, 2007

Hildreth, Wes, Fierstein, Judy, and Calvert, A.T., 2007, Blue Mountain and The Gas Rocks; rear-arc dome clusters on the Alaska Peninsula: in Haeussler, P.J., and Galloway, J.P., eds., Studies by the U.S. Geological Survey in Alaska, U.S. Geological Survey Professional Paper 1739-A, 27 p., available at http://pubs.usgs.gov/pp/pp1739/a/ .

[2] Geology of the Ugashik-Mount Peulik volcanic center, Alaska, 2004

Miller, T. P., 2004, Geology of the Ugashik-Mount Peulik volcanic center, Alaska: U.S. Geological Survey Open-File Report 2004-1009, 19 p., 2 sheets, scale 1:63,360.
full-text PDF 1.7 MB
plate 1 PDF 660 KB
plate 2 PDF 142 KB

[3] Map and tables showing geochronology and whole-rock geochemistry of selected samples, Ugashik and part of Karluk quadrangles, Alaska, 1992

Wilson, F.H., and Shew, Nora, 1992, Map and tables showing geochronology and whole-rock geochemistry of selected samples, Ugashik and part of Karluk quadrangles, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1539-E, 34 p., 2 sheets, scale 1:250,000.

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