Unnamed Occurrences (ARDF - PE111; on Nelson Glacier), Petersburg Mining District, Wrangell City and Bourough, Alaska, USAi

Regional Level Types
Unnamed Occurrences (ARDF - PE111; on Nelson Glacier)	- not defined -
Petersburg Mining District	Mining District
Wrangell City and Bourough	Borough
Alaska	State
USA	Country

Location: These occurrences are in an area that covers most of the center and upper portions of the Nelson Glacier. Much of the glacier was covered by claims from 1964 to 1981, when there was considerable exploration to the west from Marsha Peak to Groundhog Basin. At least one occurrence is on a small nunatak on the glacier, and there is a deep hole in the upper basin of the glacier that went through 621 feet of ice before it struck rock and cut a thin intercept of mineralization (see the Geologic Description for details) This area is essentially Map no. 105 of Still and others (2002) and the coordinates are at about its center.
Geology: From about 1964 to 1981 when there was considerable exploration across a wide swatch from from Glacier Basin to Groundhog Basin, a succession of companies considered the potential of the ground under Nelson Glacier. Much if not all of the Glacier were first staked in 1964 and first optioned to Bunker Hill Mining Company. The claims were subsequently optioned to Humble Oil and Refining Company from 1968 to 1970 and they drilled two holes through the ice in the upper part of the glacier. El Paso optioned the claims from 1971 to 1973 and AMAX Exploration Inc. optioned the claims from 1976 to 1981. Still and others (2002) did some limited sampling on or adjacent to the glacier. In 2002. there were no active claims on the glacier. The rocks west of and under the center of the Nelson Glacier and from Glacier Basin, through Marsha Peak, and along Groundhog Basin consists mainly of Tertiary biotite and hornblende schist and gneiss with local marble interbeds, an assemblage that has been metamorphosed from Mesozoic and/or Paleozoic sedimentary and volcanic protoliths (Gault and others, 1952; George and Wyckoff, 1973; Gehrels and Berg, 1992, Brew, 1997) . The metamorphic rocks are intruded by a small 16.3 Ma stock of tin granite just north of Groundhog Basin that probably is the source of numerous rhyolite dikes and sills that cut the metamorphic rocks around Nelson Glacier as well as the source for the mineralization in the Groundhog Basin area. West of Groundhog Basin, the metamorphic rocks are intruded by several large plutons of Cretaceous tonalite, quartz diorite, and granodiorite. At the east side of the Nelson Glacier, the rocks are dominated by a thick 70-90 Ma Tertiary tonalite sill that forms the west boundary of the Coast Range igneous-metamorphic complex that extends the length of southeastern Alaska. The Tertiary metamorphic rocks and rhyolite in particular probably underlie most of the Nelson Glacier. Many of the other prospects and occurrences along the ridges between Glacier Basin and Groundhog Basin either border Nelson Glacier or may extend beneath it ; there has been considerable speculation about mineralization under Nelson Glacier and some effort to locate it. Humble drilled two 1,700-foot, vertical holes through the ice (Humble Oil and Refining Company, 1970a and 1970b). One (H1), about 0.6 mile north-northeast of Marsha Peak, went through 491 feet of ice into gneiss but did not intersect mineralization. The other (H2), went through 621 feet of ice into gneiss; the best intercept in it was 10 feet that averaged 0.5 ounce of silver per ton, 0.4 percent lead, and 1.7 percent zinc. El Paso National Gas (Quigley, 1973) flew an aerial magnetometer survey over the area and traced several faults zones under the glacier. Still and others (2002) found float at several areas on the glacier, most notably on a nunatak about 1.1 mile east-southeast of Marsha Peak. Samples contained up to 8.43 ounces of silver per ton, 1.5 percent copper, 8.21 percent lead, 25.95 percent zinc, and 904 parts per million tin.
Workings: From about 1964 to 1981, when there was considerable exploration across a wide swatch from from Glacier Basin to Groundhog Basin, a succession of companies considered the potential of the ground under Nelson Glacier. Much if not all of Nelson Glacier was first staked in 1964 and first optioned to Bunker Hill Mining Company. The claims were subsequently optioned to Humble Oil and Refining Company from 1968 to 1970 and they drilled two holes through the ice in the upper part of the glacier. El Paso optioned the claims from 1971 to 1973 and AMAX Exploration Inc. optioned the claims from 1976 to 1981. Still and others (2002) did some limited sampling on or adjacent to the glacier.
Age: Probably related to a 16.9 Ma tin granite pluton near Groundhog Basin and the numerous rhyolite dikes and sills that intrude the metamorphic rocks in the area.
Reserves: None.

Commodities (Major) - Ag, Cu, Pb, Sn, Zn
Development Status: None
Deposit Model: Banded Ag-Cu-Sn-Pb-Zn tabular replacement bodies, veins, and stringers.

Other Databases

Link to USGS - Alaska:	PE111

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References