Analytical results and sample locality map of stream-sediment and heavy-mineral-concentrate samples from the Healy quadrangle, Alaska

Abstract

We collected samples at 1066 sites (plate 1). At nearly all of those sites, we collected both a stream-sediment sample and a heavy-mineral concentrate. We analyzed 1064 stream-sediment samples and 1045 panned-concentrate samples, for a sampling density of about 1 sample site per 6 mi^ for the stream sediment and heavy-mineral concentrate. The drainage basins sampled ranged from 3 to 6 mi. Stream-sediment samples Analyses of the stream-sediment samples represent the chemistry of the rock material eroded from the drainage basin upstream from each sample site. Such information is useful in identifying those basins which contain concentrations of elements that may be related to mineral deposits. The stream-sediment samples consisted of active alluvium collected primarily from first-order (unbranched) and second-order (below the junction of two first-order) streams as shown on USGS topographic maps (scale = 1:63,360). Where stream sediments were not available due to glacial ice cover in the drainage basin, a glacial-debris sample was collected. The sample consists of detrital material that has been mechanically introduced into a moraine from the bedrock and colluvium. Like the stream sediment, the glacial debris represents the chemistry of the rock material eroded from the drainage basin Glacial-debris samples and heavy-mineral concentrates of glacial-debris samples were collected at the following sites: 143-150, 156-157, 217-233, 488-490, 704-705, and 748-750. Heavy-mineral-concentrate samples We panned heavy-mineral-concentrate samples from the same active alluvium as the stream-sediment samples. Each bulk sample was passed through a 2.0-mm (10-mesh) screen to remove the coarse material. The sediment passing through the screen was panned until most of the quartz, feldspar, organic material, and clay-sized material was removed. The sample was oven dried at 16°C.