| Abstrakt: |
A reconnaissance investigation in the Bering Strait shows that a series of marine processes transport offshore sediment northward and northeast of Cape Prince of Wales, which forms the eastern Bering Strait headland. As a result, marine sands are hydraulically sorted, with the heavy mineral fraction becoming concentrated within and just north of the high-energy strait while lighter fractions are winnowed and transported farther north-northeast. Upon exiting the Bering Strait, fine-sized sorted sand is transported by diverging currents to form the 35-km-long Prince of Wales Shoal and northeast to form barrier islands along more than 100 km of coastline. A succession of present and past sediment-accumulation processes in the northern Bering Sea and continuing marine sediment transport, climatic, littoral, and eolian processes are present. Heavy mineral concentrations in excess of eight percent by weight occur over several km2 immediately northeast of the strait in the area bounded to either side by the diverging currents. Neither the northern extent nor thickness of the heavy mineral concentration have yet been determined. Data from shallow seafloor cores show that the shoal, as well as sediment delivered eastward to the beach, are depleted in the heavy mineral fraction. Sediment delivered onshore continues to be driven by littoral and eolian processes, particularly by dune progressions, forming the extensive Shishmaref spit and barrier islands along the northwest Seward Peninsula coast. The minerals of potential economic interest include titanium as ilmenite, anatase, rutile, and titanite; lesser rare-earth minerals monazite and xenotime, plus zircon, and trace to accessory columbite, wolframite, and cassiterite. Trace to anomalous levels of gold and platinum metals are also found in assays of the heavy mineral splits of seafloor samples. The heavy minerals are mostly derived from sediments reworked during multiple late Quaternary to Holocene transgressions of the Bering Land Bridge (Beringia). These glacial and paleofluvial sediments originated in the expansive and highly mineralized metallogenic provenances of the eastern Chukotka (Russia) Peninsula and the Seward (Alaska) Peninsula, as well as erosion of several drowned bedrock terranes. Closer to the Bering Strait, sediment is derived from the well-known western Seward Peninsula tin district where cassiterite has been historically mined from both placer and lode deposits. [ABSTRACT FROM AUTHOR] |
