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T. D. Hessin

Publications and source records attributed to T. D. Hessin.

13 recordsLinked to original sources
USGS1983

Origin of concretionary Mn-Fe-oxides in stream sediments of Maine, U.S.A.

Studies of stream and sediment-pore waters largely explain the genesis of concretionary Mn-Fe-oxides in Maine. Waters of two small streams near Jackman, Maine, were studied in terms of pH, Eh, dissolved oxygen, dissolved organic carbon, dissolved Mn, total dissolved Fe, and ferrous and ferric Fe. Pyrite Creek has profuse concretions and coatings of Mn-Fe-oxides, whereas West Pyrite Creek has only sparse Mn-Fe-oxide stains. Pyrite Creek drains boggy terrain and West Pyrite Creek drains well-drained terrain. In West Pyrite Creek, stream and subjacent pore waters have chemical characteristics that do not differ greatly. However, dissolved Mn, ferrous Fe, dissolved oxygen, and in situ Eh measurements show that a steep Eh gradient exists between stream and subjacent pore waters of Pyrite Creek. The steep Eh gradient is manifested by the common zonation of coatings and stains on rocks in stream sediment. The bottom zone has no deposition of oxides, the middle zone is red and consists mostly of Fe-oxides, and the upper zone is black or dark-brown and consists of Mn-oxides with varying amounts of Fe-oxides. The zonation agrees with theoretical predictions of oxide stability as one moves from a reducing to an oxidizing environment. At locations where concretionary Mn-Fe-oxides form, pore waters are depleted of oxygen because of abundant decaying organic material in the stream sediment. The pore waters are charged with dissolved Mn and Fe because mechanically deposited Mn-Fe-oxides are remobilized due to the low-Eh conditions. Groundwaters also contribute dissolved Mn and Fe. Stream waters, on the other hand, are oxygenated and the high-Eh conditions result in low concentrations of dissolved Mn and Fe in stream waters because of the insolubility of Mn-Fe-oxides in high-Eh environments. Therefore, concretionary Mn-Fe-oxides form at the interface between pore and stream waters because Mn- and Fe-rich pore waters, which are undersaturated with respect to Mn-Fe-oxides, mix with oxygen-rich stream waters, which are saturated with respect to Mn-Fe-oxides. ?? 1983.

Chemical Geology↗
USGS1979

The Alaskan Mineral Resource Assessment Program: Background information to accompany folio of geologic and mineral resource maps of the Big Delta quadrangle, Alaska

The geology, geochemistry, geophysics, and Landsat imagery of the Big Delta quadrangle, 16,335 km 2 in the Yukon-Tanana Upland of east-central Alaska, were investigated, and maps and reports were prepared by an interdisciplinary research team for the purpose of assessing the mineral potential. The quadrangle is dominantly a complex terrane of greenschist- to amphibolitefacies metamorphic rocks that have been intruded by Mesozoic and Tertiary dioritic to granitic rocks and are overlain by Tertiary sedimentary and volcanic rocks. Serpentinized peridotite and associated greenstone, graywacke, and chert crop out in some places. The quadrangle is bisected by the northeastward-trending Shaw Creek fault, which, on the basis of aeromagnetic interpretation and geologic data, is postulated to have left-lateral offset of as much as 48 km. On the northwest side of the Shaw Creek fault, metamorphic rock units have a northwesterly regional trend, and the oldest rocks could be Precambrian in age. Gneiss and schist in the southwestern part of the quadrangle are derived from both igneous and sedimentary protoliths, some of which may be as old as Precambrian. Other rock units, which include calcareous schist and thin-layered marble, black quartzite, semischist, and cataclastic rocks, are considered to be of probable Paleozoic age, although no fossils have yet been found in these rocks. Radiolarians and conodonts in chert associated with greenstone and ultramafic rocks indicate that the chert is of Permian age. Potassium-argon ages on igneous rocks of the Big Delta quadrangle fall into two groups: those with biotite, muscovite, hornblende, and sanidine ages between 50 to 69 m.y.; and those with biotite, hornblende, and sanidine ages between 88 to 105 m.y. The younger of these two groups appears to indicate the time of a plutonic event marked by intrusion of mostly small, isolated plutons, including hypabyssal stocks, and the eruption of silicic volcanic rocks. Most of the plutons are quartz monzonite to granite. The older group of ages (88 to 105 m.y.) on igneous rocks includes ages on the largest plutons of the Yukono-Tanana Upland. The rocks range from diorite to quartz monzonite in composition. The potassium-argon ages on the metamorphic rocks of the Big Delta quadrangle, like those obtained elsewhere in the Yukon-Tanana Upland, appear to have been partly or completely reset by subsequent thermal events. Vein and placer gold deposits have been mined in the Big Delta quadrangle, and although indications of mineralization are widespread, no other mineral deposits have yet been identified. The geologic, geochemical, and geophysical data are compatible with several types of deposits, including porphyry copper, massive sulfide, and skarn deposits. In certain aspects, the geology of the quadrangle is similar to areas in the eastern part of the Yukon-Tanana Upland and Canada where mineral deposits are known.

Alaska↗