Teuchet Creek; TC Prospect, Fairbanks Mining District, Fairbanks North Star Borough, Alaska, USAi

Regional Level Types
Teuchet Creek; TC Prospect	Prospect
Fairbanks Mining District	Mining District
Fairbanks North Star Borough	Borough
Alaska	State
USA	Country

Location: The TC prospect is situated in the headwaters of Teuchet Creek. Teuchet Creek drains north into the East Fork of the Chena River. The TC prospect covers approximately 3 square miles. The approximate location of center of the prospect is in NW1/4SW1/4 section 15., T. 1 N., R. 11 E., of the Fairbanks Meridian. It was not identified as a separate location by Cobb (1972; MF-388) or by Cobb and Eberlein (1980).
Geology: The prospect is in the Chena Slate Belt, originally delineated by Menzie and Foster (1979), and later defined by Dusel-Bacon and others (1998). They describe the region as thrust sheets of ductilely deformed, metasedimentary and metaigneous rocks of uncertain age and origin that are overlain by klippen of weakly metamorphosed oceanic rocks, and intruded by post-kinematic, Lower Jurassic, Cretaceous, and Tertiary granite. Based on stratigraphic similarities and limited fossil ages and a U-Pb zircon age of 356 Ma, Mortenson (1992) interpreted that the rocks are similar to metamorphosed rocks in the eastern Alaska Range, western and southeastern Yukon (Dusel-Bacon and others, 1998), and unmetamorphosed rocks of the Selwyn Basin (Murphy and Abbott, 1995). The Chena Slate Belt is composed of siliceous and carbonaceous black quartzite, slate, and phyllite. At the Teuchet Prospect, drilling encountered 30 meters of tan sericitic phyllite underlain by at least 550 meters of interlayered gray to black siliceous phyllite and quartzite. Mineralization of the prospect consists of layered zones parallel to foliation that contain a variable combination of sulfides, including boulangerite, galena, pyrite, and sphalerite, along with minor arsenopyrite, chalcopyrite, and pyrrhotite. The best mineralization is 4.6 meters thick and contains 0.92% Zn and 0.32% Pb; and 12 centimeters thick containing 10.1% Zn, 3.6% Pb, and 38 ppm Ag. Massive sulfide layers of up to 52 centimeters thick with bands of red-brown sphalerite, galena, and pyrite up to 12 centimeters thick. Pyrite occurs as subhedral cubes and porphyroblasts. Sphalerite occurs as anhedral lenses with a composition of approximately 84% ZnS. Galena is interstitial to pyrite and sphalerite. Boulangerite and selenium-rich galena were found with galena in one interval of drill core (Dusel-Bacon and others, 1998). The original sedimentary features in the carbonaceous rocks have been eliminated by ductile shearing, folding, and low- to medium-grade metamorphism. Early, near-vertical, quartz veining is cut by low angle shears, which commonly contain pyrite. Deformation of the sulfides indicates that mineralization of the TC Prospect predates regional metamorphism. Pyrite deposition occurred both before and after quartz veining and shearing events (Dusel-Bacon and others, 1998). Isotopic Pb data from galena collected from the Chena Slate Belt indicates a mineralization age of Devono-Mississippian. In addition, a 346.4 +/-1 Ma U-Pb zircon age was obtained from interlayered felsic tuffs from the eastern section of the Chena Slate Belt. These dates and the presence of sulfide deposition textures parallel to metamorphic foliation and compositional layering indicate a syngenetic origin for the sulfides (Dusel-Bacon and others, 1998). Exploration of the Chena Slate Belt was conducted intermittently from 1981 through 1994. A preliminary stream-sediment sampling program defined a 30-kilometer belt of anomalous Zn. In 1991, further soil and rock geochemistry, gravity surveys, and airborne and horizontal-loop EM surveys delineated three Zn-Pb zones at the TC Prospect. Subsequently, eight drill holes totaling 1,600 meters were completed (Dusel-Bacon and others, 1998). There is no production reported for the TC Prospect.
Workings: Exploration of the Chena Slate Belt was conducted intermittently from 1981 through 1994. A preliminary stream-sediment sampling program located a 30-kilometer belt of anomalous Zn. In 1991, further soil and rock geochemistry, gravity surveys, and airborne and horizontal-loop EM surveys delineated three Zn-Pb zones at the TC Prospect. Subsequently, eight drill holes totaling 1,600 meters were completed (Dusel-Bacon and others, 1998).
Age: Probably Devonian to Mississippian (?). Younger than U-Pb age of 356 Ma.
Production: There is no production reported for the TC Prospect.

Commodities (Major) - Pb, Zn; (Minor) - Ag, As, Cu, Sb
Development Status: None
Deposit Model: Sedimentary exhalative Zn-Pb? (Cox and Singer, 1986; model 31a). Volcanogenic m

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Link to USGS - Alaska:	BD050

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References