|Quadrangle map, 1:250,000-scale||BD|
|Quadrangle map, 1:63,360-scale||D-4|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The Drone Creek, or DC, Prospect is situated on a north-facing slope to Munson Creek, about 2 miles south of the junction of Munson Creek and Wheeler Creek (BD047). The exact location and extent of the Drone Creek prospect is not well defined. The approximate location of the center of the prospect is in section 4., T. 1 S., R. 6 E., of the Fairbanks Meridian. It was not identified as a separate location by Cobb (1972; MF-388) or by Cobb and Eberlein (1980).|
The prospect is part of 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 ductilly 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 Drone Creek Prospect, drilling encountered 45 meters of sulfide-bearing zones. Mineralization of the prospect consists of layered zones parallel to foliation that contain a variable combination of sulfides, including boulangerite, galena, pyrite, and sphalerite, with minor arsenopyrite, chalcopyrite, and pyrrhotite. The best intervals include: 1) 17 meters of black, carbonaceous slate with laminae containing 5 percent to 7 percent sphalerite, galena, pyrite, and pyrrhotite; and 2) a sphalerite-rich zone, 1.2 meters thick containing 1.88 percent Zn, 820 ppm Pb, and 4.4 ppm Ag. Pyrite occurs as subhedral cubes and porphyroblasts. Sphalerite, with an 84 percent ZnS composition, occurs as anhedral lenses. Galena is interstitial to pyrite and sphalerite (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 indicated that mineralization of the DC Prospect predates regional metamorphism. Pyrite deposition occurred both before and after quartz veining and shearing (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 a Zn-Pb zone at the DC Prospect. Subsequently, the prospect was drilled (Dusel-Bacon and others, 1998). There is no production reported for the DC Prospect.
|Geologic map unit||(-145.952415743102, 64.8596021262924)|
|Mineral deposit model||Sedimentary exhalative Zn-Pb? (Cox and Singer, 1986; model 31a)? Volcanogenic massive sulfide deposit? (Cox and Singer, 1986; model 28a), similar to Selwyn Basin deposits in Yukon, Canada (Murphy and Abbott, 1995).|
|Mineral deposit model number||31a? or 28a?|
|Age of mineralization||Probably Devonian to Mississippian (?). Younger than U-Pb age of 356 Ma.|
|Workings or exploration||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 a Zn-Pb zone at the DC Prospect. Subsequently, the prospect was drilled (Dusel-Bacon and others, 1998).|
|Indication of production||None|
|Production notes||There is no production reported for the DC Prospect.|
Dusel-Bacon, Cynthia, Bressler, J.R., Takoaka, H., Mortenson, J.K., Oliver, D.H., Leventhal, J.S., Newberry, R.J., and Bundtzen, T.K., 1998, Stratiform zinc-lead mineralization in Nasina assemblage rocks of the Yukon-Tanana Upland in east-central Alaska: U.S. Geological Survey Open-File Report 98-340, 26 p.
Murphy, D.C., and Abbott, G., 1995, Northern Yukon-Tanana terrane: The equivalent of Yukon's western Selwyn Basin offset along the Tintina fault? [abs.]: Geological Society of America, Abstracts with Programs, v. 27, no. 5, p. 66.
|Reporters||Cameron S. Rombach (ADDGS)|
|Last report date||4/26/1999|