Occurrence, Probably inactive

Commodities and mineralogy

Main commodities Ag; Pb; Zn
Other commodities Cu
Ore minerals chalcopyrite; galena; pyrite; pyrrhotite; sphalerite
Gangue minerals calcite; chlorite; quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale B-1
Latitude 63.2587
Longitude -144.2487
Nearby scientific data Find additional scientific data near this location
Location and accuracy The DDX prospect is at an elevation of about 5,200 feet and is a mile southeast of peak 7440. It is in the NW1/4 section 15, T. 17 N., R. 6 E., Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

The DDX zone of massive sulfides crops out in a creek; one layer of mineralization 10 to 20 inches thick is exposed, as are several thinner bands 1 to 2 inches thick. The thicker layer is a banded massive sulfide dominated by pyrite; it has more chalcopyrite at its base and more sphalerite and galena at its top. The mineralization occurs within a 15-foot-thick black carbonaceous phyllite enclosed by felsic metavolcanic schist. The massive sulfide is exposed for about 30 feet before it lenses out or is covered by talus (R.A. Blakestad and others, unpublished Resource Associates of Alaska, Inc. report, 1978). Samples from the DDX exposure average 0.5 percent copper, 3.3 percent lead, 5.5 percent zinc, 54 parts per million (ppm) silver, and 0.1 ppm gold (Dashevsky and others, 2003).
The DDX occurrence occupies the same mineralized unit or layer as the DD North prospect (MH319); it is along the upper contact of the Drum felsic unit and beneath the Tok River sequence. The Tok River unit is a thick assemblage of metasedimentary rocks that consist of chloritic phyllites, quartz-sericite (-chlorite) schist, phyllitic quartz-eye metagrits, carbonaceous phyllite, and minor marble. Some of the metagrits contain feldspathic detritus and are locally calcareous. The protolith of the Tok River unit is about three-quarters sedimentary and one-quarter volcanic. It has minor interbeds of felsic volcanic rocks similar to the rhyolite and rhyodacite of the Drum unit (Dashevsky and others, 2003).
Geologic map unit (-144.250948237187, 63.2583222094172)
Mineral deposit model Kuroko massive sulfide (Cox and Singer, 1986; model 28a).
Mineral deposit model number 28a
Age of mineralization The associated Drum stratigraphic unit has been dated at the Devonian-Mississippian boundary on the basis of one SHRIMP U-Pb zircon age of 359+/- 6 Ma determined at the DD South deposit (MH325) (Dashevsky and others, 2003).
Alteration of deposit Weak disseminated pyrite +/- quartz.

Production and reserves

Workings or exploration The DDX occurrence has been explored by surface mapping, sampling, and airborne and ground geophysics as part of the broader exploration of the DD North (MH319) and DD South (MH325) prospects.
Indication of production None

Additional comments

Unpublished data cited is available for viewing by contacting Grayd Resources Inc. in Vancouver, B. C., Canada (www.grayd.com), or Northern Associates Inc. in Fairbanks, Alaska.