|Quadrangle map, 1:250,000-scale||PR|
|Quadrangle map, 1:63,360-scale||D-5|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The Maquis Zone prospect is about 1.8 miles northwest of the north end of Hall Cove on Duke Island. It is at the northeast corner of section 16, T. 80 S., R. 93 E. at an elevation of about 450 feet. The location is accurate.|
The Maquis Zone prospect is on northwestern Duke Island, well known as the type locality of the Alaska-type, Cretaceous zoned ultramafic complex (Irvine, 1974). The ultramafic complex is concentrically zoned outward from a core of dunite and peridotite, succeeded by shells of olivine pyroxenite and hornblende pyroxenite. The complex is distinguished by locally conspicuous graded layering and other cumulate features, especially in the dunite, peridotite, and olivine pyroxenite. It has long been known (Berg and Cobb, 1967) that the dunite contains small lenses and disseminated chromite; the hornblende pyroxenite contained segregations of titaniferous magnetite that have been drilled; and rare specks of pyrrhotite, pyrite, pentlandite, and chalcopyrite occur widely (PR001). However, until recently no deposit of substantial size had been identified on Duke Island.
In 2001 and 2005, Quaterra Resources (2011) drilled 11 holes totaling 5,971 feet in two area: 8 holes in the the Maquis Zone and 3 in the Raven Zone (PE121) on mineralization they consider unlike anything that had previously been identified on Duke Island (Freeman, 2006). They interpret the mineralization as possibly related to the layered mafic complex.
The Maquis Zone mineralization is in a small plug of dunite about a half mile in diameter between hornblende-magnetite pyroxenite and gabbro (Freeman, 2006; Quaterra Resources, Inc., 2011). The best intercept in the 2001 drilling at the Maquis Zone was 99.5 feet that averaged 2,230 parts per million (ppm) copper and 140 parts per billion platinum and palladium, 40 to 608 ppm cobalt, and 102 to 2,730 ppm nickel (Quaterra Resources, 2005). The mineralization consists of disseminated chalcopyrite, pyrrhotite, and pentlandite in serpentinized clinopyroxenite and olivine pyroxenite. Rounded and tear-drop-shaped sulfide blebs suggest sulfide-silicate immiscibility during sulfide deposition. Additional drilling was done on the Maquis Zone in 2005 and also at the Potato Patch area about 1.1 kilometer to the west. The best intercept in the drilling was 149 feet that contained 2,086 ppm copper.
No drilling was done in 2007. However, the data was reviewed and several other areas of interest were identified. In February, 2008, Quaterra had a 388-line-mile airborne geophysical survey flown over the area. Quaterra's work suggest that the mineralization extends for 14.5 kilometers along strike and is 3.8 kilometers wide.In 2010, Quaterra optioned the property to Copper Ridge Explorations Inc. (2010 [News, June 16]) and they drilled five holes that totaled 1,537 meters (Copper Ridge Explorations Inc., 2010 [News, Sept. 10]). The drilling was designed to test mineralization along the basal contact of the mafic-ultramafic complex or within the feeder of the Maquis zone. The drill targets were based on geologic mapping, historical drilling, and three-dimensional modeling from several geophysical surveys. No significant mineralization was intersected in 4 of the holes. However one hole intersected 4.9 meters with 0.294 percent copper and 0.075 percent nickel, and 13.4 meters with 0.148 percent copper and 0.039 percent nickel. That hole collared in pyroxenite and was in gabbro for about 48 meters at the bottom of the hole. The gabbro contained 1-15 percent pyrrhotite and masses of graphitic country rock. The drilling indicated that the zoning within the complex is more complicated than was expected and what had been thought to be the basal contact of the complex from geophysical interpretations was in fact a contact with disseminated sulfides and sedimentary rocks with a high graphite content.
|Geologic map unit||(-131.397775258601, 54.9393644100465)|
|Mineral deposit model||Disseminated copper, nickel, and platinum-group elements in a layered mafic complex.|
|Age of mineralization||The Duke Island complex is about 110 Ma; this mineralization is probably genetically related to it.|
|Alteration of deposit||The host rocks are serpentinized.|
|Workings or exploration||In 2001 and 2005, Quaterra Resources (2011) drilled 11 holes totaling 5,971 feet in two area: 8 holes in the the Maquis Zone and 3 in the Raven Zone (PE121) on mineralization they consist unlike anything that had previously been identified on Duke Island (Freeman, 2006). No drilling was done in 2007. However, the data were reviewed and several other areas of interest were identified. In February, 2008, Quaterra had a 388-line-mile airborne geophysical survey flown over the area. In 2010, Copper Ridge Explorations Inc. drilled 5 holes on the Maquis zone.|
|Indication of production||None|
Berg, H.C., and Cobb, E.H., 1967, Metalliferous lode deposits of Alaska: U.S. Geological Survey Bulletin 1246, 254 p.
Irvine, T.N., 1974, Petrology of the Duke Island ultramafic complex, southeastern Alaska: Geological Society of America Memoir 138, 240 p.
Quaterra Resources Inc., 2008b, Duke Island NiS project: http://www.quaterraresources.com/uploads/projects/Duke%20Island%20NiS%20Prospect.pdf (as of May 5, 2008)
|Reporters||D.J. Grybeck (Port Ludlow, WA); D.J. Grybeck (Contractor, USGS)|
|Last report date||2/28/2011|