|
Chugach Alaska Corporation (Chugach) is one of thirteen regional Native Corporations created by the Alaska Native Claims Settlement Act of 1971. As a result of that legislation, Chugach was able to select its land entitlement from an area of roughly 10 million acres in south-central Alaska, extending 465 miles from the southern tip of the Kenai Peninsula to the 141st meridian near the Malaspina Glacier on the Gulf Coast. The Chugach mineral rights entitlement includes about 378,000 acres of full-fee estate and 550,000 acres of subsurface estate. The Chugach Region was once one of the foremost mining areas of Alaska. Historically gold, chromium, copper and coal have been mined in the Chugach Region, as was the first producing oil wells in Alaska. Much of Chugach’s land was selected for its mineral values and the Corporation is actively soliciting exploration partners to evaluate and develop mineral prospects within its region. Chugach Alaska Corporation Goals are to: Encourage
new exploration efforts for minerals in its region. A substantial portion of the Chugach Region is included in Chugach National Forest (4.4 million acres) or National and State Parks and Refuges (2.2 million acres). Bureau of Land Management (BLM) and state lands comprise 2.3 million acres. Access is good with some of the most prospective of Chugach’s 928,000 acres of land located at or close to tidewater. Much of the region is easily accessed by boat or by helicopter for the inland tracts. Communities in the region have good infrastructure including airport, railroad, road, and marine highway connections. Some of the tracts have networks of logging roads and mine access trails. Chugach’s tracts on Knight Is., Latouche Is. and near Tatitlek village contain several patented mining claims on abandoned copper mines. MINING
AND EXPLORATION HISTORY Placer gold was mined as early as 1850 on the Kenai Peninsula and lode gold deposits were developed around the turn of the century in the Chugach Region. Eight areas in the Chugach Mountains have had lode gold production, the majority of which occurred prior to World War II and continued sporadically through the mid 1950’s. Five of these gold mining districts are in the Chugach Region and three are on the Kenai Peninsula adjacent to Chugach land. Districts in the Chugach Region are from west to east as follows: Nuka Bay District; Ailak District, Port Wells District; Valdez District; Central VMS District; Bremner District; McKinley Lake District; Yakutat District Systematic copper mining in Prince William Sound began when Kennecott developed the Beatson Mine in 1903 and the Ellamar Mine in 1906. Together, they produced over 200 million pounds of copper, 52,000 ounces of gold and 1.7 million ounces of silver. The completion of the Copper River Railroad from McCarthy to Cordova in 1911 and the subsequent shipment of the rich Kennecott Mine copper ores provided a transportation network which contributed to the economic success of the Region's mineral industry. Copper mining in the region ceased in 1930 with the closure of the Beatson Mine. From
1984 to late 1986, the U.S. Bureau of Mines (USBM) and U.S. Geological
Survey (USGS) conducted a regional resource assessment of Chugach
National Forest that clearly delineated the most prospective trends.
That study, along with other research, has confirmed the volcanogenic
character of Prince William Sound deposits. No major mining companies
have conducted systematic regional exploration throughout the Chugach
Region. GEOLOGIC SETTING The geology of the Gulf of Alaska consists of four fault-bounded terranes that extend from Kodiak Island to Southeast Alaska. They are respectively from west to east and oldest to youngest as follows:
Gold Deposits Lode gold deposits that occur within the Chugach Terrane metamorphosed Valdez Group rocks as gold-quartz veins emplaced along shear zones, faults, and joints. Fracturing is sometimes pronounced and individual fissures can be traced for long distances (¼ mile plus) where vein matter is sometimes absent then reappears further along the shear zone. Most of the veins are narrow (few exceed 2-3 feet) but larger veins and disseminated mineralized zones can occur at contacts with intrusions. Placer gold deposits derived from erosion of vein lode deposits occur throughout the Chugach Terrane. Several active placer gold mines are present in the Chugach Terrane on the Kenai Peninsula. Other, more remote placers documented elsewhere in the Chugach Region are inactive at this time. The eastern Gulf of Alaska beach deposits are also derived from erosion of the Chugach Terrane combined with reworking of recent glacial deposits. These deposits for the most part occur on the inter-tidal lands owned by the State of Alaska. However, inland paleobeach placers created by marine transgressions and regressions could occur on Chugach lands. Copper
Deposits Over 300 base-metal occurrences, many of which have volcanogenic massive sulfide (VMS) affinities, have been documented in the Chugach Region. The majority of these occur in three distinct mineralized trends that are spatially and genetically related to three volcanic belts in the Prince William Terrane. The Prince William Sound VMS deposits are classic Fe-Cu-Zn systems with local significant precious metals dominated by pyrite, pyrrhotite, chalcopyrite, and sphalerite. They contain minor phases of cubanite, arsenopyrite, tetrahedrite, and secondary marcasite. Alteration consists of quartz, chlorite, sericite, talc and calcite. Primary sedimentary features are ubiquitous within the deposits and well preserved in the massive sulfides. Fluid inclusions, stable isotopes, and whole-rock data further indicate that these deposits are sea-floor volcanogenic massive sulfide deposits that formed in both sediment starved (Cyprus type) and sediment rich (Besshi type) mid-ocean ridge settings. All of the early exploration (1890's - 1930's) focused on copper deposits. Potentially valuable zinc deposits were essentially ignored because of metallurgical problems. Some of the documented showings have zinc values in excess of 20%. Additionally many of the prospects have reported high precious metal values, which are common in some high-grade Besshi and Cyprus-type deposits elsewhere in the world. The lack of systematic district-wide exploration programs utilizing modern geophysical and lithogeochemical techniques makes the Prince William Sound district one of the most under-explored VMS districts in North America. Other Minerals Chromium (Cr), cobalt (Co), molybdenum (Mo), manganese (Mn), nickel (Ni), tin (Sn), tungsten (W) antimony (Sb), silver (Ag), zinc (Zn), and lead (Pb) all occur in the Chugach Region. Co, Ni, Sn, Pb, and Zn typically occur as minor components of copper deposits while Ag, Sb, Pb and Zn are common in gold veins. Chromium and manganese occur in discrete deposit types. Polymetallic veins in the Miners/Columbia Bay area as well as Mo, Sn, and W found scattered throughout the region may indicate potential for porphyry Cu/Mo deposits in the region. An active exploration program based upon information already available that utilizes new technology and modern exploration concepts may reveal new economically viable deposits elsewhere in the region. Prospective Chugach lands for Sedex-Zinc The Poul Creek Formation has significant, unexplained, highly anomalous zinc, copper, and barium sample values that were found during the 1984 USBM study. The host rocks are highly organic, fine-grained, pyritic clastics deposited in a deep-water anoxic environment along with basaltic sills and dike like intrusions. They were deposited along a subducting spreading ridge feature which could have produced seafloor fumaroles that can form sedimentary exalative (Sedex) zinc deposits. No mining company geologists have followed-up these anomalies. Chromium Deposits of the southern Kenai Peninsula Small podiform chromite deposits were mined at Claim Point during World War I. An estimated 2000 tons of reserves remain on patented claims adjacent to Chugach lands. The USBM did a concentrate test in 1983 that showed anomalous values of 1.2 ppm Platinum and 2.5 ppm Palladium in the chromite. Many new logging roads have recently been constructed in the area and have not been explored by geologists. Manganese Deposits During a recent evaluation of the strategic and critical minerals in the Chugach National Forest the USBM discovered two manganese deposits of interest. One is a bedded rhodochrosite, pyroxmangite, and magnetite interbedded with chert and calcareous shale that assays up to 37% manganese. The other, nodular masses that assayed from 29 to 35% manganese were found in a rubble area. This occurrence could represent primary sea floor nodules that if preserved in sedimentary beds could be of economic interest.
For
more information on Chugach Alaska Corporation's mineral interests
contact:
|
