Copper-bearing Fissure Veins, Keweenaw County, Michigan, Lake Superior Native Copper District (Part 3)

Rosemeyer, Tom

doi:10.3200/rmin.84.4.320-323part3

Cited by 2 publications

(4 citation statements)

References 14 publications

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“…Surficial exposures of Portage Lake Volcanic bedrock are highlighted in dark gray. Comparisons with Charles Whittlesey’s map confirm that prehistoric mine pits were commonly located on surficial exposures of the Portage Lake Volcanic bedrock, which contained deposits of native “fissure vein” copper …”

Section: Introductionmentioning

confidence: 85%

“…The copper deposits on the Keweenaw Peninsula (Michigan, United States) are the largest source of native copper in North America . Surveys of the region during the middle and late 19th century identified thousands of mine pits with widespread evidence of prehistoric human activity in the form of hammerstones and tailing piles concentrated along the ∼100 km copper-bearing ridge in the interior of the peninsula (Figure ). , Surveyors excavating the prehistoric pits uncovered large masses of worked native copper, , scaffolding, ladders, and other mining tools .…”

Section: Introductionmentioning

confidence: 99%

“…The Michigan copper district is located on the northern shore of the Upper Peninsula and on Isle Royale. The principal copper-bearing rock is the Portage Lake Volcanic unit, which is primarily composed of Middle Proterozoic metamorphosed basalt flows . Historic mining on the Keweenaw Peninsula began in 1843 AD, expanded until 1920 AD, and declined until 1997 AD when mining ended .…”

Section: Introductionmentioning

confidence: 99%

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Lake Sediments Record Prehistoric Lead Pollution Related to Early Copper Production in North America

Pompeani

Abbott

Steinman

et al. 2013

Environ. Sci. Technol.

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The mining and use of copper by prehistoric people on Michigan's Keweenaw Peninsula is one of the oldest examples of metalworking. We analyzed the concentration of lead, titanium, magnesium, iron, and organic matter in sediment cores recovered from three lakes located near mine pits to investigate the timing, location, and magnitude of ancient copper mining pollution. Lead concentrations were normalized to lithogenic metals and organic matter to account for processes that can influence natural (or background) lead delivery. Nearly simultaneous lead enrichments occurred at Lake Manganese and Copper Falls Lake ∼8000 and 7000 years before present (yr BP), indicating that copper extraction occurred concurrently in at least two locations on the peninsula. The poor temporal coherence among the lead enrichments from ∼6300 to 5000 yr BP at each lake suggests that the focus of copper mining and annealing shifted through time. In sediment younger than ∼5000 yr BP, lead concentrations remain at background levels at all three lakes, excluding historic lead increases starting ∼150 yr BP. Our work demonstrates that lead emissions associated with both the historic and Old Copper Complex tradition are detectable and can be used to determine the temporal and geographic pattern of metal pollution.

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Section: Introductionmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Lake Sediments Record Prehistoric Lead Pollution Related to Early Copper Production in North America

Pompeani

Abbott

Steinman

et al. 2013

Environ. Sci. Technol.

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“…The Portage Lake Volcanic bedrock was targeted for mining because it contains large deposits of native copper ‘fissure veins’ and vesicles containing secondary native copper (Figure 1) (Pompeani et al, 2013; Rosemeyer, 2009). Copper mines and related piles of poor rock, tailings, and soil (i.e.…”

Section: Introductionmentioning

confidence: 99%

Copper mining on Isle Royale 6500–5400 years ago identified using sediment geochemistry from McCargoe Cove, Lake Superior

et al. 2014

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Isle Royale, in Lake Superior, contains evidence of indigenous copper mining; however, the timing and geographical extent of mining activity is poorly known. We analyzed metal, carbon, nitrogen, and organic matter concentrations to document past mining pollution in sediment cores recovered from McCargoe Cove; a long, narrow inlet of Lake Superior on Isle Royale that receives drainage from a watershed that contains numerous ancient copper mines. At McCargoe Cove, concentrations of lead, copper, and potassium increase in the sediments after ad 1860 and between 6500 and 5400 years before ad 1950 (yr BP). Metal pollution increases at McCargoe Cove exceed natural (or background) levels and coincide with radiocarbon dates associated with copper artifacts and existing lead pollution reconstructions from lakes on the Keweenaw Peninsula. Interestingly, a coherent cessation of lead emissions at multiple study sites after ~5400 yr BP coincides with the onset of dry conditions found in regional paleoclimate proxy records. After ~5000 yr BP, lead concentrations on both Isle Royale and the Keweenaw Peninsula remain at background levels until the onset of modern lead pollution ~ad 1860.

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Copper-bearing Fissure Veins, Keweenaw County, Michigan, Lake Superior Native Copper District (Part 3)

Abstract: II supplied much of the information on the mineralogy of the veins.

Cited by 2 publications

References 14 publications

Lake Sediments Record Prehistoric Lead Pollution Related to Early Copper Production in North America

Lake Sediments Record Prehistoric Lead Pollution Related to Early Copper Production in North America

Copper mining on Isle Royale 6500–5400 years ago identified using sediment geochemistry from McCargoe Cove, Lake Superior

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