| Abstract: | Lead from galena of massive sulphide deposits in the metavolcanic belt of northern Wisconsin was probably derived from 3700 m.y. old source material 1800-1900 m.y. ago. Approximately 3500 m.y. old rocks occur within 100-300 km to the north and west. The U-Th-Pb systems of the metavolcanic and granitic rocks in the belt were reset about 1600 m.y. ago during retrogressive metamorphism. The ages from lead isotope data are in accord with Rb/Sr whole-rock, Rb/Sr and K/Ar mineral, and U-Th-Pb zircon dating. A concordia plot of whole-rock lead data shows that many of the rocks lost lead 200-400 m.y. ago during uplift and erosion. Meta-volcanic rocks near Crandon, Wisconsin, had lead isotope compositions 20 m.y. ago that match those in the Pb-Zn ores in Palaeozoic rocks of the upper Mississippi valley. Possibly the volcanic rocks were a source of lead for the Pb-Zn ores. Similar ores might therefore occur between the northern Wisconsin metavolcanic belt and the upper Mississippi valley.-G.J.N. |
| Genre: | Article |
| ProdID: | 70013342 |
| Citation Author: | Afifi, A.; Doe, B. R.; Sims, P. K.; Delevaux, M. H. |
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| Citation End Page: | 353 |
| Citation Issue: | 2 |
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| Citation Language: | English |
| Citation Larger Work Title: | Economic Geology |
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| Citation Number Of Pages: | 16 |
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| Citation Search Results Text: | U-Th-Pb isotope chronology of sulfide ores and rocks in the early Proterozoic metavolcanic belt of northern Wisconsin.; 1984; Article; Journal; Economic Geology; Afifi, A.; Doe, B. R.; Sims, P. K.; Delevaux, M. H. |
| Citation Start Page: | 338 |
| Citation Volume: | 79 |
| Citation Year: | 1984 |
| Type: | citation/reference |
| Text: | U-Th-Pb isotope chronology of sulfide ores and rocks in the early Proterozoic metavolcanic belt of northern Wisconsin.; 1984; Article; Journal; Economic Geology; Afifi, A.; Doe, B. R.; Sims, P. K.; Delevaux, M. H. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Sun, 1 Jan 1984 00:00 -0600 |
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