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The Idaho cobalt belt
The Idaho cobalt belt (ICB) is a northwest trending belt of cobalt (Co) ± copper (Cu)-bearing mineral deposits and prospects in the eastern Salmon River Mountains of east-central Idaho, U.S.A. (Fig. l).The Blackbird Co-Cu deposit is near the center of the ICB, where it is over 10 km wide. From the Blackbird area, the ICB extends at least 25 kin to the southeast and northwest. Ore zones and prospects of the ICB are hosted in Mesoproterozoic metasedimentary strata of the Lemhi sub-basin of the Belt-Purcell intracratonic basin. Most are within or near the banded siltite unit of the Apple Creek Formation, which consists of about 2 km of interlayered gray siltite and argillite within a 14-km-thick section of predominantly gray fine-grained siliciclastic strata (Evans and Green,. 2003). Metamorphic grades increase northwestward along the ICB, from greenschist facies at its southeast end, to .amphibolite facies ± garnet ± chloritoid in its central part, to upper amphibolite-facies± sillimanite at its at its northwest end.