Stratiform chromitite at Campo Formoso, Bahia, Brazil
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Abstract
Serpentinized ultramafic rocks of pre-Minas age (Precambrian) crop out in an elongate belt 1 km wide and 15 km long on the west side of the Serra de Jacobina near Campo Formoso, Brazil. The original stratiform ultramafic body has been so metamorphosed, faulted, and eroded that only narrow dismembered segments occur along the thrust-faulted west side of the Serra de Jacobina. The most economically important segment is that near Campo Formoso where chromitite layers can be followed for about 8 km near the base of the intrusion. Three to five chromitite layers of minable thicknesses have been mapped, the thickest being 1.4 to 1.8 m. The aggregate thickness of chromitite is about 5 m and the average grade is about 43.5 percent Cr203. The Cr:Fe ratio ranges from 1.6:1 in weathered friable chromite to 3:1 in massive unweathered chromitite; in cleaned chromite concentrates the ratio is as much as 3.3:1. Estimates of indicated chromite ore reserves range from 16 to 20 million metric tons, of which only an estimated 6 million tons can profitably be mined. Factors preventing full exploitation of the chromite include (1) the local presence of as much as 7 m of overlying colluvium, (2) the extremely faulted character of the chromitite layers, (3) the presence of an overlying quartzite thrust plate very near the line of chromitite outcrops, and (4) the steep dips of the chromitite layers, 15° to 40° along the Pedrinhas-Limoeiro trends and 50° to 65° along the Cascabulhos trend.
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Stratiform chromitite at Campo Formoso, Bahia, Brazil |
| Series title | Journal of Research of the U.S. Geological Survey |
| Volume | 2 |
| Issue | 5 |
| Year Published | 1974 |
| Language | English |
| Publisher | U.S. Geological Survey |
| Description | 12 p. |
| First page | 551 |
| Last page | 562 |
| Country | Brazil |
| State | Bahia |
| City | Campo Formoso |
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