SEDIMENTARY-HOSTED BASE-METAL DEPOSITS IN THECAMAQUÃ BASIN, SOUTHERN BRAZIL: A REVIEW

Remus, MVD¹; Toniolo, JA²; Formoso, MLL¹; Tassinari, CCG³; Nunes, LC³IGeo UFRGS(marcus.remus@ufrgs.br)¹; CPRM-SUREG-POA²; IGeo-USP³

INTRODUCTION

LOCALIZATION

STRATIGRAPHY

Minas do

Camaquã

Fig 1: Geographic localization of deposits in south Brazil.

Fig 2:Geologic setting of main base-metal sedimentary hosted deposits in south Brazli

Fig 3: Geology of Camaqua and Santa Maria Deposits.

GEOLOGIC SETTING

Fig 5: Stratigraphic column of Camaqua Deposit.

0,25 mm0,25 mm

Exsolution textures of chalcoite and bornite (Camaqua )Depositde 200x,

Galena surrounded by quartz (Santa Maria) (1) 100x,

Galena and sphalerite intergrowht with pyrite and chalcopyritewith pyrite and cjhalcopyrite inclçusions 25 x.

0,3 mm0,3 mm

0,45 mm0,45 mm

0,45 mm0,45 mm

CONCLUSIONS

1

2

0,5 mm0,5 mm

ORE MINERALOGY

Mineralization is coeval and related to a magmatic eventbetween 594 to 545 Ma (shoshonitic to alkaline magmaticevents) and show some simiraties with IOGC models.

The Camaquã deposits consist of NW veins, stockworks anddisseminated ores with chalcopyrite, pyrite, bornite, chalcocite,gold, silver. Chlorite, white mica, quartz, albite, carbonate andlater barite and hematite are the main gangue minerals. The orelodes are enclosed in conglomerates and sandstones. Galenaand sphalerite of the Santa Maria deposit are disseminated inarenites and conglomerates, or occur as massive lodescrosscutting thestratigraphy. Sphalerite and galena intergrowthsare the dominant texture in the ores, while chalcopyrite andchalcocite are minor; carbonate, chlorite, adularia and barite arethe gangue minerals. The Cerro dos Martins ores consist of a setof NW-trending Cu-sulfide veins and disseminations within thevolcanic-sedimentar sequence. Chalcocite and bornite are themain ore minerals with minor chalcopyrite, galena and sphalerite,whereas carbonates, barite, quartz and hematite are the gangue.The volcanic host rocks show an alkaline affinity

This paper reviews the origin and age of Au- and base-metalores hosted by Neoproterozoic volcanosedimentary sequencesof the Bom Jardim Group in the Camaquã basin, southern Brazil(Camaquã Cu-Au; Santa Maria Cu-Pb-Zn and Cerro dos MartinsCu deposits). In these deposits, the sulfide ores are mainlyfracture-controlled and also disseminated in the matrix ofsiliciclastic sequences.

Pyrite chacopyrite intregrow and galena and later sphalerite(Santa Maria Deposit) Luz refletida com aumento de

200x, amostra 375

Fig 4: Geologic cross-section showing the geometric distribution of ores in theCamaqua and Santa \maria Deposits