Espiritu Santo

Minas Gerais, Brazil

Main commodities: Au
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The Morro Velho complex of mines is located approximately 10 km south-east of the city of Belo Horizonte in Minas Gerais, Brazil, in the northern part of the Quadrilatero Ferrifero district. The mines of the complex have been worked for over 200 years, while Morro Velho itself was in continuous operation from 1834 to 1960.

The mineralisation at the Morro Velho complex is hosted by the volcano-sedimentary Nova Lima Group. Gold mineralisation is associated with sulphides and quartz veins in banded iron formation (BIF), mafic and ultra-mafic sequences and as disseminations throughout the volcano-sedimentary sequence.

The current (2001) genetic theory involves an epigenetic model with strong structural control and an association of deep granitic intrusions. The host rocks at Morro Velho are BIF, Lapa Seca (a quartz-dolomite-ankerite rock) and mafic (principally basaltic) volcanics. Mineralisation is commonly associated with large scale shear zones and their associated structures. Where BIF is mineralised (as at the old Morro Velho mine) the ore is stratabound due to the selective sulphidation of the iron rich layers. Steeply plunging shear zones tend to control the ore shoots and commonly plunge parallel to intersections of shears and other structures.

At Morro Velho the controlling structures were apparently the intersection of a thrust fault and tight isoclinal folds in a ductile environment. Mineralisation is believed to result from the interaction of low salinity CO2 rich fluids with the high iron BIF and basalts and the carbonaceous graphitic schists.

Sulphide mineralisation comprises pyrrhotite and arsenopyrite with subordinate pyrite and late stage post gold chalcopyrite. Wall rock alteration is typically carbonate, potassic and silicic.

Mining in the complex has in recent years been restricted to the Espiritu Santo open pit and the Cuiaba and Mina Velha underground mines.

During 1999, some 6.1 t (197,500 oz)of gold were produced at a cash cost of USD 124 per oz and a total production cost of USD 176 per oz. The recovered grade was 7.01 g/t Au. The operation is controlled by AngloGold Ashanti through its wholly owned subsidiary Morro Velho.

The most recent source geological information used to prepare this summary was dated: 2001.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.

Espiritu Santo

  References & Additional Information

Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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