Sadiola Gold Mine

 mine, gold mine

The Sadiola mining permit covers an area of 302 km² in a remote part of Mali with little infrastructure and is owned by IamGold/AngloGold Ashanti joint venture and is operated by AngloGold Ashanti. The minesite is accessed by a regional gravel road to Kayes and there is an airstrip at the Sadiola Gold Mine capable of handling light chartered aircraft. Kayes is serviced by rail, road and air from Bamako and from Dakar, the capital of Senegal. Bamako has an international airport with daily flights to many West African and European destinations. Dakar is a major port of entry to West Africa by sea and air and the primary supply route for imported goods coming to the minesite.

The Sadiola deposit is located within the Malian portion of the Kenieba–Kedougou window, a major Palaeoproterozoic inlier along the northeast margin of the Kenema–Man shield. The Birimian components of the window can be interpreted as a collage of at least two N-S trending terranes. To the west, an older (+/- 2.2 Ga) volcano-sedimentary succession intruded by major calc-alkaline batholiths belongs to the Saboussire Formation. It is separated from the dominantly sedimentary Kofi Formation by the major north to northeast trending Senegalo-Malian Shear Zone. The Kofi Formation is significantly younger and intruded by calc-alkaline batholiths dated at 2.0 – 2.05 Ga. Metamorphic grade attains greenschist facies, with amphibolite grades developed locally near major intrusions. The Senegalo-Malian Shear Zone hosts several significant gold deposits along its splays including Sadiola, Yatela, Loulo and Yalea.

The Sadiola deposit is located in the north central section of the window and is hosted by sediments of the Kofi Formation, which have been intruded by numerous felsic intrusives. The sediments consist of fine-grained greywacke, probably distal turbidites, and impure carbonates with minor tuffs and acid volcanics.

The deposit occurs along the 010º striking Sadiola Fracture Zone (“SFZ”), which is interpreted as a brittle-ductile splay off the Senegalo-Mali Shear Zone at a sinistral releasing bend. The SFZ follows the steeply west dipping contact between greywacke to the west and impure carbonate to the east. The SFZ and its wallrock are intruded by discontinuous diorite dykes, which may contain a weak mineral foliation and rarely intense ductile deformation. Quartz-feldspar-porphyry (QFP) dykes intrude younger, 020º striking and steeply west dipping faults and preserve more brittle deformational features.

Pervasive gold mineralisation ranging in grade from 2 g/t to 20 g/t occurs along the SFZ over a strike length of approximately 2,500 metres and remains open to the north and south. The location and geometry of high grade mineralisation appears to be controlled by the confluence of the SFZ with the 020º striking splays, resulting in steeply to vertically plunging zones within the plan of the SFZ.

Gold mineralisation occurs in all of the four major rock types (marble, greywacke, diorite and quartz-feldspar porphyry), and is spatially associated with a complex alteration pattern. Alteration assemblages identified to date include calcsilicate, potassic, chlorite–calcite and carbonate and point to a mesothermal origin for gold mineralisation. Gold is associated with both arsenic and antimony dominated sulphide assemblages including arsenopyrite, pyrrhotite, pyrite, stibnite and gudmundite. Primary gold is extremely fine grained, dominantly less than 15 microns, with rare grains approaching 50 microns.

The Sadiola deposit has been intensely weathered to depths of up to 220 metres. The operation has mainly exploited soft oxide ore since startup with the current known oxide reserves scheduled to be mined out by 2012. A significant mineral resource of hard sulphide ore occurs below the final Sadiola pit design and is currently the subject of a prefeasibility study.


Reference for information:
www.iamgold.com/English/Operations/Operating-Mines/Sadi...