The Mombuca Project is located approximately 100km north-east of the Minas Gerais state capital of Belo Horizonte, and offers outstanding gold and iron ore potential.
The Project is located in the southern segment of an extensive gold-palladium belt, defined by a series of north-south trending lineaments of thrust faults of Brasiliano orogeny, coincident with occurrences of gold-palladium-platinum mineralisation, artisanal workings and, in some cases, iron ore and gold mines (such as Itabira and Gongo Soco).
A magnetic anomaly on the Mombuca tenement has dimensions of 4.8km by 3.5km and is one of the strongest anomalies in the region. It is of a similar scale to the world-class Itabira Iron Ore mine (located just 20km south-east), which has been operating for over 60 years.
The Project is located exactly at the interference of two major thrust systems and is in a tectonic setting that is preferential for metasomatic fluids generated during tectonics. Such an alteration zone has been identified at Centaurus’ primary maiden target – the Initial Target Zone (“ITZ”).
The ITZ is defined by a large gold-in-soils geochemical anomaly that extends over a SW-NE trend of approximately 1.5km, coincident with crustal scale structures as well as several historical artisanal workings and adits from the 19th century. Face sampling from these adits has returned gold intercepts of up to 6m at 5.3g/t Au and 8m at 1.8g/t Au.
Located in a metavolcanic-sedimentary sequence the ITZ is made up of quartzites, iron formations (itabirite), mafic and ultra-mafic schists with the sequence dipping shallowly to the east-southeast. Strong sericite-carbonate and talc-chlorite hydrothermal alteration is present in the mafic and ultra-mafic schists respectively. The main gold mineralisation identified at the ITZ is hosted by pyrite-bearing quartz veins within altered and tectonized quartzite and mafic schist. Previously reported rock chip sample assays from the mineralised quartz veins included results of up to 12.2g/t Au.
Trenching work undertaken by Centaurus intersected multiple flat-lying gold-bearing quartz veins at different locations with gold assays of up to 3.1g/t Au returned over a 0.5m interval in the trenches. These intersections demonstrate the sub-surface strike continuity of structurally controlled gold mineralisation in quartz veins across multiple lithologies displaying common alteration assemblages, reinforcing the presence of a primary gold mineralisation system and supporting the potential for a larger mineralised system. This interpretation has been significantly strengthened by results of an Induced Polarisation survey completed in the first half of 2016.
The IP survey identified a number of open-ended high chargeability zones that extend to more than 250m depth. These chargeability anomalies, which indicate the likely presence of sulphides, correlate extremely well with the gold-bearing sulphide mineralisation identified at surface. Interestingly, a number of these IP chargeability targets are coincident with magnetic low features found within a broader magnetic high anomaly. This type of geophysical feature is a good indicator of iron oxide (magnetite) depletion zones due to sulfidation or hydrothermal upgrade of hematite-rich zones, both of which present excellent targets for drilling.
Centaurus completed a maiden round of exploration drilling at the Mombuca Project in September 2016, comprising five deep diamond drill holes over the ITZ and Bela Prospects. Assay results from these drill holes indicate the presence of a hydrothermal mineralising system, however, they failed to adequately explain the strong IP chargeability anomalies.
IP anomalies of these dimensions and with chargeability readings of up to 20msec (considered very high) are generally associated with significant amounts (1‐5%) of disseminated sulphides, iron oxides or other geological conditions that can explain the anomalies (e.g. graphitic schists, black shale units, etc).
The diamond drill holes that targeted these IP anomalies only returned trace amounts of disseminated sulphides and iron oxides or boxworks of the same within intervals of silica, sericite and chlorite alteration. The zones were often locally fractured and brecciated with strong signs of fluid movement and oxidisation along the zone.
Logging of the core by experienced geologists identified strong evidence of the presence of a hydrothermal mineralising system. This, together with the absence of any other geological features which could explain the high chargeability signals, means that the IP anomalies remain unexplained, especially considering their strength.
Before any further exploration drilling is undertaken, Centaurus will collate all geological, structural, geochemical, petrographic and geophysical data and undertake a comprehensive review in conjunction with its geological and geophysical experts.
The Company will analyse the results relative to the interpreted position of the anomalies and structural controls of the project.
From this work, additional exploration programs – including further drilling – will be planned in an attempt to explain the strength of the geophysical targets and vector into potential accumulations of sulphides.