Mchinji rutile-graphite-gold

Introduction

The Mchinji licence covers 870 km2 and is adjacent to areas with known mineral potential, some of which are licenced including the Mkango’s Chimimbe Hill nickel-cobalt licence to the south. The Mchinji licence has been granted for the exploration of nickel, cobalt, gold, base metals, graphite, platinum group metals, ilmenite, vanadium, chromium, uranium and rare earth metals.

The licence is initially awarded for a 3-year term, after which it can be renewed twice for further two-year periods with a 50% reduction in the licence size required with each renewal.

Location

The majority of the licence is located in Mchinji District, with its western border just east of the town of Mchinji, while the southeastern corner of the licence falls within Lilongwe District. The town of Nkotakata and Kamwendo Trading Centre lies in the middle of the licence, 90km along the M12 highway from Malawi’s administrative capital, Lilongwe. The M18 highway runs north from a junction with the M12 at Nkotakata. The main railway line from Zambia traverses the licence alongside the M12 road and runs to the deep-water port of Nacala in Mozambique. There are numerous dirt roads and tracks offering easy access throughout the licence. Elevation is approximately 1,050–1,150m, with higher elevated parts mainly in the west, and a number of small hills standing above the broad plain of the region. The eastern border of the Mchinji licence adjoins a large licence owned by McCourt Mining Pty Ltd, a wholly owned subsidiary of Sovereign Metals Ltd, that hosts Sovereign's Kasiya and Bua projects where exciting rutile discoveries have been announced in 2020.

Infrastructure map of the Mchinji licence (EPL 0544) adjoining the Chimimbe Hill licence (EPL 0475) to the south showing rutile and ilmenite sampling sites. Grid is UTM Zone 36 S.

Historical Exploration

The earliest known work was carried out in 1908 by T.E.G. Bailey of the Imperial Institute Mineral Survey of British Central Africa. He identified the main metasupracrustal and igneous rock types, remarking that “what little evidence we now have points to a uniform granite basement” and pointed out that the gold-bearing reefs then being worked at Missale and Chifumbazi in Mozambique were in metasupracrustal rocks close to their contact with the granite.

The Anglo-American Company prospected the area in 1937, and New Consolidated Goldfields Ltd in 1957-58. Later investigations associated with the siting of water supply boreholes were confined to very small areas.

Geological mapping was carried out concurrently with geochemical drainage reconnaissance by the Geological Survey of Malawi in 1964. This work included the collection of alluvial samples at half-mile intervals at all streams and dambo (broad, grass-covered, swampy valleys) together with alluvial samples from watershed areas far from active drainage patterns. The samples were analysed for copper, lead, nickel, chromium, tin, silver, beryllium, and arsenic. Bulletin 24 of the Geological Survey Department, Malawi Ministry of Natural Resources (Thatcher, E.C. and Wilderspin, K.E., 1968) contains a geological map and a summary of the geochemical reconnaissance, and remarks that graphite deposits are particularly noteworthy in the area.

Geology and Geophysics

Virtually all geological knowledge of the licence is reported in Thatcher E.C. and Wilderspin K.E. (1968), ‘The Geology of the Mchinji-Upper Bua Plain’, Bulletin 24 of the Geological Survey Department, Malawi Ministry of Natural Resources. This publication covers Mkango’s Mchinji and Chimimbe Hill licences but extends north and east.

The surficial geology of the area is characterized by a plain of residual soils, colluvium and alluvium, punctuated by hills of granitic gneisses and quartzite, with sporadic exposures of various gneisses and schists interpreted to be of supracrustal origin. All of these rocks are believed to belong to the Proterozoic Mozambique Mobile Belt.

A dendritic pattern of watercourses and dambo, not generally controlled by the underlying geology, drains into the Ludzi and Bua rivers which run east before turning north just outside the northeast corner of the licence.

The magnetic pattern of the licence reveals a number of major geological structures or features in the basement rocks. Some are related to a northwest-southeast trending interpreted shear belt that dominates the southern part of the licence. There is also a large east-west trending fault in the north of the licence, and a north-south trending probable dyke of regional extent (hundreds of km, beyond the limits of the countrywide geophysical survey) that enters and exits the northwest of the licence.

The ternary radiometric image of the licence shows domains that coincide with the interpreted major geological structures, particularly in the south. This suggests that the extensive soil cover is largely residual, offering reasonable confidence that soil geochemistry will be the best initial exploration method.

New Exploration

In mid-2020, Mkango carried out a reconnaissance shallow soil sampling and auger programme within the Mchinji licence. The results demonstrate the presence of interesting grades of rutile plus anatase (both naturally occurring mineral forms of titanium dioxide: TiO2) mineralisation of up to 1.07%, with overall TiO2 grades in the range 0.51 to 4.10% in auger samples and 0.14–2.38% in soil samples; also ilmenite grades of 1.30 to 3.40% (average 1.85%) – see table below.

The grades of the TiO2-bearing minerals in the best auger hole are in the range 0.63 to 1.07% rutile plus anatase (average 0.73%) and 1.30 to 3.40% ilmenite (average 1.85%), hosted in free-dig saprolite material accessible from surface.

Twelve vertical auger holes (prefixed A- on the map above) were drilled to depths of 0.45 to 9.40m, for a total of 35.8m, from which 41 samples were collected. Eight holes were terminated at 2m depth or less due to saturated ground in or adjacent to the Ludzi river channel. The other four holes were drilled in saprolite on higher ground between the Ludzi’s tributaries.

Soil sampling was carried out in pits dug to 50cm (‘B horizon’) on a 500m staggered grid in four areas of the licence, producing 134 samples (pink dots on the map above).

Sample preparation and analysis was provided by Scientific Services laboratory in Cape Town, employing two-acid microwave digestion and ICP-OES techniques suitable for multi-element determination and following strict internal QAQC procedures inserting blanks and standards. Internal laboratory QAQC was also completed to include standards and blanks.

The highest TiO2 grades were returned by nine consecutive samples in a single auger hole (A6), drilled to a depth of 8.9m, that contain between 4.10 and 9.01% total heavy minerals (specific gravity > 2.95) and grade between 3.17 and 4.09% TiO2. These samples were processed by heavy mineral separation and magnetic separation, and the separated fractions were sent to XRD Analytical and Consulting CC in Pretoria for quantitative determination of the heavy minerals by X-ray diffraction (“XRD”). Results are given in the table below for vertical auger hole A6:

Auger hole A6 Total heavy minerals
%
TiO2
%
Rutile + anatase
%
Ilmenite
%
0 – 1 m 5.32 4.09 0.66 3.40
1 – 2 m 4.95 3.74 0.66 2.87
2 – 3 m 7.12 3.29 0.69 1.71
3 – 4 m 8.04 3.21 0.66 1.31
4 – 5 m 7.78 3.17 0.63 1.30
5 – 6 m 9.01 3.24 0.74 1.41
6 – 7 m 5.79 3.56 0.65 1.44
7 – 8 m 4.10 3.89 0.85 1.58
8 – 8.9 m 4.18 3.81 1.07 1.62
Weighted average 6.28 3.55 0.73 1.85


Geochemistry of the soil samples reveals anomalous TiO2 values around auger holes A6 and A11, suggesting potential for follow-up and indicating that soil geochemistry may be a useful regional exploration tool.

Mkango is currently completing an exploration programme of more extensive soil sampling, hand-auger drilling and mineralogical test work to identify rutile prospects over the Mchinji licence. The exploration programme is funded from the Company's existing working capital.

Rutile Market

  • Rutile, anatase and ilmenite are naturally occurring titanium dioxide (TiO2) minerals, whose main uses are 90% for pigments, 5% production of titanium metal and 5% welding. Rutile is the purest, highest-grade natural form of TiO2 and is the preferred feedstock in manufacturing titanium pigment and producing titanium metal.
     
  • Finely powdered rutile is a brilliant white pigment and is used in paints, plastics, paper, foods, and other applications that call for a bright white colour. It has also been widely used in the production of glass, porcelain, and ceramics, as it is a valuable colouring agent. It can also be used to add colour to steels and copper alloys.
     
  • Titanium also has specialty uses including in welding, aerospace and military applications.
     
  • Sierra Rutile in Sierra Leone, owned by Iluka Resources Limited (“Iluka”), is the only high-grade, large-scale, operating primary-source natural rutile mine in the world.
     
  • Iluka reports that, considering current deposits and operations, the industry is facing declining grades and assemblages (relative weightings of each mineral) for deposits in the development pipeline.
     
  • The rutile market fundamentals are robust with current and forecast pricing remaining strong. Iluka, in its Q3 2020 quarterly review, declared a weighted average received price for rutile of US$1,225 in the year to date, an increase of 7.3% over the full-year 2019 price. The current price is US$1,345 (source: FerroAlloyNet.com, 29 October 2020).

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