Magembe Project Details

The previous owner recovered 41 diamonds in 12 of the 60 test samples on the Magembe Property.

The 46.05 square kilometers Magembe Property (PL 3920) is located in the Kishapu District, Shinyanga Region of the United Republic of Tanzania, approximately 35 kilometers north-northeast of Shinyanga town, along the main road to Mwanza. The Magembe Property surrounds the famous Williamson Diamond Mine also known as Mwadui Mine.

The Magembe Property is situated within the Archaean Craton of Tanzania, which consists of rocks metamorphosed to greenschist facies. The dominant lithologies comprise of granitoids, mafic and ultramafic volcanics and intrusives, felsic volcanics and schistose meta-sediments. These lithologies have been intruded by late kimberlite dykes and plugs of Mesozic age and overlain by recent covers.

Dominant structure grains in the area show prominent NE-SW, E-W, NW-SE and NNW-SSE orientations, which interpreted as faults, foliations, minerals lineation, shear zones, dykes and sills.

Alluvial diamonds are being mined in the southwestern part of the property, which are believed to come from diamondiferous kimberlites located within and/or around Mwadui Mine. High-resolution aeromagnetic data reveal the possibility of the property having kimberlite intrusions in the northern part of the property, which is overlain by mbuga and granitic soil cover. The Magembe Property is located in the Tanzania Craton of Archaean age, which comprises of granitoid, mafic and ultramafic volcanics and intrusives, schistose meta-sediments, quartzite, porphyry (dykes and masses) and felsic volcanics. The stratigraphy has been intruded by kimberlite dykes and plugs of Mesozoic age. The overall stratigraghy is overlain by recent covers, which comprise of mbuga clays, sands and gravels. The granitoid suite is made up of equigranular biotite granite, which dominates the area, porphyritic granite characterized by mega-crystals of potassic feldspars (microcline) seating within matrix made up of quartz, feldspar and biotite; gneissic biotite granite which shows faint banding and well developed foliation fabrics and granodiorite which is poorly exposed. The group of rocks consists of mafic volcanics and intrusives, porphyries and schists are poorly exposed except in streams and river sections.

Regional structure grains show prominent NE-SW, E-W, NW-SE and NNW-SSE orientations, which have been interpreted as faults, foliations, mineral lineations, shear zones, dykes and sills. The geological description of Magembe Property based on the geological mapping program completed on the property. The descriptions focus on lithology, structure and mineralization. The area is poorly exposed with limited outcrops observed in the western part and very few in the eastern part of the property. Dominant lithologies comprise of granitoid, mafic volcanic and schistose metasediment. The granitoid suite, which dominates the area, is made up of:

• Medium-to coarse-grained biotite-microcline-quartz granite developed weak foliation fabrics and faint composition banding.
• Porphyritic granite characterized by megacrystals of microcline feldspar phenocrysts seating within fine-to medium-grained matrix made up of biotite, feldspar and quartz.
• Granodiorite – The rock is composed of essentially quartz, plagioclase, hornblende and biotite.

The biotite-granite is dominant with large outcrops exposed in the western part of the concession. The rock characterized by coarse-grained equigranular texture composed of biotite, feldspar and quartz. The rock also developed weak foliation fabrics and localized composition banding.

Few porphyritic granite outcrops were documented in the western part of the area, adjacent to biotite-granite. The rock is characterized by porphyritic texture whereby megacrystals of microcline feldspar phenocrysts are seating within matrix made-up of biotite, feldspar and quartz.

Granodiorite is poorly exposed with a single outcrop documented in the western part along the road cut. The rock is equigranular composed essentially quartz, plagioclase, hornblende and biotite.

Schistose metasediment is poorly exposed, and only a few subcrops and rubbles were documented in the western part of the area in the shallow artisanal pits located adjacent to river Mangagi. The schistose metasediment unit is characterized by weak and localized sericite and chlorite alterations.

Maficigneous rock, which was interpreted as sills was observed in the western and eastern part of the area, occur as sub-crops adjacent to biotite-granite exposed on the riverbeds along river Karonga. The dominant structure type, which was documented during the mapping exercise, was foliation. A total of 54 foliation measurements were recorded and analyzed by using DIPS software.

Two dominant trends of foliation were interpreted from 54 structural measurements. The planes are oriented at 076 /47 and 260 /56 -strike/dip right format (Fig 2). Intersection of two major planes interpret a fold structure with its axis oriented 02@ 078 (plunge @ plunge direction) and limbs dip to the SSE Thus far, the known diamond mineralization in the Magembe Property (PL 3920) occurs as alluvial deposit located in the southern part of the area. Alluvial diamonds seem to be associated with the transported gravels and are believed to be derived from known diamondiferous kimberlites located within and/or around Mwadui Mine. The primary source of the diamonds is kimberlite intrusions. So far, there is no kimberlite identified in the area by surface geological mapping as the most part lies under recent covers. The soil and stream sediments sampling program in the northern part was aimed at identifying any kimberlite intrusion supported by geophysics data. Several layers of high resolution aeromagnetic data were utilized to pinpoint the areas with suspected kimberlite bodies (plugs and dykes), which show similar signatures with those hosting diamonds at Mwadui Mine. Based on the aeromagnetic data, two areas located in the northern part of the property (Fig 3 and 4 on the map page) were outlined and visited during the mapping program. There was no single outcrop observed as the area lies under recent covers. However, soil and stream sediments sampling techniques were employed aimed at tracking indicators minerals associated with kimberlite intrusions. Stream and soil sampling programs were executed over the property. The sampling was concentrated on the artisanal workings, streams and areas with good-looking magnetic signatures. The objective of the sampling programs were to evaluate the alluvial diamond potential in the southern part of the property, where there is high concentration of active artisanal activities as well as looking for possible kimberlite intrusion in the northern part of the property, based on the airborne magnetic signatures. A total of 67 samples were collected, but only 25 samples were submitted to the SEAMIC laboratory for heavy minerals analysis. Results are still pending.

The sampling was effective in the artisanal workings and streams. The sampling over the magnetic anomalies was not effective as the area lies under mbuga cover and wet ground due to ongoing rains over the area. However, a few samples were collected aimed at tracking of heavy minerals, which are usually associated with kimberlite intrusions. These minerals are pyrope garnet, ilmanite, chrome-diopside, olivine and chromite. There was no kimberlite intrusion observed during the mapping program. The area is dominated by granitoid intrusion with minor fine grained mafic / ultramafic igneous lithologies interpreted as dykes and sills and schistose metasedimentary sequences.

Dark green to black, fine grained mafic / ultramafic intrusion observed in the far west, outside the Magembe Property (PL 3920). There is evidence of diamond mining in the area as is concentrated with active and inactive artisanal workings which seems to be not associated with alluvial diamond potential transported from Mwadui Mine kimberlites. This area belongs to local artisanal miners, and needs to be monitored and if possible quick soil and stream sediments sampling programs (heavy mineral sampling) should be carried out after permission is granted by the owner.

A pitting program is recommended over the magnetic anomalies, which lie under mbuga cover in the northern part of the property, despite of few soil samples being taken over the anomalies. The pitting program was not possible during recent field work due to wet ground resulting from ongoing rains. This program will be reviewed and executed during the dry season. The aim of pitting is to collect the representative samples below the mbuga cover.

The artisanal mining activity in the southern part of the property is purely for alluvial diamond deposit. All workings are concentrated along recent and paleo-streams drained away from known Mwadui Mine kimberlites. The ongoing artisanal mining activities within and in the adjacent areas may suggest a big alluvial diamond potential in the area.

Based on the observation made during the recent field work over the Magembe Property, the following was summarized:

• There are possible kimberlite intrusions in the northern part of the property, which lie under mbuga cover. This is based on high-resolution aeromagnetic data, which are similar to those of the known diamondiferous kimberlites of Mwadui Mine.
• The ongoing mining activities in the southern part of the property are for alluvial potential with the possible source of diamond being Mwadui Mine kimberlites. In this case, the possibility of having a big alluvial diamond potential in the area is high.
• There is a possibility of diamond-bearing kimberlite intrusion far west of Magembe Property (PL 3920) based on the presence of active and inactive artisanal workings and of fine-grained mafic/ultramafic rock equivalences.