Igawa-Msusule Prospect.

A group of gold prospects occur in crystalline rocks in a zone running close to the Mbeya-Dar es Salaam road for 20 km west from Igawa. Igawa is 116km east of Mbeya town (Fig.41). The prospects consist of a cluster of placer and bedrock occurrences of gold in little more than trace amounts. Stockley (1948) provides cursory descriptions and suggests the area could be the geological continuation of the Lupa Gold Field, which lies close to the northwest. There are no records of systematic prospecting in this area.

Kitowero Prospect.

This area in the Masasi High sector of the Usagaran Palaeoproterozoic province was described by STAMICO geologists in 1981 as the Ngurumahinga River alluvial gold prospect. It is far from any mining or other development except artisanal mining of gemstones and minor gold. The topography is rolling and covered with tropical scrub. Rock exposures are limited to a few inselbergs.

STAMICO had been attracted to the area by reports of alluvial gold in the Ngurumahiga and Mbemkuru rivers (Fig. 36), and by the history of modest gold production (400 gm) from the area in 1933-34. In addition, Geological Survey geologists in 1950 reported finding alluvial gold at the mouth of the Mbemkuru River, some 30km to the east. The prospects lie at the east margin of the Selous Basin, where Karoo and younger sedimentary rocks are in fault contact with Proterozoic rocks consisting of granitic gneiss, biotite schist, garntiferous amphibolite and quartzite. "Magnetic ironstone" was noted on Kitowero Hill and a few pegmatites were also noted (Fig. 36). The regional structural trend appears to be northerly.

STAMICO carried out a stream sediment survey and found gold in heavy mineral concentrates from several streama including the Mbemkuru, Ngurumahiga,Muhuwesi, and Lumesule rivers. The proportion of heavy minerals to total sample was not recorded. Assays of the heavy mineral fraction as high as 12 g/t gold were obtained. STAMICO geologists concluded that the alluvial gold was derived from an unspecified source. Since most of the gold bearing streams drain Proterozoic rocs and basins of Karoo and younger ages, there are a number of potential sources.

Gold in the Kitowero alluvial prospect could interpret as derived from a lode source in an area between Kitowero and Ligwerro Hills (where outcrops of pegtmatites and amphibolite occur to the southwest) (Fig. 36), where the Proterozoic rocks are greenstones, here metamorphosed to almandine amphibolite facies. The amphibolite on Ligwero Hill, the magnetic ironstone on Kitowero Hill, and the swarm of "pegmatites", possibly meta-cherts or quartz veins, could be the actual source rocks. The above interpretation could be tested by further field examination of the area for metamorphosed remnants of an older, possibly Archaean, mineralized greenstone sequence.

Samba Nguru Hill Prospect.

Gold in the Dodoman basemen is described by Barth, Massola and Weiser (1996), as observed from prospects discovered by artisanal miners. Gold mineralisation in the Dodoman basement is clearly associated with granitized relics of a deeply eroded greenstone belt, and occur in poorly silicified shear zones in the granitoid migmatites, in places closely related to contact aureoles of prominent granite intrusions.

Mafulungu Prospect (Simba Nguru Hill).

Gold was discovered and a gold mining village was established in 1992 at the south- western edge of the Simba Nguru Hill by artisanal miners. The hills consist of a 12km long, narrow raft of Dodoman metaquartzite (fuchsite quartzite), which consists of migmatitic falser gneisses. The ore body being mined is not in the metaquartzites of the Simba Nguru Hills but it in the basement migmitites. Altered greenstones are abundant in waste dumps in the mine area.

Te gold assay of three bulk sample yielded an average of 75 g/t gold for the fine grade ore pounded and ready for panning. Barren quartz stringers and waste rock contained 2 g/t gold. One sample of black hybrid metagranite from the Kisigo River near the mine yielded 58 g/t gold. Microprobe analysis revealed silver content of 4 to 5%, while only traces of copper (2%) were detected.

Nzuguni (Mdengi Hill) Prospect.

Nzuguni is located 12km east of Dodoma Municipality. History of gold mining at Nzuguni began with artisanal mining in 1932, after the discovery of eluvial and alluvial placers; it lasted only for a short period. In 1992, artisana; miners resumed mining activities and established a mining village at Nzuguni.

The prospect consists of quartz veins associated with a major shear zone striking NE-SW. Assay of 90 samples yielded an average grade of 2,.3g/t gold (Williams 1936). Microprobe analysis yielded silver contents of 3-20%.

Iluma Hill Prospect.

Iluma Hill in the Muhesi River Game Reserve is a prominent summit. Iluma granite is intrusive into the basement migmatite series, striking 110-120. The sequence is cut by prominent dolerite dyke striking 160 which produce prominent magnetic lineaments. The ore body is in a silicified shear zone in the outermost part of the Iluma granite aureole, located between metamorphic rafts and intruding granite. The grade of the crude ore was assayed at 80 g/t gold (1 bulk sample); a sample containing traces of visible gold yielded only 5 g/t gold. The microprobe analysis yielded silver contents in the gold of 12% and 14%.

Lukarasi Prospect.

Lukarasi prospect is to considerable significance. It has been worked by artisanal miner since early the 1990s. A speculative resource of 253,000t with an average an 6.5 g/t gold has been

Crushing of ore using a ball mill at Sambaru gold small scale working (Photo by P.Semkiwa)

Estimated by UMICO, for the first 10m from the surface. Mineralisation below 10m has not yet been investigated. A small-scale mine is operated by UMICO since 1998.

Other prospects.

Several gold occurrences are known to have local placer and or reef gold mineralisation within Palaeoproterozoic rocks. These include Ruvu, Mvomero, Mindu, Matombo (placer) Melela (reef)in Morogoro Region; Kwampepo (placer and reef) in Ruvuma Region; Nachingwea in Lindi Region; Mchauru-Masasi (placer) in Mtwara Region; Muhintiri, Matongo, Sambaru and Londoni (reef and placer) in Singida Region; and Kilindi, Sakale (reef and placer) in Tanga Region.