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 | |  Twangiza (Oxide) became Banro's first producing open pit gold mine when it entered production in October 2011. With a mill throughput at full capacity of 1.7 million tonnes per year, Twangiza (Oxide) is projected to produce some 120,000 ounces of gold each year with an expected mine life of seven to eight years from currently-defined reserves. Twangiza is the most advanced of Banro's five properties, with a growing deposit that currently comprises Measured and Indicated Resources of 5.60 million ounces of gold and Inferred Resources of 400,000 ounces. The property is located 45 kilometres south-southwest of Bukavu in South Kivu Province and consists of six Exploitation Permits covering 1,164 square kilometres in the highly-prospective 210km long Twangiza-Namoya gold belt.
The most recent technical report with respect to Twangiza that has been filed by Banro on SEDAR is dated March 9, 2011 (as revised on March 24, 2011) and entitled "Economic Assesment NI43-101 Technical Report, Twangiza Phase 1 Gold Project, South Kivu Province, Democratic Republic of the Congo." A copy of this report may be accessed at www.sedar.com. History
The Twangiza gold deposit was discovered by Miniere des Grande Lac (MGL) in the 1950s. The company followed the occurrence of alluvial gold deposits upstream from the Mwana River to the present-day Twangiza deposit. MGL tested the deposit through 8,200 metres of trenching and 12,100 metres of adits on seven levels, collecting a total of 17,400 samples. In the mid-1970s, Charter Consolidated undertook detailed exploration, including the excavation of numerous close-spaced adits into the mineralized zone. In 1996, Banro acquired control of the Twangiza property, and during the following year, undertook a US $9 million exploration program, which included 10,490 line-kilometres of airborne geophysics, 1,613 samples from 16 adits, and 8,577 drill core samples from 9,122 metres of core drilling along 800 metres of strike. This represented less than 20 percent of the identified mineralized trend. MineralizationThe Twangiza area is underlain by sediments of Proterozoic age that have been intruded by porphyry sills, folded into a series of broad anticlines and synclines and subjected to very low-grade metamorphism. The gold mineralization at the Main Twangiza deposit is hosted within mudstones, siltstones, greywackes and porphyries along the crest of a major anticlinal structure. Gold mineralization is of hydrothermal origin and is associated with sulfides which occur in quartz-carbonate veins, and disseminations throughout the host rocks. Unlike the Twangiza Main deposit, the mineralization at Twangiza North is associated predominantly with feldspar porphyry sills that have intruded westerly dipping shales and siltstones, with the mineralization in this lithology being non-refractory. This mineralization is open at depth and to the north where recent regolith mapping has indicated that the gold-in-soil anomalism has been masked by recent colluvial and alluvium material. Other significant gold occurrences on Banro's Twangiza's concessions include Tshondo and Mufwa; these occurrences will be examined as part of the current exploration program. Independent consultants, CME Consulting Ltd., determined in a report prepared for Banro in April 2003 that all fieldwork undertaken during Banro's 1997-1998 exploration program was compliant with NI 43-101 and provided an updated mineral resource. This mineral resource was subsequently updated in September 2006, January 2007, June 2007, January 2008 and June 2008. In January 2009, SRK Consulting (UK) Ltd. ("SRK") prepared an independent estimate of the Mineral Resources at Twangiza, which has now been separated into "oxide" and "non-oxide" components as set out in the table below. The estimate is based on a cut-off grade of 0.5 g/t gold.
The following oxide mineral reserves were estimated by SRK (SA) to be contained in a practical pit design in respect of the Twangiza Phase 1 oxide project. TWANGIZA PHASE 1 OXIDE MINERAL RESERVE ESTIMATE (EFFECTIVE DATE: MARCH 4, 2011)
2011 Exploration ProgramThe 2011 exploration program will focus 1) on targets near the mine face to fully evaluate the Twangiza East and West flanking structures and to identify new drill targets within the Twangiza anticlinal structure; and 2) on regional targets located outside the Twangiza anticline but which have the potential to add substantial resources to the current Twangiza Mineral Resource. The regional exploration activities will consist of stream sediment sampling, gridding, geological mapping, soil, trench and adit sampling, auger drilling and diamond drilling. These activities will be undertaken at the Mufwa, Ntula, Tshondo and Kaziba artisanal sites and at the radiometric and southern anomalies targets that have been generated from LIDAR, airborne magnetic and radiometric surveys. Recent press releases with respect to the Twangiza project were issued on: Maps
2008 - 2010 Exploration & Development ProgramsBanro recorded significant progress at Twangiza during 2008, completing almost 40,000 metres of core drilling at the Twangiza North and Twangiza main deposits, with the objective of upgrading the existing mineral resources to higher confidence resource categories and extending these deposits. The results of this work were integrated into the Twangiza full Feasibility Study, the results of which were announced in the Company's press release of January 26, 2009. The Feasibility Study was updated in the Company's press release of June 8, 2009. In August 2009, Banro announced its intention to begin construction of "Phase One" of its Twangiza project, and to that end acquired a gold plant capable of processing 1.3 million tonnes of ore per year. Reconstruction of roads and bridges and infrastructure development near the mine site was completed in the first half of 2010 and by December 2010, mechanical construction of the gold plant was 50% complete. It is expected that the Twangiza mine will enter production in late 2011. The Company plans to expand annual production at the Twangiza mine in future years from 100,000+ oz Au to 300,000+ oz Au. Banro's exploration goal in 2010 is to continue expansion of the project's oxide and transitional resources. The Company is exploring several neighbouring targets at Twangiza which are within trucking distance of the proposed Twangiza plant site, namely the Twangiza West and Twangiza East flanking structures, the newly discovered Ntula workings, the Kaziba prospect, the Kakeru Grid, the Karhundu area and a Radiometric Anomaly within close proximity of Twangiza. Future fieldwork and drilling programs are planned for the Mufwa and Tshondo prospects. These potential deposits are expected to strengthen the robustness of the Twangiza project and boost the ounce profile over and above the numbers released in the updated Feasibility Study. 2005 Exploration ProgramBanro returned to the Twangiza property in September 2005 and in October launched an aggressive exploration program with the primary goal of identifying targets and preparing sites for an accelerated 2006 drilling program. By year-end, the Company had successfully mapped 50 percent of a 7 kilometre by 2 kilometre NNW-SSE grid along strike to the north of the existing mineral resource at Twangiza. Soil geochemical sampling was undertaken along the grid, with 1,976 samples submitted for gold assaying. In addition, five trenches, totaling 463 metres, were excavated and mapped and 482 samples were submitted for assaying. Site preparation for the first phase of core drilling, including preparation of 14 drill pads, was also completed. The initial geochemical assay results delineated a prominent soil geochemical anomaly - greater than 100 ppb Au in soil with maximum values up to 2.77 g/t - along a strike length of 880 metres and directly along strike from the existing Twangiza deposit. This remains open to the north and west. Trench results received within this soil anomaly included 33.7 metres grading 5.15 g/t Au, 11.0 metres grading 5.97 g/t Au and 16.0 metres at 3.14 g/t Au. Two and a half kilometres to the north of the Twangiza deposit and along strike at the Lukungurhi workings, initial trenching results included 10 metres averaging 16.06 g/t Au and 8 metres at 1.5 g/t Au. Management believes that these exploration results demonstrate significant potential for increasing the existing Twangiza mineral resource base from the current strike length of 800 metres to a further strike of 1,550 metres, including 880 metres directly to the north of the Twangiza deposit and 670 metres of additional strike at Lukungurhi. Photos
October / November 2005
Maps
2006 Exploration ProgramThe year proved to be exceptionally rewarding for Banro's Twangiza project. Following three months of intense groundwork, the Company began drilling in February 2006, focusing primarily on the southern part of the Twangiza mineralized trend, with the goal of increasing the total resource base and upgrading the Inferred resource ounces. By year-end, the four core rigs operating at Twangiza had completed 71 core holes (71,065 metres). Throughout the year, this ongoing core drilling program continued to intersect wide, multiple zones of gold mineralization within the Main Twangiza deposit where previous drilling was too widely spaced to outline higher confidence mineral resources. The results of this successful program enabled the Company to increase and upgrade the Twangiza resource base in September 2006 and again in January 2007. Total resources at Twangiza grew by 75% over the year, with Measured and Indicated Resources increasing by 49% to 3.009 million ounces of gold. The Inferred Resource at January 31, 2007 was 2.63 million ounces of gold. The Company views the significant increase in the total resource base at Twangiza as exceptionally encouraging and demonstrates the potential for this project to develop into a major open pit gold mining operation with a significant component being in good grade, near surface, oxide and transitional material. In addition to the ongoing drilling of the Main Twangiza deposit, results from two boreholes drilled 1,400 metres to the north between the Kashegeshe and Lukungurhi workings indicated good potential for the delineation of additional resources outside the Main Twangiza deposit. This new mineralized zone comprises a sedimentary package of mudstone, carbonaceous mudstone and siltstone that have been intruded by feldspar porphyry sills. Sulphide mineralization consists of disseminated and massive, pyrite and arsenopyrite. Surface structural mapping indicates a NNW-SSE bedding plane trend which is similar in orientation to the Main Twangiza deposit. The more southerly of these holes, located 150 metres north of the Lukungurhi workings, is interpreted as having been drilled into the hanging wall of the mineralized trend. Further drilling is being undertaken to determine the resource potential of this new mineralized zone. In November, the Company also announced preliminary metallurgical test results for the Twangiza project. Eleven composite drill hole samples of approximately 10 kilograms each were submitted to the SGS Lakefield laboratory in South Africa for initial diagnostic leaching testwork to establish the gold-mineral association within oxide, transitional and fresh rock materials. The diagnostic testwork procedure involved the sequential solubilizing of the least-stable minerals via various pre-treatments (cyanidation, hydrochloric and nitric acid) and extraction of the associated gold by cyanidation/CIL. Results for the four oxide samples gave recoverable gold by CIL (carbon-in-leach) processing of between 88.92% and 95.63%. For the four transitional material samples, expected recoverable gold by carbon-in-leach processing varied between 27.33% and 90.01%. The three fresh rock samples gave expected recoverable gold by carbon-in-leach processing of between 42.19% and 61.96%. These preliminary results demonstrate the high metallurgical recoveries of the oxide material at Twangiza. Further submission of samples for mineralogical and leaching testwork are being undertaken for the transitional material to investigate the wide variation in metallurgical recoveries, to better define the leach characteristics of this material type and to optimize metallurgical recoveries. Additional mineralogical and metallurgical testwork is being conducted on the fresh rock material to identify processing methods for optimizing metallurgical recoveries. Photos
Trench Photos Corresponding to the Press Release of January 17, 2006
MapsDecember 2006
November 2006
July 2006
May 2006
2005
2007 Exploration and Development ResultsAmong the highlights of the 2007 exploration program was the discovery and expansion of the gold deposit at Twangiza North, a new trend of approximately 2,500 metres in length, extending directly north from the Twangiza Main deposit. The full Twangiza trend now consists of 3,200 metres of gold mineralization. This new discovery was a result of drilling out a +100 ppb gold-in-soil anomaly that has a strike length of approximately 1.8 kilometres. Unlike the gold mineralization at the Twangiza Main deposit, which is hosted predominantly in shales and siltstones, the mineralization at Twangiza North is associated predominantly with feldspar porphyry sills that have intruded westerly dipping sediments (shales and siltstones). The mineralization in this lithology is non-refractory and open at depth and to the north. The Twangiza North discovery, together with continued infill drilling along the Twangiza Main deposit, led to a significant increase in resources at the property during the year, with Measured and Indicated Mineral Resources at Twangiza as a whole increasing by 29% to 3,872,000 ounces of gold (53,629,000 tonnes grading 2.25 g/t Au). The Inferred Mineral Resource at Twangiza increased slightly to 2,705,000 ounces of gold (46,188,000 tonnes grading 1.82 g/t Au). The exploration progress achieved at Twangiza in 2007 resulted from an intensive drilling program of 120 core holes totaling 26,411 metres, with the primary objective being to upgrade and increase the previously defined Inferred Mineral Resource. Between the resumption of drilling in February 2006 and year-end 2007, Banro completed a total of 191 core holes totalling 43,476 metres at Twangiza. Four drill rigs are currently deployed at the Twangiza property, with additional rigs to be mobilized in 2008. 2007 also saw Banro begin exploration of the Twangiza property outside the main trend. The Company established a new exploration camp at the major artisanal site at Mufwa, situated 13 kilometres northwest of the Twangiza Main deposit, and initiated field work in other target areas including the promising artisanal workings at Tshondo. Additional rigs are being mobilized to Twangiza so this new prospect can also be drilled during the coming months once groundwork has been completed. LIDAR, airborne magnetic and radiometric surveys were also completed of the entire Twangiza property; to date serveral promising new targets have been identified for follow-up work. Preliminary Assessment In July 2007, the Company announced the results of a preliminary assessment (scoping study) of Twangiza. This work included the results of evaluations of in pit mineral resources, capital and operating costs, infrastructural requirements and financial modelling. An increased amount of metallurgical testwork was also undertaken to further evaluate the oxide, transitional and sulphide ore types. The significant projections of the Twangiza scoping study included the following:
Photos
MapsSeptember 2007
May 2007
January 2007
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