Xtierra Inc.: final steps for Bilbao feasibility study
TORONTO, ONTARIO–(Marketwire – June 7, 2012) – Xtierra Inc. (TSX VENTURE:XAG) ("Xtierra" or the "Company"), is pleased to report that at the Annual Meeting held in Toronto on June 6, 2012, shareholders were provided with an update on the progress of the Feasibility Study at the Company's Bilbao project, which is anticipated to be completed in the third quarter of 2012.
Bilbao Feasibility Study
In 2010, Xtierra retained DRA Americas, a consulting engineering firm with expertise in process engineering, to oversee and complete the Bilbao Feasibility Study. DRA is involved in oversight of all of the component parts of the Feasibility Study as well as managing all the metallurgical test work. The Feasibility Study is comprised of metallurgical test work on the oxide, mixed and sulphide mineralization, geotechnical studies, hydrogeological studies, topographic surveys, mine planning and engineering studies, capital and operating costs and environmental and permitting studies.
During Q1 2012, work was conducted in developing a detailed mine plan for the underground areas, including evaluation of underground mining methods and design of an access ramp and necessary stope development. Xtierra has retained Golder Associates to advise on tailings disposal and related plant design work. In order to optimize water consumption, reduce and simplify the design of the tailings disposal impoundment infrastructure and generate material for back filling the underground stopes, production of paste tailings is being considered.
Geotechnical, hydrogeology and electrical power distribution infrastructure studies have been completed and are under review by DRA.
Based on the metallurgical results received to date it is expected that the Feasibility Study will recommend the initial development of an underground mine and the processing of the sulphide and transition resources. The development of the open pit mine and processing of the oxide ore would be deferred and would occur later in the mine life, subject to further metallurgical optimization of the oxide process flow sheet and open pit resource optimization.
Items to be completed in the Feasibility Study include final optimization of the sulphide and transition ore process flow sheet to possibly include the production of a copper concentrate in addition to lead and zinc concentrates, completion of underground mine plans and schedules, completion of tailing disposal plans, completion of a final EIA, securing surface and water rights, and finalization of operating and capital cost estimates.
Metallurgical Testing and Studies
Because the mineralization at Bilbao comprises both oxide and sulphide material, together with some mixed transitional mineralization, much of the Company's efforts has focused on developing metallurgical approaches to economically recover the various mineralized types and this has involved multiple stages of metallurgical testing and design.
The first reported metallurgical studies were carried out during 1994-1995, by Lakefield Research as part of a consulting consortium consisting of Watts Griffis & McOuat and Kilborn Engineering. The results of those studies presented a case for open-pit mining with differing scenarios for metallurgical processing and metal recovery. At that time Lakefield investigated gravity, flotation and leaching with thio-urea and cyanide without satisfactory recovery of lead or silver. Copper and zinc would be recovered by leaching with sulphuric acid and use of solvent extraction with electrolytic precipitation of the copper and zinc.
Additional metallurgical test work was carried out by Xtierra in 2008/2009 at the Metallurgical Institute of the University of San Luis Potosí using a process of wet high intensity magnetic separation (WHIMS) and acid leaching on oxide mineralization.
Based on the WHIMS results a decision was made to proceed with a pilot plant test program to confirm the process flow sheet and enable the design of a processing plant to treat the oxide mineralization. Four composite samples were extracted from two underground levels (historic workings) and from near surface, representing the majority of the oxide resource. A pilot plant sized crusher, ball mill and WHIMS were set up at the Bilbao project site to prepare and produce a pre-concentrate, which was shipped for processing to the SGS laboratories in Durango, Mexico and Lakefield, Ontario. The initial test results indicated only moderate recoveries, particularly for lead, from the oxide ore.
Since 2010, DRA has been overseeing the ongoing metallurgical test work. DRA recommended that further open circuit bench scale laboratory test work be concluded on both pre-concentrated and whole ore (no pre-concentration) prior to conducting a closed circuit or locked cycle test programme. This test work was initially performed at the SGS Laboratory in Durango, Mexico and subsequently at the SGS Laboratory in Lakefield, Ontario.
After numerous tests conducted on optimizing the pre-concentration process for oxide ores by means of wet high intensity magnetic separation it was concluded that there was no appreciable benefit in reducing overall acid consumption relative to processing whole ore. It was also concluded that there is no meaningful benefit in including the WHIMS pre-concentration process in the flow-sheet for the treatment of the oxide ore.
The results of the test-work on the oxide ore completed to date indicates that while it is possible to achieve acceptable recovery levels the costs involved in doing so, particularly for the amounts of reagent consumption required, would be expensive. Further metallurgical test work on the oxides to optimize economic metal recoveries, including the recovery of lead by means of gravity separation, has shown some promise and additional metallurgical test-work will be continued at a later date.
In 2011, DRA recommended a final phase of metallurgical test work on the sulphide and mixed transition ores, including locked cycle test work. Two drill holes were completed in the Q3 2011 for metallurgical sample purposes, generating material for flotation test work as well as grinding determinations. The flotation test work, conducted at SGS laboratories in Lakefield, Ontario, began in November 2011 and completed in Q2 2012, was carried out on both sulphide and transition ores and included locked cycle testing with good results indicated. Testing of the effects of co-mingling the mixed transition ores with the sulphide ore was also conducted.
It is anticipated that the remaining planned metallurgical test work will be completed and the final metallurgical reports will be received by the end of Q2 2012 and incorporated into the Feasibility Study.
Bilbao Mineral Resources
The Bilbao deposit is a replacement-style deposit with a skarn overprint and is located adjacent to the La Blanca granodiorite. The Bilbao mineralization forms zones dipping at shallow angles ranging up to about 45 degrees. The mineralization has been oxidized to a depth of about 70m below the surface, below which there is an irregular zone of mixed oxide-sulphide mineralization varying between 20 – 100m in thickness. The sulphides continue to a depth of about 230m.
Between 2006 and 2009 the Company carried out a series of exploration drilling programs as a result of which the size of the deposit was increased from the original historical estimate of about 3.45 million tonnes to about 6.0 million tonnes. Subsequent drilling in 2010 and 2011 further expanded the resources to the current level of 10.6 million tonnes and the deposit remains open, particularly to the south where recent exploration drilling has identified two silver targets immediately to the south of the Bilbao deposit. Further infill drilling is currently being carried out on the deposit.
An independent resource estimate was prepared in April 2011 by R.T.G. Parker, C.Eng., an independent consulting mining geologist and a 'Qualified Person' within the meaning of NI 43-101 – Standards of Disclosure for Mineral Projects of the Canadian Securities Administrators. The resource estimate was calculated using a 3% zinc equivalent cut off and includes sulphide, oxide and mixed ore categories and is summarized in the table below.
Technical Report dated April, 2011 entitled "Geology and revised Minerals resources of the Bilbao Silver-Lead-Zinc Deposit – State of Zacatecas, Mexico" by RTG Parker, Consulting Geologist.
The resource, comprising the current Bilbao deposit, is made up of primary sulphide mineralization below approximately 70 metres depth (50% of the resource) and oxide mineralization which extends from surface to a depth of about 70 metres (35% of the resource). There is a narrow but irregular zone of transition mixed mineralization between these two categories comprising 15% of the resource.
|BILBAO INDICATED RESOURCES AT 3% ZNEQ CUTOFF (APRIL 2011 RTG PARKER – INDEPENDENT QUALIFIED PERSON)|
Information of a scientific or technical nature contained in this release has been prepared by or under the supervision of Terence N. McKillen, P.Geo., Chief Executive Officer, Gerald J. Gauthier, P.Eng., Chief Operating Officer and Dr. Anthony C. Gallon, C.Eng., Chief Geologist, all 'Qualified Persons' within the meaning of National Instrument 43-101 – Standards of Disclosure for Mineral Projects of the Canadian Securities Administrators.
About Xtierra Inc.
Xtierra Inc. is a Toronto based exploration and development company listed on the TSX Venture Exchange under the symbol "XAG". There are 103,272,142 shares issued and outstanding. The Company is completing a feasibility study on its Bilbao silver-zinc-lead-copper project in Zacatecas, Mexico. Xtierra's objective is to become a mid-tier producer of precious and base metals through the development of its Bilbao project as well as through exploration, organic growth and M & A opportunities.
For further information visit www.xtierra.ca.
Neither the TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or the accuracy of this release.
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