Montero Revises High-Grade REE Resource in the Twiga Zone to 0.47 Million Tonnes Averaging 5.2% LREO5 at the Wigu Hill Rare E...
06 Agosto 2013 - 4:32PM
Marketwired Canada
Montero Mining and Exploration Ltd. (TSX VENTURE:MON) ("Montero") has revised a
portion of its initial NI 43-101 compliant Inferred Mineral Resource estimate of
3.3M tonnes at 2.6% LREO5 (Light Rare Earth Oxides) for the Tembo and Twiga
Zones (See News Release dated September 12, 2011) on its Wigu Hill Rare Earth
Element ("REE") Project. The updated resource estimate is only for the Twiga
Zone and is based on data from the initial 15 core boreholes (1,560m) used in
the initial resource estimate and data from infill drilling of 17 boreholes at
25m intervals (986m) completed in 2012. The data used in the revised Twiga Zone
overall resource has outlined a higher grade REE deposit for this zone.
The newly defined high grade REE resource at the Twiga Zone is located on the
south-eastern ridge of the Wigu Hill carbonatite complex. A total Inferred
Mineral Resource of 1.9 million tonnes at a grade of 2.7% LREO5 has been
estimated from the preliminary and infill drilling of 32 boreholes (2,546m) for
the Twiga Zone to a depth of 50m. A sensitivity analysis at a cut-off grade of
3% LREO5 has shown that the Inferred Mineral Resource contains a higher-grade
portion consisting of 0.47 million tonnes averaging 5.2% LREO5. The independent
estimate was prepared by AMEC Earth & Environmental Services (UK) Limited
(AMEC).
Dr Tony Harwood, President and Chief Executive Officer of Montero
commented, "The revised REE resource estimate for the Twiga Zone has
defined a higher grade portion consisting of 0.47 million tonnes
averaging 5.2% LREO5 to a depth of 50m from surface. The Twiga Zone
sits at the base of Wigu Hill close to current infrastructure and roads
and could potentially represent an initial starter open pit. Montero is
studying this zone with a view to direct shipping of a pre-sorted
mineral concentrate product for REE refining."
Overview
The carbonatite dikes on the Twiga Zone at Wigu Hill are intruded into fenitized
and carbonate altered, well foliated gneisses and amphibolites of the Paleo
Proterozoic Usagaran Mountain belt 20km west-south-west of Dar es Salaam. The
carbonatites are mainly fresh and coarsely crystalline, consisting of dolomite,
lesser calcite and varying amounts of ankerite and are mineralized with
bastnaesite, synchisite and minor amounts of monazite. Carbonate alteration and
fenitization close to the dikes is intense and weakens with increasing distance
away from the intrusives.
The carbonatites have intruded along a conjugate set of fractures within the
gneisses. Two principal dike directions have been identified at Twiga, 050
degrees (NE) and 220 degrees (SW). The mineralized carbonatite dikes at the
Twiga Zone occur in an area about 340m x 200m in extent. Although some
outcropping dikes are evident, the extent and thickness of the intrusives at
surface was delineated by trenching. The most continuous dike direction is
referred to as the "NE" dike striking at 050 degrees over a distance of over
200m and dipping to the NW at 35 degrees to 50 degrees. The other predominant
dike direction is referred as the "SW" dikes that dip steeply to the NE at
between 70 degrees to 88 degrees. The widths of the carbonatite dikes vary from
a few centimetres to 10m and the continuity of individual dikes is difficult to
trace both along strike and in depth.
This review of the rare earth resources at the Twiga Zone was designed
specifically to outline the potential for a smaller, higher grade REE resource
within the larger deposit. The drillhole and trench database used for the 2011
estimate was updated to incorporate the results for holes TW015 to TW030, and
combining an extra 181 assayed samples representing 273.5 m of cored intercepts
to support this estimate. This has enabled the Twiga Zone overall resource to be
updated independently of the adjacent Tembo Zone.
Full details of the Inferred Mineral Resource estimate for Twiga totaling 1.9Mt
grading 2.7% LREO5 is provided in Table 1 (REE grades) and Table 2 (REO grades).
Table 1: Twiga Inferred Mineral Resource estimate - REE grades (Cut-off
grade 1% LREO5)
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Principal resource grades (c.90% of contained REE
value)
Domain Tonnage LREE5 La Ce Pr Nd Sm
Mt % % % % % %
1 Twiga NE 1.23 2.00 0.78 0.95 0.07 0.18 0.01
2 Twiga SW 0.70 2.63 1.03 1.25 0.10 0.24 0.01
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TOTAL 1.93 2.23 0.87 1.06 0.08 0.20 0.01
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By-product resource grades (greater uncertainty to economic
value)
Domain Eu Gd Tb Dy Ho Er Tm
ppm ppm ppm ppm ppm ppm ppm
1 Twiga NE 26 38 4.1 13 1.7 3.0 0.3
2 Twiga SW 30 41 4.3 13 1.7 3.2 0.4
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TOTAL 27 39 4.2 13 1.7 3.1 0.3
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By-product resource grades (greater Deleterious
uncertainty to economic value) elements
Domain Yb Lu Y TREE15 SrO Th U
ppm ppm ppm % % ppm ppm
1 Twiga NE 1.7 0.3 37 2.01 0.8 83 1.1
2 Twiga SW 1.9 0.3 38 2.64 1.1 67 0.9
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TOTAL 1.8 0.3 38 2.24 0.9 78 1.0
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Notes:
1 The effective date for the 2013 estimate is 8 February 2013. The
Qualified Person responsible for this resource estimate is
Edmund Sides, EurGeol, PGeo.
2 A selective mining unit (SMU) size of 3m by 3m by 3m was assumed
when creating the block model.
3 Reported grades are based on consideration of the grades of
mineralised material and weakly to non-mineralised wallrock
material estimated to fall inside each SMU.
4 The reported Mineral Resource estimates are based on a grade
cut-off grade of 1.0% LREO5 (sum of estimated grades of La2O3,
CeO2, Pr6O11, Nd2O3 and Sm2O3). A minimum value of 0.1 for the
estimated carbonatite indicator was also applied (i.e. only
blocks considered to contain greater than 10% mineralised
material are included in the reported resource totals).
5 The assessment of prospects for economic extraction is based on
the estimated grades for the four main light REEs (La, Ce, Pr
and Nd) which represented about 90% of the contained value of
REEs at the date of estimation. There is greater uncertainty
associated with the estimated grades for the other elements
reported above due to the low grades of the heavier REEs and the
limited quality control information available with which to
assess the accuracy of these analyses. Grades for these elements
are reported in order to facilitate comparison with other REE
deposits.
6 The Mineral Resources for the Twiga deposit have been
constrained by an optimised pit shell defined obtained using the
following assumptions; slope angles of 50 degrees; a mining
recovery of 100% and mining dilution of 0% (already incorporated
in the SMUs); a mining cost of USD2.85/t; process operating
costs of USD12.0/t; G&A costs of USD 3.0/t material to be
processed, with 90% recovery of REOs to a 45% LREO5 bastnaesite
concentrate; and a concentrate price of USD10/kg.
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Table 2: Twiga Inferred Mineral Resource estimate - REO grades (Cut-off
grade 1% LREO5)
----------------------------------------------------------------------------
Principal resource grades (c.90% of contained REE
value)
Domain Tonnage LREO5 La2O3 CeO2 Pr6O11 Nd2O3 Sm2O3
Mt % % % % % %
1 Twiga NE 1.23 2.40 0.92 1.17 0.09 0.21 0.01
2 Twiga SW 0.70 3.15 1.21 1.54 0.12 0.27 0.02
----------------------------------------------------------------------------
TOTAL 1.93 2.67 1.02 1.30 0.10 0.23 0.01
----------------------------------------------------------------------------
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By-product resource grades (greater uncertainty to economic
value)
Domain Eu2O3 Gd2O3 Tb4O7 Dy2O3 Ho2O3 Er2O3 Tm2O3
ppm ppm ppm ppm ppm ppm ppm
1 Twiga NE 30 44 4.8 15 1.9 3.4 0.3
2 Twiga SW 35 47 5.1 15 1.9 3.7 0.5
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TOTAL 31 45 4.9 15 1.9 3.5 0.3
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----------------------------------------------------------------------------
Additional resource grades (greater Deleterious
uncertainty to economic value) elements
Domain Yb2O3 Lu2O3 Y2O3 TREO15 SrO ThO2 U2O3
ppm ppm ppm % % ppm ppm
1 Twiga NE 1.9 0.3 47.0 2.42 0.8 95 1.3
2 Twiga SW 2.2 0.3 48 3.17 1.1 76 1.1
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TOTAL 2.0 0.3 48 2.69 0.9 88 1.2
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----------------------------------------------------------------------------
Notes:
1 The effective date for the 2013 estimate is 8 February 2013. The
Qualified Person responsible for this resource estimate is
Edmund Sides, EurGeol, PGeo.
2 A selective mining unit (SMU) size of 3m by 3m by 3m was assumed
when creating the block model.
3 Reported grades are based on consideration of the grades of
mineralised material and weakly to non-mineralised wallrock
material estimated to fall inside each SMU.
4 The reported Mineral Resource estimates are based on a grade
cut-off grade of 1.0% LREO5 (sum of estimated grades of La2O3,
CeO2, Pr6O11, Nd2O3 and Sm2O3). A minimum value of 0.1 for the
estimated carbonatite indicator was also applied (i.e. only
blocks considered to contain greater than 10% mineralised
material are included in the reported resource totals).
5 The assessment of prospects for economic extraction is based on
the estimated grades for the four main light REEs (La, Ce, Pr
and Nd) which represented about 90% of the contained value of
REEs at the date of estimation. There is greater uncertainty
associated with the estimated grades for the other elements
reported above due to the low grades of the heavier REEs and the
limited quality control information available with which to
assess the accuracy of these analyses. Grades for these elements
are reported in order to facilitate comparison with other REE
deposits.
6 The Mineral Resources for the Twiga deposit have been
constrained by an optimised pit shell defined obtained using the
following assumptions; slope angles of 50 degrees; a mining
recovery of 100% and mining dilution of 0% (already incorporated
in the SMUs); a mining cost of USD2.85/t; process operating
costs of USD12.0/t; G&A costs of USD 3.0/t material to be
processed, with 90% recovery of REOs to a 45% LREO5 bastnaesite
concentrate; and a concentrate price of USD10/kg.
----------------------------------------------------------------------------
A higher-grade, near-surface portion of the Twiga Mineral Resource straddling
the "EW" dikes is of particular interest. Based on the updated Mineral Resource
estimate for Twiga Zone, AMEC has reassessed the potential of this portion of
the Mineral Resource in the following manner:
-- Several alternative optimum pit shells were generated using different
processing and recovery factors so as to identify 'high-value' pits
centred on the highest grade near surface mineralisation.
-- An initial assessment of the results obtained was carried out in order
to identify the appropriate cut-off grade to apply in order to delineate
approximately 500,000 tonnes of near surface, higher grade material
within the mineral resource. A cut-off grade of 3.0% LREO5 was selected
on this basis.
-- The selected pit shell was then plotted on sections and plans and
summaries of the high grade portion falling inside the selected pit were
generated for the Inferred Mineral Resource, and also for the
mineralised portion of each block (undiluted estimate of material
potentially amenable to pre-concentration).
-- Following a review of the initial results it was noted that a portion of
the optimum pit went to depths of more than 50 m around drill hole TW014
where there is a zone of mineralisation based on limited information. In
order to reduce the uncertainty associated with the estimation of this
zone, and to meet likely constraints on the maximum depth for an initial
trial open-pit, a revised summary was generated which excluded all
blocks which are more than 50 m below surface. Such blocks were
identified by checking their location with respect to a wireframe
surface generated by projecting the topography vertically downwards by
50 m.
The results obtained in this investigation are presented in Table 2 and indicate
that a cut-off grade of 3.0% LREO5 defines a subset of the Inferred Mineral
Resource amounting to 0.47 million tonnes averaging 4.4% LREE5 (equivalent to
5.2% LREO5). This is equivalent to an estimated contained rare earth oxide
content of approximately 24,400 t LREO5.
Table 3: Twiga SW Sensitivity sub-set of Inferred Mineral Resource
(based on highest value mineralisation using a cut-off grade of 3.0% LREO5,
within 50m of surface)
----------------------------------------------------------------------------
Principal resource grades (c.90% of contained REE
value)
Domain Tonnage LREO5 La2O3 CeO2 Pr6O11 Nd2O3 Sm2O3
Mt % % % % % %
1 Twiga NE 0.24 4.65 1.80 2.26 0.17 0.40 0.024
2 Twiga SW 0.22 5.87 2.26 2.87 0.21 0.50 0.030
----------------------------------------------------------------------------
TOTAL 0.47 5.24 2.02 2.56 0.19 0.45 0.026
----------------------------------------------------------------------------
----------------------------------------------------------------------------
By-product resource grades (greater uncertainty of economic
value)
Domain Eu2O3 Gd2O3 Tb4O7 Dy2O3 Ho2O3 Er2O3 Tm2O3
ppm ppm ppm ppm ppm ppm ppm
1 Twiga NE 52 73 8.0 23 2.9 4.7 0.5
2 Twiga SW 60 81 8.5 23 3.0 5.3 0.6
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TOTAL 56 76 8.2 15 2.9 4.9 0.5
----------------------------------------------------------------------------
----------------------------------------------------------------------------
By-product resource grades (greater Deleterious
uncertainty of economic value) elements
Domain Yb2O3 Lu2O3 Y2O3 TREO15 SrO ThO2 U2O3
ppm ppm ppm % % ppm ppm
1 Twiga NE 2.4 0.3 66 4.68 1.4 139 1.5
2 Twiga SW 2.7 0.5 70 5.90 1.4 110 1.4
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TOTAL 2.5 0.3 67 5.26 1.4 125 1.5
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Using the block estimates of the mineralized indicator variable and the separate
block grade estimates for mineralized and unmineralized material, it is
estimated that the maximum amount of the Inferred Mineral Resource that would be
amenable to pre-concentration is 0.28 million tonnes averaging 7.1% LREE5
(equivalent to 8.5% LREO5). AMEC notes that this is an indicative total based on
the resource estimate and represents the maximum upgrading that could be
achieved with perfect segregation of mineralized and waste material. Under
actual operational conditions it is likely that the practical amount that could
be recovered would fall somewhere between these two estimates (subject to the
Mineral Resource estimate proving to be a reliable prediction of the actual
amounts and grades of the in situ mineralization).
AMEC considers that this high-grade sub-set of the mineral resource forms an
appropriate target for assessment during the next stage of the project. More
detailed work on open pit design and extraction scheduling is not warranted
until more information is available on the likely costs and recoveries for
alternative processing options.
In addition to updating the grade estimates for the five light REEs (Ce, La, Nd,
Pr and Sm) AMEC also estimated grades for the additional nine heavy REEs and
Yttrium, as well as uranium, thorium and strontium. There is greater uncertainty
associated with the estimated grades for the HREEs and strontium due to the
limited quality control information available with which to assess the accuracy
of these analyses as well as the low grades of the HREEs. Grades for these
elements are reported in order to facilitate comparison with other REE deposits.
Further analytical work is required in order to assess the accuracy of the
analyses for these elements.
The assessment of prospects for economic extraction of the reported Mineral
Resource for Twiga is based on the estimated grades for the four light REEs (La,
Ce, Pr and Nd) which represented about 90% of the contained value of REEs at the
date of estimation. In terms of contained value the next most important elements
are considered to be Eu, Dy and Gd based on the values reported above; these are
likely to be recovered to a mixed REO concentrate and could potentially realize
some value. Strontium is also present is varying amounts within the mineralized
carbonatites in close association with the rare earth element mineralization;
the potential added value of extracting SrO as an additional by-product will be
assessed in future metallurgical testwork.
Resource classification
To support an assessment of reasonable prospects for economic extraction, AMEC
used a pit shell that was developed to constrain the reported Mineral Resource
so as to exclude isolated zones of mineralization which were unlikely to be
amenable to economic extraction. The parameters used to develop the resource pit
shell were unchanged from the values used for the pit shell used for the 2011
resource estimate, as indicated in footnote 6 at the bottom of Table 1.
Based on considerations of the evaluation database used, geological and grade
continuity and economic factors, the reported resource has been classified as an
Inferred Mineral Resource.
Risk/opportunity issues
Readers are referred to the previous Technical Report on the initial Mineral
Resource estimate for the Twiga and Tembo deposits for a discussion of risks and
opportunities associated with the Mineral Resource estimates.
The changes in REO prices over the past two years were assessed during the
current resource update and it was considered that the REO mineral concentrate
price of USD 10/kg used in the assessment of the resource pit shell was still
valid at the time of reporting. Based on early 2013 prices, about 90% of the
contained REE value relates to the contained La, Ce, Pr and Nd content and at
this stage the assessment of reasonable prospects of eventual economic
extraction does not rely on any value attributed to the other elements. Possible
additional costs and value associated with the recovery of the other REEs and
strontium into concentrates needs to be assessed in future metallurgical
testwork. In addition further analytical work is required in order to assess the
accuracy of the analyses for the HREEs and strontium which have a lower quality
than analyses for the five LREEs.
Thorium and uranium represent deleterious elements which may incur additional
processing costs in order to remove them from the REO concentrates and in the
handling of radioactive waste products. The contents reported here are
relatively low compared with many other REE deposits but their impact on
processing costs will need to be assessed in future metallurgical testwork.
Metallurgical processing of the mineralisation to recover saleable rare earth
mineral products is identified as one of the main areas of concern for the next
stage of the project. The updated resource estimate reported on here provides a
suitable basis for guiding metallurgical testwork and for assessing the
possibility of trial mining in the next stage of the project. A small open pit
could potentially be developed at the Twiga Zone where access is good at the
base of Wigu Hill and where high grade bastnaesite-rich carbonatite can be
accessed from the surface.
Future work programs
The high grade resource identified at Twiga is being considered as a possible
opportunity to provide a REE mineral concentrate produced by mechanical or hand
sorting to the market, or with further positive flotation recovery results, a
flotation concentrate. Metallurgical testwork on samples from the property are
ongoing and Montero has already achieved success in producing samples of
saleable product for marketing purposes. The current tonnage itself may appear
to be small, however, this resource reflects the potential of only a small near
surface fraction of the Wigu Hill Complex. Exploration drilling has identified a
more extensive set of carbonatite dikes on the Nyati Target in the central part
of the Wigu Hill carbonatite complex where initial drilling has returned
positive results (see news release dated: April 10, 2012). Future drilling at
the Nyati Target and other targets is envisaged to outline the potential for a
larger resource.
Definition of REE Terminology
The sum of the analyses of the five most abundant REEs, namely Ce, La, Nd, Pr,
and Sm, is referred to as LREE5 in the tables presented in this press release
(and LREO5 for the corresponding sum of the oxide grades). The following oxide
formulae were used: CeO2, La2O3, Nd2O3, Pr6O11 and Sm2O3; these are based on the
compositions used for marketed REOs for which price information is generally
quoted. Grades for these five REEs make up over 99% of the REE content at Wigu
Hill; the other ten REEs (Eu, Er, Dy, Gd, Ho, Tb, Tm, Lu, Y and Yb) are present
in trace amounts only. AMEC notes that due to the lack of certified analytical
standards the analytical accuracy for these ten REEs is considered to be of
lower quality than for the five light REEs and consequently they are considered
by-products and were not relied upon when assessing the prospects of economic
extraction of the reported Mineral Resource. (Note: Assay results reported in
some previous press releases used the 'laboratory convention' of REE2O3 for the
REO grades which will give slightly different grades for the oxides of Ce and
Pr).
Quality Assurance/Quality Control (QA/QC):
Montero has used blanks, field duplicates and one analytical standard to monitor
the sampling and analytical quality. Results to date for the blank and field
duplicates show acceptable quality for the main REEs of interest. The standard
used was prepared on behalf of Montero using material from Wigu Hill and has
certified analytical values for Ce, La, Pr and Sm based on analyses from 16
different laboratories. A review of the QA/QC results was completed by AMEC who
concluded that the results for Ce, La, Pr, Nd and Sm were acceptable for use in
the assessing the prospects for economic extraction and reporting of an Inferred
Mineral Resource.
Qualified Person's Statement
The technical information contained in this press release has been reviewed by
Mr. Mike Evans, M.Sc. Pr.Sci.Nat., who is a qualified person for the purpose of
National Instrument 43-101 and a consulting geologist to Montero. The
independent resource estimate was prepared by AMEC Earth & Environmental
Services (UK) Ltd (AMEC) and is reported according to CIM Definition Standards
(2010). The Qualified Person responsible for the resource estimate is Edmund
Sides, EurGeol, P.Geo. an AMEC employee.
The Wigu Hill Rare Earth Project does not contain a mineral reserve and is not
currently in production. Any decision to place the Wigu Hill Rare Earth Project
into production requires the support of a feasibility study prepared in
accordance with National Instrument 43-101. At this time the Company has
completed a series of laboratory and pilot scale testwork, but this does not
satisfy the requirements of a feasibility study. Accordingly, any decision to
commence production on the Wigu Hill Rare Earth Project is neither imminent nor
assured, and investors cannot assume that the Wigu Hill Rare Earth Project hosts
an economic mine at this time.
About Montero Mining & Exploration
Montero Mining and Exploration Ltd. is a mineral exploration and development
company focused on achieving production of rare earths primarily from its
flagship Wigu Hill project in Tanzania. With China's control over rare earth
export quotas; it is becoming imperative that the rest of the world develops new
rare earth resources to meet the increasing demand from "green" technology and
high-tech applications. Montero has a highly experienced Board and Management
team that has built and operated mines and refineries in Africa, which brings
significant credibility to our strategy of becoming a rare earth producer. In
addition to rare earths, Montero has phosphate assets in South Africa and
uranium assets in Tanzania and Quebec, Canada for sale or joint venture.
Signed. Dr. Tony Harwood - President and CEO
CAUTIONARY STATEMENT: Neither 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 accuracy of this release. This News
Release includes certain "forward-looking statements", which often, but not
always, can be identified by the use of words such as "believes", "anticipates",
"expects", "estimates", "may", "could", "would", "will", or "plan". These
statements are based on information currently available to Montero and Montero
provides no assurance that actual results will meet management's expectations.
Forward-looking statements include estimates and statements with respect to
Montero's future plans, objectives or goals, to the effect that Montero or
management expects a stated condition or result to occur, including Montero's
estimates with respect to mineral resource quantities, grades and economic
potential. Since forward-looking statements are based on assumptions and address
future events and conditions, by their very nature they involve inherent risks
and uncertainties. Actual results relating to, among other things, results of
exploration, project development, reclamation and capital costs of Montero's
mineral properties, and Montero's financial condition and prospects, could
differ materially from those currently anticipated in such statements for many
reasons such as: changes in general economic conditions and conditions in the
financial markets; changes in demand and prices for minerals; litigation,
legislative, environmental and other judicial, regulatory, political and
competitive developments; technological and operational difficulties encountered
in connection with Montero's activities; and other matters discussed in this
News Release and in filings made with securities regulators. This list is not
exhaustive of the factors that may affect any of Montero's forward-looking
statements. These and other factors should be considered carefully and readers
should not place undue reliance on Montero's forward-looking statements. Montero
does not undertake to update any forward-looking statement that may be made from
time to time by Montero or on its behalf, except in accordance with applicable
securities laws.
FOR FURTHER INFORMATION PLEASE CONTACT:
Montero Mining and Exploration Ltd.
+1 416 840 9197
+1 866 688 4671 (FAX)
ir@monteromining.com
www.monteromining.com
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