Macarthur Minerals Increases Its Snark and Drabble Downs Direct Shipping Hematite Mineral Resource by 46% to 14 Million Tonnes-The Total Resource Now Stands at 25 Million Tonnes

THIS NEWS RELEASE IS NOT FOR DISTRIBUTION TO UNITED STATES SERVICES OR FOR DISSEMINATION IN THE UNITED STATES

VANCOUVER, BRITISH COLUMBIA -- (Marketwire - Sept. 21, 2011) - Macarthur Minerals Limited (TSX VENTURE: MMS) (OTCQX: MMSDF) (“the Company“) is pleased to advise of a 46% increase in the Hematite Goethite Mineral Resource estimate for its Snark & Drabble Downs potential DSO (“potential direct shipping ore“) Mineral Resource located at its Macarthur Iron Ore project in Western Australia.

The Company is undertaking a comprehensive “drillout“ of the Snark, Drabble Downs and Snark North areas. Of the 414 RC holes assayed to date, 294 holes have intercepted mineralisation and have been incorporated into this interim Mineral Resource statement. An additional 248 drilled RC holes are awaiting assay results and are not included in this interim Mineral Resource statement.


Pre-Feasibility Study

MMS has been awaiting these results in order to provide an appropriate Mineral Resource inventory for the completion of the Company's pre-feasibility study.

The Mineral Resource referred to in this release has been estimated by independent mining consultancy group CSA Global Pty Ltd (“CSA“) based on the Company's geological interpretations.


2011 Potential DSO RC Drilling Update

This year 595 RC holes have been completed at the Snark, Drabble Downs and Snark North prospects. This programme has increased the total Mineral Resource inventory and elevated some 8.630 Mt from the Inferred to the Indicated category. The ongoing program is expected to continue to increase the size and confidence level of the Mineral Resource inventory.

Further results from the remainder of the 2011 programme will be incorporated into the Mineral Resource as part of future Mineral Resource updates. Table 1 presents the total potential DSO Mineral Resource for the Macarthur Iron Ore project.

The remainder of the year will see a continuation of resource definition drilling in the Snark, Drabble Downs and Snark North areas. RC drilling has also commenced at the Company's Central area with a view to identifying further potential DSO Hematite resources.


Table 1 - Goethite/Hematite (Potential DSO) –Indicated and Inferred Mineral

Resource Estimate
Category Deposit Tonnes Fe% P% SiO2% Al2O3% LOI%
Indicated Snark 7,320,000 55.1 0.07 8.4 4.4 7.5
Drabble Downs 1,310,000 53.5 0.06 8.1 5.4 9.0
Total 8,630,000 54.9 0.07 8.3 4.6 7.9
Inferred Snark 4,110,000 55.1 0.07 8.7 4.2 7.6
Drabble Downs 1,380,000 55.9 0.06 5.9 4.6 8.6
Banjo – Lost World 5,500,000 55.7 0.07 8.1 4.7 7.1
Moonshine 600,000 52.8 0.06 13.3 3.9 5.8
Central 4,800,000 55.2 0.06 8.2 4.5 8.0
Total 16,390,000 55.3 0.07 8.3 4.6 7.6

Notes:
• Figures contained within Table 1 have been rounded.

• A block model was constructed using three dimensional geological wireframes.

• Part of the June 2011 Mineral Resource has been upgraded to indicated due to the determination of densities of the mineralisation, both from diamond core wet immersion techniques and geophysical probing of selected holes. CSA has used an assigned density of 2.9t/m3 for all mineralised zones.

• The CSA Mineral Resources were estimated using constraining wire framed solids based on a lower limit cut-off grade of 50%Fe. The resource was quoted from blocks above 50% Fe.


Table 2 – Mineral Resource Comparisons, Snark and Drabble Downs (CSA Global)

Date Category Tonnes (Mt) Fe% P% SiO2% Ai2O3% LOI%
September 2011 Indicated 8,630,000 54.9 0.07 8.3 4.6 7.9
Inferred 5,490,000 55.3 0.072 7.95 4.30 7.8
June 2011 Inferred 9,650,000 55.0 0.075 8.87 4.33 7.6
December 2010 Inferred 7,070,000 55.9 0.071 7.78 4.23 7.59

Table 2 above provides a history of the Mineral Resource estimates for the Snark prospect and stands to demonstrate the growing level of consistency and confidence in the geological investigation of this area.

The mineral resource was classified as Indicated and Inferred according to the reporting guidelines of NI43-101. The classification level is based upon an assessment of geological and mineralisation continually, quality control results and an analysis of available density information.

Macarthur Minerals President and CEO, Mr Alan Phillips commented “The increase in the resource inventory provides the Company with the confidence and the opportunity to commence Stage 1 mine planning at Snark. In parallel with this task we will continue to focus on delineating additional tonnages to further extend mine life at the planned initial production rate of 2 mtpa. Towards the end of Q3/Q4 a Pre-Feasibility Study is expected to be released and will link with the comprehensive environmental and impact assessment studies that have already been completed in over the Snark region.


Quality Assurance and Quality Control (QAQC):

Intersections reported have been verified by the Company's QAQC protocols. All samples from drill holes are prepared by Ultra Trace and Amdel Laboratories and pulverised to 90% passing 75 microns then analysed for the iron suite using XRF.


QUALIFIED PERSON

Mr David Williams, BSc (Hons), a member of the Australian Institute of Geoscientists, who is a full-time employee of CSA Global Pty Ltd and is an Independent Qualified Person, has reviewed and approved the above technical information relating to Mineral Resource estimates contained in this release, in the form and context in which it appears.

Further information on Macarthur Minerals Limited and technical reports on the Macarthur Iron Ore project can be found on the company's website www.macarthurminerals.com or www.sedar.com.


ABOUT MACARTHUR MINERALS LIMITED (TSX VENTURE:MMS)(OTCQX:MMSDF)

Macarthur Minerals Limited is an Australian based resource development company (listed on the TSX-V and OTCQX) focused on developing its potential Macarthur Iron Ore Project, located in the Yilgarn region of Western Australia. A standard gauge railway is in place to the Port of Esperance and its use will involve upgrades including construction of unloading facilities at the Menzies railhead, which is 110 km from the Company's potential Iron Ore Project. The railway is administered and operated by WestNet Rail on behalf of the Government of Western Australia. The Company has entered into discussions with WestNet Rail and is considering further study work. The project has an inferred mineral resource of 1.3 billion tonnes of magnetite at 30.1% Fe (press release dated December 15, 2010) that has been reported in accordance with National Instrument 43-101 and inferred & indicated mineral resources of 25.021 million tonnes at 55% Fe (this press release dated September 21, 2011) of goethite/hematite. The Company has completed a positive scoping study on the magnetite and a prefeasibility study for the hematite is well advanced.


On behalf of the Board of Directors,

MACARTHUR MINERALS LIMITED

Alan Phillips
President, Chairman & CEO



Caution Regarding Forward Looking Statements

Certain of the statements made and information contained in this press release may constitute forward-looking information and forward-looking statements (collectively, “forward-looking statements“) within the meaning of applicable securities laws. The forward-looking statements in this press release include but are not limited to, the listing of the Company's common shares on the TSX and reflect the current expectations, assumptions or beliefs of the Company based upon information currently available to the Company. With respect to forward-looking statements contained in this press release, assumptions have been made regarding, among other things, the reliability of information prepared and/or published by third parties that are referenced in this press release or was otherwise relied upon by the Company in preparing this press release. Although the Company believes the expectations expressed in such forward-looking statements are based on reasonable assumptions, such statements are not guarantees of future performance and no assurance can be given that these expectations will prove to be correct as actual results or developments may differ materially from those projected in the forward-looking statements. Factors that could cause actual results to differ materially from those in forward-looking statements include unforeseen technology changes that results in a reduction in iron or magnetite demand or substitution by other metals or materials, the discovery of new large low cost deposits of iron magnetite and the general level of global economic activity. Readers are cautioned not to place undue reliance on forward-looking statements due to the inherent uncertainty thereof. Such statements relate to future events and expectations and, as such, involve known and unknown risks and uncertainties. The forward-looking statements contained in this press release are made as of the date of this press release and except as may otherwise be required pursuant to applicable laws, the Company does not assume any obligation to update or revise these forward-looking statements, whether as a result of new information, future events or otherwise.

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Contact Information

The Buick Group
Jonathan Buick
Corporate Relations
416-915-0915
jbuick@buickgroup.com

Macarthur Minerals Limited - Australia
Alan Phillips
+61 418 726 230
aphillips@macarthurminerals.com
www.macarthurminerals.com