Weld Range

Western Australia, WA, Australia

Main commodities: Fe
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The Weld Range iron deposits are located in the 2.7 to 2.6 Ga Gyr greenstone belt of the Murchison Terrane in the Yilgarn Craton, some 65 km SW of Meekatharra, 50 km NW of Cue and 360 km NE of the Indian Ocean port of Geraldton in Western Australia.

The Weld Range is a marked physiographic feature, comprising a series of parallel ridges that rise up to 250 m above the surrounding plains, separated by deeply incised valleys. The range extends over a length of nearly 60 km and has a width of 3 to 5 km.

In the Weld Range, the Gyr greenstone belt is predominantly composed of metabasites showing mainly doleritic and minor basaltic and gabbroic textures. Exposures of these lithologies occur between the ridges which are defined by weathered, steeply dipping beds of resistant banded iron formation (BIF) which form less than 10% of the thickness of the sequence. Poorly exposed, very fine grained clastic metasediments are only a very minor part of the sequence. Metamorphism is relatively low grade, varying from lowermost greenschist facies in the north to approximately greenschist-amphibolite transition facies in the south.

High grade iron mineralisation in the Weld Range area occurs as a series of outcrops of massive goethite-haematite lodes.

A representative drill hole below a prominent ridge of one such highly weathered banded iron-formation intersected two beds of BIF, an upper 8 m thick and lower 105 m width, within a sequence of very fine-grained quartz-chlorite-rich metasediments. Most of the BIF was reported to show some evidence of secondary oxidation due to weathering, while even in the deepest parts of the hole, sections of the BIF were found to be altered. In the least weathered sections of core, the BIF has well preserved, arrested reaction textures showing a texturally early mineral assemblage overprinted by several generations of later minerals. The mineral assemblage recorded in the BIF, in a general decreasing order of abundance, are minnesotaite, siderite, quartz, magnetite, greenalite, stilpnomelane, pyrite and chamosite. Trace amounts of pyrrhotite, arsenopyrite, chalcopyrite and apatite are widely distributed, and rockbridgeite occurs in trace amounts in two samples. The proportions of the various minerals vary widely and over large sections of the core some of the minerals listed are absent. Much of the BIF is meso-banded, and very different mineral assemblages commonly occur in adjacent meso-bands (Gole, 1980).

Bands of 2 to 30 cm thick massive to laminated Fe-rich shales occur within the BIF, with both mineralogically sharp and gradational contacts with the enclosing BIF. The mineralogy of these shales, in approximate decreasing order of abundance, are chamosite, stilpnomelane, siderite, greenalite, pyrite, magnetite, minnesotaite and quartz. Trace amounts of ilmenite, chalcopyrite, and apatite are also present (Gole, 1980).

The earliest recognisable mineral assemblage contains AI-bearing greenalite, quartz, siderite, chamosite, magnetite, pyrite and rarely pyrrhotite. This assemblage is overprinted by stilpnomelane, sometimes accompanied by a secondary AI- and Mg-poor greenalite. Minnesotaite was developed after stilpnomelane from the reaction of earlier silicates and siderite. The suite of minnesotaite-quartz ±magnetite ±pyrite represents the complete reaction of the earlier assemblages. The observations in this and the previous two paragraphs are quoted from Gole, (1980).

Iron mineralisation in the Weld Range had first been recognised in the late 19th century, while modern exploration commenced in 1959 followed by drilling programs between 1970 and 1981, together with the development of two exploration adits.

Total mineral resources in two main deposits, Beebyn and Madoonga, 22 km to the SW (SRK Consulting, for Sinosteel-Midwest, 2008), was:
    Beebyn - 61.2 Mt @ 60.9% Fe, 1.9% Al2O3, 4.9% SiO2, 0.10% P, 5.2% LOI.
    Madoonga - 94.4 Mt @ 56.1% Fe, 2.0% Al
2O3, 8.4% SiO2, 0.08% P, 8.1% LOI.
    TOTAL - 155.5 Mt @ 58.0% Fe, 2.0% Al
2O3, 7.0% SiO2, 0.09% P, 7.0% LOI.

Exploitation would require the construction of a 360 km rail link to the proposed deepwater port at Oakajee north of Geraldton in cooperation with other projects in the same region.

The most recent source geological information used to prepare this summary was dated: 2006.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.

  References & Additional Information
   Selected References:
Duuring P, Hagemann S G, Novikova Y, Cudahy T and Laukamp C,  2012 - Targeting Iron Ore in Banded Iron Formations Using ASTER Data: Weld Range Greenstone Belt, Yilgarn Craton, Western Australia : in    Econ. Geol.   v.107 pp. 585-597
Duuring, P., Santos, J.O.S., Fielding, I.O.H., Ivanic, T.J., Hagemann, S.G., Angerer, T., Lu, Y.-J., Roberts, M. and Choi, J.,  2020 - Dating hypogene iron mineralization events in Archean BIF at Weld Range, Western Australia: insights into the tectonomagmatic history of the northern margin of the Yilgarn Craton: in    Mineralium Deposita   v.55, pp. 1307-1332.
Gole M J,  1980 - Mineralogy and petrology of very-low-metamorphic grade Archaean banded iron-formations, Weld Range, Western Australia: in    American Mineralogist   v65 pp 8-25

Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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