Rio Tinto reports 3,000 Mt of additional iron ore resources

Rio Tinto has further strengthened its leading position in Western Australia’s Pilbara with a 3,000 Mt addition to its iron ore resource base. This came through the discovery of a major, newly discovered resource at Caliwingina (875 Mt at 56.9% Fe), and significant improvement in confidence of resources associated with known deposits. The chief executive of Rio Tinto Iron Ore, Sam Walsh, said significant technical and study work has led to increased confidence in Rio Tinto’s position in the Pilbara. “Rio Tinto occupies the largest mineralisation and land position in the Pilbara, one of the world’s great iron ore producing regions. This advantage is strengthened by addition of the newly discovered Resource at Caliwingina, comprising 875 Mt of iron ore only 15 km from our railway and only 150 km from our ports at Dampier and Cape Lambert, as well as significant additions around known deposits,” Walsh said.

The Caliwingina resource is within the Mt Pyrton Project area which lies 100 km north northwest of Tom Price. It is situated within the Late Archaean to Early Proterozoic (2765-2470 Ma) Hamersley Basin. The Lower Hamersley Group rocks within this area form rounded outcrops on the edge of the Fortescue River basin with the Upper Hamersley Group rocks forming larger steeper hills behind. Lithologies comprise meta-sedimentary rocks from the Hamersley Group and cover units of the Tertiary and Quaternary.

Rio Tinto initially conducted exploration for Channel Iron Deposit (CID) in the southern part of Caliwingina using geophysical techniques and an extensive reverse circulation (RC) drilling programme during 2002-2003 which delineated a 6 km continuous length of CID. During 2005/2006 Rio Tinto continued an RC drilling programme to the north following the CID channel to the out wash area in the Fortescue Valley.

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The Caliwingina North area now has sufficient drilling coverage (173 RC holes for 11,503 m on a nominal 500 by 200 m grid spacing) to define an Inferred CID Mineral Resource. All drilling was sampled at 2-m intervals using appropriate Standard and Duplicate check sample methods, followed by QA/QC analysis. A 3D geological block model of the domains, including the CID, within the channel was built using 100 by 100 by 2 m blocks followed by grade estimation using Inverse Distance.

Caliwingina North CID Deposit Inferred Mineral Resources (for Fe >55%).

Caliwingina North Tonnes (Mt) Fe % Density
Total 875 Mt 56.9 2.6

Drill evaluation work will continue in the Caliwingina Prospect during 2008/09 to update the resource base. Also diamond drilling will be conducted to improve grade estimation confidence as well as for metallurgical and density test work.

Reporting of Brockman Process Ore

Brockman Process Ore is being reported here for the first time (apart from Tom Price). The additional resource is contained within the mineralisation envelope that also defines the high grade (HG) for 15 known deposits. Only bedded Dales Gorge (DG1 to DG3), Joffre (J1 to J6) and footwall zone Process Ore is reported. All Process Ore is reported as in-situ tonnes and grade. The newly reported resource only requires application of standard processing technology to be won from material that will be extracted according to the long term mining schedule.

Undeveloped Brockman Process Ore (=50% Fe <60% Fe and =3% Al2O3 <6% Al2O3).

Brockman Un-Developed Process Ore Tonnes (Mt) Fe %
Measured
Indicated
Inferred
Total
220
460
1,105
1,785
57.6
57.5
54.4
55.6

Reported Brockman Deposits incorporating Brockman Process Ore are:

  • B1 Deposit
  • B26 Deposit
  • Brockman 2
  • Brockman 4
  • Channar
  • Eastern Range
  • Giles Mini
  • Koodaideri
  • Paraburdoo Brockman Deposits
  • Paraburdoo Western Range
  • Rhodes Ridge Central
  • Section 10
  • Section 17
  • Texas
  • Turee Syncline
Increase in Hope 4 resource base

Re-estimation work on Hope 4 during 2007 has added an additional 290 Mt of resource. Hope Downs 4 has added an additional 95 Mt of HG (reported in a separated release in December 2007) (Fe =60% Fe)

Hope Downs 4 High Grade Tonnes (Mt) Fe %
Indicated
Inferred
Total
100
205
305
62.3
62.4
62.4

195 Mt of Brockman Process Ore for Hope Downs 4. (=50% Fe <60% Fe and =3% Al2O3 <6% Al2O3)

Hope Downs 4 Process Ore Tonnes (Mt) Fe %
Indicated
Inferred
Total
80
115
195
56.4
57.1
56.8