The geology and mineralisation of the Carina Iron Deposit, central Yilgarn Craton, Western Australia

Abstract

The Carina iron ore deposit is 105 km northeast of Southern Cross, WA. The area designated the Yilgarn Iron Ore Project (YIOP) comprises five prospects along an east–southeast trending greenstone belt that extends from the Helena-Aurora Ranges in the northwest to the Yendilberrin Hills in the southeast, over a strike length of approximately 40 km. The YIOP project encompasses the previously identified iron deposits of Bungalbin, Bungalbin East and Mt Walton. The Carina deposit was discovered in May 2007. The Carina deposit is located within and parallel to the structurally complex northwest trending Mount Dimer Shear Zone. The volcano-sedimentary Archaean greenstone sequence consists of ultramafic and mafic lavas and flows with interbedded sedimentary rocks dominated by chert and banded iron formation (BIF). Supergene enrichment processes formed a goethite ore body replacement of BIF sequences within a doubly plunging synclinal fold structure. Mineralised outcrops dominated by goethite form a low ridge 1500 m long, up to 90 m wide and drilled to over 200 m in depth. In the vicinity of the Carina deposit, iron occurrences have been identified over at least a 12 km strike length. The current exploration in the area began in 2006. Target generation in the area used existing state geological survey maps and regional magnetic survey data to focus on BIF occurrences associated with major structures. Early field investigations resulted in the identification of a large outcrop of predominantly goethite mineralisation at Carina. Detailed geological and structural mapping was completed, followed by close-spaced reverse circulation and diamond drilling. The mineralisation is predominantly goethite with specular and coarse platy hematite localised along structures that cut the goethite mineralisation. Mineralised zones are moderately vuggy and larger cavities occur in proximity to fault zones that transect the ore body. There is a capping by a thin veneer of canga or ferricrete up to 9 m thick. By July 2010, 184 reverse circulation and 11 diamond drill holes (seven surface holes, four tails) were completed. The current JORCcompliant resource estimate is based on assays from 170 RC and 11 diamond drill holes and using a 55% Fe cut-off is quoted as an Inferred Resource of 26·7 Mt at 58·9% Fe, 1·2% Al2 O3, 3·2% SiO2 , 0.11% P, 0·08% S, and 9·5 % LOI. Mining is planned to commence in early July 2011.