Channel iron deposits of the Hamersley Province, Western Australia

Abstract

The fluvial goethite-hematite channel iron deposits (CID) of the Pilbara region of Western Australia, formerly known as the 'Robe Pisolite', represent a major source of iron ore mined in the Hamersley Province. The CID occupy Early Tertiary palaeochannels that are typically less than 1 km but range to several kilometres in width and from 1 to ~100 m thick. The Robe palaeochannel is the longest, with CID partly preserved over a distance of 150 km, whereas the Marillana palaeochannel contains CID along 80 km of its length. The CID range from goethitic mudstone to fine hematite-goethite gravel and intraformational conglomerate varying in distribution along the channels in a range of massive, bedded and altered types. The granular type that forms the bulk of the ore is typically ooidal, comprising pelletoids with goethite cortices around hematite nuclei (which often consist of fossilised wood), with typically abundant coarse goethitised wood fragments, a varied proportion of peloids, minor pisoids, and a diverse porous goethitic matrix. The Robe deposits tend to have more spherical pelletoids, with more regularly developed layering, and smaller cores than CID from the Yandi deposits of the Marillana valley. Generally, the presence of ferruginised fossil wood is the principal diagnostic field criterion used to distinguish CID from other comparable goethite-hematite detrital deposits. Electron microprobe X-ray maps reveal that lattice Al and Si increase from the hematitic nuclei to the matrix, and then the cortex. In the Robe CID, alumina in the nuclei varies between 0.5 and 2.8%, whereas at Yandi, alumina in the nuclei ranges from 0.2 to 0.7%. The goethite cortex of a granule is usually richer in both alumina and silica than its nucleus, in a cortex : nucleus ratio of ~2:1 at Robe and 3:1 at Yandi. The nucleus and cortex of individual pelletoids generally exhibit a similar trace-element distribution, which can often be related to the surrounding country rock and, with the exception of Al, is different to that shown by the matrix. A visual classification (labelled co-manual) based on the relative amount of cortex (co), matrix (ma) and nucleus (nu) enables an estimate of the deleterious minor elements, mainly aluminium (al), for separating samples into ore, near-ore and non-ore.

Characterisation of hyporheic exchange in a losing stream using radon-222

“…This alluvial deposit is predominantly underlain by a palaeochannel deposit of fractured pisolitic goethite (Ramanaidou et al, 2003) that extends to a depth of up to 50 m, with a hydraulic conductivity on the order of 10 m d…”

Pre‐Quaternary landscape inheritance in Australia

“…Palaeochannels in the Hamersley Province of northwestern Australia contain high-grade pisolitic, goethite-haematite iron-ore deposits that are usually referred to as channel iron deposits (CID). They are iron-rich Tertiary fluvial deposits up to 100 m thick that occupy meandering palaeochannels typically <1 km wide, but which may be up to several kilometres wide (Ramanaidou et al, 2003). Mining of the two longest palaeochannel deposits, the Robe CID (150 km long) and the Yandi CID (80 km long), accounts for nearly 50% of the total iron ore production from the Hamersley Province.…”

“…At Yandi, the palaeochannel deposits are named the Marillana Formation, which crops out as a series of low mesas along the modern-day Marillana Creek. It is divided into three members (Ramanaidou et al, 2003;Macphail and Stone, 2004): the basal Munjina Member (pebble conglomerate with clay lenses, partly carbonaceous), the middle Barimunya Member which is the main ore horizon (clast-supported conglomerate comprising subangular to rounded pisolites of goethite-hematite, maghemite and fossil wood, cemented in a goethitic matrix) and the upper Iowa Eastern member (thin clay and CID units). Pollen from the basal Munjina Member indicates an Early Oligocene (ca.…”

Life inhabits rocks: clues to rock erosion from electron microscopy of pisolite at a UNESCO heritage site in Brazil

“…Stratigraphy and sedimentary features of the Tertiary Yandi channel iron deposits in Hamersley Province, Western Australia are reported by Ramanaidou et al (2003) and Stone et al (2003). The fluvial goethite-hematite channel iron deposits of the Pilbara region of Western Australia, formerly known as the ''Robe Pisolite'', represent a major source of the iron ore now mined in the Hamersley Province.…”