Summary:
Mineralisation at the West Angelas deposit occurs as goethite/ haematite within the banded iron formations of the Marra Mamba Formation. Some detrital mineralisation also occurs.
The West Angelas project area includes sixteen discrete areas of mineralisation. These deposits lie on the limbs of the east-west trending, west plunging Wonmunna Anticline located in the eastern part of the Ophthalmia Fold Belt. The West Angelas deposits, are comprised mainly of the Marra Mamba Iron Formation with mineralisation occurring in both NE1 and NE2 of the Mt Newman Member. Mineralisation is found in limited quantities in the Macleod Member and the lower portion of the West Angelas Member below AS3. Tertiary Detrital material derived from both the Marra Mamba and Brockman Iron Formations also accumulates throughout the project area.
Material from the MacLeod and Mt Newman Members of the Marra Mamba Iron Formation has been observed to contain pyrite and based on drill hole assay data material from the MacLeod and Nammuldi Members are expected to pose a low to moderate risk of AMD (RTIO 2016).
Deposit A (2 Pits)
Deposit A is situated on the Southern Limb of the Wonmunna anticline. Mineralisation occurs within second order synclines. It has a strike length of 6.5 km and varies in width from 400 m to 1,500 m. Most of the iron enrichment occurs in the upper two thirds of the Mt Newman Member of the Marra Mamba Iron Formation, with minor mineralisation in the lower 6 m of the overlying West Angela Member of the Wittenoom Formation.
Deposit A West (3 Pits)
Deposit A West, sits on the southerly limb of the west plunging, east west trending Wonmunna Anticline. It strikes west for approximately 6.4 km from the western extent of A Deposit. Bedding at Deposit A West is typically dipping south at approximately 35 degrees and characterised by minor folding along the strike. Mineralisation in Deposit A West is predominately contained in the Mt Newman Member, mostly in the N2U and N2L layers. Mt Newman Member mineralisation is typically goethite-hematite rich material.
Deposit B (1 Pits)
Deposit B is located on the northern limb of the Wonmunna anticline. The strike length is approximately 7.6 kilometres long and is structurally complex, existing as a doubly plunging syncline that is truncated by two shallow dipping thrust faults to the West. High-grade hematite-goethite mineralisation occurs generally in the Mt Newman Member of the Marra Mamba Iron Formation. Lower grade mineralisation occurs occasionally within the lower West Angela Member of the Wittenoom Formation and in the MacLeod Member of the Marra Mamba Formation.
Deposit C (3 Pits)
Deposit C is in the eastern part of the Ophthalmia Fold Belt. The strike length is approximately 8 km. The deposit has two distinct regions, the east is relatively simple, with bedding typically dipping north at approximately 30 degrees and is characterised by minor folding along strike. In the west, bedding becomes strongly folded. Bedding mineralisation in the deposit is typical Marra Mamba sequence, with thick Wittenoom Formation shale, into Mt Newman, McLeod and Nammuldi Members. Mineralisation is typically goethite-hematite rich material that is predominately contained in the Mt Newman member, primarily in the N2U and N2L layers.
Deposit D (5 Pits)
West Angelas Deposit strikes for approximately 15 km from the nose of the fold to the western most extent of Deposit A. Structurally, Deposit D has two distinct regions. The eastern region is relatively simple, with bedding typically dipping south at approximately 35 degrees and characterised by minor folding along strike. In the west, bedding becomes somewhat more complicated with a synclinal structure interpreted. Bedding in the deposit is typical Marra Mamba sequence, with thick Wittenoom Formation shales, into Mt Newman, McLeod and Nammuldi Member.
Deposit E (2 Pits)
The West Angelas Deposit extends approximately 3.5 km in strike, 300 m in width, with varying thickness of 45 m to 60 m. Deposit E is defined by strong folding and faulting of the West Angela Member and the underlying Marra Mamba Iron Formation. Most of the bedded mineralisation occurs within the Mt Newman Member of the Marra Mamba Iron Formation. This mineralisation occurs predominantly within the NE2 unit with occasional low-grade enrichment within the NE1 unit. Minor low grade (>50% to 58% Fe) mineralisation occurs within the West Angela Member.
Deposit F (7 Pits)
Deposit F orebody has an interrupted geometry of approximately 7.5 km in strike length and up to 1 km in width. Mineralisation is found in the tertiary mature detritals that blanket the paleo-topography, as well as the E-W striking folded Marra Mamba Iron Formation, with economic interest focussed on the mineralised Mt Newman Member. The iron ore resource at Deposit F North is found within tertiary mature detritals that blanket the paleo-topography and in the E-W striking folded Marra Mamba Iron Formation. Newman and sometimes the Macleod Member. Immature detrital, clay and quaternary alluvial material overlies the mineralised zone with thicknesses from 2 to 80 metres.
Deposit G (3 Pits)
The bedded mineralisation in the The West Angelas deposits is divided into a northern orebody and a southern orebody that is separated by the northern fault. The Northern orebody is present mostly under cover and is constrained by synclinal structure which gently plunges to the west. The Southern orebody is northerly dipping, getting steeper as you go west. It is localised within a series of antiform and synform structures within an interpreted graben structure which is controlled by two WNW-ESE trending normal faults in the area. Most of the bedded mineralisation occurs within the Mt Newman Member of the Marra Mamba Iron Formation.
Deposit H (2 Pits)
Deposit H is the 5.5 km long deposit is approximately 3.5 km east of adjacent Deposit B, and 9 km north-east of infrastructure at West Angelas Mine. Geologically Deposit H is similar to the eastern part of Deposit B, with the majority of mineralisation occurring in the limbs of the anticline, with limited mineralisation in the surrounding hills. Structurally Deposit H is an asymmetric doubly plunging syncline of mineralised and unmineralised Marra Mamba Members. Bedded mineralisation is primarily observed in the upper Newman Members, with low grade material also found in the West Angela Shale and MacLeod Members.
Deposit J (4 Pits)
Deposit J is divided into an Eastern and Western side by an open colluvium valley. The stratigraphic sequence of the Eastern Hill includes a strongly folded sequence of Mt Sylvia to Joffre. On the Western side of the colluvium valley, the Dales Gorge and McRae Shale outcrop as a series of tight upright to overturned folds. Mineralisation is discontinuous and generally confined to the Dales Gorge Member with isolated patchy mineralisation in the Joffre Member and Whaleback members.
Mount Ella East (2 Pits)
Mount Ella East (MTEE) is predominantly a detrital deposit. It is a mostly concealed deposit with some altered Brockman mapped in the hills to the south. Mineralisation occurs in layers of variably pisolitic/magnetic detritals, hematite-rich with siliceous clay matrix, overlying a distinctly limonitic/goethitic detrital sequence. There are some pods of general mature detritals, pisolitic waste, and internal or basal clay.
Western Hill (3 Pits)
Western Hill (WSTH) lies along the Northern limb of the Wonmunna Anticline, and consists predominantly of lower Brockman Iron Formation rocks, flanked by secondary detrital deposits.