Some thoughts on the magnetic survey.
The linearity of the magnetic anomalies almost certainly means that the magnetic highs are banded iron formation (BIF). Banded iron formation is formed in the shallow marine environment, where bacteria produce oxygen which reacts with dissolved iron to precipitate iron oxide inter-banded with very fine sediment layers. This is usually low grade and harder to process.
Hematite (DSO) deposits are mostly formed by the weathering of primary magnetite deposits (usually BIFs). While the underlying magnetite deposits are usually low grade, high grade hematite ore is formed when weathering dissolves out the impurities at surface.
See below a schematic cross section of some BHP iron ore deposits in the Pilbara. They are all situated on the Brockman (yellow) or Mara Mamba (light blue) iron formations which are low grade magnetite, but the ore grade material has been upgraded by weathering to hematite (light brown). Note Yandi is different. It was formed in a palaeo-channel without an underlying iron formation.
Magnetite is magnetic, while hematite is not. The Satrakola magnetic survey is exclusively picking up the underlying magnetite iron formations and not the hematite.
Many rock chip samples sit on the magnetic highs. Given the high grades, these samples are most likely hematite that has been upgraded by weathering and is sitting on top of its primary magnetite formation. This is analogous to South Flank in the BHP diagram.
A significant number of rock chips are located off magnetic highs. These could be primary hematite deposits (eg banded hematite formation which is uncommon), laterite derived deposits or palaeo-channel deposits. The latter two are probably more likely.
Laterite iron ore deposits and palaeo-channel iron deposits can be high grade and quite attractive targets. Several of these are mined by the big miners in the Pilbara.
Laterite and palaeo-channel iron deposits are formed by a sustained period of tropical weathering. Tropical conditions (rain and heat) are required to dissolve out all the silica and aluminum to leave the iron. If Satrakola went through an extended episode of tropical weathering, then that could be very good news for our chances of finding a significant DSO iron resource. Clearly the underlying iron source is there and if the upgrading mechanism is also there, then we are in luck!
The degree of weathering at Bekisopa may be different to the degree of weathering at Satrokala, because logically Bekisopa being intrusion related, post dates the formation of Satrokala.
There could be some very juicy DSO deposits at Satrokala. I'm getting excited.
