Gold mineralisation at LJN4 is hosted in a sequence of ultramafics, massive carbonate (marble) and chert intruded by felsic porphyries. This sequence is cut by a major N-S braided shear complex known as the Chatterbox Shear Zone (CSZ) which is known to host significant mineralisation to the north. Petrological studies are in progress to determine if the carbonate and chert units are in fact forms of intense carbonate and silica alteration associated with the CSZ.
Mineralisation and alteration styles include:
- Quartz stockworks in silicified ultramafic with minor disseminated pyrite.
- Silica-sericite altered felsic porphyry with minor disseminated pyrite.
- Quartz veins, often on porphyry margins.
- Discrete silica-pyrite zones (lodes).
The quartz stockworks and silica-sericite altered porphyry tend to host broad zones of mineralisation while the silica-pyrite lodes host higher grades zones.
The Chatterbox shear zone is a complex N to NNE-trending, east-dipping structural corridor which can be traced for some 22km extending from Magnetic Resources’ southern boundary at Mt Jumbo and through Lady Julie North 4 and as far north as the Beasley Creek gold deposit on Magnetic’s NE boundary (Figure 1). Within Magnetic’s tenements the shear zone can be traced for a distance of 12km. The shear zone is interpreted to comprise a series of braided faults and shears within a corridor ranging from 100m to 250m wide and is interpreted to have formed as a reverse fault on the limb of the regional Margaret Anticline during the latter stages of its folding.
Importantly, this shear zone is closely associated with, gold mineralisation at several locations along its length including Magnetic’s LJN4 and Mt Jumbo deposit. This shear is gold rich and gold deposits further north of Magnetics tenements contains the Beasley Creek and Apollo deposits and is interpreted to extend south towards the world class Wallaby deposit. It is evident in aeromagnetic imagery and in gravity images (Figure 1).