Understanding Fracture Distribution within Intrusive Sills the Cordeaux Crinanite a Case Example from the Illawarra Coal Measures - Luc DaigleRecent diamond drill hole coring by BHP Billiton Illawarra Coal was used to characterise the distribution of fracturing within the Cordeaux Crinanite intrusive body. Geological data obtained from recent exploration boreholes and surface outcrops provided sufficient information to determine the pattern and history of fracture emplacement within the intrusive body.
The Cordeaux Crinanite is an intrusive sill complex consisting primarily of thick olivine rich dolerite (crinanite) sills and thinner olivine cumulate (picrite) sills. Outcrop exposures of the complex are present along parts of Cordeaux Reservoir and form the bedrock to the Upper Cordeaxu Number 1 Dam and Upper Cordeaux Number 2 Dam and much of their catchments.
The intrusive body is roughly circular in plan with a domed top and largely planar base with local bowl shaped features. The intrusive is commonly referred to as a sill but drill intersections show that it gradually cross-cuts stratigraphy. The base ranges from approximately the Balgownie Seam to above the Bulli Seam and into the Coalcliff, the roof may extend up to the Stanwell Park Claystone. Understanding-Fracture-Distribution-within-Intrusive-Sills-the-Cordeaux-Crinanite-a-case-example-from-the-Illawarra-Coal-Measures-L.Daigle.pdf312 KB