A Middle Triassic age for felsic intrusions and associated mineralisation in the Doradilla prospect area, New South Wales
The Doradilla prospect area, containing a skarn-type deposit, lies 45 km south-east of Bourke in western New South Wales. Tin and other base metal mineralisation is genetically associated with the highly fractionated I-type Midway granite. In this study, the SHRIMP zircon U–Pb dating technique has been used to determine that the Midway granite and comagmatic quartz–feldspar porphyry dykes are of Middle Triassic age. Hence, it is concluded that the mineralisation is also Middle Triassic in age. No other granites of this age are known in the Bourke region. However, highly fractionated, weakly oxidised to reduced granites of Early to Middle Triassic ages with associated tin, gold and base metal mineralisation occur approximately 500 km to the east-northeast within the New England Orogen. This suggests that the Early to Middle Triassic pulse of magmatism that occurred in northern New South Wales is of greater extent than previously suspected and suggests that similar fertile granites may occur beneath cover within the Bourke–Brewarrina–Byrock region.
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Quarterly Notes, Issue No. 125 |
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