Summary of results for the Joint GSNSW-GA geochronology project: New England Orogen 2009-2010

This report presents new SHRIMP U-Pb zircon results for fifteen samples from the New England region of New South Wales (Fig. i and Table i). The work was carried out under the auspices of the National Geoscience Agreement (NGA) between Geoscience Australia and the Geological Survey of New South Wales. The data and age interpretations contained in this report are available in Geoscience Australia's Geochron Delivery database (http://www.ga.gov.au/geochron-sapub-web/).
Summary of results and significance:

The 'coastal granitoids' occurring to the east of the main geographically continuous axis of granites in the central portion of the batholith range in age from 238 Ma for Round Mountain Leucoadamellite; ~230 Ma for the Yarrahapinni Granite and Valla Adamellite; ~220 Ma for Glen Esk Adamellite and Smokey Cape Adamellite; to 212 Ma for the Middle Brother Monzodiorite. Granitoid magmatism in this region has not occurred in a single early Triassic flourish, but episodically, and generally younging eastwards to the coast. 
Leucoadamellites previously considered to be 'Triassic' (i.e. younger than the main stage of the batholith), have been shown to be older. These units - the Oban River Leucoadamellite (252 Ma) and Red Range Leucoadamellite (253 Ma) - are the same age as the major units of the Moonbi and Uralla supersuites.
The Mount Duval Monzogranite and Newholme Monzogranite are indistinguishable in age. The Newholme Monzogranite was recognised as a discrete unit in the Mount Duval pluton on the basis of geophysics, petrography and geochemistry.
The Highlands Complex, though petrographically and geochemically distinct from most other magmatism in the New England Batholith is the same age as the main magmatic stages of the Moonbi and Uralla Supersuites. 
The Emmaville Volcanics in the Yarraford area, near to the Glen Eden porphyry tin deposit is the same age as other members of the Wandsworth Volcanic Group and the main magmatic stage (252 Ma) of the batholith. The mineralisation at Glen Eden, which is partially hosted by the volcanics, is Triassic in age, although anomalously old Re-Os ages have been determined from molybdenite within the deposits. 
Elsmore Granite age at 250 Ma is close to in age, but just younger than that of the adjacent tin mineralised Gilgai Granite. The Elsmore Granite forms a distinct satellite intrusion to the Gilgai Granite.
The Culaden Granodiorite (informal) is one of a number of small porphyritic granodiorite stocks and dykes in the Emmaville-Tent-Hill-Ottery area. The 252 Ma age indicates they are not contemporaneous with the Mole Granite and predate tin mineralisation in the area. They are essentially the same age as the Wandsworth Volcanic Group. 
The tin mineralised Pringles Monzogranite in the Watson Creek area near Bendemeer is shown to be 289 Ma, indistinguishable in age from the host Bundarra Supersuite, indicating that the intrusion and its attendant tin mineralisation is not related to younger magmatism elsewhere within the batholith.


Tags: AU-NSW, Earth Sciences, GA Publication, Published_External, Record
Organization: Geoscience Australia Data