New Zealand Journal of Geology and Geophysics abstracts

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Short communication

⁴⁰Ar/³⁹Ar ages of adularia from the Golden Cross, Neavesville and Komata epithermal deposits, Hauraki Goldfield, New Zealand

Jeffery L. Mauk

Geology Department
The University of Auckland
Private Bag 92 019
Auckland, New Zealand

Chris M. Hall

Department of Geological Sciences
The University of Michigan
Ann Arbor, MI 48109-1063, USA

Abstract  New ⁴⁰Ar/³⁹Ar ages of adularia from three epithermal vein deposits in the Hauraki Goldfield constrain when these deposits formed. Adularia from veins at Neavesville has ⁴⁰Ar/³⁹Ar plateau and isochron ages of 6.89 ± 0.02 and 6.86 ± 0.02 Ma, respectively, similar to the ⁴⁰Ar/³⁹Ar plateau and isochron ages of adularia from veins at Golden Cross of 6.96 ± 0.04 and 6.93 ± 0.03 Ma, respectively. In contrast, Komata mineralisation formed at 5.99 ± 0.02 to 6.07 ± 0.03 Ma, based on the ⁴⁰Ar/³⁹Ar isochron and plateau ages of the adularia in these veins, similar to the previously reported 6.0 Ma age of mineralisation at Waihi/Favona. These preliminary data suggest that mineralisation in the Hauraki Goldfields occurred episodically.

Keywords  Hauraki Goldfield; epithermal; Golden Cross; Komata; Neavesville; ⁴⁰Ar/³⁹Ar; absolute ages

G03070; Received 4 December 2003; accepted 29 March 2004; Online publication date 20 May 2004
New Zealand Journal of Geology & Geophysics, 2004, Vol. 47: 227–231
0028–8306/04/4702–0227 © The Royal Society of New Zealand 2004

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