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Testing ore deposit models using in situ U-Pb geochronology of hydrothermal monazite; Paleoproterozoic gold mineralization in northern Australia

Birger Rasmussen, Stephen Sheppard and Ian R. Fletcher
Testing ore deposit models using in situ U-Pb geochronology of hydrothermal monazite; Paleoproterozoic gold mineralization in northern Australia
Geology (Boulder) (February 2006) 34 (2): 77-80

Abstract

The inability to establish absolute ages for gold deposition in the Pine Creek orogen of northern Australia has led to conflicting ore deposit models, ranging from intrusion related, which predict that gold mineralization was synchronous with granite magmatism (ca. 1835-1820 Ma), to orogenic, which place ore deposition nearly 100 m.y. later. Here we present ion microprobe U-Pb geochronology for a mineralized quartz reef from Tom's Gully mine, Mount Bundey, Northern Territory, Australia, and nearby granitic rocks and associated contact aureoles. Isotopic dating of zircon and monazite indicates that intrusion and contact metamorphism occurred ca. 1825 Ma, whereas hydrothermal monazite from the auriferous quartz reef gives a mean (super 207) Pb/ (super 206) Pb age of 1780 + or - 10 Ma, interpreted as the time of gold mineralization. Mineralization therefore postdated intrusion by approximately 45 m.y. and preceded a postulated ca. 1740-1730 Ma cratonwide orogenic gold event by approximately 50 m.y. Hence, neither the intrusion-related model nor the recently proposed orogenic model is applicable. Combined with a reevaluation of age data from the nearby Goodall gold deposit, our data suggest that mineralization coincides with, and may be related to, an episode of regional low-grade metamorphism, deformation, and fluid circulation (Shoobridge event). Our results demonstrate the importance of high-precision in situ geochronology and detailed petrography for deciphering age relationships in ore deposits, and of testing the veracity of models for ore formation.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 34
Serial Issue: 2
Title: Testing ore deposit models using in situ U-Pb geochronology of hydrothermal monazite; Paleoproterozoic gold mineralization in northern Australia
Affiliation: University of Western Australia, School of Earth and Geographical Sciences, Crawley, West. Aust., Australia
Pages: 77-80
Published: 200602
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 22
Accession Number: 2006-021464
Categories: Economic geology, geology of ore depositsGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2006021
Illustration Description: illus. incl. geol. sketch map
S12°00'00" - S11°30'00", E131°30'00" - E131°30'00"
Secondary Affiliation: Geological Survey of Western Australia, AUS, Australia
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200611
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