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UPb zircon geochronology from the Alexander terrane, southeast Alaska: implications for the Greens Creek massive sulphide deposit

Citation

Sack, PJ and Berry, RF and Gemmell, JB and Meffre, S and West, A, U-Pb zircon geochronology from the Alexander terrane, southeast Alaska: implications for the Greens Creek massive sulphide deposit, Canadian Journal of Earth Sciences, 53, (12) pp. 1458-1475. ISSN 0008-4077 (2016) [Refereed Article]

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DOI: doi:10.1139/cjes-2016-0032

Abstract

This paper presents results of a laser ablation - inductively coupled plasma - quadrapole mass spectrometer (LA-ICP-QMS) U-Pb dating study of small in situ zircon grains from samples collected in the vicinity of the Greens Creek massive sulphide deposit, on northern Admiralty Island, southeast Alaska. The Greens Creek mine is a volcanogenic massive sulphide deposit in the central portion of the Alexander Triassic metallogenic belt (ATMB) and is one of the top global silver producers despite having a dominantly mafic metavolcanic stratigraphic footwall. The stratigraphic footwall is a Mississippian mafic metavolcanic sequence with a protolith age of approximately 340-330 Ma. The first U-Pb zircon constrained chronostratigraphy for the area places the deposit near, or at, the base of the host Late Triassic stratigraphy just above an approximately 100 million year old unconformity and probably 10-15 million years older than mineralization at the Palmer and Windy Craggy deposits in the northern portion of the ATMB. The stratigraphic location of the Greens Creek deposit is atypical for a syngenetic massive sulphide deposit, and this may, at least partly, explain its unusual metal endowment. Pre-mineralization Permian U-Pb zircon metamorphic ages are consistent with published 273-260 Ma white mica ages related to the collision of the Admiralty and Craig subterranes, the basement to the ATMB. The much older age of the footwall rocks and their Permian pre-mineralization metamorphism demonstrates that though the mafic volcanic rocks are not genetically linked to the deposit, they likely influenced the style of alteration and mineralization.

Item Details

Item Type:Refereed Article
Keywords:U-Pb zircon geochronology, Alexander terrane, Alaska, Greens Creek, massive sulphide deposit
Research Division:Earth Sciences
Research Group:Geology
Research Field:Ore Deposit Petrology
Objective Division:Mineral Resources (excl. Energy Resources)
Objective Group:Other Mineral Resources (excl. Energy Resources)
Objective Field:Mineral Resources (excl. Energy Resources) not elsewhere classified
UTAS Author:Sack, PJ (Mr Patrick Sack)
UTAS Author:Berry, RF (Associate Professor Ron Berry)
UTAS Author:Gemmell, JB (Professor Bruce Gemmell)
UTAS Author:Meffre, S (Dr Sebastien Meffre)
ID Code:112172
Year Published:2016
Deposited By:CODES ARC
Deposited On:2016-10-28
Last Modified:2017-11-02
Downloads:0

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