ORCID Profile
0000-0002-1636-6723
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Publisher: Elsevier BV
Date: 10-1997
Publisher: American Geophysical Union (AGU)
Date: 05-04-2011
DOI: 10.1029/2010GC003405
Publisher: Society of Economic Geologists
Date: 05-1992
Publisher: Society of Economic Geologists
Date: 05-1992
Publisher: Society of Economic Geologists
Date: 03-04-2017
Publisher: Society of Economic Geologists
Date: 06-2008
Publisher: Society of Economic Geologists
Date: 08-2001
Publisher: Society of Economic Geologists
Date: 08-2001
Publisher: Society of Economic Geologists
Date: 30-10-2014
Publisher: Informa UK Limited
Date: 02-04-2016
Publisher: Canadian Science Publishing
Date: 12-2016
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 s les 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.
Publisher: Society of Economic Geologists
Date: 06-2008
Publisher: Elsevier BV
Date: 09-2015
Publisher: Elsevier BV
Date: 05-1996
Publisher: Springer Science and Business Media LLC
Date: 10-06-2022
Publisher: Elsevier BV
Date: 10-2018
Publisher: Geological Society of London
Date: 12-02-2020
Publisher: Society of Economic Geologists
Date: 03-2020
DOI: 10.5382/ECONGEO.4714
Abstract: Current portable X-ray fluorescence (pXRF) technology can rapidly and inexpensively yield concentrations of geologically significant elements, typically with instrument detection limits below several tens of parts per million. Based on conventional XRF whole-rock geochemical data, both the Ishikawa alteration index and the chlorite-carbonate-pyrite index increase with proximity to sulfide mineralization at Myra Falls. However, available pXRF technology is typically unable to detect all the elements required to calculate these alteration indices. As a result, there is a need to utilize the elements that are readily detectable using pXRF and apply these to hydrothermal alteration assessment. We propose that Rb/Sr ratios provide a robust proxy for the Ishikawa alteration index and demonstrate that conventional whole-rock XRF analytical results for Rb and Sr can be reproduced using pXRF analysis from drill core surfaces. At Myra Falls, the Rb/Sr ratios vary from & .1 for least altered rocks, 0.1 to 0.5 for weakly altered rocks, 0.5 to 1.0 for moderately altered rocks, 1.0 to 2.0 for strongly altered rocks, and & .0 for intensely altered rocks. Downhole profiles of alteration intensity generated from systematic pXRF analysis of drill core surfaces can be used to inform drilling and targeting decisions. The application of the Rb/Sr ratio as a proxy for alteration intensity extends beyond this case study and can be applied to other hydrothermal systems that produce phyllosilicate minerals as alteration products of feldspar.
Publisher: Society of Economic Geologists
Date: 08-2001
DOI: 10.2113/96.5.1037
Publisher: Elsevier BV
Date: 05-2015
Publisher: Informa UK Limited
Date: 12-1995
Publisher: Elsevier BV
Date: 03-2002
Publisher: Elsevier BV
Date: 03-2003
Publisher: Society of Economic Geologists
Date: 06-2020
DOI: 10.5382/ECONGEO.4735
Abstract: The giant, high-grade Resolution porphyry Cu-Mo deposit in the Superior district of Arizona is hosted in Proterozoic and Paleozoic basement and in an overlying Cretaceous volcaniclastic breccia and sandstone package. Resolution has a central domain of potassic alteration that extends more than 1 km outboard of the ore zone, overlapping with a propylitic halo characterized by epidote, chlorite, and pyrite that is particularly well developed in the Laramide volcaniclastic rocks and Proterozoic dolerite sills. The potassic and propylitic assemblages were overprinted in the upper parts of the deposit by intense phyllic and advanced argillic alteration. The district was disrupted by Tertiary Basin and Range extension, and the fault block containing Resolution and its Cretaceous host succession was buried under thick mid-Miocene dacitic volcanic cover, obscuring the geologic, geophysical, and geochemical footprint of the deposit. To test the potential of propylitic mineral chemistry analyses to aid in the detection of concealed porphyry deposits, a blind test was conducted using a suite of epidote-chlorite ± pyrite-altered Laramide volcaniclastic rocks and Proterozoic dolerites collected from the propylitic halo, with s les taken from two domains located to the north and south and above the Resolution ore zone. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) data of epidote provided indications of deposit fertility and proximity. Competition for chalcophile elements (As, Sb, Pb) between coexisting pyrite and epidote grains led to a subdued As-Sb fertility response in epidote, consistent with epidote collected between 0.7 and 1.5 km from the center of a large porphyry deposit. Temperature-sensitive trace elements in chlorite provided coherent spatial zonation patterns, implying a heat source centered at depth between the two s le clusters, and application of chlorite proximitor calculations based on LA-ICP-MS analyses provided a precisely defined drill target in this location in three dimensions. Drilling of this target would have resulted in the discovery of Resolution, confirming that epidote and chlorite mineral chemistry can potentially add value to porphyry exploration under cover.
Publisher: Society of Economic Geologists
Date: 11-2001
Publisher: Society of Economic Geologists
Date: 12-2011
Publisher: Society of Economic Geologists
Date: 08-2001
Publisher: Society of Economic Geologists
Date: 2014
DOI: 10.5382/SP.18.07
Publisher: Elsevier BV
Date: 08-2004
Publisher: Society of Economic Geologists
Date: 02-2019
No related organisations have been discovered for John Bruce Gemmell.
Start Date: 2015
End Date: 2019
Funder: Newcrest Mining Limited
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Funder: Lakehead University
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Funder: AMIRA International Ltd
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Funder: Newmont Asia Pacific
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Funder: Kennecott Greens Creek Mining Company
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Funder: British Columbia Government
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Funder: Australian Research Council
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Funder: AMIRA International Ltd
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Funder: Aurora Gold, P.T. Indo Muro Kencana
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Funder: Australian Research Council
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Funder: Australian Research Council
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Funder: Australian Research Council
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Funder: University of Tasmania
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Funder: Australian Research Council
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Funder: Australian Research Council
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Funder: Newcrest Mining Limited
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Funder: University of Melbourne
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Funder: Minerals Council of Australia
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Funder: Mineral Resources Tasmania
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Funder: Rio Tinto Exploration
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Funder: Zinifex Australia Ltd
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Funder: AMIRA International Ltd
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Funder: Oz Minerals Australia Limited
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Funder: ARC C of E Industry Partner $ to be allocated
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Funder: University of Queensland
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Funder: Newmont Australia Ltd
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Funder: Teck Cominco Limited
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Funder: Barrick (Australia Pacific) PTY Limited
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Funder: Australian National University
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Funder: Anglo American Exploration Philippines Inc
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Funder: AngloGold Ashanti Australia Limited
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Funder: Newcrest Mining Limited
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Funder: BHP Billiton Ltd
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Funder: CSIRO Earth Science & Resource Engineering
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Funder: St Barbara Limited
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End Date: 2013
Funder: Australian Research Council
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