ORCID Profile
0000-0001-9826-5661
Current Organisations
US Geological Survey
,
James Cook University
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Publisher: American Association of Petroleum Geologists AAPG/Datapages
Date: 12-2014
Publisher: US Geological Survey
Date: 2020
DOI: 10.3133/OFR20201038
Publisher: US Geological Survey
Date: 2022
DOI: 10.3133/FS20223008
Publisher: US Geological Survey
Date: 2021
DOI: 10.3133/OFR20211041
Publisher: Geological Society of London
Date: 31-05-2017
DOI: 10.1144/SP453.4
Publisher: US Geological Survey
Date: 2022
DOI: 10.3133/OFR20191023E
Publisher: Springer Science and Business Media LLC
Date: 27-02-2023
DOI: 10.1007/S00126-023-01161-3
Abstract: Graphite Creek is an unusual flake graphite deposit located on the Seward Peninsula, Alaska, USA. We present field observations, uranium-lead (U–Pb) monazite and titanite geochronology, carbon (C) and sulfur (S) stable isotope geochemistry, and graphite Raman spectroscopy data from this deposit that support a new model of flake graphite ore genesis in high-grade metamorphic environments. The Graphite Creek deposit is within the second sillimanite metamorphic zone of the Kigluaik Mountains gneiss dome. Flake graphite, hosted in sillimanite-gneiss and quartz-biotite paragneiss, occurs as disseminations and in sets of very high grade (up to 50 wt.% graphite), semi-massive to massive graphite lenses 0.2 to 1 m wide containing quartz, sillimanite, inclusions of garnet porphyroblasts, K-feldspar, and tourmaline. Restitic garnet, sillimanite, graphite, and biotite accumulations indicate a high degree of anatexis and melt loss. Strong yttrium depletion in monazite, high europium ratios (Eu/Eu*), and excursions of high strontium and thorium concentrations are consistent with biotite dehydration melting. Monazite and titanite U–Pb ages record peak metamorphism from ~ 97 to 92 million years ago (Ma) and a retrograde event at ~ 85 Ma. Raman spectroscopy confirms the presence of carbonaceous material and highly ordered, crystalline graphite. Graphite δ 13 C VPDB values of − 30 to − 12‰ and pyrrhotite δ 34 S VCDT values of − 14 to 10‰ are consistent with derivation from organic carbon and sulfur in sedimentary rocks, respectively. These data collectively suggest that formation of massive graphite lenses occurred approximately synchronously with high-temperature metamorphism and anatexis of a highly carbonaceous pelitic protolith. Melt extraction and fluid release associated with anatexis were likely crucial for concentrating graphite. High-temperature, graphitic migmatite sequences within high-strain shear zones may be favorable for the occurrence of high-grade flake graphite deposits.
Publisher: Elsevier BV
Date: 2022
Publisher: Elsevier BV
Date: 2015
Publisher: US Geological Survey
Date: 2021
DOI: 10.3133/OFR20211058
No related grants have been discovered for George Case.