Insights into the metamorphic history and origin of flake graphite mineralization at the Graphite Creek graphite deposit, Seward Peninsula, Alaska, USA

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 δ13CVPDB values of − 30 to − 12‰ and pyrrhotite δ34SVCDT 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.

Performance and Heavy Metal Analysis of Graphite Tailings Cured Using Cementitious Materials

“…Graphite is a nonmetallic material that is indispensable to today's high-tech military and modern industrial development [1,2], and is mainly mined in China, India, and Brazil [3]. Due to its good natural floatability, all graphite can be purified using flotation [4].…”

Proterozoic Deep Carbon—Characterisation, Origin and the Role of Fluids during High-Grade Metamorphism of Graphite (Lofoten–Vesterålen Complex, Norway)

“…Graphite, a mineral composed of pure C, forms during the higher-grade metamorphism of sediment rich in organic matter [1,2], by reaction and deposition from COH-rich fluids in granulite [3] or igneous terranes [4]. Graphite in Precambrian crustal rocks has been reported worldwide, including in Sri Lanka [5], India [6], Mozambique [7], Madagascar [8] and Greenland [9].…”

“…Meanwhile, the presence and importance of graphite [6,24] and its deposition during volatile processes [3,4,25] have been debated. Case et al [2] described the metamorphic effect on the formation of graphite deposits. Stable C isotopes of graphite have been used to investigate the carbon origin of graphite formation [26][27][28].…”