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 δ¹³C_VPDB values of − 30 to − 12‰ and pyrrhotite δ³⁴S_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.

Graphite Creek 是一个不寻常的片状石墨矿床，位于美国阿拉斯加的苏厄德半岛。我们展示了该矿床的实地观察、铀铅 (U-Pb) 独居石和钛矿地质年代学、碳 (C) 和硫 (S) 稳定同位素地球化学以及石墨拉曼光谱数据，这些数据支持鳞片石墨矿成因的新模型高级变质环境。Graphite Creek 矿床位于 Kigluaik 山片麻岩圆顶的第二硅线石变质带内。鳞片状石墨，寄生在硅线石-片麻岩和石英-黑云母副片麻岩中，以散布形式出现，并以非常高品位（高达 50 wt.% 的石墨）、0.2 至 1 m 宽的半块状至块状石墨透镜的形式出现，包含石英、硅线石, 石榴石内含物斑岩、钾长石和电气石。石榴石、硅线石、石墨、和黑云母堆积表明高度深熔和熔损。独居石中的强钇消耗、高铕比 (Eu/Eu*) 以及高锶和钍浓度的偏移与黑云母脱水熔化一致。独居石和钛矿 U-Pb 年龄记录了大约 97 至 9200 万年前 (Ma) 的峰值变质作用和大约 85 Ma 的逆行事件。拉曼光谱证实了含碳材料和高度有序的结晶石墨的存在。石墨δ 独居石和钛矿 U-Pb 年龄记录了大约 97 至 9200 万年前 (Ma) 的峰值变质作用和大约 85 Ma 的逆行事件。拉曼光谱证实了含碳材料和高度有序的结晶石墨的存在。石墨δ 独居石和钛矿 U-Pb 年龄记录了大约 97 至 9200 万年前 (Ma) 的峰值变质作用和大约 85 Ma 的逆行事件。拉曼光谱证实了含碳材料和高度有序的结晶石墨的存在。石墨δ¹³ C _VPDB值为 − 30 至 − 12‰，磁黄铁矿 δ ³⁴ S _VCDT值为 − 14 至 10‰，分别与沉积岩中有机碳和硫的推导一致。这些数据共同表明，块状石墨透镜的形成与高含碳泥质原岩的高温变质和深熔大致同步发生。与深熔相关的熔体提取和流体释放可能对浓缩石墨至关重要。高应变剪切带内的高温石墨混合岩序列可能有利于高品位鳞片石墨矿床的出现。