Graphite One Inc. through its wholly-owned subsidiary, Graphite One Alaska Inc., owns and will operate the Graphite Creek property.
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Summary:
Since the Graphite One project graphite deposit occurs in a quartz-granite-biotite-sillimanite schist, which is a high-grade metamorphic rock, the Graphite Creek mineralization is considered to be of a flake-graphite-type mineralization.
The Graphite Creek graphite deposit is located on the north side of the Kigluaik Mountains (at about 230 m elevation). The graphite-bearing units occur in the upslope and footwall block of the Kigluaik normal fault. The Kigluaik Fault generally strikes at an azimuth of 250° and defines the boundary between the uplifted Kigluaik Mountains to the south and the sediment-filled Imuruk Basin to the north. The location of the hanging wall block of the Kigluaik Fault is presently unknown. The dip of the fault has been previously estimated at 75° along the range front, but drilling has constrained the fault dip to ~45° within the pit area (Gierymski et al., 2022). The Kigluaik Fault is generally parallel to the graphitic schist at the range-front scale, but it is not directly parallel to the bedding/foliation of the schist with the pit area. A well-indurated and massive unit of quartz diorite has been logged as the uppermost bedrock unit beneath the Kigluaik Fault in many of the drillholes within the pit area.
Graphite occurs as high-grade massive to semi-massive segregations and disseminations hosted within two distinct schistose to migmatic paragneiss units. Carbon isotopes indicate an organic carbon origin of the graphite (Case et al., 2023). One unit is a strongly foliated sillimanite-quartz-feldspar-biotite-graphitegarnet schist (QBGSS), locally gneissic, containing intervals (10-20 cm thick) of dense garnet porphyroblasts. The second unit is a quartz-feldspar-biotite schist (QBS) with minor pyrrhotite and very little garnet or sillimanite and appears massive or banded. The QBS unit also contains local calcareous layers and intervals of calc-silicate rock. Sillimanite- and graphite-bearing leucosomes, biotite-rich melanosomes, and pegmatitic granite are abundant in both units and indicate partial melting took place. Intervals of concentrated sillimanite, garnet, and biotite that contain little quartz are consistent with restite and strongly suggest the loss of some of this melt. Silicate melt loss and the resulting concentration of remaining rock constituents (including carbon) have been proposed as a primary mechanism for the formation of the observed graphite segregations (Case et al., 2023).
Mineralization
There are two distinctive graphite-bearing schist intervals at Graphite Creek. The first is sillimanite-garnet-biotite-quartz schist (QBGSS), that contains coarse, semi-massive, and massive graphite segregations and disseminated graphite. The other interval unit is biotite-quartz schist (BQS), that typically contains disseminated graphite. The QBGSS is the principal host to higher-grade graphite and makes up two distinctive layers in the metasedimentary sequence along the north flank of the Kigluaik Mountains. A third potential horizon is defined by 'pods' of sillimanite-quartz-biotite-garnet gneiss. The QBGSS and QBS layers strike obliquely to the mountain front and dip north to northeast at 40° to 78°.
The QBGSS typically is fine- to coarse-grained, weathers grey, has a wavy and crenulated schistosity, has garnet porphyroblasts (up to 2 cm across), and has augen-shaped quartz segregations. Discontinuous segregations (lenses and streaks) of high-grade graphite from centimeters to a few meters thick are common. These high-grade graphite lenses in the QBGSS have up to 60% coarse crystalline graphite and were likely the sources of hand-sorted graphite produced in the early 1900s. Disseminated flakes of graphite up to 1 mm or more across, account for several percent of the rock.
The BQS is fine-grained, weathers rusty ochre, and has regular subplanar layering with individual layers commonly 3 to 10 cm thick. Graphite occurs as disseminated flakes up to about 1 mm across and can account for several percent of the rock. Higher-grade graphite-rich layers varying from 3 to 25 cm in width are present but are not as common as in the QBGSS.
The other logged schist units at Graphite Creek, garnet-biotite-quartz schist (QBGS) and sillimanite-biotite-quartz schist (QBSS), are usually not well mineralized. Graphite is observed in at least trace amounts in all lithologies other than quartz diorite (QDIO) and INM.