Observations on the Shumagin-Orange Mountain-Aquila and Apollo-Empire Ridge trends, southeast Unga Island, Alaska

Transcription

1 Research applied to mineral exploration Observations on the Shumagin-Orange Mountain-Aquila and Apollo-Empire Ridge trends, southeast Unga Island, Alaska 6-km portion of Shumagin trend, looking NE, from Aquila veins through silicic and quartz-alunite lithocap of Orange Mountain (including lake sediments), to the Shumagin veins, with continuous alteration along the trend Report for: Redstar Gold Corp. July, 2016 Prepared by: Jeffrey W. Hedenquist Hedenquist Consulting, Inc. 160 George Avenue, Suite 2501 Ottawa, Ontario K1N 9M2 Canada Tel: 1(613)

2 Contents page Summary and recommendations 3 Introduction 6 Background 6 Observations 8 Orange Mountain 9 Aquila 17 Shumagin 19 Apollo-Empire Ridge 22 Discussion 26 Summary 32 Recommendations 35 Qualifications 37 2

3 Summary and recommendations The veins on Unga Island share characteristics with numerous intermediate sulfidation-style deposits around the world, including: volcanic arc setting, association with andesitic rocks and more felsic rocks; advanced argillic alteration on structural trends (e.g., Comstock Lode, Nevada), and location adjacent to a barren lithocap of residual quartz (e.g., Selene, Peru, and Kushikino, Japan), although there are examples of the associated lithocap being mineralized (e.g., Lepanto lithocap and ore body with nearby Victoria veins, Philippines); the common occurrence of polymictic phreatomagmatic breccias with a syn-hydrothermal timing; variable base-metal content and Ag:Au ratio (e.g., multiple events noted in Mexican veins), and quartz associated with rhodochrosite, plus up to ~300+ m vertical extent of mineralization in veins. Tuffs are abundant at Orange Mountain, with the most permeable having served as aquifers for the flow of acidic condensates that leached the unit to create lithocaps. On either side of main silicic body, which is ~600 m long (with discontinuous outcrops to the ENE in the area drilled), the adjacent tuffs dip SW on the west side, and SE on the east. This may suggest an eruptive source associated with the area of the main silicic body, possibly a coherent lava dome (?), and thus a center of the system, bisected by the Shumagin structural trend. The silicic alteration is sulfide rich, and although scattered sampling suggests some Au anomalies, overall the lithocap near the surface may be largely barren; however, it is cut by quartz veins and barite, reflecting structures that are mineralized elsewhere along the Shumagin trend. Results of mining at Apollo, as well as reports from surface and drill hole samples at Shumagin and Aquila (Amethyst) indicate moderate to strong grade development, locally at the level of 10s g/t Au, indicating focused upflow and boiling both favored by hydrothermal brecciation in zones of dilation and the resulting deposition of gold. At Shumagin, good grades in a plunging shoot show evidence for up to 300 m of vertical extent. At Apollo the vertical extent of mined high grade (~15 g/t Au) was 200 m, dependent on the surface elevation, i.e., level of erosion. The Apollo vein system is also associated with a deeper horizon of base metal sulfides with a lower Au content, another common feature of many epithermal veins (La Guitarra and San Sebastian, Mexico, and Cerro Bayo, Chile). Most work on Unga has been focused on <4 km strike extent in three areas on two structures where there are outcropping veins, mostly with highly anomalous Au grades. Most drilling has focused on ~400 m strike extent at Shumagin, with other drilling at Shumagin (<60 m depth) as well as at Aquila (~700 m of strike extent, <60 m depth) being too shallow. By contrast, most drilling at Apollo, beyond the mined interval, from Sitka to California, tested levels below the potential Au zone, intersecting deeper sulfide-rich structures with variable base metals and Ag. Well-mineralized intervals near the coast, at Shumagin, extend from ~100 m to 200 m elevation, whereas at Apollo the Au-mineralized interval is ~200 m elev. to sea level; the higher elevation of the mineralized interval is due to the higher paleosurface elevation at the time of hydrothermal activity. As with other mineralized epithermal districts worldwide, the level of the top of mineralization may be at a relatively similar depth below the paleosurface, perhaps m deep. Evidence for paleosurface (e.g., sinter, steamheated alteration) was not observed at Shumagin or Apollo, and the outcropping veins with locally high Au grades and variable crystallinity of quartz suggest that they may have been eroded at least 100 m below paleosurface. By contrast, the phreatomagmatic deposits with altered clasts and interbedded lacustrine sediments, between Orange Mountain and Aquila, indicate the level of a syn-hydrothermal paleosurface at ~200 m elevation in this area, i.e., Aquila drilling just to the SW was likely too shallow to test the vein potential in the area. Based on the >14 km extent of the Shumagin and Apollo structures, with only <4 km of this extent tested by drilling, and <1.5 km tested by mining or drilling to appropriate depths, there appears to be several intervals with untested potential, not to mention possible subsidiary 3

4 structures along these corridors, and numerous other prospects on the island. Areas with untested potential include: 1) deeper veins NE and SW of the Shumagin mineralized shoot, 2) a possible conjugate structure in the hanging wall of the Shumagin vein, across the valley to the SE toward the dome, 3) the strike extent to the SW of Shumagin, up the slope toward Orange Mountain, 4) deeper testing at Aquila and Amethyst, 5) possible conjugate structures SE of Amethyst, 6) the SW extension from Aquila to the coast; and on the Apollo structure, 7) relatively shallow drilling on unmined portions between Sitka and California shafts, 8) NE and SW strike extents of the Apollo structure, where altered, even if there is not a significant geochemical anomaly. Prior to such testing, and in order to determine priorities and specific targets, the corridors along these structures must be mapped in detail, with structures and orientations plus alteration noted. A critical aspect will be reconstruction of the volcanic morphology based on the host lithologies, in order to estimate the relative depth of erosion below the paleosurface at the time of hydrothermal activity, in conjunction with alteration mineralogy and textures plus geochemical signatures (e.g., Hg rich at shallow paleodepths). At present Orange Mountain is not a target of high priority, even though it may be the center of the hydrothermal system, given 1) its characteristics and 2) the significant and untested structure-related potential to the NE and SW, as well as 3) the potential on the Apollo trend. It is critical to characterize the complete systems at Shumagin-Orange Mountain-Aquila and Sitka-Apollo-Empire Ridge-California, and their extensions, given the indications of continuous surficial alteration despite intermittent outcrops of veins with low to high metal concentrations at surface. Ore deposits of epithermal veins do not necessarily outcrop at the surface, certainly not with ore grades, as shown in numerous examples around the world at deposits that are now mines. Magmatic centers and associated epithermal systems can have scales of up to 10 km, and large portions of such systems can be blind at the present erosion surface, at least in terms of outcropping geochemical anomalies. The reasons include: various levels of mineralization relative to the paleosurface (with top of high grades 100s of m deep), different erosional levels across a district, and post-mineral cover. Thus, only assessing outcropping veins with good geochemical anomalies may be like only examining the tip-ofthe-iceberg in terms of district potential. Assessment of a large district is challenging, particularly where there is limited evidence of buried veins, such as structural lineations, alteration indications, weak geochemical anomalies, and geophysical evidence. This requires a systematic assessment and with a good technical foundation and strategy. Recommendations The epithermal potential in the SW portion of Unga Island should be considered from a district perspective, assessing structural trends, particularly those with evidence of hydrothermal alteration. An initial assessment should be conducted regardless of strength of geochemical anomaly, particularly if the clay alteration mineralogy indicates a low paleotemperature (i.e., shallow level of erosion). Shumagin trend Map the corridor (over 1 km wide), from the Shumagin vein (including NE to the shore), up the slope to the SW to the vicinity of Orange Mountain. Identify altered areas and vein outcrop/subcrop, and measure orientations of structures; use SWIR equipment to characterize the clay minerals along sample traverses. Traverse the Shumagin trend with a magnetometer on 100-m lines (or closer in areas of structural offset) for 1 km along strike, to orient a ground magnetic survey. Extend the survey to the SW for 3-4 km, and again from Aquila to the coast, to help identify linear demagnetized zones in andesite that may be related to alteration halos of veins. Continue to sample talus fines above the valley to the NW of this NE-SW corridor, between Shumagin vein and the upper portion of the slope, about 3 km to the SW. 4

5 Integrate observations in the Orange Mountain area, including the silicic ridges and lithocap horizons to the NW of the main NE-trending ridge, and the silicic trends to the WSW. Define the limits of advanced argillic (quartz±alunite±dickite) alteration, particularly NE, SE and SW of Orange Mountain. Record bedded (laminated) deposits that include clasts of residual quartz and where matrix is silicified (i.e., synhydrothermal paleosurface). Reconstruct the volcanic centers, where possible, based on identification of altered and fresh volcanic tuffs, noting the size and composition of lithics, and orientation of bedding. Observe and record structures that cut the residual quartz, both at Orange Mountain and in other areas (e.g., the altered corridor from Norm's vein north toward Orange Mountain), and also note the presence and orientation of cross-cutting quartz veins. Selectively sample and analyze the quartz veins that cut the earlier silicic alteration; however, negative results do not necessarily mean no potential at depth. Map the area of the Aquila veins and to the SW; extend talus/soil sampling to help define the source(s) of the stream-sediment anomalies. Apollo trend As with the Shumagin trend, map the corridor along the full length of the structure that cuts across the whole island. Examine the alteration mineralogy along the trend (supported by SWIR measurements), both temperature-sensitive clays as well as advanced argillic minerals indicative of acidic alteration, to see if the center can be determined of the paragenetic-early leaching from which the vein system may have radiated along the Apollo structural trend (similar to that at Orange Mountain on the Shumagin trend). Assess areas of higher paleotemperature based on clay mineralogy, i.e., deeper erosion, vs areas with low-temperature clays that may indicate either a distal position or a shallow depth below paleosurface. If the Shumagin ground magnetic survey is useful, extend it to the Apollo trend, to identify changes in orientation of structures as well as blind structures and veins. Drill targets Based on surface mapping, sampling, alteration studies, and ground magnetic input, identify viable targets for drill testing, with rationale that will stand up to independent scrutiny. Continue assessing the orientation of structures to identify offsets as well as potential zones of dilation, like those at Shumagin, which may have focused the upflow of mineralizing fluid. Several possible targets have been mentioned above, and these await further constraints to allow a ranking of priority of all targets that are identified. Drilling will have to test at least ~ m below paleosurface, as defined by geological (e.g., lacustrine sediments with altered clasts) and alteration constraints. Other areas Although the complete Shumagin and Apollo trends (in excess of 7-8 km each) are the priority for assessment, with the goal to define drill targets, there may be other potential in the SW portion of Unga Island, possibly related to dome margins. Peterson et al. (1982) identified numerous targets around the island, away from the two principal structural trends. Use a consistent approach to present data for each prospect area, to allow for intercomparison, first presenting the overall constraints and targets, followed by details of supporting observations. Standardize the legends for soil and rock geochemical results, as well as alteration and lithologies. 5

6 Introduction Jesse Grady, VP Exploration of Redstar Gold Corp, requested the author to examine the epithermal project on Unga Island in the Alaskan Peninsula. The author spent six days in the field with Grady while Bill Burnett, Steve Enns, and Cody Pink mapped and sampled, and also examined drill core in the base at Sand Point airport on nearby Popof Island. Grady and the author, with helicopter piloted by Chris Kim, walked over much of the Shumagin to Orange Mountain to Aquila trend, >7 km in extent NE to SW, as well as adjacent altered areas. Part of the trend of the Apollo mine SW to Empire Ridge (about 4 km SE of Orange Mountain) was also examined. Grady is thanked for his observations and input to this report. Background The Apollo vein mine on Unga Island operated between 1892 and 1914, and up to 1905 produced about $2 million worth of gold ($20.67/oz) plus silver at ~0.4 oz/ton (12.5 g/tonne), indicating about 240 kt of quartz vein ore. The nearby King and Sitka vein mines also reported minor production (Riehle, 1999, USGS Open-file report ). Production came from one tunnel 360 m long, with a second 95 m deeper and 970 m long, working three subparallel veins less than 15 m apart. The main ore chute extended from outcrop to 10 m below the upper tunnel, and the lower tunnel produced from a zoned vein with a 240 m long ore shoot, where free gold gave way to galena, sphalerite, and chalcopyrite at depth. Riehle (1999) reviewed reports that indicate four distinct ore shoots m long on the Apollo system, between the surface to at least 245 m depth, distributed along ~1500 m of strike. Fig. 1. Simplified geology of southern Unga Island (Riehle, 1999), with magnetic low lineations (white traces; Cady and Smith, 1999) apparently related to elongate zones of alteration. "Intense silicification" (darkest green) at Orange Mountain is residual quartz after volcanic horizons; along the Apollo trend this narrow silicification is also due to residual quartz, reopened by quartz veins. Symbols: Tpdu: Lava domes, undifferentiated: locally carapace of pumiceous tuff. Tpdb: Basaltic andesite domes; Tpda: Andesitic domes; Tpdd: Dacitic domes; Tpdr: Rhyolitic domes. Tpth: Hornblende tuff: Dacitic ash-flow tuff; Tptb: Biotite tuff: Dacitic ash-flow tuff. Tps: Volcaniclastic rocks: Volcanic breccia with ashflow tuffs. Tpu: Popof volcanic rocks, undifferentiated: Mainly andesite to basaltic andesite lava flows and flow breccias. Sequence Late Eocene to Oligocene in age. 6

7 Riehle et al. (1999, in Riehle, 1999) reviewed the geology of the southeast portion of Unga, from which this summary is taken (Fig. 1). The oldest rocks are shallow marine sandstone and siltstone of the Stepovak Formation (unit Ts; late Eocene to early Oligocene age). These were deformed by Popof submarine lava flows (latest Eocene or earliest Oligocene; unit Tpu). There was contemporaneous sedimentation and volcanism, including volcaniclastic peperite deposits in unit Tps. Possible vents with opposing dips of stratocone deposits are 2 km south of Apollo Mountain and in the northwestern corner of Acheredin Bay. The early lavas on Unga Island are andesitic; domes (unit Tpd), separate from unit Tpu, are possible vent sites, and include small dacitic and rhyolitic domes. Dacitic ash-flow deposits include biotite-bearing tuff (Tptb) and (strongly altered) hornblende-bearing tuff (Tpth). Volcanism (31-38 Ma) was joined by hypabyssal activity (31-34 Ma) as domes of basaltic andesite to rhyolitic composition were extruded from numerous vents; local ash-flow tuffs originated at the domes. Known gold and silver mineralization is concentrated in two major, northeast-trending zones of faulting, brecciation, and quartz veining that extend across southeastern Unga Island (Fig. 2). K-Ar ages of vein adularia (34 Ma) and sericitic vein alteration (32 Ma) indicate that vein alteration was contemporaneous with magmatism. OM 3 km Fig. 2. Shaded relief (Riehle, 1999) of southern Unga Island, showing the strong NE-SW structural features that cut the SE portion of the island, and which are altered and mineralized (the Shumagin and Apollo trends). Many of the distinct topographic highs on the SE portion of the island are related to dome extrusions. The massif in the upper center is a Miocene dome encircled by carapace breccia and tuff. White dashed line is the division between Eocene-Oligocene rocks to the SE and Miocene volcanic products to the NW; alteration of Miocene rocks is also reported (Riehle, 1999). OM, Orange Mountain. Several companies have explored veins in the district, with drilling on the Shumagin, Aquila and Empire Ridge trends (Fig. 1). UNC Teton Exploration Drilling worked on Unga Island in , conducting extensive prospecting (Peterson et al., 1982), as well as drilling at Aquila. Alaska Apollo Gold Mines drilled 23 shallow holes at Shumagin from 1983 to 1987 (2823 m total, with an average depth of 123 m). This work led to identification of a resource in a shoot with double digit grades of gold with Ag:Au of ~4 (White and Queen, 1989; USGS 7

8 Open-file Report ). They also drilled 21 holes along the Empire Ridge-Apollo trend in 1983 (Pilcher, 1983), a total of 4440 m (>220 per hole). Ballatar Explorations Ltd. drilled 16 more holes on the Shumagin vein in (~1830 m, an average of ~113 m per hole). Battle Mountain Gold Mines Inc. flew DIGHEM in 1990 and produced resistivity and magnetic images for the district, then drilled BMS-01 at Shumagin, 311 m long; at 274 m they intersected a vein swarm 5.5 m wide with 0.47 oz/ton (14.7 g/t); a check assay returned a value for the interval of 41.0 g/t (perhaps due to the nugget effect of free gold). White and Queen (1989) noted the highest gold values from these drill campaigns on the Shumagin vein were g/t. Subsequently, Redstar Gold Corp acquired the property in 2011 and initially drilled 10 holes at Shumagin in 2011, 11SH , followed by eight holes in Redstar reported intersections in five of eight 2015 holes of 11.6, 16.9, 17.4, 19.9, 20.9, 35.3, and 41.2 g/t Au over 1.0 to 4.0 m core intervals, plus one 1.9 m interval containing 202 g/t; three other holes reported 3.4 to 6.1 m vein intervals with 0.3 to 1.2 g/t Au (long section; Fig. 3). The high grades are related to free gold (electrum), locally dendritic, associated with colloform bands of quartz in brecciated intervals, a characteristic epithermal texture. The USGS compiled further historic and resource information for the Apollo and Shumagin veins at ( and Fig. 3. Long section showing grade*thickness results (g*m) for the Shumagin vein; the drilled portion is ~800 m long, although drilling along about half of this trend does not extend below sea level. Grades of g/t over m were reported in trenches above 100 m elevation; >30 g*m has been intersected below 100 m elevation, albeit in an apparently NE-plunging ore shoot. Upper bar = 500 m. Source of this and most other diagrams: Redstar Gold Corp, at Observations Two principal structures, Shumagin and Apollo, are subparallel and oriented ~NE-SW; they cut the complete SE portion of Unga Island (Fig. 2). Alteration of the volcanic rocks is closely associated with these two structural trends, relatively narrow on the Apollo trend to the south and broader on the Shumagin trend to the north (Fig. 1). Most of field time focused on the nature of alteration and the potential for mineralization along the Shumagin trend, which stretches for over 8 km (Fig. 2). Orange Mountain is bisected by the Shumagin trend, and has received relatively little exploration attention compared to the Shumagin and Aquila veins to the NE (title page frontispiece) and SW (Fig. 4a), respectively. However, based on observations, veins appear to be associated with the Orange Mountain center of residual quartz, characterized by silicic lithocaps and a halo of advanced argillic alteration (Fig. 4b). 8

9 Orange Mountain Orange Mountain gets its name from the well-developed quartz-alunite-clay alteration that is a halo to residual quartz bodies (Fig. 4a), previously called silicification (e.g., Peterson et al., 1982; Riehle, 1999). It is approximately located in the middle of the Shumagin NE-SW structural trend, with the Shumagin (title page frontispiece) and Aquila (Fig. 4a) vein trends to the NE and SW, respectively. The silicic alteration of residual quartz forms resistant bodies with cliff-like relief, particularly on the NW margin of the main body (Fig. 4b, 5a). Fig. 4. a) NE margin of advanced argillic alteration at Orange Mountain, looking SW to the NE-trending dike outcrop on the shore, a distance of ~5 km (compare with view to the NE over Orange Mountain, frontispiece on title page). The silicic core of Orange Mountain is a highly resistant body, with silicic lithocaps to the right (NNW), and silicic ribs and advanced argillic alteration to the SSW. An area of polymictic fragmental material with bedded sedimentary horizons occurs to the SW, with the Aquila vein system further to the SW. b) To the SE over Orange Mountain, showing the massive silicic body and horizons of silicic lithocaps in the foreground, looking ~4 km SE to the Sitka-Apollo-Empire Ridge vein trend that cuts structurally controlled silicic alteration along a parallel NE-SW trend (grey line, NE-SW, in foreground ~500 m long). 9

10 Fig. 5. a) Looking south to SSW along the SW-trending silicic bodies of Orange Mountain, with steep outcrops to the NW, eroded to scree slopes. b) Top of Orange Mountain, with silicic outcrop cut by NE-SW fracture face. Looking SW, toward the area of lacustrine sediments incorporated within a deposit of polymictic fragmental material. c) Residual quartz, with massive silicic 3 (strong silicic) cementation of brecciated rock. d) Silicic alteration cut by massive cryptocrystalline quartz vein, with open-space fill of barite. Fine quartz veinlets cut silicic elsewhere, near minor Au anomalies (<0.2 g/t). e) Barite cement in a late fracture atop Orange Mountain. 10

11 The main body of Orange Mountain (right half of Fig. 5a) consists of residual quartz with a silicic 2 to 3 degree (moderate to strong). The original lithology here is difficult to discern, given the strong silicic alteration (silicification) of the rock after the leaching event that produced the residual quartz. Locally there are textures that indicate brecciation (Fig. 5d) prior to the strong silicification. Subsequently the silicic alteration was cut by veins of massive cryptocrystalline quartz (Fig. 5d), with open-space fill of barite in places. To the west and NW of the principal silicic body there are relatively thin lithocap horizons (Fig. 6a) of silicic 2 with vuggy texture (Fig. 6b, c); these horizons appear to be lithic tuff, although the texture may also in places be due to post-silicic brecciation and silicification (Fig. 6c). These tuff horizons dip to the SW to WSW on the west side of Orange Mountain. To the east and SE of the main silicic body, the lithology appears to dip to the SE (Fig. 4a, 7a), beneath reportedly fresh basaltic andesite (Redstar presentation, v. 3, 2016). To the SW and WSW of the main silicic body there are several SW-trending silicic ribs, as well as patches of quartz-alunite (Fig. 4a) and, in more distal locations, alunite-clay (dickite, kaolinite) alteration (Fig. 7a). The lithology in this area appears to be tuffaceous (Fig. 7b), but there are also fragmental units with rounded clasts of vuggy silicic material (Fig. 7c). Also to the SW of the main silicic body a polymict fragmental unit with laminated sediments outcrops (Fig. 6a), located at slightly lower elevation than the top of the main silicic body (Fig. 8a, e). crater lake sediments Fig. 6. a) Panoramic view Orange Mountain to SW and WSW (305 to 270 m elevation along the ridge, NE to SW). NW of the silicic ridge are lithocap horizons at lower elevation (dip ~SW) with silicic alteration; ribs of silicic alteration in the distance, to the right; on the horizon to the right, is the polymict fragmental unit with laminated (lacustrine?) sediments ("crater lake sediments"), top at ~230 m elevation. b) Lithocap of vuggy quartz, silicic 2, after tuff horizon. c) Lithocap of vuggy quartz after lithic tuff, with lithics also altered to vuggy quartz. 11

12 The laminated sediments are moderately sorted, with a sharp contact up with a horizon of fragmental material (Fig. 8b). The laminated horizon dips to the SE and is weakly warped, suggesting that the area may have been water saturated and placed under a load. The polymict fragmental unit consists of lithic clasts that were silicic altered prior to brecciation, as well as clay-altered irregular clasts that were likely juvenile in origin (Fig. 8c-e). Some of the polymict material is also weakly sorted and bedded, suggesting a lacustrine depositional setting. These sedimentary features plus the fragmental and polymictic nature of the unit suggests that the material may have been deposited in a phreatomagmatic eruption crater that was water-filled at times, about 1 km SW of the main silicic body. In addition to the silicic and quartz-alunite alteration that is visible to the SE to SW and WSW of the main silicic body, for a distance of km from the SW extent of the silicic body (Fig. 4a, 5b), there are also areas of advanced argillic and silicic alteration to the north (Fig. 9a). The discontinuous exposure extends as far as Norm's vein, 4 km to the NNE (Fig. 9b), with silicic 2 alteration along a structural trend that was in turn cut by a quartz vein. Closer to Orange Mountain (Fig. 9c), there are areas of clay alteration (kaolinite) with narrow structures of silicic 1 (Fig. 9d), cut by quartz vein material (Fig. 9e). Fig. 7. a) ENE to silicic ribs and in distance, Orange Mountain silicic body (305 m elev. to the NE, and 270 m at the SW end) with quartz-alunite to east (right), from distal area of alunite-clay alteration (150 m elev.). b) Fragmental unit, silicic 2 alteration, including rounded clasts of vuggy quartz, from area of foreground in a). c) Lithic tuff, silicic 2 alteration, with fine vugs in lithic clasts, from silicic ribs. 12

13 Fig. 8. a) Sedimentary laminations, looking NE to Orange Mountain in distance; sediments are hosted by polymict fragmental unit. b) Laminated sediments; laminations appear to be bent (due to loading?), and dip at a low angle to the SE. c) and d) Polymict fragmental unit, with silicic 2-3 clasts as well as clay-altered lithics (arrow), likely of a juvenile origin. e) Variably sorted (possibly water lain), weakly bedded polymict fragmental material, with silicic clasts and soft juvenile clasts, looking past polymict fragmental unit (right) to Orange Mountain. 13

14 Fig. 9. a) Looking south to Orange Mountain silicic body, with silicic lithocap horizons in front of the massif; polymict fragmental unit to right across valley at top of ridge, above silicic ribs. b) Area east of Norm's vein, NNE ~4 km from center of Orange Mountain. Looking SSW at silicified structure, dip ~70 o to west; structure cuts silicic 2 hypogene acidic alteration, with sulfides. c) SSW 2.5 km to Orange Mountain; here alteration is silicic 1 plus pyrite (and iron oxide). d) SSW, tuffaceous unit (in paleovalley?), altered to kaolinite plus quartz, cut by silicified structures in corridor ~N-S projecting toward the west side of Orange Mountain. Fresh basaltic andesite locally cut by altered zones along structures. e) Residual quartz, silicified with local open-space filled by quartz crystals, in structure seen in d). 14

15 The main silicic body of Orange Mountain (Fig. 1) had three holes drilled on its NE margin in the 1980s (185 to 297 m at 45 to 60 o ; Fig. 10), to a maximum depth of ~60 m elevation. Based on the drill logs, the lithology of the three holes, drilled NE of the main silicic body (Fig. 10), were tuffs, from crystal to lithic; relatively narrow intervals (to a maximum of ~30 m) were massive silicic (i.e., lithocaps after tuffs; Fig. 11). Most of the intervals were clay altered, and pyrite was abundant, from %. The few pieces of silicic core available (Fig. 11) do not indicate the nature of the tuff; it is likely that the most silicic horizons were also the most permeable tuffs (Peterson et al., 1982). The overall Orange Mountain silicic body reports a poor geochemical anomaly based on a 1980s soil grid, with line spacing of 150 m (Fig. 10). Most results are <10 ppb, although one line returned four samples with 50 to >200 ppb Au; other anomalous results are scattered. Rock samples are scattered, and returned <250 ppb (Fig. 10). The area with best, albeit weak, anomalies was subsequently drilled. Although surface sampling is sparse (with the few soil anomalies potentially related to quartz veins, e.g., Fig. 5d), the existing results suggest the potential for a barren lithocap at the level of erosion. Recent sampling of talus fines, with material collected from lower elevation slopes, was conducted in the summer of 2016, with analytical results still pending at the time of this report being written. main silicic body Fig. 10. Vertical aerial photograph of Orange Mountain, showing old soil geochemistry results (up to > ppb Au); scattered rock samples returned <250 ppb Au. Residual quartz (silicic; steep relief due to resistance to erosion) and the halo of advanced argillic alteration (quartz-dickite-kaolinite; light colored) is clear; silicic lithocap horizons outcrop at lower elevation up to ~ m north of the main silicic body. The collars and traces of OM-1 (185 m at 45 o from 265 m elev.), OM-2 (297 m at 60 o from 312 m elev.) and OM-3 (266 m at 60 o from 292 m elev.) are shown to the NE of the main silicic zone (of continuous cliff outcrop), which is ~600 m long NE-SW. Drill hole logs from 1983 by UNC Teton Exploration Drilling, Inc., record that the lithologies are principally crystal, crystal lithic and crystal pumice tuffs, dominantly clay altered but with horizons of moderate to strong residual quartz (silicic) alteration (Fig.11), influenced by a permeable andesitic crystal lithic tuff. Pyrite is typically 5-25+% except in narrow brecciated intervals of supergene oxidation (Fig. 11, OM ' and 222'). Silicic horizons locally (one interval in OM-2 at 240 m and three intervals above 100 m in OM-3) returned anomalous intervals of 5-8 m with 0.1 to 0.4 g/t Au, with one value over 1.5 m in OM-2 of 1.2 g/t Au at ~100 m elevation; the maximum anomaly in OM-1 was 45 ppb Au. OM-3 returned 0.5 m with >2 wt% Cu and high As and Sb at 224 m elev. (Fig. 11, 265.9' and 266.5'). The dominance of clay over silicic alteration in these drill holes may have been related to their location to the NE of the main silicic body. 15

16 Fig. 11. Core from Orange Mountain drill hole OM-3, showing silicic alteration with some brecciation, the latter cemented by iron oxides (original pyrite that was supergene oxidized, likely along structures related to the brecciation); 199.5' and 222'; 0.34 and 0.08 g/t Au, respectively, with 62 and 252 ppm Cu. Samples from 244' to 266.5' are unoxidized, with 265.9' and 266.5' showing a metallic black sulfide (tennantite-tetrahedrite or enargite?) from an interval with >2 wt% Cu, >1000 ppm As and 1700 ppm Sb, plus 45 ppm Bi and 420 ppm Ba; Au is 20 ppb, with 1 ppm Ag - the other two unoxidized silicic core samples contain 15 and 25 ppb Au. In summary, residual quartz (silicic 2-3) alteration of tuffaceous horizons at Orange Mountain occurs over a central area of ~1 x 1 km, with more extensive silicic ribs plus quartz-alunite and alunite-clay alteration to the WSW (Fig. 7a). The hypogene advanced argillic alteration is characteristic of magmatic vapor condensates related to a shallow intrusion. A syn-hydrothermal polymict fragmental unit with juvenile clasts <1 km from the main silicic body indicates syn-hydrothermal magmatism and eruption, with a crater-lake setting indicated by the laminated water-lain sediments. Following this alteration, including in distal locations, there were cross-cutting quartz veins in this area at the surface, as well as to the NE and SW along structural trends toward the Shumagin and Aquila vein systems. 16

17 Aquila The Aquila area lies SW of Orange Mountain (Fig. 12a, c, d, e), and includes NE-trending veins at both Aquila and, to the SE, at Amethyst, both of which have been tested by about a dozen shallow drill holes (Fig. 13) in the 1980s. The structural trend continues to the SW (Fig. 12b, f), including the Origin vein on strike from Aquila (Fig. 13), and extends 1+ km to Fig. 12. Aquila area. a) Looking NE from Aquila vein, over valley with quartz vein float (~260 m elev.) in area of fresh basaltic andesite; Orange Mountain is present on the right horizon. b) To west, with drainage to SW containing stream sediment anomalies, up to 7 g/t Au. c) Looking NNE over structural trend associated with the Amethyst shoot, Orange Mountain beyond. Valley depression to right is similar to NE-SW depression in the main Aquila area, seen in b). d) Collar area of drill hole AQAME-1, Amethyst shoot. Quartz-adularia veinlets with cockscomb textures; trench from earlier work reported 11 g/t Au over 2 m, and nearby dozer cut had ~10 g/t over ~4 m (AQAME-2 targeted this area, best grade of a dozen holes at Aquila, with ~100 g/t Au reported over ~0.5 m at ~40 m vertical depth. e) NNE along narrow sheeted veinlets (1-2 cm), N50E, near vertical (locally change orientation to N80E; 220 m elev.). f) To SSW along same sheeted-veinlet trend, with NEtrending (reportedly fresh) dike on horizon (to left) cutting visibly altered area. 17

18 the SW, to the coast, with several veins mapped (Fig. 1). The Aquila area has a strong NE- SW lineation of valleys (Fig. 12b, c), possibly due to horst and graben-style faulting (Fig. 13). The strong NE-SW lineations of magnetic low anomalies (Fig. 1) in this area indicates that the Shumagin trend continues to the coast, with associated hydrothermal alteration at the surface and some vein outcrops. Soil lines across the Aquila to the Origin veins returned mainly <20 ppb Au, although some samples are highly anomalous, up to 0.2 ppm Au (Fig. 13). Similarly, scattered rock (vein?) samples are mostly <0.5 g/t Au, but a couple are >1.5 g/t. By contrast, stream sediment results are highly anomalous, with numerous samples >1.5-7 as well as >7 g/t Au (Fig. 13), likely indicating erosion of restricted outcrops of high-grade veins. Drilling of 12 holes for a total amount of 1355 m (~112 m per hole) encountered grades of 1-2 g/t Au over ~1-5 m at depths of ~30 to 60 m in about half of the holes, with two holes returning 1 m at ~8 g/t and 0.5 m at ~100 g/t Au. Of the 17 trenches (total of 1008 m), a third returned ~2-4 m with ~3 to 11 g/t Au. This work was conducted in by UNC Teton Exploration Drilling, with a detailed sketch map of outcrops and veins in the Aquila area. Fig. 13. Aquila area of parallel vein trends, including the Aquila and Amethyst veins, SW of Orange Mountain and the moat sediments. Geochemical results (most from the 1980s) are plotted, including locally anomalous rock samples, highly anomalous stream sediment samples, and variable soil samples. At least nine historic holes were drilled to shallow depths, indicating narrow well-mineralized intervals (up to ~100 g/t Au over ~0.5 m in AQAME-2 at Amethyst; Fig. 12d). 18

19 Shumagin The Shumagin vein system near the NE extent of the Shumagin trend has had the greatest amount of assessment conducted since the 1980s, with Redstar focusing much of its efforts, including drilling, in this area since acquisition of the property in A comprehensive description of this vein system, including lithologies, parageneses, cross sections and core photographs, is available at The following comments are based on the Redstar summary by J. Grady and additional personal observations. The vein system is oriented NE with a steep SE dip that defines the contact between basaltic andesite in the FW and a HW sequence of dacitic pyroclastic flows and overlying epiclastic sedimentary units, including mudstones and siltstones plus conglomerates. The epiclastic unit, which fills the valley to the SE of the vein scarp (Fig. 14a), contains lithic clasts that appear to have an alteration style distinct from the matrix, with the latter in turn altered and cut by quartz-carbonate veins and stockwork. These observations suggest that the epiclastic unit may have accumulated during hydrothermal activity, with extension causing a basin to form. If so, there is likely a conjugate fault system to the SE, on the other side of the basin and adjacent to the dacite dome; if present, such a fault may have similar vein potential to that of the Shumagin system but does not outcrop due to talus from the adjacent dome (Fig. 15a). Along the Shumagin vein system contact there are polymict fragmental units with clasts of altered lithics as well as juvenile clasts (Fig. 14c, d) that J. Grady interpreted to be due to a phreatomagmatic origin; they have a syn-hydrothermal timing, as evidenced by the altered lithics and the subsequent cross-cutting veins. They were subsequently intruded by mafic dikes along a 200-m strike extent, within the HW. Adjacent to the contact in the FW there are pyrite-marcasite quartz veins with fine banding and gold grades up to 2-4 g/t, characterized by low Ag:Au ratios and relatively high As and Sb; this vein stage is relatively early, as evidenced by clasts occurring in the brecciated vein system that constitutes the main mineralization stage. The main or principal stage is restricted to the contact between the FW and HW, and is closely associated with the location of the units of phreatomagmatic breccia. This main stage consists of a wide, up to 7-10 m zone of brecciated vein material, with local bonanza grades of Au, variable to high Ag:Au ratios, and up to ~1 wt% each of Pb, Zn and Cu in galena, sphalerite and chalcopyrite; As and Sb concentrations are relatively low compared to the early stage. The brecciation was multi-episodic, disrupting cockade- and crustiform-banded quartz-adularia-rhodocrosite-clay veins (Fig. 14e), stockwork and vein breccias; there are also bands of colloform (colloidal) silica (Fig. 26b). Local clusters of visible gold (electrum) occur within quartz, typically after adularia deposition and prior to rhodochrosite (Fig. 26b). Pervasive silicification and anomalous quartz-sericite-pyrite veins form a halo to the vein system, up to 10 m into the HW (J. Grady observation). To the SW from the Shumagin outcrop there is a corridor (Fig. 15a) of intermittent outcrops that are variably clay altered (Fig. 15b-f) for a distance of ~2 km to the far ridge at ~360 m elev. (Fig. 15a). The alteration varies from clay (Fig. 15b, c) to narrow structures (Fig. 15e, f) with quartz-clay-pyrite in andesite where the magnetite has been destroyed; the structures are defined by sub-mm (Fig. 15d) vein stockworks to cm-size quartz veins (Fig. 15f). These altered outcrops can have quartz-vein float (Fig. 15b), and to a large extent occur upslope from a 1980s soil grid, which reported anomalies up to 100 ppb occurring from the uppermost sample of the grid. 19

20 Fig. 14. a) Shumagin ridge, to NE; SE-dipping vein on right dip slope of ridge, with left road in the footwall of the vein tested by drilling. Two styles of mineralization were defined; a polymictic fragmental with brecciated vein material in the main structure (intervals up to a maximum of 738 g/t Au and 5403 g/t Ag over a sulfide-rich zone with up to ~0.9 wt% each of Cu, Pb and Zn), and a quartz vein in the footwall (2-4 g/t Au and 5-9 g/t Ag with high As, <3350 ppm, and Sb, <230 ppm). b) Outcropping Shumagin vein on dip slope, open spaces due to leached (Mn?) carbonates. c) 11SH m, early polymict fragmental with angular rock clasts and juvenile pumice (clay altered). d) 11SH7-250 m, polymictic fragmental with altered and juvenile clasts, cut by veinlets. e) 11SH-225 m, clasts of polymict fragmental with altered and juvenile clasts (upper left), brecciated to angular fragments and sealed by bands of quartz + adularia plus native gold (pointer), then overgrowths of rhodochrosite (brown oxidation). f) 11SH m ( 68 m elev.), 0.5 m of 738 g/t Au and 408 g/t Ag in plunging ore shoot (Fig. 3); bonanza grade due to the native electrum and fine (likely Ag) sulfosalts in milky white crystalline quartz vein, pyrite-chlorite altered andesite, HW of brecciated structure. 20

21 Fig. 15. a) View over ridge of Shumagin veins (upper outcrop ~120 m elev.) to the SW along a corridor of alteration as the slope rises ~4 km to the Orange Mountain hydrothermal center (over skyline); distance to ridge at ~360 m is ~2 km (shown by yellow trace). Valley to SE of Shumagin ridge (left), separates it from the andesite dome (left margin) and Bloomer Ridge dacite dome (far left). b) View to NE, Shumagin vein area, with dome to right; area of alteration (~290 m elev.) with float of quartz vein fragments. c) View to NE from top of ridge (here ~360 m elev.) to Shimigan vein. d) Stockwork of sub-mm quartz veinlets (area of c). e) SE over Shumagin corridor, toward area known as Pray's siliceous ridge, quartz-clay-pyrite alteration, locally strong (280 m elev.). f) Quartz veinlets in sheeted fractures (N65E) in andesite (without magnetite), altered halos of quartz-clay-pyrite (area of e). Here close to the NE end of 1980s soil grid, below an area with ppb soil anomalies (3 samples at the up-slope limit of the survey). 21

22 Apollo-Empire Ridge The Apollo mine (Fig. 16) was in production during and , with two tunnels 350 and 975 m long plus two shafts 140 and 240 m deep, producing an estimated 240 kt of ore at a grade of ~0.4 oz/ton (~12.5 g/t; Berg and Cobb, 1967, USGS Survey Bulletin 1246). Most of the mined ore was free milling at shallow depths, whereas Au in deeper ore is associated with sulfides. A 1935 report referenced by Brown (1947, Alaska Territorial Department of Mines Report MR 138-1) suggested that there were four ore shoots m long, along 1500 m strike to a depth of 400 m. Most of the ore mined came from two shoots, the largest of which was up to 5 m wide, and extended down dip for 150 m, with an ore shoot plunge of 60 to 70 o NE (Wilson et al., 1996, USGS Miscellaneous Field Studies Map MF F). In 1983, Alaska-Apollo Gold Mines compiled the results of underground sampling in the 1920s (Fig. 19a) and conducted trenching and drilled nine holes totaling 2900 m. They suggested a resource of 748 kt at a grade of ~23 g/t Au, with ~3:1 Ag:Au ratio ( most of this would have been in the shallow oxide zone, as the deeper sulfide zone is base metal rich (reportedly galena, sphalerite, chalcopyrite and tetrahedrite, with vein intersections containing up to 25% Pb+Zn; Pilcher, 1983), higher Ag:Au than in the overlying oxide zone, and relatively low Au values. Fig. 16. a) Apollo vein, open cut, looking ~NNE, from ~210 m elevation to ~170 m elevation at NE end. b) Looking ~ENE over the Apollo vein, with trenches on the Sitka vein, with trenches visible across the valley to the NE. c) Apollo vein cut, looking ~NE, dipping steeply to the NW, with secondary veinlets dipping to the SE. d) Apollo, to N10E along veinlet outcrop, locally brecciated, nearly vertical, in hanging wall. 22

23 Fig. 17. Empire Ridge (elev. ~230 m). a) Looking NE along highly resistant silicic structure; SW end of the Apollo open cut is just visible near break in slope. b) Looking SW, steeply SE-dipping structures; early drill holes were drilled from NW to SE, assuming a similar dip to the Apollo vein, present a few 100s m to the NE. c) Apollo Ridge, polymict fragmental, silicic, cut by milky quartz vein. d) Vuggy texture after phenocrysts, residual quartz host to later veins. e) Massive silicic 2 residual quartz, after brecciation, prior to any vein event. 23

24 On strike from the Apollo mine to the SW is the Empire Ridge (Fig. 17a), with the resistant nature of the ridge (Fig. 17b) due to strong silicification. This alteration is residual quartz with vuggy to massive texture and showing evidence of brecciation (Fig. 17c-e); subsequent to the massive silicification, the structure was reopened and infilled by milky (massive cryptocrystalline) quartz vein material (Fig. 17c). This is similar to the situation at Orange Mountain, with residual quartz being refractured and filled by quartz vein material, although the early silicic alteration is confined to relatively narrow zones along structural trends along the Apollo trend, which includes Empire Ridge (Fig. 1). The linear occurrence of what has been mapped as strong silicification is most likely related to early leaching and formation of residual quartz along the Apollo trend. Recent (2014) soil lines and surface rock sampling (Fig. 18) shows highly anomalous soils where the vein outcrops, but little soil anomaly (e.g., furthest NE line, Fig. 18) where the vein does not outcrop but is present at depth, based on the location of the underground workings. The linear silicification has been mapped to extend from Sitka, Apollo and Empire Ridge through the California mine, SW to the coast, a distance of ~6 km (Fig. 1), indicating that this structure is through-going. However, although the structure and silicification plus clay alteration are largely continuous across the island, the structure has only been tested by drilling where it outcrops. Mining over a century ago was restricted to the oxide zone of high gold grades down to about sea level (Fig. 19a), with this zone underlain by base metal-rich ore at deeper levels. The deep drilling by Alaska-Apollo Gold Mines in 1983 intersected the structure from Sitka to California shafts, a distance of over 2.5 km (Fig. 19b). Silicic-rich alteration and high sulfide content was cut below ~60 m elev. at California, but mainly between sea level and 200 m elev. along the Apollo structure (Redstar compilations of 1983 drill logs). Fig. 18. Compilation of 2014 soil and rock geochemical results along the Apollo trend. Note the relative lack of anomaly in soils over the NE extension of the Apollo vein, despite the subsurface presence of the vein, as shown by the surface projection of underground workings. 24

25 200 m 300 m Sealevel 1 km Fig. 19. a) View of the Apollo to Sitka underground workings (long section looking NW), sampled and reported by F.R. Brown (1922) and information compiled by Bowdridge (1993). The upper oxide zone was mined in 1892 to 1913, producing an estimated 240 kt of ore at a grade of ~0.4 oz/ton (~12.5 g/t Au). Based on a variety of information, including the 1920s underground sampling, a resource of 678 kt at 26 g/t Au and 74 g/t Ag was estimated by Alaska-Apollo Gold Mines in 1983 (Bundzen et al., 1991). The Au-rich oxide horizon is underlain by a sulfide horizon that is relatively Au-poor. The Sitka shaft is ~50 m elev., Salmon Creek is ~20 m elev., and the SW end of the Apollo stope is ~210 m elev. b) Alaska-Apollo Gold Mines conducted drilling of relatively deep holes in 1983; drill hole traces with logged lithology based on Redstar compilation. Traces of underground workings shown in blue. Hanging wall of Apollo structure, which dips to NW, is andesite, whereas the relatively deep sulfide-rich structures (beneath the Au-rich oxide zone, shown the long section) are hosted mainly by dacite. The structure at Empire Ridge appears to dip to the SE (Fig. 17b), hence the lack of intersection of any structure. Figure compilations by J. Grady, Redstar. 25

26 Discussion Magmatic and magmatic-hydrothermal activity The Shumagin structural trend radiates from Orange Mountain, with the major structure (and likely structural intersections) responsible for focusing intrusive, extrusive and subsequent hydrothermal activity. The early alteration was related to condensation of volcanic vapor and acidic alteration. This alteration produced residual quartz with a vuggy texture and related halos of advanced argillic alteration that occurs in the main silicic body at Orange Mountain and adjacent lithocaps; similar alteration occurs in more distal positions, e.g., along structures to the north. Although there does not appear to be a similar center on the Apollo trend like that on the Shumagin trend, there is evidence that the veins at Empire Ridge cut earlyformed, structurally controlled residual quartz with a vuggy texture. Thus the early magmatic condensate that was present along much of the Shumagin trend, with subsequent fracturing and vein development at Shumagin and Aquila, also was present along the Apollo trend. There is further evidence of syn-hydrothermal magmatism along the Shumagin trend, with juvenile clasts in phreatomagmatic breccias that were subsequently brecciated within vein material (Fig. 26b). Similar evidence for juvenile clasts with altered lithic clasts in synhydrothermal (altered) fragmental deposits between Orange Mountain and Aquila also indicates dike intrusion and fragmentation during hydrothermal activity; in this case, bedded syn-hydrothermal deposits indicate a lacustrine setting, likely formed within an eruptive crater. In addition to the syn-hydrothermal magmatic activity, there was also syn-hydrothermal structural movement, as implied by the offsets documented by J. Grady for both Shumagin (Fig. 20a) and Apollo (Fig. 20b), interpreted to be dilational events that led to depressurization and brecciation followed by fluid ascent, rapid boiling (flashing), and subsequent deposition of colloidal silica and high grades of gold. At the same time, or earlier in the Shumagin hydrothermal history, there was intrusion of phreatomagmatic breccias occurred prior to, or with, mafic dike intrusion. In addition, the incorporation of altered clasts in the epiclastic valley fill to the SE of Shumagin ridge indicates that structural movement included a dip-slip component to cause uplift and erosion of early-altered material. Insight from similar deposits The Comstock Lode in Nevada (257 t Au production) is a large intermediate sulfidation (IS) vein system. There are linear occurrences of advanced argillic alteration (Fig. 21a) on the surface that correlate with subsurface stopes of high Au grade. However, the advanced argillic alteration formed ~1-2 m.yr. before the same structures were reopened by a later system that deposited quartz, adularia and gold. Somewhat similarly, the Kushikino IS vein system in Kyushu, Japan (55 t gold production) has advanced argillic alteration in the district, but it occurs as halos to silicic ribs at several 100s m higher elevation and 1-3 km east of the quartz-adularia-carbonate-gold veins. The advanced argillic alteration (Fig. 21b) followed volcanism and intrusion, and at the same time but at lower elevation, down the hydraulic gradient to the west - away from the volcanic center - the quartz veins and IS mineralization formed. Both of these examples may be relevant on Unga, where quartz veins are observed to cut silicic alteration atop Orange Mountain and elsewhere (e.g., Norm's vein and Empire Ridge). There are also structures that radiate from the intrusive and hydrothermal center, e.g., the Shumagin trend to the NE, away from Orange Mountain, with vein mineralization below ~100 m elevation in contrast to the upper extent of advanced argillic alteration, to ~ m. 26

27 400 m 400 m Fig. 20. Plan maps of structures at a) Shumagin and b) Apollo-Sitka, with interpretation by J. Grady of portions of veins that have opened where fractures change direction, allowing fluid ascent to be focused along (NE plunging) ore shoots. The main high-grade plunging shoot at Shumagin (Fig. 3) matches the portion of the vein where there has been dilation. The altered clasts in the HW to the SE of the Shumagin structure implies that there was also a dip-slip component of movement, with relative uplift to the NW. Figures prepared by J. Grady, Redstar. Scales of both areas are the same. Other insight comes from the Victoria-Teresa-Nayak IS vein system (~2 Moz Au) in northern Luzon, Philippines (Fig. 22a). The main veins pinch out at ~1100 m elevation, and yet there is an alteration halo that extends for up to ~300 m higher elevation, with a zonation that indicates the center of the deep veins. Despite there being no veinlets at the present surface, there are subtle but real trace-element anomalies over the veins. Distal equivalents of the Teresa veins outcrop in the in the river valley (~1 km south of Fig. 22a) at ~1250 m elev. At Selene, an IS vein system in Peru (~3000 t Ag), a dacite dome in the center of the district is advanced argillic altered but barren (Fig. 22b), whereas quartz veins are ~0.5 to 1 m.yr. younger. These quartz-rhodochrosite veins have Ag grades ~0.5 to 1.5 km from the dome; there are distinct clay alteration halos to the veins or the vein projections to the surface. 27

28 Fig. 21. a) Comstock Lode, Nevada, intermediate sulfidation vein deposit with recorded production of 257 t Au and 6000 t Ag (Hudson, 2003, Economic Geology). Advanced argillic alteration follows structural trends (pyrophyllite-diaspore-dickite-kaolinite), formed at Ma. The same structures were reopened by a subsequent hydrothermal system that deposited quartz-adularia and gold-siver at Ma. b) Kushikino intermediate sulfidation Au vein mine (55 t Au production), Kyushu, Japan. A high elevation (500 m Age of volcanism, based on K-Ar dating (Izawa and Zeng, 2001, Resource Geology) was Ma, followed by the proximal silicic structures with advanced argillic alteration halos ( Ma); quartz-adularia-gold veins formed 1-3 km to the west at the same time ( Ma). 28

29 E A Fig. 22. a) Victoria and Teresa intermediate sulfidation veins, Mankayan district, Philippines (south of the Far Southeast porphyry deposit and associated Lepanto high sulfidation mine). Surface alteration is subtle over the veins, from smectite to interstratified illite-smectite and levels of >250 and <250 m above the ~1100 m tops of veins. Blue line shows the pseudosection. b) Pseudosection through the Victoria deposit showing the tops of veins and the alteration halo to the present surface, with very weak geochemical signatures at the present surface; vein alteration overprints earlier lithocap-associated advanced argillic alteration (Chang et al., 2011, Economic Geology). c) Dome with (barren) advanced argillic alteration, Selene district, Peru; slightly younger (0.5-1 m.yr.) mineralized veins on the dome margin, with structural corridors and quartz veins well defined by temperature-sensitive alteration minerals (inner zones of high-temperature sericite and illite out to halos of illitekaolinite and interlayered illite-smectite; inset paleotemperature indication). Low-grade (at surface) quartz veins follow (cut) the Pucanta structure with dickite-kaolinite advanced argillic alteration (inset photograph, along Pucanta to the Parachata dome). The Cerro Moro IS vein district in Patagonia, Argentina (2.4 Moz Au eq.), covers a large area (Fig. 23a), with most veins oriented NW-SE, but some at right angles. A ground magnetic survey shows the demagnitized alteration halo to some of the veins. The veins present typical IS characteristics, with quartz and rhodochrosite, plus common brecciation, colloform (colloidal silica) and bladed textures (Fig. 23b). 29

30 Fig. 23. a) Cerro Moro intermediate sulfidation vein district, Patagonia, Argentina, showing geology and vein trends, overlain by ground magnetic survey results. Several vein corridors are indicated by magnetic lows due to alteration halos to the veins. b) Cerro Morro vein characteristics; quartz and rhodochrosite, brecciation, colloidal silica, quartz, with bladed textures. From Exeter presentation. 30

31 Fig. 24. a) Map of the Guanajuato Ag-Au vein district, Mexico (from Simmons et al., 2005). b) Map and long section of the Veta Madre, Guanajuato, showing the distribution of kaolinite-dominated alteration in the hanging wall of the vein, likely due to steam-heated alteration above ore shoots. From Buchanan, The Guanajuato epithermal Ag-Au vein district in Mexico (Fig. 24) illustrates the local distribution of kaolinite-dominated alteration above ore shoots. This alteration was likely due to boiling of liquids that ascended along ore shoots, with condensation of the vapor above the paleogroundwater and oxidation of H2S to sulfate that generated strong kaolinite alteration. 31

32 Summary The veins on Unga share characteristics with numerous intermediate sulfidation-style deposits around the world, including: volcanic arc setting, association with andesitic rocks and more felsic rocks; advanced argillic alteration on structural trends (e.g., Comstock Lode, Nevada), and location adjacent to a barren lithocap of residual quartz (e.g., Selene, Peru, and Kushikino, Japan), although there are examples of the associated lithocap being mineralized (e.g., Lepanto lithocap and ore body with nearby Victoria veins, Philippines); common occurrence of polymictic phreatomagmatic breccias with a syn-hydrothermal timing; variable base-metal content and Ag:Au ratio (e.g., multiple events in numerous Mexican veins), and quartz associated with rhodochrosite, plus up to ~300+ m vertical extent of mineralization in veins (general characteristics summarized by; Sillitoe and Hedenquist, 2003, SEG SP 10). Tuffs are abundant at Orange Mountain, with the most permeable having served as aquifers for the flow of acidic condensates that leached the unit to create lithocaps. On either side of main silicic body, which is ~600 m long (with discontinuous outcrops to the ENE in the area drilled), the adjacent tuffs dip SW on the west side, and SE on the east. This may suggest an eruptive source associated with the area of the main silicic body, possibly a coherent lava dome (?), and thus a center of the system, bisected by the Shumagin structural trend. The silicic alteration is sulfide rich, and although scattered sampling suggests some Au anomalies, overall the lithocap near the surface may be largely barren; however, it is cut by quartz veins and barite, reflecting structures that are mineralized elsewhere along the Shumagin trend. Results of mining at Apollo, as well as reports from surface and drill hole samples at Shumagin and Aquila (Amethyst) indicate moderate to strong grade development, locally at the level of 10s g/t Au, indicating focused upflow and boiling both favored by hydrothermal brecciation in zones of dilation and the resulting deposition of gold. At Shumagin, good grades in a plunging shoot show evidence for up to 300 m of vertical extent. At Apollo the vertical extent of mined high grade was 200 m, dependent on the surface elevation, i.e., level of erosion. The Apollo vein system is also associated with a deeper horizon of base metal sulfides with a lower Au content, another common feature of many epithermal veins (La Guitarra and San Sebastian, Mexico, and Cerro Bayo, Chile). Most work on Unga has been focused on <4 km strike extent in three areas on two structures where there are outcropping veins, mostly with highly anomalous Au grades. Most drilling has focused on ~400 m strike extent at Shumagin, with other drilling at Shumagin (<60 m depth) as well as at Aquila (~700 m of strike extent, <60 m depth) being too shallow. By contrast, most drilling at Apollo, beyond the mined interval, from Sitka to California, tested levels below the potential Au zone, intersecting deeper sulfide-rich structures with variable base metals and Ag. Well-mineralized intervals near the coast, at Shumagin, extend from ~100 m to 200 m elevation, whereas at Apollo the Au-mineralized interval is ~200 m elev. to sea level; the higher elevation of the mineralized interval is due to the higher paleosurface elevation at the time of hydrothermal activity. As with other mineralized epithermal districts worldwide, the level of the top of mineralization may be at a relatively similar depth below the paleosurface, perhaps m deep. Evidence for paleosurface (e.g., sinter, steamheated alteration) was not observed at Shumagin or Apollo, and the outcropping veins with locally high Au grades and variable crystallinity of quartz suggest that they may have been eroded at least 100 m below paleosurface. By contrast, the phreatomagmatic deposits with altered clasts and interbedded lacustrine sediments, between Orange Mountain and Aquila, indicate the level of a syn-hydrothermal paleosurface at ~200 m elevation in this area, i.e., Aquila drilling just to the SW was likely too shallow to test the vein potential in the area. Based on the >14 km extent of the Shumagin and Apollo structures (Fig. 2), with only <4 km of this extent tested by drilling, and <1.5 km tested by mining or drilling to appropriate 32

33 depths, there appears to be several intervals with untested potential, not to mention possible subsidiary structures along these corridors, and numerous other prospects (Peterson et al., 1982) on the island. These areas with untested potential include 1) deeper drilling to the NE and SW of the Shumagin mineralized shoot, 2) a possible conjugate structure in the hanging wall of the Shumagin vein, across the valley to the SE toward the dome, 3) the strike extent to the SW of Shumagin, up the slope toward Orange Mountain (Figs. 25, 26), 4) deeper testing at Aquila and Amethyst, 5) possible conjugate structures SE of Amethyst, 6) the SW extension from Aquila to the coast; and on the Apollo structure, 7) relatively shallow drilling on unmined portions between Sitka and California shafts, 8) NE and SW strike extents of the Apollo structure, where altered, even if there is not a significant geochemical anomaly. Prior to such testing, and in order to determine priorities and specific targets, the corridors along these structures must be mapped in detail, with structures and orientations plus alteration noted. A critical aspect will be reconstruction of the volcanic morphology based on the host lithologies, in order to estimate the relative depth of erosion below the paleosurface at the time of hydrothermal activity, in conjunction with alteration mineralogy and textures plus geochemical signatures (e.g., Hg rich at shallow paleodepths). The historic surface sampling results from Orange Mountain suggest that this residual quartz body and related lithocap horizons may be barren at the surface, albeit associated with strong pyrite. Although there will be a feeder structure proximal to the main silicic body somewhere, the lithocaps at lower elevation to the NW appear to be relatively thin horizons restricted to tuffaceous units; the latter are likely to be weakly if at all anomalous in Au. The feeder structure, wherever it is located in the roots of the main silicic body, will likely have a high concentration of sulfides, at least pyrite, and if it is found to be Au mineralized, there may be As-rich sulfides as well. At present Orange Mountain is not a target of significant priority, even though it may be the center of the hydrothermal system, given 1) its characteristics and 2) the significant and untested structure-related potential to the NE and SW, as well as 3) the potential on the Apollo trend. Untested interval Fig. 25. View looking ~WNW, with long section ~SW to NE, across the island from the Aquila veins in the SW to Orange Mountain and Shumagin in the NE, a strike extent of 8 km. There is at least 2 km of untested potential SW of the outcrop of the Shumagin veins that have been tested by drilling (drill traces shown in profile) to the crest of the hill, NE of the Orange Mountain silicic body; further SW, the area of the Aquila veins is largely untested by properly located holes drilled to sufficient depth to assess these veins, which are exposed at a shallow depth below paleosurface, as indicated by the syn-hydrothermal lacustrine sediments to the NE. 33

34 It is critical to characterize the complete systems at Shumagin-Orange Mountain-Aquila and Sitka-Apollo-Empire Ridge-California, and their extensions, given the indications of continuous surficial alteration despite intermittent outcrops of veins with low to high metal concentrations at surface. Ore deposits of epithermal veins do not necessarily outcrop at the surface, certainly not with ore grades, as shown in numerous examples around the world at deposits that are now mines. Magmatic centers and associated epithermal systems can have scales of up to 10 km, and large portions of such systems can be blind at the present erosion surface, at least in terms of outcropping geochemical anomalies. The reasons include: various levels of mineralization relative to the paleosurface (with top of high grades 100s of m deep), different erosional levels across a district, and post-mineral cover. Thus, only assessing outcropping veins with good geochemical anomalies may be like only examining the tip-ofthe-iceberg in terms of district potential. Assessment of a large district is challenging, particularly where there is limited evidence of buried veins, such as structural lineations, alteration indications, weak geochemical anomalies, and geophysical evidence. This requires a systematic assessment and with a good technical foundation and strategy. Fig. 26. Corridor of untested potential southwest of Shumagin vein outcrop on ridge (near roads, ~120 m elev., about 1.5 km NE of viewpoint). Margin of andesitic dome to right. Quartz vein float in altered area to left (~290 m elev.), in NE-SW Shumagin corridor; assessment should include detailed mapping of alteration (including mineralogy by SWIR) and vein (veinlet) outcrop plus orientation; ground magnetic traverses (orientation first over Shumagin veins) may help to identify alteration halos to veins. Vein targets may have to be tested below ~100 m elev., i.e., more than 200 m vertical depth. Popof Island beyond. b) Drill core from Shumagin vein (11SH m, 2.7 g/t Au); evidence for at least three brecciation events, with deposition of colloidal silica, adularia, crystalline quartz and rhodochrosite, plus locally bonanza grades of visible gold (e.g., Fig. 14e, f). 34