Livengood; Old Smoky; Ruth Creek; Lillian Creek Prospect, Tolovana Mining District, Yukon-Koyukuk Census Area, Alaska, USAi

Regional Level Types
Livengood; Old Smoky; Ruth Creek; Lillian Creek Prospect	Prospect
Tolovana Mining District	Mining District
Yukon-Koyukuk Census Area	Census Area
Alaska	State
USA	Country

Location: This site is at about the center of an east-trending area about a mile long and a half mile wide that in 2008 was being intensively studied and drilled by International Tower Hill Mines Ltd. The center of the area is about 0.5 miles northwest of Money Knob and about 0.6 mile west-northwest of the center of section 23, T. 8 N., R. 5 W., of the Fairbanks Meridian. The area includes several older prospects--Old Smoky, Ruth Creek, and Lillian Creek--that have similar mineralization and are now collectively called the Livengood prospect by International Tower Hill. The location is accurate.
Geology: In 2006, work began at the Livengood prospect by International Tower Hill Mines Ltd. (Klipfel, 2008); it covers a large area near Money Knob that includes several smaller and older prospects including the Lillian Creek, Ruth Creek, and Old Smokey prospects that individually are now mainly of historic interest. The Lillian Creek prospect consisted of narrow auriferous arsenopyrite-quartz-scorodite veins in and near a limonite-stained dike in altered and contorted graywacke-argillite country rock; samples contained from 0.5 to 48 parts per million (ppm) gold (Foster, 1968). Joesting (1942, ATDM Pamph. 1), reported a mineralized zone in a cut bank that contains stibnite and traces of cinnabar and gold. The Ruth Creek prospect consists of numerous, nearly vertical quartz veinlets striking S20-60E, that contain pyrite and arsenopyrite (Mertie, 1918). Some of these veins contain up to 0.58 ounces of gold per ton . The veinlets are cut by calcite veins carrying some gold and sulfides (Mertie, 1918). Contiguous mineralized zones are up to 36 inches wide in altered dolomite-calcite-quartz-sulfide rock (Foster and Chapman, 1967). The best known of the older prospects near Money Knob was the Old Smoky prospect. Trenching near the head of Olive Creek exposed narrow, northwest-trending auriferous arsenopyrite-quartz veins in ferruginous quartzite near the intersection of an altered, porphyritic, biotite-monzonite dike, and a potassium feldspar-porphyry dike (Foster, 1968). The mineralization is in shale, argillite, fine-grained sandstone, and pebbly conglomerate (Allegro, 1984; Athey, Szumigala, and others, 2004; Athey, Werdon, Newberry, and others, 2004; Athey, Werdon, Szumigala, and others, 2004; Athey and Craw, 2004;. Narrow zones of thermal metamorphism occur along sheared contacts between the sedimentary rocks and hypabyssal igneous intrusive rocks. Most of the intrusive rocks at the Old Smokey prospect and some of the sedimentary host rocks have experienced variable degrees of metasomatic hydrothermal alteration followed by lower temperature supergene alteration (Allegro, 1984, p. 4). Allegro described four types of hydrothermal alteration: 1) silicification, as partial to complete replacement of the host rock by a dense network of quartz veinlets generally localized along contacts between the intrusive and sedimentary rocks; 2) sericitization, as fine- to medium-grained white mica in selvages along quartz veins, as anastomosing sericite-opaque mineral veinlets, and as patchy to massive sericitic replacement of feldspar, ferromagnesium minerals and quartz; 3) deposition of trigonal nets of needle-like rutile often associated with secondary quartz and minor feldspar; and 4) epidote +/- sericite as a replacement of calcic plagioclase and ferromagnesian minerals resulting in massive aggregates, pseudomorphs, veins, and vug fillings of epidote commonly associated with sericite, opaque minerals, and quartz. Allegro's (1984) investigation and sample data reveal that the mineralization in the southern portion of the Old Smoky cut is localized along the contact zones between the biotite monzonite and the surrounding sedimentary rocks, and along a contact between biotite monzonite and feldspar porphyry. Channel and chip samples of arsenopyrite-stibnite quartz veins from these zones contained 1.0 to 29.8 ppm gold. Selected samples from the prospect contain 3 to 13 ppm gold as determined by atomic absorption, and 1.6 to 7.0 ppm gold as determined by fire assay-atomic absorption (Foster, 1968, p. 2). Adjacent to the sheared contact zone, the intrusive rocks are either highly silicified with abundant rutile and some epidote, sericite, arsenopyrite, and minor stibnite, or contain epidote with sericite, rutilated quartz and arsenopyrite (Allegro, 1984, p. 6). Other rocks from the contact zone show intense supergene effects such as clay alteration, covellite and iron-oxides. In some cases these zones contain gold. Green scorodite is present throughout the mineralized areas. In the northern portion of the Old Smoky prospect, the most abundant mineralization is located along the contact area between the feldspar porphyry and a roof pendant of sandstone and shale (Allegro, 1984). A massive 1-meter-wide stibnite lens surrounded by a bleached sericite zone occurs along the northern contact of the roof pendant. Channel samples along this contact zone range from 0.5 to 4.3 ppm gold (Allegro, 1984, p. 6). Some gold is also associated with saprolitic zones in all the intrusive phases but these zones are not limited to shear zones or contacts (Allegro, 1984, p. 6). In recent years, several companies have worked in the area near Money Knob (Klipfel, 2008): Homestake drilled 6 holes in 1976; Occidental Petroleum drilled 6 holes in 1981; Amax Exploration drilled 3 holes in 1991 and did surface geochemistry and sampling; Placer Dome drilled 9 holes in 1995 and 1996, and Cambior explored in 2001-2002. In 2003, AngloGold Ashanti (USA) Exploration began work and drilled 12 holes. In 2006, International Tower Hill Mines Ltd. acquired the property and began an aggressive exploration program and in 2007, they drilled 12 holes and defined a mineralized area of about 2 square kilometers with potential for expansion on all sides. In addition to drilling there has been considerable geologic mapping and sampling and geochemical and geophysical surveys by the various companies. As interpreted by International Tower Hill ((2008, Resource; Livengood) the mineralization consists of multi-stage gold-quartz veins with pyrite, arsenopyrite, stibnite, and other sulfides in addition to disseminated mineralization. The mineralization is associated with 92 to 93 Ma dikes and sills of monzonite, diorite, and syenite in thrust-bounded, Devonian sedimentary and volcanic rocks and in older metamorphic rocks. The dikes and sills are probably apophyses of a deeper Cretaceous intrusion. The mineralization is considered to be intrusion related and associated with a series of northwest-trending faults. The 27 holes drilled by AngloGold and International Tower Hill Mines suggests the a bulk tonnage gold deposit; the average thickness of the mineralization in those holes is about 70 meters with a grade of 0.9 grams of gold per ton. The first 5 holes drilled in 2007 included 28 meters with 1.7 grams of gold per ton and 16 meters with 2.1 grams of gold per ton. The area of the known mineralization is associated with a much larger gold-in-soil anomaly. Early in 2008, International Tower Hill (Klipfel, 2008) announced that their initial inferred gold resource of the Livengood project was 181 million tonnes of ore with an average grade of 0.54 ounce of gold per ton and 0.30 grams of silver per ton, at a cut-off grade of 0.3 gram of gold per tonne, A resource of 3.629 million ounces of gold and 1.789 million ounces of silver. The deposit is still open in several directions.
Workings: Thin gold-quartz veins have been known in the area since at least 1918 but major exploration did not begin in the Money Knob area until the 1970's (Klipfel, 2008): Homestake drilled 6 holes in 1976; Occidental Petroleum drilled 6 holes in 1981; Amax Exploration drilled 3 holes in 1991; Placer Dome drilled 9 holes in 1995 and 1996; and Cambior explored in 2001-2002. In 2003, AngloGold Ashanti (USA) Exploration began work and drilled 12 holes. In 2006, International Tower Hills, Mines acquired the property and began an aggressive exploration program; they drilled 15 holes on the property in 2007. In addition to drilling there has been considerable geologic mapping and sampling and geochemical and geophysical surveys by the various companies.
Age: Probably Cretaceous based on its associated with the periphery of a Cretaceous intrusion.
Alteration: Allegro (1984) described four types of hydrothermal alteration: 1) silicification, as partial to complete replacement of the host rock by a dense network of quartz veinlets generally localized along contacts between the intrusive and sedimentary rocks; 2) sericitization, as fine- to medium-grained white mica in selvages along quartz veins, as anastomosing sericite-opaque mineral veinlets, and as patchy to massive sericitic replacement of feldspar, ferromagnesium minerals and quartz; 3) deposition of trigonal nets of needle-like rutile often associated with secondary quartz and minor feldspar; and 4) epidote +/- sericite as a replacement of calcic plagioclase and ferromagnesian minerals resulting in massive aggregates, pseudomorphs, veins, and vug fillings of epidote commonly associated with sericite, opaque minerals, and quartz.
Reserves: None.

Commodities (Major) - As, Au, Fe, Sb
Development Status: None
Deposit Model: Gold-quartz veinlets and disseminated mineralization associated with sills and d

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Link to USGS - Alaska:	LG202

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