Elder Creek

The Elder Creek Project is a porphyry copper-gold project with secondary structural gold-silver mineralization. Timberline explores the property as the operator of an earn-in Joint Venture (JV) agreement with a subsidiary of McEwen Mining.

 

A detailed NI43-101 Technical Report on the Elder Creek Copper-Gold Project, Humboldt and Lander Counties, Nevada, is available on SEDAR and under the “Reports” tab.

Property Description and Ownership

Elder Creek is a porphyry copper-gold-molybdenum-silver exploration property located in northern Nevada, 8 miles west-northwest of Battle Mountain near the northern end of the Battle Mountain-Eureka Trend, one of Nevada’s prolific mineral belts.    The project lies in the Battle Mountain mining district and covers approximately 9,600 acres which includes 583 unpatented lode mining claims. 

Timberline controls the Elder Creek property through a Joint Venture (JV Agreement) with a subsidiary of McEwen Mining. 

The underlying Elder Creek JV with McEwen grants Timberline, as operator of the project, terms of earn-in to acquire a 51% ownership for $2.6 M expenditure over 4 years by December 31, 2021, and a 65% ownership for an additional $2.5M expenditure for a total commitment of $5.1M over 6 years by December 31, 2023. There are no underlying royalties on the property. 

Infrastructure is excellent at the project site with interstate highway and railroad immediately adjacent to the property, and high voltage power crossing the property.  

Exploration and Mining History

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Several exploration and mining companies have explored the project area since the 1960’s.  Early exploration was directed at copper but with most drilling located north of the current property core.  Later exploration was directed primarily at gold to the north and northeast with numerous shallow drillholes completed.  The core of the property area remains largely untested by drilling.

The Battle Mountain mining district currently includes 3 producing mines and 1 copper-gold development project along with several yet undeveloped discoveries including:

  • Newmont’s
    • Lone Tree Gold Mine
    • Phoenix Gold & Copper Mine
    • Copper Basin Copper-gold development
  • SSR Mining’s Marigold Mine Complex

Geology

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In the western part of the Elder Creek area, the Dewitt Thrust fault places Ordovician Valmy Formation cherts and shales on top of Cambrian Harmony Formation quartz-feldspathic-sandstones and shales, which are locally calcareous.   Faults at Elder Creek dip steeply, strike north-northwest to north-northeast and show normal and oblique-slip offset.The Elder Creek Fault indicates normal, down-to-the-west movement.

Generalized Geology of the Battle Mountain Area

 

The Harmony Formation is intruded by dikes and stocks of the Eocene Elder Creek porphyry center.  In addition there are older dioritic and andesitic dikes in the area as well as Eocene pebble dikes that contain lithic fragments of the Devonian Scott Canyon Formation.  The porphyry center comprises three major phases of variably porphyritic granodiorite intrusions  which have been dated by K-Ar to be 37.3 +0.7 Ma and 35.4 +1.1 Ma, respectively.  A recent (2018) Re-Os age date on molybdenum mineralization indicates 42.6 ± 0.6 Ma. 

Hydrothermal breccias are locally present in the Elder Creek complex and are dominated by quartz and rock flour matrix which supports sub-rounded to sub-angular clasts of Harmony Formation and porphyry phases.  Clasts are typically pervasively altered and occasionally mineralized with copper oxides. 

Alteration

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Mineral alteration is extensive at Elder Creek and typical of large porphyry systems.  Alteration occurs in broad annular zones that suggest a large magmatic-hydrothermal center(s) is present within the Elder Creek porphyry system. The intense stock-work fractured and quartz veined core of the system is northeasterly-elongate and exceeds 3.0 km by 1.5 km. Surface exposures indicate the limit of potassic (biotote+K-feldspar) alteration is about 4.0 km by 2.5 km and the outer limit of biotite-pyrite-pyrrhotite hornfels in the Harmony Formation sandstones exceeds 4.5 km by 3.5 km.  Several northerly-trending zones of late-stage, feldspar-destructive quartz-sericite-pyrite alteration occurs in the outer portions of the Elder Creek porphyry system with the largest zone exceeds 2.0 km by 1.5 km.

Geochemistry

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Trace element analyses from over 5,500 soil and rock samples confirm strong zonation in the magmatic-hydrothermal system at Elder Creek. 

Gold is common in base-metal-bearing vein systems that flank the porphyry center particularly to the east and south. The central part of the porphyry system, characterized by moderate to strong stock-work quartz veins which coincide with a zone of Ag/Au enrichment. In contrast, the vein systems along the flanks of the system typically indicate notably lower Ag/Au ratios.

Zones of copper enrichment in soil / rock occur over a 2.0 km by 1.5 km area in the center and eastern side of the zone of increased quartz veins.  The distribution of Mo and W shows strong anomalies in the central part of the area and in a northerly elongate zone that extends from the Big Pay mine to the Morning Star mine.  Bi and As appear concentrated along the northerly elongate zone. The increased abundance of Li and relative lack of Bi in the central area suggests that this area is probably less eroded than the eastern area with the north-south anomalous trend. 

The distribution of key trace elements suggests there may be two primary centers of mineralization at Elder Creek including: 1) Cu-Mo-Ag-W-As-Li centered over the the central part of the area and 2) Cu-Au-Mo-W-Bi-As in the northerly elongate zone further east on the property.

As a model for Elder Creek, the zoned enriched trace-element (Cu-Mo-W-Li-Bi, and As) distribution and their position relative to the copper ore body in a schematic cross-section through the Ann-Mason porphyry deposit, Yerington, Nevada.  Zinc and other trace-elements are depleted in the central part of the system and from a distal halo to Cu-Mo mineralization. The Cu/Zn values increase from the peripheral to central parts of the system. 

Gold Distribution in Rocks and Soils Showing Anomalous Concentrations

Copper Distibution in Rocks and Soils Showing Anomalous Concentrations

Lithium, Arsenic, and Bismuth Distibution in Rocks and Soils

Summary of Zoned Trace-element Distribution at Ann-Mason Porphyry Desposit as a Model for Elder Creek

Geophysics

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Airborne magnetics at Elder Creek documents a classic porphyry system magnetic “donut” pattern which coincides with the outer limit of biotite-hornfels alteration that is known to contain pyrrhotite (a magnetic mineral). The cause of the central magnetic low could be non-magnetic intrusions that lack pyrrhotite, or pyrrhotite- destructive alteration. Magnetite has not been documented in the Elder Creek area.

Historic Total Field Magnetics for the Elder Creek Project Area

 

A historic Bouguer 1st vertical derivative gravity image for the Elder Creek project area is also shows a donut-like pattern that mimics the magnetic data interpretation.

Historic Bouguer Gravity for Elder Creek Project Area

In 2018, Timberline completed an initial Induced Polarization/Resistivity (IP) Survey at Elder Creek. 

The IP defines a strong anomaly thought to represent a distinct body of sulfide mineralization ≥ 1,600 m long and 500 – 800 m wide within a very large (4 km) circular copper-molybdenum-gold-silver porphyry mineral system.  Furthermore, the IP suggests that previous drilling completed earlier in 2018 did not test the strongest part of the large mineral system.  In addition, historic drilling was too shallow (typically <200m depth) to intersect the anomaly.  As such, the IP anomaly remains effectively untested by drilling.

 

Plan Map of IP Anomaly at Elder Creek

Elder Creek IP Oblique 3D Sections

Mineralization and Drill Assays

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Mineralization recognized at the Elder Creek porphyry copper project includes sulfide assemblages with chalcopyrite, arsenopyrite, pyrrhotite, pyrite, scheelite, wolframite, galena, sphalerite along with Pb-Sb-Ag-Bi-bearing sulfosalt minerals.  Mineralization occurs as disseminated sulfides, fracture-controlled, mesh/net sulfides, and as locally concentrated, structurally controlled massive sulfide veinlets and veins.

Drilling in 2018 by Timberline confirmed the presence of copper oxide and sulfides in reverse circulation drill hole RCEC18-01 with assay results highlighted in the following. 

Drill Hole RCEC18-01 Assay Summary

 

Core hole CCEC18-02 intersected visible chalcopyrite and molybdenite mineralization throughout, with mineralization best developed in hydrothermal breccias between 1313.5 – 1365 feet.  Key assay results are summarized as follow.   

Drill Hole CCEC18-02 Assay Summary

Exploration Plans

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Timberline plans additional geologic mapping and follow-up exploration at Elder Creek to include expansion of the very successful IP survey to identify additional chargeability and resistivity anomalies, and follow-up drilling. 

Drilling will focus on testing the IP anomaly for copper-molybdenite sulfide mineralization, and follow-up drilling on the copper oxide zone tested by Timberline’s initial drill hole.  Additional deep drilling is planned in the porphyry core including deepening of core hole CCEC18-02.