Cortez Summit Property

The Cortez Summit property is located in the southern Cortez Mountains between the historic Buckhorn district and the Horse Canyon portion of the Cortez district, Eureka County, Nevada. The property consists of 83 100%-owned unpatented lode claims (BH 1-18, 20, and 22-85) located in sections 25, 26, 35 and 36, T27N, R48E; and section 31, T27N, R49E; and section 6, T26N, R49E, MDBM. The east edge of the property lies 0.5 miles southwest of the Buckhorn mine, and the west edge of the property lies 1.6 miles northeast of the Horse Canyon mine. Barrick’s new Cortez Hills operation (11 MM oz gold pre-production reserve/resource) lies 4 miles west of the property.  The southwest corner of the property lies 1.2 miles north-northeast of Barrick’s new Red Hills discovery area in Horse Canyon.

Cortez Trend

Two types of mineralizing systems exist on or adjacent to the Cortez Summit property: 1) Carlin-style sediment-hosted Au, and; and 2 Buckhorn-style volcanic-hosted low sulfidation Au-Ag). Probable late Eocene Carlin-style mineralization at the Horse Canyon mine is controlled by a combination of NNW-, ENE- and NW-trending structures as well as favorable Devonian stratigraphy.  Similar controls are reported in the Red Hills area and at Cortez Hills.  The Buckhorn-style mineralization is associated with an extensive Miocene hot springs system (14.6 Ma) which is controlled by NNW-trending Northern Nevada rift structures.

Carlin Gold identified the area as prospective in 2007 based on the premise that published maps have misinterpreted an important stratigraphic interval in the Cortez area within the lower plate of the Roberts Mountains Thrust (RMT). In the Cortez region, a significant interval of siliciclastic and calcareous clastic rocks conformably overlies carbonate rocks of the Devonian Wenban Formation. These rocks have been misidentified as upper plate Ordovician Vinini Formation, resulting in the Roberts Mountains Thrust (RMT) being erroneously placed at the stratigraphic break between carbonate and clastic rocks. The clastic rocks actually represent the Horse Canyon member of the upper Wenban Formation. The Horse Canyon member is analogous to the Rodeo Creek Formation on the Carlin Trend – both are sequences of Devonian siliciclastic and calcareous clastic rocks that conformably overlie Devonian carbonates within the lower plate of the RMT. Both sequences are also host to Carlin-type mineralization.

The upper limestone member and the lower portion of the Horse Canyon member of the Wenban Formation comprise a favorable stratigraphic interval that hosts the Horse Canyon deposit, as well as portions of other deposits on the Cortez Trend. The Horse Canyon member strikes northeasterly and dips moderately northwest on the western edge of the property.  As you approach the property from the west, therefore, you are traveling down-section in the Horse Canyon member. The favorable stratigraphic interval described above may be at a relatively shallow depth under the southwestern portion of the property.

On the west side of the property, the Horse Canyon rocks are unconformably overlain by a Tertiary (Eocene? to Miocene) volcano-sedimentary sequence consisting of a lower gravel unit and an upper series of Miocene (15-16 Ma) basaltic andesite flows. The Tertiary sequence varies in thickness from <50 ft. on the west side of the property to 400+ ft. on the east side. The Buckhorn deposits are primarily hosted by the basaltic andesite.  Dikes, plugs and minor flows of Miocene (15 Ma) rhyolite locally intrude and overlie the gravel and basaltic andesite units. 

Two intrusive phases are recognized just west of the property including: 1) quartz monzonite of the Mill Canyon pluton; and 2) probable Tertiary-age quartz porphyry dikes and small intrusive bodies. These quartz porphyry intrusives may be correlative with early Oligocene quartz porphyry dikes which are common at the Horse Canyon, Cortez Hills and other Cortez district deposits.

Two structural orientations dominate the Cortez Summit area: 1) N10-20W horst and graben structures that define the Northern Nevada Rift structural trend and control mineralization along the Aspen and Buckhorn mineralized trends, and 2) less well-defined ENE-trending structures exhibited by the drainage patterns eroding the basaltic andesite (ie. Willow Creek structure). The rhyolites of upper Willow Creek intrude the inferred structural intersection between the ENE-trending Willow Creek structure and the NNW-trending Fourmile structure. This structural intersection is coincident with an inferred basement structural high indicated by thinning Tertiary stratigraphy. The Northern Nevada Rift structures associated with Buckhorn-style mineralization may also represent deep-seated feeder structures that may be involved in older Carlin-style mineralization at depth.  A third, potentially important, structural trend is indicated by the gravity data that Carlin Gold has collected.  In addition to defining the ENE structures referred to above, the horizontal gradient of the complete bouguer anomaly also defines several strong NS features.  The westernmost of these features appears to project to the south in the vicinity of the Red Hills fault zone, and important feature associated with the mineralization in Barrick’s Red Hills drilling area.

Cortez Trend – Barrick Activity

Cortez Hills Section

Carlin Gold’s primary focus is for Carlin-style mineralization in a structural setting similar to that at the Cortez Hills mine.  The geologic environment is similar to Cortez Hills (and the nearby Red Hill discovery). An untested conceptual structural and stratigraphic target exists in the upper limestone and lower Horse Canyon members of the Wenban Formation at depth in proximity to the Fourmile structure and/or north extension Red Hills fault zone.  Much of this target is blind, being covered by post-mineral gravel and basaltic andesite. Sampling along the Fourmile structural zone has yielded gold values of 447 and 263 ppb on the west edge of the property in altered Horse Canyon siliciclastic rocks. The most favorable area to test the target concept is in the southwest portion of the property in the vicinity of the Fourmile and/or Red Hills fault zone structures.

Carlin Gold has conducted a detailed gravity survey (500 x 500 ft. grid) over the entire property and adjacent areas. Given the variations in density within the Tertiary section, interpretation of the gravity data has proven to be difficult. The survey data was, however, effective in defining certain potentially important features.  The complete bouguer data appears to define several WNW features trending across the property.  These may represent blocks where the Paloezoic target sequence may be shallower (less Tertiary volcanic/gravel cover), and thus a more favorable location for first phase exploratory drilling.  Additionally, the horizontal gradient of the complete bouguer anomaly is effective in defining the ENE structures referred to above, as well as a series of potentially important NS structures.

The Cortez Summit property is well-situated between the Horse Canyon and Buckhorn mines, and Barrick’s new Cortez Hills mine is located 4 miles west.  In recent years, Barrick has been very active drilling their Red Hill discovery area in Horse Canyon just 1.2 miles south-southwest of the property (100+? rotary and core holes in 2006-2010). The property location in the midst of the expanding Cortez Trend of gold deposits, in addition to the geologic similarities in deposit environments, makes Cortez Summit a high quality target for Carlin-style gold mineralization. Carlin is planning a Phase I drill program for fall 2011. 

Cortez Summit

Cortez Trend - Barrick Activity