Main Ridge Project, Jamaica
The Project: Special Exclusive Prospecting Licence 562 (hereinafter referred to as SEPL 562 or Main Ridge) encompasses 32 km2 of the Cretaceous Central Inlier in central Jamaica.
It is immediately adjacent to the Pennants Gold Mine and surrounds all but the southern side of the mining lease.
The Main Ridge SEPL is transected by the Rio Minho and sits mainly on highly deformed, altered and mineralized Cretaceous rocks primarily volcanics within the Central Inlier of Jamaica (Map 1). The Spaniards mined placer gold in the 16th Century within the Central Inlier. Subsequently, no significant exploration or development was undertaken until the 20th century when exploration was focused to the southeast at Bellas Gate for copper.
There appears to be little recorded exploration at the Main ridge property prior to 1986 when the Canadian International Development Agency (“CIDA”) reveled a major poly-metallic geochemical anomaly described as, "One of the most significant anomalies of the survey…The elevated gold values, combined with a consistent anomalous pattern, indicate that this area should be ranked as one of the most promising on the island.” BHP followed up the CIDA target and delineated a 6km long Au in soil anomaly. Data from this program subsequently lead to the discovery and development of the Pennants gold mine where 16,000oz of gold was produced from 40,000t ore. The majority of this anomaly is covered under the Main Ridge SEPL and is yet to be tested. Grades from Pennants were recorded as high as high as 13.4 oz/t Au and recent chip sampling by Carube has revealed Samples with up to 0.84% Cu over 1m near Trout Hall on the property.
Geology and Mineralization
Regional Geology: Jamaica is a part of the Greater Antilles island arc system, situated on the northern Caribbean Plate margin, which is sliding eastward along the North American Plate. Hispaniola, Puerto Rico and Jamaica all lay on the northern margin of the Caribbean Plate. Most geologists believe that the three islands have similar stratigraphy and metallogeny, which opens the potential for porphyry Cu deposits in Jamaica similar to those in Puerto Rico and major gold deposits, such as Pueblo Viejo in the Dominican Republic. Jamaica is an emergent part of the Nicaraguan Rise, a broad, anticlinal, dominantly submerged belt of crustal thickening extending from Honduras to east of Jamaica.
Jamaica itself is comprised of three major groups of rocks:
- a Cretaceous basement complex;
- post-Cretaceous trough sediments, volcanic and intrusive; and
- overlying Cenozoic (Tertiary) limestones.
The Cretaceous basement complex consists of volcanic, volcaniclastics and associated intrusive and coarse clastics. It is believed that the volcaniclastics represent an eroded island arc system. At the end of the Cretaceous period, the basement was uplifted, resulting in an unconformity making the Cretaceous-Tertiary boundary.
The Tertiary white and yellow limestones, unconformably overlying the Cretaceous basement complex and conformably overlying Cretaceous trough sediments, cover approximately 70% of the island. Intrusive activity was confined largely to the Cretaceous, Paleocene and Miocene, with major deformation occurring during the early Tertiary.
In areas where the limestone cover is breached, the older sedimentary, igneous and metamorphic rocks are exposed through windows known as inliers. There are seven major and twenty-one minor inliers on Jamaica. The three largest are the Central, the Lucea and the Blue Mountain Inliers. The Central Inlier located in the center of what’s labelled the Clarendon Block on the island structural diagram is a 45km by 15km Inlier, dissected by the Crawle River-Rio Minho strike-slip fault zone (most recent movement).
Central Inlier Geology: The Central Inlier is dominated by volcanic rocks of the early to mid-Cretaceous namely Arthur’s Seat Formation, Bull Head Formation and the Summerfield formation. Geology of Main ridge is dominated by the Bull Head formation host to the mineralization at Pennants (Map 2).
Numerous faults cross the Central Inlier. The Rio Minho-Crawle River strike-slip fault appears related to plate tectonics and a splay off of this has been interpreted as a possible pathway for mineralization at Pennants. Other faults seem to be oriented in a NW-SE, N-S and NE-SW directions. The former two systems may have provided passage-ways for intrusions and mineralized fluids. The NE-SW fault appears to be a later faulting system that transacts all earlier faults.
Central Inlier Mineralization and Alteration: The Main Ridge Project surrounds Pennants, the only modern gold operation in Jamaica. Mineralization there is low-sulfidation epithermal though there is potential at Main ridge for disseminated or porphyry-type mineralization associated with roofed intrusive bodies. Much of Main Ridge is covered by the large gold in soil anomaly; but the exact nature of this anomaly and possible source mineralization is yet to be determined.
Three types of deposits are possible at Main Ridge.
(1) Epithermal systems characterized by quartz-carbonate, low sulphidation mineralization, paralleling steeply dipping faults in volcaniclastic units interbedded with andesitic flows. This mineralization appears to have the best potential to provide for an economic-size deposit, either adjacent to Pennants Gold Mine at depth along strike or under the gold in soil anomaly on Main Ridge. At the latter, mineralization may not always be exposed at surface due to low angle thrusting (as is suggested at the Pennants Gold Mine). A shallow dipping high grade gold deposit could be present also, but, if similar to Pennants, its variability of grade might make it more problematic for development.
(2) Oxide copper in weakly cemented Cretaceous conglomerates surrounding Main Ridge. The true nature of the copper mineralization reported from near Trout Hill is not clear. It is possible that late stage fluids caused the mineralization, or, alternatively, if some of the clasts in the conglomerate contain mineralization, that the copper was leached from the clasts and precipitated throughout the matrix.
(3) Porphyry copper lying below Main Ridg where broad areas of soil have copper contents exceeding 200 ppm.
Identified Mineralized Trends: BHP covered a large portion of the Main Ridge SEPL with a widely spaced soil sampling grid which delineated a 6km long Au in soil anomaly (Map 3). Subsequently this data was followed (Figure 1) up leading to the development of Pennants.
1. Main ridge Au +/- Cu anomaly: The gold in soil anomaly that crosses the Main Ridge SEPL is interpreted to represent gold mineralization similar to that at the Pennants Gold Mine, i.e. low sulphidation quartz-carbonate veining emplaced at a shallow depth over a strike length of 4 km plus along a projected NW–SE fault trace. If circumstances are similar to that at Pennants, grades will be between 5 and 8 g Au/t over 2 to 4 m thickness on average. At the Pennants Gold Mine, the dip of the outcropping zone mineralization is shallow, but steepens as the zone projects below the surface; if similar mineralization crosses Main Ridge, its geometry will only become apparent after further exploration and drilling has been completed. It may be partially buried due to rock emplaced over it by thrust faulting at the near-surface.
HISTORY OF EXPLORATION AT MAIN RIDGE
Sediment Sampling: At Main Ridge, little recorded exploration appears to have pre-dated the Canadian International Development Agency’s (“CIDA’s”) stream sampling program in 1986, during which ~3000 stream sediment samples were collected across Jamaica, primarily from areas underlain by older, Cretaceous volcano-sedimentary rock. These data revealed a major, poly-metallic geochemical anomaly centered on Main Ridge. The highest concentration of gold in the anomalous zone—460 ppb in the unconcentrated <0.105 mm fraction—was from a sample collected along Bennett Creek.
In early 1990, BHP conducted soil sampling in the vicinity of the anomalous stream sediment samples at Bennett Creek, and extended this sampling 6000 m northwest along the Main Ridge. The soil samples were taken at a depth of 0.5 m every 25 m along lines spaced 100 m apart except where trails made sampling easier. A 6000 m long, NE–SW trending gold anomaly was identified. Values for copper, arsenic and antimony exhibit weak anomalism that is only roughly coincident with the BHP gold anomaly. Isolated copper anomalies are observed in soil samples at Trout Hall (3000 ppm) and Main Ridge (>1000 ppm).
Drilling: Most of the gold-in-soils anomaly that crosses SEPL 562 remains undrilled, except for five holes drilled by BHP (MD16, 17, 19, 20 and 21 to test a gold-in-soils anomaly along the Trout Hall Pass road, which is ~2 km northwest (along strike) of the Bennett Zone soil/stream-sediment anomaly. The exact locations and the results of the Trout Hall Pass drill holes are unknown. The Bennett Zone anomaly, located just south of SEPL 562, has been drilled extensively.
PLANNED EXPLORATION PROGRAMS
Strategy: At Main Ridge Carube intends to further define the NW-SE trending Au-Cu anomaly. This is adjacent to, and on strike with the Benett zone which hosts the past producing Pennants Gold mine. Programs will be designed with this priority while concurrently delineating extents of Cretaceous oxide Cu mineralization and locating pathfinders for roofed porphyry systems.
Action: In addition to completing airborne magnetics and radiometrics, infilling and extension of the soil sampling grid (done by BHP in the past) is necessary to better define the full extent of the presently-defined gold and copper anomalies. Restricting the maximum distance between lines is required for complete anomaly definition. These lines are to be extended to lower elevations where secondary copper mineralization is known to exist. Detailed geology and prospecting of Main Ridge in total is required before any targeted drilling or trenching is undertaken.