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Guaimarote Basin
Recent geological mapping in the Trinidad and Rincón Abajo Concessions on targets in the Guaimarote volcano-sedimentary basin has established the presence near surface of epiclastic and sedimentary rocks in an area previously thought to be underlain by deep colluvium. These new exposures add several square kilometers to an area which is stratigraphically equivalent to the volcano-sedimentary basin infill units of the Pueblo Viejo district. The sedimentary sequence in the Guaimarote Basin includes epiclastic, carbonaceous and carbonate sediments and is overlain by massive limestones of the Hatillo Formation.
Near the western margin of the Guaimarote basin, a number of mineralized hydrothermal feeder structures have been recognized and traced into the basin sediments. The current program includes detailed geologic mapping focused on the hydrothermal conduits and their relationship with the adjacent epiclastic sediments, and an induced polarization survey to identify zones of strong silicification and sulphide replacement within the hydrothermal corridors. The exploration model is based on the geology of Pueblo Viejo and assumes that gold-bearing hydrothermal fluids rose along near-vertical conduits and then spread along shallow conformable contacts into the overlying epiclastic sedimentary section.
Doña Loretta
In 2004, Doña Loretta was identified as a large scale copper porphyry system. The mineralization consists mainly of chalcopyrite and chalcocite in breccia pipes within quartz-feldspar porphyry. The mineralization appears to be confined to the breccia pipes, and to the porphyry between breccia pipes, with very limited dissemination into the surrounding porphyry systems. The system is open in all directions and at depth.
The deposit is located 5 kilometers to the east of Doña Amanda. Doña Loretta may represent the eastern extension of the Managuá volcanic system. The two areas are separated by a 4-kilometer wide valley, covered by marine sediments, which effectively mask geophysical and geochemical signatures. Drilling at Doña Loretta was carried out by Falconbridge (1990 and 1999), and by GlobeStar in 2003/04. In the GlobeStar program, the best drilling intersection (CC-01) returned 64 meters grading 2.0% copper, while its twin hole (CC-07) returned 53.4 meters grading 1.2% copper. In 2004, detailed mapping was carried out by GlobeStar over a large induced polarization anomaly with co-incident elevated copper in soils over a 3.5 kilometer by 800 meter area. An area of over 1 square kilometer in the southern part of the Doña Loretta system showed anomalous gold in soils overlying the previous drill successes. In mid-2004, 8 drill holes were completed. The best results were obtained in the area of the southern anomaly where hole CC-08 intersected 98 meters grading 0.6% copper. Drilling in the northern part of Doña Loretta did not result in anomalous intersections. The induced polarization anomalies extend north-westwards from the identified mineralization at Doña Loretta under the masking alluvium, indicating that mineralization may extend in that direction.
Future exploration will include deep induced polarization surveys and additional drilling in order to further define the mineralization.
Doña Amanda
The Doña Amanda copper deposit is located on the Rincón Abajo Concession where copper occurs in a zone of supergene enrichment above a lower grade protore. The host rock is a dacitic dome with strong phyllic and sulphidic alteration in a pyroclastic tuff breccia apron. This is cut locally by pyrite- and chalcopyrite-bearing quartz stockworks. The hydrothermal alteration continues westwards onto the Managuá Concession. The enrichment blanket was discovered by drilling and is known to exist between a minimum depth below surface of 10 meters and a maximum of 150 meters. The deposit was drilled by Falconbridge prior to acquisition by GlobeStar. The longest intersection in the Falconbridge drilling was in hole DA 06 which returned 117 meters grading 0.41% copper. The highest grade intersected was in the lower part of hole DA 03, where 24.6 meters averaged 0.65% copper and 0.30 grams per tonne gold. Separated by an 8-meter barren section, mineralization higher in the same hole showed 34.9 meters grading 0.45% copper and 0.18 grams per tonne gold.
A geophysical program by GlobeStar identified a series of induced polarization anomalies, running 4,000-meters north from the known mineralization coincident with copper and zinc in soil anomalies. These anomalies were drilled in a 7 hole program in 2002, but without significant results. In 2003, a further 19 holes were drilled and representative samples were sent for metallurgical testing at SGS Lakefield Research in Canada. It was demonstrated that the material may be amenable to solvent extraction/electrowinning for copper.
In 2004, two step-out holes were drilled and an intersection of 21.3 meters grading 0.51% copper was returned some 300 meters to the northwest of the known deposit.
In 2007, a large well-defined electromagnetic/magnetic anomaly was identified at Doña Amanda by a Fugro HeliGEOTEM® airborne survey. Inversion work shows a highly conductive deep core system underlying the southern portion of the Doña Amanda enrichment blanket. The interpretation of the anomaly suggests the conductor may be at a depth of 180 meters, at least 400 meters by 150 meters in size (along a north-south trend) and continues below the detection depth of the airborne geophysical equipment. The anomaly was tested with 2 drill holes in 2007 with no relevant results. Further drilling needs to be completed to fully test this deep geophysical target.
Cerro Kiosko
The Cerro Kiosko zone lies to the west of the Managuá volcanic centre which, although in a different geological setting, is likely to be related to the same metallogenic source. The Cerro Kiosko zone is located in the southwest corner of the Managuá Concession and consists of a system of crustiform banded, chalcedonic to microcrystalline, milky quartz veins with moderate to high sulphide content. The zone is controlled by northwest-striking normal faults dipping around 60° to the southwest. Drilling to date has shown that the vein system varies from 1.25 to 22 meters in thickness and has been traced 1,100 meters along strike and to a depth of 400 meters. Cerro Kiosko is open along strike and at depth.
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