Buenaventura
Buenaventura is a project with Fe-Cu-Au mineralization ( IOCG type) located 50 km al north of Copiapo city, inside the structural system known as the «Atacama Fault Zone” (AFZ).
It is a hydrothermal system with iron oxides, copper and gold mineralization (IOCG), which occurs in an extended area of volcanic rocks from the «Punta del Cobre Formation» ,intruded by diorites from the San Juan pluton, in addition to extensive alluvial and colluvial deposits from Pliocene-Holocene.
It is part of the IOCG belt deposits like Manto Verde mine (Mantos Copper) and Candelaria mine (Lundin Mining).
Mineralization is in: magnetite-hematite veins in the Longotoma mine, veins, veinlets and breccias with hematite, magnetite, specularite, copper oxides and chalcopyrite relicts in Cerro Brecha, copper oxides in fractures and disseminations in Loma Negra, magnetite, copper oxides and minor gold in Cerro Amada and breccias with quartz, apatite, actinolite and copper in Cerro Berta.
The geological information to date point to locate the mineralization center below the alluvial cover close to an important magnetic anomaly along the Chivato regional fault.
The surface sampling and the drill holes indicate copper and gold mineralization in the following places: Cerro Brecha (2 km2), Cerro Amada (1,5 km2), Loma Negra (1 km2) and Cerro Berta (3 km2). These hills are separated by flat areas with alluvial cover named Pampa Area (30 km2).
Works performed are:
1.- Geological mapping at scales: 1:2.000, 1:5.000, 1:20.000,
2.- Rocks and soils sampling with Cu, Au and multi elements analysis (+5.000 analysis)
3.- Geophysical studies: magnetometry, IP, resistivity, gravimetric, ZTEM
4.- About 20.000 meters of drill holes RC and DDH, from 50 to 651 m long
Principal geological characteristics are:
1.- Outcrops of volcanic rocks (Upper J – Lower K), dioritic to granodioritic intrusions, hydrothermal alteration and extended Miocene alluvial deposits
2.- Hydrothermal alteration: silicification; sericite-quartz; chlorite-sericite; K feldspar ; quartz-albite; breccias: quartz-tourmaline and chlorite-actinolite.
3.- Two alteration-mineralization events are recognized ( K-Ar total rock) during the Lower Cretaceous: 130±4 Ma in Cerro Brecha and 105±5 Ma in Cerro Amada
4.- Structural systems: faults and regional lineaments NS to NNW, Salitrosa fault NW and Chivato fault NE
5.- IOCG mineralization constituted by magnetite, hematite, specularite, copper oxides, chalcopyrite, pyrite and gold, located in Neocomian volcanic rocks from the Punta del Cobre Formation. Showing an strong structural control as is possible to observe in:
- Amada Hill: veins system WSW to WNW related to an extensional elbow
- Brecha Hill: veins and breccias systems NW to NNW associated to an structural corridor that cross the district to the Manto Verde Mine
Geophysical studies show:
- A NE belt of magnetic anomalies by which borders is founded the Cu-Co-Au mineralization
- Deep gravimetric and IP anomalies (>300 m) in Brecha Hill, probably related to sulfides bodies.
- Low magnetic and gravimetric anomalies in Amada Hill
The exploration programs carried out lead to detect:
1.- Presence of strong magnetic, gravimetric and IP anomalies in Pampa Area, Brecha Hill and Amada Hill.
2.- Several drill holes intercepts with Fe and Fe-Cu in Brecha Hill, with 10 to 20 % Fe and 0,1 a 2% Cu.
3.- Copper and gold mineralization and anomalies in Amada Hill and Berta Hill.
Main Targets
Two principal target areas were defined:
- Brecha Hill
- It is an area of altered volcanic rocks with an strong system of NNW to NW veins, veinlets and breccias with specularite, hematite, Cu oxides, chalcopyrite-pyrite and gold.
- The mineralized belt is 1.000 meters long by 400 to 500 m width. It could extend more under the alluvial cover .
- There are potential resources in the order of >100 M ton with 0,2 to 1,2% Cu y 0,1 a 0,3 g/t Au.
- Amada Hill
- It is an area of volcanic and intrusive rocks strongly altered with veins and veinlets WSW to WNW with hematite, specularite, magnetite, Cu oxides, anomalous content of gold y and a primary zone of sulfides under 150 to 170 meters deep with pyrite-chalcopyrite.
- The area with mineralizes structures is 1.200 meters long by 200 to 300m de width.
- There are potential resources in the order of 80 to 100 M ton with 0,3 to 0,9% Cu in the oxide zone
Secondary Targets
Other sectors of interest are:
- Pampa NW, some intercepts show magnetite ore bodies with >20% Fe
- Berta, some gold values were founded in siliceous structures
- Loma Negra, Cu- Fe anomalies
Expectation
The prospect is a potential target to discover one or more Cu-Au ore deposits similar to Manto Verde or Candelaria, which could have over 200 M tons with 0.6 to 0,9 % Cu and 0.2 a 0.3 g/t Au. Also there are bodies with10 to 25% Fe y anomalous values of Co
Mining Rights Are constituted by 20 exploitation concessions covering an area of 3.820 hectares.
