Norsemont Mining - Chiloroya South

The recently discovered Chiloroya South area, with dimensions of 3.5km by 3.5km is located about 5.5 kilometres south of the Constancia-San Jose deposit, within a 3 km wide, southwest-oriented mineralized corridor that includes the Cu-Au-Mo Pampacancha discovery.

Evaluation at Chiloroya South began in March 2009, including mapping at 1:2000 and 1:5000 scale, as well as the collection of more than 700 rock samples. The mineralization and alteration is coincident with several chargeability and magnetic anomalies.

Strong evidence of porphyry-related copper-gold-molybdenum mineralization occurs at the southern sector in an area of about 2.5km by 2km. Scattered outcrops of fine-grained siltstones and felspatic sandstones are the host for the mineralization exposed on surface. At the western sector a series of east-west-oriented quartz-limonite brecciated structures hosted by feldspatic sandstones occur in an area of about 500 metres by 500 metres. On the crest of the hill oxidation and leaching of former sulphides have been strong, leaving limonite crusts and gossanous areas where former sulphides were massive. Evidence of copper oxide mineralization is observed about 50 metres down slope where copper oxides precipitated on fractured surfaces in feldspatic sandstones, visible at only few tens of centimetres below surface.

Of 152 rock samples taken from this area, 52% returned values from 0.1 up to 7.84 gpt Au (averaging 0.89 gpt Au), 85% were anomalous in copper, returning from 70ppm up to 1.33% Cu and 40% were anomalous in molybdenum, with values in the order of 10 up to 446ppm Mo. This area is coincident with a magnetic high and a composite 800 metre by 900 metre chargeability anomaly, the latter extending westward to an area covered by post-mineral quaternary deposits.

One kilometre to the south, there is another hill containing several south-east-oriented quartz-tourmaline-limonite brecciated structures which occur in an area of 750 metres by 340 metres. Most of the quartz–tourmaline structures are emplaced mainly concordant with the sediments. Evidence of multistage brecciation events have been seen on the outcrops, including massive quartz-tourmaline replacements, quartz-tourmaline-limonites (after sulphides) matrix-supported breccias and massive limonites (sulphides) brecciated structures. A total of 48 samples were collected directly from the quartz-tourmaline breccias, where 79% were anomalous in gold, from 0.1 up to 5.32 gpt Au; 65% anomalous in copper, from 71 up to 693 ppm and 53% anomalous in molybdenum, from 8 up to 75ppm Mo. This area lies within a large, 1,000 metre by 900 metres chargeability anomaly at depth, partly coincident with a high magnetic anomaly. Extending below the post-mineral quaternary alluvium westward of the edge of the breccia outcrops, two composite, north-south-oriented, 1,200 metre by 800 metre chargeability anomalies occur.

About 2 kilometres to the northeast of the quartz-tourmaline breccias a 2 metre wide, south-southwest -oriented, quartz-sericite-altered felsic porphyry is emplaced discordantly within fine-grained hornfelsified siltstones. The felsic porphyry is strongly altered, showing randomly-oriented quartz veinlets and carrying pyrite, chalcopyrite and bornite. Three samples taken from the porphyry dyke returned up to 2.1% Cu, 32ppm Mo and 265ppb Au. The porphyry is thought to be associated with a 500 metre by 700 metre chargeability anomaly located to the east of the porphyry outcrop. There are several copper occurrences hosted by the Chiloroya sediments associated with shear zones and vein-like structures. Approximately 500 metres southwest of the felsic porphyry there is an open cut exposing green copper oxides with randomly-oriented chalcopyrite veinlets. Mineralization is not well exposed on surface, but starts to be clearly defined just 0.50 metres below surface. Five samples taken from this area returned up to 1.49% Cu, 2.88 gpt Au and 521 ppm Mo. The maximum molybdenum value coming from this type of structures attained 765ppm.

Chilaroya South Geology, Geophysics and Rockchip Geochemistry for Au