LATIN AMERICA — Lucero eyes Cielo target on Macromin project in Chile — Junior still bullish following pull-out by Rio Tinto

In spite of disappointing results from early drilling on the Cerros Bayos target, Lucero Resources‘ (LCR-V) remains optimistic about the potential of its Macromin project in the Antofagasta region of northern Chile.

No economically significant copper or gold values were encountered in an 8-hole program of reverse-circulation drilling on the 14,000-ha Cerros Bayos porphyry-copper target. As a result, Rio Tinto (RTP-N) has opted to drop out of its recent option agreement with Lucero. The mining giant had the right to earn a 60% interest in the Cerros Bayos portion of the Macromin property by spending US$13 million on exploration over five years.

Lucero can earn a half-interest in the Macromin property from privately owned Sol Resources by making cash payments totalling US$1.1 million, issuing 1 million shares and spending US$3 million on exploration before Sept. 15, 2000. Within 60 days of vesting its option, Lucero will have the right to acquire the remaining 50% interest by issuing a combination of shares and cash based on the market value of Sol’s interest in the property at the time.

The Macromin property totals 65,000 ha and hosts three principal porphyry targets: Cerros Bayos, Quebrada Pereda and Cielo. Cerros Bayos is on the northern section of the property, whereas Cielo and Quebrada Pereda are in the south.

Cerros Bayos is typical of copper porphyrys in that it includes quartz feldspar intrusives, widespread hydrothermal alteration and a structurally controlled stockwork system.

Quebrada Pereda outcrops over a small area and consists of a strongly clay-altered feldspar porphyry containing limonite and hematite-coated fractures and quartz veinlets. The intrusive measures 200 metres in diameter and is characterized by brecciated sedimentary rocks.

Lucero has focused its efforts on the Cielo zone, 15-20 km south of the Cerros Bayos target. The company expects to begin an extensive, 40-hole program of reverse-circulation drilling on Cielo in October.

In the Cielo zone are seven smaller, hydrothermally altered zones, which are spatially associated with a large monzodiorite intrusive stock. These zones — dubbed Corazon, Cielo West, Cielo Central, Cielo South, Cielo East, Umbral and Luzappear — are related to late-stage feldspar and quartz-feldspar porphyries, and to clusters of tourmaline breccia bodies. The zones are extensively oxidized and show evidence of intense acid leaching.

• Corazon — The Corazon zone is the most southerly outcrop and consists of bleached, silicified, fine-grained sediments that are intruded by quartz-sericite altered and quartz-feldspar dykes. Quartz veining is rare along the western part of the exposure but increases in intensity toward the east.
• Cielo West — This is a large (1.2-by-2.5-km), north-trending alteration zone, in the southwestern portion of which are quartz-sericite-altered feldspar porphyries flanked by intensely silicified and brecciated limestone sediments. The porphyries and sediments are strongly leached and said to contain jarosite, limonite and hematite. This portion of the zone measures 500 by 1000 metres.

  Another potential target within the Cielo West zone occurs in the northern sector and measures about 300 by 600 metres. The area is said to contain porphyry dykes and sandstones cut by a moderate-to-strong stockwork of limonite and hematite veinlets.

• Cielo Central — This zone occurs along the western edge of the monzodiorite stock and measures 400-by-1000 metres. It is characterized by moderate-to-strong silicification, fine-grained sericitization and tourmalization which is associated with extensive fracturing and brecciation. Reportedly, 11 tourmaline breccias have been mapped in the core of the zone, which is characterized by an abundance of jarosite.
• Cielo South — This zone is 1 km wide and extends beneath volcanic ignimbrite cover to the southeast of the Cielo Central zone. Sediments within the zone are strongly silicified and locally brecciated jarosite, limonite and hematite are abundant.
• Cielo East — Measuring 0.8 by 1.5 km and occurring along the eastern edge of the monzodiorite stock, this zone is centred over a quartz-feldspar plug about 600 metres in diameter. The monzodiorite and quartz-feldspar porphyry are bleached, silicified and moderately sericitized.
• Umbral — Reported to be the strongest of the alteration zones, Umbral is centred over a porphyry stock measuring 400 metres in diameter. The Umbral zone closely resembles a classic leached porphyry cap. It is intensely sericitized, as are sediments adjacent to the stock. Jarosite, hematite and limonite are all present in abundance. A stockwork of strongly leached hematite-limonite quartz veinlets and fractures occurs throughout most of the alteration zone.
• Luz — This, an ovoid alteration zone measuring 2.3 by 1.2 km, is about 1 km north of the Umbral zone. The central portion of the zone is covered by volcanic ignimbrite. A tourmaline-altered, fine-grained granodiorite is partly exposed along the northern edge of the zone and is in contact with an altered monzodiorite. In the southern portion of the zone, sericitized and hydrothermally brecciated quartz-feldspar porphyry intrudes into siltstones.