Location
The Cuiú Cuiú district is located 180 kilometers southwest of the small city of Itaituba, the regional hub for the Tapajós Mineral Province (TMP) in northern Brazil. Itaituba is located approximately midway between Belém and Manaus; both are cities of greater than two million people located on the Amazon River. Access to the property is by small plane from Itaituba, or by boat along the Tapajós and Crepori Rivers.
Cuiú Cuiú is Magellan Minerals' most important property. It is arguably the most famous garimpo in the Tapajós, with estimated historic gold production in the order of 1.5M to 2M oz; it is considered a gold district in its' own right. Magellan property holdings cover the entire district and consist of two exploration licenses, four license applications and 76 PLGs (artisinal mining claims) totaling over 47,000 hectares (> 470 km2).
History
Cuiú Cuiú's heyday as an alluvial gold producer was from 1972 to 1992, when it was part of the largest gold rush in history. Over 1,000,000 people rushed to northern Brazil to seek their fortunes, and approximately 300,000 of these miners or "garimpeiros", ended up working the rich alluvial deposits draining into the Tapajós River. At Cuiú, 5,000 to 10,000 people lived and worked in the area.
This frenzy of activity attracted the attention of both major and junior mining companies, and in the mid to late 90's, several major mining companies as well as a handful of juniors arrived on the scene. During the period from 1996 to 1999, TVX, Phelps Dodge, RTZ and Altoro Resources all carried out work at Cuiú Cuiú. This work included gridding, soil/rock-chip sampling and a minor amount of shallow drilling. However due to the inability of any of these companies to make satisfactory agreements with the majority of the local miners, and also due to the fall of the gold price in 1997-98, interest in the area waned.
In 2004, Magellan Minerals acquired the DNPM mineral exploration rights over the area, and in 2005 Magellan management reached an historic agreement with the owners of the traditional surface rights whom have historically worked and lived at Cuiú.
Of the approximately 1.5 to 2 million ounces of gold exploited at Cuiú, greater than 95% was won from alluvial and near-surface saprolitic and lateritic material, over an area covering 11 kms x 7 kms in size (see figure below). The mineralized structure, stretches for more than seventeen kilometers from southeast to northwest across Magellan's license area. Exploration work carried out by Magellan has identified five major gold soil anomalies (>1km2) as well as several minor anomalies along this zone. This mineralized structure is coincident with the large-scale regional lineament that controls the Sao Jorge, Palito, Tocantinzinho and Bom Jardim garimpos*.
The five major soil anomalies so far identified by Magellan at Cuiú Cuiú are as follows :
- Central - The largest gold-in-soil anomaly with significant historic artisinal workings. This soil anomaly extends over approximately 2km x 450m and is oriented NW-SE. Surface sampling at Central has identified sheeted veining and stockwork mineralization on surface with channel sampling reporting values up to 16m @ 6.4g/t Au and 25m @ 3.7g/t Au. Previous drilling by Magellan in part of this anomaly returned values of 134m @ 1.1g/t Au and 157m @ 0.91g/t Au.
- Pau de Merenda - This gold-in-soil anomaly is located approximately 2kms NW of Central along same trend and is 1100 x 650m in extent. Previous garimpo workings are coincident with the soil anomaly which has not yet been tested by drilling. The gold in this area is currently unknown.
- Jerimum Cima - An important garimpo with coincident gold-in-soil anomaly located approximately 3 kms ENE of Central, which covers an area of approximately 850m by 1km. Sheeted veining and stockwork mineralization within historic garimpo workings returned 84m @ 1.6g/t Au in a continuous channel sample. Limited shallow drilling by TVX in this area reportedly returned values up to 10m @ 2.7g/t Au. The bulk of the soil anomaly and the historic grarimpo pit have not been drill tested.
- Jermum Baixo - This gold-in-soil anomaly located approximately 1km south of Jerimum Cima covers an area approximately 700 x 500m in size. Historic garimpo workings are located on the SE edge of the anomaly and stockwork and sheeted vein mineralization have been mapped at this location. Surface sampling of these workings returned 8m @ 5.0g/t Au and 42m @ 1.0g/t Au. A single previous drill hole completed by Magellan intersected 1.9m @ 3.1g/t Au. The bulk of the anomaly however remains untested.
- Moreira Gomes - gold in soil anomaly located 1.5km SE of Jerimum Baixo covering an area of 1.5km x 650m. Narrow vein mineralization has been located in drainages below the anomaly but the source of the large gold in soil anomaly itself remains unknown.
Geology and Mineralization
The Cuiú Cuiú area consists of a series of intensely mined rivers, streams and artisinal workings called garimpiero pits or "garimpos", covering an area of approximately 80 km2. The garimpo pits are small to medium-sized excavations, generally developed hydraulically, within or adjacent to creeks and drainages. These garimpos occur throughout the entire license area of approximately 47,000 ha, and number more than 100.
The majority of the gold exploited at Cuiú Cuiú was surficial alluvial and colluvial material which hosts transported, fine grained to nugget sized, native gold. However, the garimpieros occasionally developed significant pits that reached depths of up to 40 meters on in-situ, mineralized saprolite.
All of the larger garimpiero workings have associated geochemical soil anomalies which extend for hundreds to thousands of meters along strike, and are tens of meters, to greater than 300m wide. In fact, most but not all of the important workings within the Cuiú license occur along a linear gold-in-soil geochemical anomaly that extends southeast to northwest for more than 17 kms through the center of the Cuiú area.
In addition, there are many garimpos at Cuiú which are located away from the main lineament, including Jerimum de Cima, one of the more important historic production centers in the area. Historically, any areas without easy access to water were not prospected by the garimpieros, who used pressurized water as their primary excavation tool. Therefore the entire Cuiú license area is prospective for gold mineralization, including those areas located away from the significant NW-striking geochemical anomaly. Note that metallogenic maps prepared by the CPRM (geologic survey of Brazil) show the Cuiú area as having a "high potential" for hosting gold mineralization.
Regional Geology
The host rocks are Proterozoic granites (approx. 1.8 Ga) containing andesite, aplite and pegmatite dykes and are part of the north-west trending Tapajós-Parima orogenic belt, one of six recognized terrains within the Amazon Craton. This belt of granitic and associated volcanic rocks begins in the Alta Floresta district of northern Mato Grosso state, passes through the Tapajós region of western Pará, continues north into Rondônia, and ends in southern Venezuela-Guyana, where several large gold mines are located (the former Omai mine in Guyana, being the most well known). Besides the TMP, the Tapajós-Parima belt includes three other important gold provinces: the Alta Floresta gold province some 450 kms southwest of the TMP, and the Uaimiri and Parima auriferous "domains", located 600 kms and 1200 kms northeast respectively, from the TMP. All four areas are underlain by mineralized Proterozoic intrusive and volcanic rocks, and saw sustained garimpiero activity during the past four decades.
The Tapajós granites vary in age from approximately 1.8 to 2.2 Ga and are thought to represent a sequence of pre-orogenic to post-orogenic intrusive phases associated with a subducting plate margin along the western edge of the ancient Amazon Craton (Santos et al), although recent work by Juliani et al, sheds some doubt on this interpretation. Within the Tapajós Mineral Province, at least three major intrusive phases, all of which host primary gold deposits, can be differentiated: 1) earliest Cuiú Cuiú and Creporizão granites/gneisses, which are usually foliated to gneissic in character; 2) later Parauarí porphyritic monzonites and granodiorites which form great batholiths and host the largest proportion of gold deposits within the TMP, including the Tocantinzinho, Sao Jorge and Palito deposits; and 3) the latest, somewhat alkaline, Maloquinha granite which forms stocks, secondary batholiths, and is thought to be co-magmatic to the Iriri volcanics.
Prospect scale geology and geomorphology
Tropical latosoils are developed over most areas at Cuiú, with thicker development on plateaus. The latosoil is 2 to 5 meters thick, brick red to ochre in color, and usually displays a well developed "stone line" or ferricrete horizon, several meters below surface, just above the transition to saprolite. Saprolite with varying degrees of relict texture, occurs below the laterite and is anywhere from 10 to 70m deep, but is usually around 20m to 30m thick. The transition from saprolite to relatively fresh rock (usually granite) is sharp, occurring over 1.5m or less.
Outcrop is uncommon. Lithology and mineralization are best observed in the garimpo pits and some creek drainages. Unfortunately most of the pits are now small lakes, so the amount of surface mineralization and geology to be observed is minimal.
The bulk of the gold mineralization identified to date within the Cuiú license is hosted by coarse grained, porphyritic granites that are believed to be of the Parauarí suite, although mineralization does occur within andesite, aplite and pegmatite dykes. The andesite dykes in particular, appear to be ubiquitous in mineralized zones, with higher grade mineralization often localized along the margins of the dykes, usually not within the dykes themselves. It appears that the contacts between andesite dykes (which have a strong rheological contrast to the granite), and the host granite are acting as permissive trap sites for the mineralizing fluids.
Mineralization
Mineralization is of two types: Low grade, more or less "disseminated style", consisting of swarms of narrow (1-3mm wide) quartz-sulfide-minor calcite veinlets. The veinlets are often sheeted, with primary orientations both NW-SE and NE-SW indicating a prolonged structural history and varying stress regimes. This style of mineralization is very similar to that which occurs at the Tocantinzinho project, 30kms southeast of Cuiú Cuiú, where Brazauro Resources has proven up a 43-101 compliant 2.1M oz. This is the style of mineralization encountered at the "Central" garimpo where hole CC03-06 returned 134m @ 1.15 g/t and hole CC02-06 returned 157m @ 0.91g/t Au.
In general, this style of mineralization can be characterized as "low sulfide", typically containing 1% to 2% pyrite, both as fine disseminations (often in association with chlorite), and hosted in narrow quartz-chlorite ± calcite veinlets. Base metal sulfides, mostly sphalerite, with lesser galena, and rare chalcopyrite occur as solitary aggregates, grains, and within gray translucent quartz veinlets. However, overall base metal concentrations are significantly less than 1%. At Tocantinzinho the occurrence of base metal mineralization is associated with high grade gold mineralization of up to 50 g/t Au.
The other type of mineralization is native, occasionally coarse-grained gold, sometimes visible, hosted in discrete vein sets. The vein sets comprise multiple (2 to 10), sheeted, quartz-sulfide veins 1 cm to 20+ cm wide, that commonly carry grades in the range of 10 to 100 g/t Au. This type of mineralization is more common than the low grade disseminated veinlet style described above, and is found in many garimpos throughout the TMP. While these high grade veins are harder to prove up in terms of overall tonnage, they are very attractive targets due to the high grade and smaller capital requirements for production. The Jerimum de Cima, Guarim, and Moreira Gomes prospects all host high grade vein style mineralization, with the latter currently producing half a kilo to one and a half kilos of gold per week, from a small 5-man artisinal operation.
Work carried out to date
To date a total of approximately C$2 million has been expended by Magellan at Cuiú. This includes a 2700m drilling program in 2006, an ongoing 6000m drill program in 2007-2008, as well as an extensive aero geophysical survey and over 6500 surface soil and rock chip samples.
A summary of results from the 2006 drill program are shown on the attached maps and tabulated below:
Drill Hole ID |
Location |
From (m) |
To (m) |
Interval (m) |
Grade g/t Au |
|---|---|---|---|---|---|
CC-01-06 |
Central |
62.4 |
64.0 |
1.6 |
1.35 |
|
|
143.2 |
186.0 |
42.8 |
0.67 |
CC-02-06 |
Central |
31.0 |
190.0 |
157.2 |
0.91 |
Incl. |
|
90.0 |
114.1 |
24.1 |
2.02 |
CC-03-06 |
Central |
141.1 |
275.6 |
134.5 |
1.10 |
CC-04-06 |
Central |
21.5 |
23.0 |
1.5 |
4.64 |
|
|
207.0 |
257.7 |
50.7 |
0.57 |
CC-05-06 |
NW of Central |
134.7 |
137.6 |
2.9 |
1.20 |
CC-06-06 |
NW of Central |
146.0 |
148.0 |
2.0 |
4.86 |
CC-07-06 |
NW of Central |
63.0 |
76.9 |
13.9 |
2.49 |
Incl. |
|
64.1 |
65.1 |
1.0 |
15.95 |
CC-08-06 |
NW of Central |
81.2 |
84.2 |
3.0 |
1.62 |
|
|
220.4 |
222.4 |
2.0 |
13.54 |
CC-09-06 |
NW of Central |
|
|
|
no significant results |
CC-10-06 |
Jer. Baixo |
55.2 |
57.1 |
1.9 |
3.09 |
A follow up drill program commenced during late 2007 and is still in progress having been recently expanded to 7000m. Thus far, a total of 30 additional diamond drill holes have been completed and the results on the holes received to date are included below.
Central
Drill Hole |
Location |
From (m) |
To (m) |
Width (m) |
Grade g/t Au |
|---|---|---|---|---|---|
CC-11-07 |
Central |
|
|
|
No significant Results |
CC-12-07 |
Central |
13.3 |
23.3 |
10.0 |
0.59 |
|
|
35.0 |
39.0 |
4.0 |
0.90 |
|
|
45.1 |
74.9 |
29.8 |
1.48 |
|
|
96.7 |
100.6* |
3.9 |
1.59 |
CC-13-07 |
Central |
41.2 |
107.0 |
65.8 |
3.54 |
|
|
incl.57.9 |
64.0 |
6.1 |
23.53 |
|
|
130.3 |
136.3 |
6.0 |
1.47 |
|
|
165.2 |
177.5 |
12.3 |
4.25 |
CC-14-07 |
Central |
71.0 |
158.9 |
87.9 |
1.11 |
CC-15-07 |
Central |
42.8 |
222.4 |
179.6 |
1.06 |
|
|
incl. 217.3 |
222.4 |
5.1 |
14.05 |
CC-16-07 |
Central |
81.8 |
83.1 |
1.3 |
1.06 |
|
|
149.3 |
150.9 |
1.6 |
1.29 |
|
|
170.1 |
344.3** |
174.2 |
1.46 |
|
|
218.0 |
277.0 |
59.0 |
2.86 |
|
|
275.0 |
277.0 |
2.0 |
36.15 |
CC-17-07 |
Central |
128.8 |
130.8 |
2.0 |
2.05 |
|
|
200.7 |
202.2 |
1.5 |
2.47 |
CC-18-07 |
Central |
|
|
|
No significant Results |
* hole CC-12-07 was lost at 100.6m depth. The final sample interval returned 2.1m @ 2.53g/t Au.
** hole CC-16-07 was stopped at 345.3m depth in a post-mineral aplite dyke.
A summary of the results obtained from holes CC-31-08 to CC-35-08 and CC-37-08 to CC-41-08, which were all drilled within the Central zone, is as follows:
Drill Hole |
Location |
From (m) |
To (m) |
Width (m) |
Gold g/t Au |
|---|---|---|---|---|---|
CC-31-08 |
Central |
131.7 |
137.7 |
6.0 |
0.79 |
|
|
147.7 |
149.7 |
2.0 |
2.47 |
CC-32-08 |
Central |
61.6 |
63.1 |
1.5 |
1.98 |
|
|
88.0 |
308.7 |
220.7 |
2.02 |
incl. |
|
88.0 |
97.8 |
9.8 |
17.91 |
and |
|
245.6 |
249.8 |
4.2 |
25.69 |
|
|
308.7 |
326.5 |
17.8 |
0.68 |
CC-33-08 |
Central |
54.7 |
55.7 |
1.0 |
3.07 |
|
|
77.1 |
78.1 |
1.0 |
2.36 |
|
|
109.4 |
110.4 |
1.0 |
1.34 |
|
|
133.7 |
136.7 |
3.0 |
1.02 |
CC-34-08 |
Central |
134.0 |
136.0 |
2.0 |
1.29 |
CC-35-08 |
Central |
34.0 |
36.0 |
2.0 |
1.51 |
|
|
100.6 |
102.3 |
1.7 |
1.53 |
|
|
127.2 |
138.1 |
10.9 |
0.85 |
|
|
202.1 |
203.1 |
1.0 |
28.45 |
CC-37-08 |
Central |
46.5 |
52.3 |
5.8 |
1.33 |
|
|
148.8 |
152.5 |
3.7 |
1.88 |
|
|
176.5 |
177.3 |
0.8 |
1.19 |
|
|
208.3 |
208.8 |
0.5 |
3.88 |
CC-38-08 |
Central |
56.1 |
57.9 |
1.8 |
1.39 |
|
|
107.3 |
130.4 |
23.1 |
0.88 |
|
|
174.7 |
275.8 |
101.1 |
0.79 |
Incl. |
|
174.7 |
176.4 |
1.7 |
3.45 |
and |
|
179.2 |
180.2 |
1.0 |
1.82 |
and |
|
190.1 |
192.4 |
2.3 |
2.66 |
and |
|
204.4 |
204.9 |
0.5 |
2.75 |
and |
|
219.5 |
238.7 |
19.2 |
1.78 |
and |
|
261.6 |
275.8 |
14.2 |
1.39 |
|
|
291.4 |
293.4 |
2.0 |
1.25 |
|
|
308.3 |
311.6 |
3.3 |
1.01 |
CC-39-08 |
Central |
90.4 |
91.6 |
1.2 |
1.23 |
|
|
108.6 |
117.2 |
8.6 |
1.23 |
|
|
151.3 |
153.8 |
2.5 |
1.43 |
|
|
220.4 |
224.3 |
3.9 |
1.12 |
|
|
230.3 |
232.6 |
2.3 |
1.05 |
CC-40-08 |
Central |
72.5 |
74.5 |
2.0 |
1.58 |
|
|
138.8 |
140.8 |
2.0 |
1.02 |
|
|
172.6 |
228.9 |
56.3 |
0.70 |
CC-41-08 |
Central |
|
|
|
No significant results |
Pau de Merenda
Drill results on an initial five diamond drill holes drilled at the Pau da Merenda target, 3km NW of the Central zone are as follows.
Drill Hole |
Location |
From (m) |
To (m) |
Width (m) |
Grade g/t Au |
|---|---|---|---|---|---|
CC-19-07 |
Pau da Merenda |
87.8 |
118.0 |
30.2 |
1.11 |
CC-20-07 |
Pau da Merenda |
21.3 |
22.8 |
1.5 |
2.13 |
|
|
76.0 |
123.1 |
47.1 |
1.76 |
|
|
143.0 |
145.0 |
2.0 |
1.27 |
CC-21-07 |
Pau da Merenda |
127.0 |
127.6 |
0.6 |
2.31 |
|
|
169.0 |
169.8 |
0.8 |
1.99 |
CC-22-07 |
Pau da Merenda |
4.6 |
12.2 |
7.6 |
1.07 |
|
|
16.8 |
18.3 |
1.5 |
1.29 |
|
|
62.8 |
71.3 |
8.5 |
5.07 |
CC-23-07 |
Pau da Merenda |
|
|
|
no significant results |
Jerimum de Cima
Drill results from an initial seven holes at the Jerimum de Cima target, 3.2 km ENE of the Central target zone soil anomaly are as follows:
Drill Hole |
Location |
From (m) |
To (m) |
Width (m) |
Grade g/t Au |
|---|---|---|---|---|---|
CC-24-07 |
Jerimum de Cima |
93.0 |
93.9 |
0.9 |
3.17 |
|
|
169.5 |
170.0 |
0.5 |
1.21 |
|
|
182.5 |
183.2 |
0.7 |
1.16 |
|
|
224.3 |
225.8 |
1.5 |
1.04 |
|
|
236.4 |
237.3 |
0.9 |
1.92 |
|
|
243.0 |
269.0 |
18.0 |
1.17 |
CC-25-07 |
Jerimum de Cima |
|
|
|
no significant results |
CC-26-07 |
Jerimum de Cima |
13.7 |
15.2 |
1.5 |
1.00 |
|
|
57.4 |
58.5 |
1.1 |
1.35 |
|
|
73.9 |
112.9 |
39.0 |
5.13 |
incl. |
|
73.9 |
75.2 |
1.3 |
1.73 |
and |
|
90.9 |
91.8 |
0.9 |
5.42 |
and |
|
97.3 |
98.1 |
0.8 |
1.53 |
and |
|
101.6 |
103.1 |
1.5 |
117.26 |
and |
|
106.2 |
107.3 |
1.1 |
4.71 |
and |
|
112.0 |
112.9 |
0.9 |
3.47 |
|
|
117.6 |
118.5 |
0.9 |
2.52 |
|
|
169.0 |
169.8 |
0.8 |
1.99 |
|
|
195.4 |
200.9 |
4.9 |
1.97 |
incl. |
|
199.9 |
200.9 |
1.0 |
7.67 |
CC-27-07 |
Jerimum de Cima |
108.4 |
112.6 |
4.2 |
1.83 |
|
|
122.5 |
123.2 |
0.7 |
1.78 |
CC-28-07 |
Jerimum de Cima |
|
|
|
no significant results |
CC-29-07 |
Jerimum de Cima |
|
|
|
lost at 62m |
CC-30-07 |
Jerimum de Cima |
156.3 |
157.6 |
1.3 |
2.02 |
Drill Hole |
Location |
From (m) |
To (m) |
Width (m) |
Gold g/t Au |
|---|---|---|---|---|---|
CC-36-08 |
Jerimum de Cima |
150.6 |
151.1 |
0.5 |
1.18 |
|
|
177.2 |
178.2 |
1.0 |
1.05 |
|
|
192.8 |
194.8 |
2.0 |
3.27 |
|
|
229.2 |
229.7 |
0.5 |
1.09 |
Drill results from the ongoing drill program will be released once final analyses have been received from the laboratory during the second quarter of 2008.
Cuiú Cuiú's other targets include:
Several other target areas have been identified within the Cuiu Cuiu district and are as follows:-
Baixão de Onça is located east of Moreira Gomes anomaly. Reconnaissance soil sampling has been completed. Channel sampling at the main garimpo pit returned 15m @ 2.6g/t Au.
Ratinho is located 6km NW of the Central anomaly in an area hosting numerous garimpo pits. High grade veins returned values of 0.6 -- 63.3g/t Au.
The Nova Limão area is a currently active alluvial/saprolitic pit measuring 350m x 100m located 8km west of Central anomaly. Reconnaissance sampling is in progress.
Escondido is a large area (4x3km) of Quaternary cover located on trend between J Cima / J Baixo and Nova Aliança areas. Small creeks draining the area are aufiferous.
Nova Aliança is in the eastern part of the claim block . It has numerous garimpo pits. Limited soil sampling has been completed over the area.
Maps & Photos
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