projects

Primavera Project

The newly discovered Primavera gold-copper porphyry system is located 7 kilometres south of the historic Santa Rita copper-gold skarn mine and is located within Calibre's Borosi Concessions of northeast Nicaragua. The road accessible project is located 1.2 kilometres from the national power grid and is 8 kilometres south of the town of Rosita. The project is situated on subdued topography with the main land use being subsistence farming and ranching. The prospect is subject to an option agreement with B2Gold Corp. (Nicaragua's largest gold producer). B2Gold has earned a 51% interest in the Primavera project and other concession areas contained in the agreement by spending CDN $8 million on exploration. They may elect to carry an individual prospect within the concession area through to a Preliminary Feasibility Study within 2 years for an additional 14% interest in the prospect.

Metallurgical Testing

In a report entitled "An Investigation into Scoping Level Testwork on Primavera Project Samples" dated February 8th, 2013 by SGS Canada Inc. of North Vancouver ("SGS Canada") four composite samples of Primavera porphyry mineralization from drill hole PR-012-16 (201.35 m grading 0.77 g/t Au and 0.36% Cu) were submitted for initial metallurgical studies. Sample head assays are outlined in Table 1. Individual sample weights ranged from 18.6 kg to 30.3 kg. The metallurgical tests conducted on the Primavera project samples included rougher flotation kinetic and cleaner flotation tests and whole ore cyanide leach tests.

Summary of Head Assays
Element Sample Number
6261 6262 6263 6264
Au, g/t 0.98 1.26 0.52 0.86
Cu, % 0.52 0.70 0.26 0.27

In optimized rougher flotation tests on the four Primavera samples gold recoveries ranged from 86% to 91% and copper recoveries ranged from 94% to 98%. Initial metallurgical tests indicate that the recovery of gold, copper and sulphur are strongly related to each other and recovering sulphur by flotation will recover most of the copper and gold. Two different grind sizes were tested during the study with the finer grind returning the best recoveries. Additionally, whole ore leach tests on the four Primavera samples extracted 90.0% to 96.6% of the gold using 1.2 kg/t to 2.43 kg/t of NaCN. Gold kinetics on the leach tests are moderately fast reaching plateau within 30 hours and gold in all leach tests exhibited free milling qualities.

See Technical Reports section of Calibre's website for a copy of the report.

Calibre Mining Corp. at the AME BC Round Up 2013


 

 

 


 


Drilling Update

Assay results returned in June 2012 from the first phase of diamond drilling (3,938 metres in 13 drill holes) confirmed the presence of wide spread gold-copper values similar to those previously reported from surface trenching. The results received are consistent with "porphyry style" mineralization within volcanic and intrusive rocks located in the "Mining Triangle" region of northeast Nicaragua. Highlights from Phase I include drill hole PR-11-001 returning 103 metres of 0.85 grams per tonne ("g/t") gold and 3,240 parts per million ("ppm") (0.324 %) copper, starting from the surface. Drill hole PR-11-002 collared from the same platform, but oriented 75 degrees from PR-11-001 and contained 0.78 g/t gold and 2,966 ppm (0.297 %) copper over 261.7 metres from 1.5 metres down hole depth. Drill hole PR-11-003 was collared over 200 metres to the southeast and intersected 146.50 metres of 0.65 g/t gold and 2,742 ppm (0.274 %) copper. Mineralization in holes PR-11-002 and PR-11-003 remains open at depth. Additional holes included PR-12-008 returning 172.35 metres of 0.48 g/t gold and 2,401 ppm (0.240 %) copper, including 55.50 metres of 0.67 g/t gold and 3,507 ppm (0.351 %) copper. Drill hole PR-12-010 returned 15.40 metres of 0.59 g/t gold and 4,325 ppm (0.433 %) copper.

Phase II diamond drilling was completed in December 2012 and consisted of an additional 8,951 metres in 20 drill holes. Assay results continue to confirm the presence of gold-copper porphyry style mineralization proximal to the initial discovery as well as porphyry and skarn style mineralization in outlying areas. Highlights from Phase II include drill hole PR-12-016 (80 metres northeast of PR-11-001) returning 201.35 metres of 0.77 g/t gold and 3,567 ppm (0.357%) copper starting from surface, including 102.50 metres of 0.93 g/t gold and 4,200 ppm (0.420%) copper. Drill hole PR-12-023 returned 346.00 metres of 0.23 g/t gold and 1,269 ppm (0.127%) copper located 125 metres northwest of PR-11-003.

The Phase II drilling program primarily focused on expansion of the main zone through large drilling step-outs. Additional drill holes investigated skarn-hornfels mineralization at Copper Hill, the intervening covered area between Primavera and Copper Hill, a northeast trending epithermal vein system located southeast of Primavera (drill hole PR-12-010 from Phase I), and several additional targets identified during the extensive soil geochemical and geophysical surveys completed during the year.

In the main zone, drilling tested the along strike (northeast and southwest) continuity and depth of higher grade mineralization intersecting thick intervals of porphyry style mineralization to depths of 250 metres and over an area approximately 250 metres x 350 metres. Major north-northeast and west-northwest oriented faults that form apparent horst and graben features control and cut the mineralization in the main zone at Primavera. Drilling across these structures intersected porphyry style mineralization but has not yet located the offset portion of the higher grade main zone. Drill hole PR-12-024, located 150 metres north of the main zone, intersected porphyry style mineralization similar to the main zone when it passed north through a west-northwest oriented fault, suggesting that the offset portion may lie further to the north.

In outlying areas of Copper Hill, drill holes intersected low grade gold and copper mineralization within skarn and hornfels horizons, suggesting widespread intrusive activity through the area that has potential to host additional significant mineralized zones. Of the numerous coincident soil geochemical and geophysical anomalies defined during the year, only one target, located 1.5 kilometres southeast of the main zone, has been drill tested and encountered sporadic anomalous copper mineralization (PR-12-028). Several sulphide-rich quartz veins and breccias mapped at surface in other parts of the Primavera region appear similar to veins encountered during drilling in the faults that cut the main zone. Many of these targets contain anomalous Au-Cu geochemistry and are intermittently exploited by artisanal miners.

Primavera Geology

The Primavera prospect is located in a 5 kilometre by 7 kilometre area dominated by Tertiary volcanics in which quartz veins, diorite intrusives, and calcareous sediments have been mapped. The prospect area is associated with coincident gravity, magnetic and radiometric high signatures identified from an airborne geophysical survey, believed to represent a large intrusive centre. The area is thought to be prospective for epithermal, porphyry and skarn mineralized systems.

Exploration efforts to date include the collection of over 350 rock samples, 4,000 soil samples, the excavation of 661 metres of trenches, and completion of detailed LiDAR, airborne magnetic, radiometric and a ground IP surveys. As a result of these exploration activities, a coincident gold-copper soil anomaly was defined over an area 1,250 metres x 400 metres with northeast-southwest elongation. Gold values within this area were consistently greater than 100 ppb and copper values were consistently greater than 250 ppm. Subsequent trenching defined a high-grade core that was drill tested in Phase I.

Drill core shows that mineralization is associated with a swarm of northeast-trending equigranular diorite dikes intruding porphyritic andesite and minor tuffaceous rocks of intermediate composition. The dike swarm coincides with a major northeast trending fault zone on the west side of the mineralization. The fault zone itself hosts sulfide rich quartz veins and breccias that occasionally contain highly anomalous gold. These veins have been mapped elsewhere in the Primavera area and occur along major structures that are in some cases exploited by artisanal miners.

The Primavera zone shows classic porphyry stockwork mineralization consisting of millimeter to centimeter scale quartz-pyrite-chalcopyrite+bornite-magnetite veins associated with potassic and propyllitic alteration of the host rock. The veins and stockwork show a preferred orientation to the northeast in the southern portion of the zone but become dominantly northwest to the north.

The highest grades are associated with strong potassic alteration in the form of K-spar in diorite and secondary biotite in the andesite porphyry. Bornite is also common in these zones. Multi-stage quartz veining indicates that the earliest mineralization predates intrusion of the diorite as diorite cuts both the andesite porphyry and earliest veins but is itself cut by later veins. In general, the equigranular diorite hosts "ore grade" mineralization but the diorite itself is also much more widespread.

Geophysical studies indicate that the structural setting at Primavera is complex with magnetic highs and lows as well as IP anomalies correlating well with some major structures. Some faults post-date mineralization and ongoing work will focus on locating offset portions of the currently defined mineralization.

Ongoing Exploration

Work in early 2013 with focus on mapping and additional surface sampling. Some of the drill targets have yet to be drill tested, such as San Isidro 3 kilometres to the west, which displays many of the same structural and geochemical characteristics as Primavera.

Follow-up drilling is planned to the north under the alluvium to locate the extension of the mineralization from the main Primavera Zone. Other regional targets identified through surface work and geophysical anomalies will also be tested in Phase III.

Porphyry deposits around the world are known to occur in clusters aligned along major structural domains (Cadia, Mirador). The drilling completed so far at Primavera suggests that temporal relationships with the intrusive occurrences are consistent with an evolving porphyry cluster. In addition, distal skarn mineralization may be indicative of widespread metal-rich fluids associated with the robust intrusive activity in the area. More surface work and drilling at Primavera will help to define mineralization and mineralized trends within these structural domains.

*Newcrest Mining Limited website.

The table below summarized the assay results returned from the complete initial program at Primavera:
Drill Hole From
(m)
To
(m)
Length
(m)
Gold
(g/t)
Copper
(ppm)
Au*
(g/t)
Gold Equivalent
PR-11-001 0.00 276.80 276.80 0.50 2,146 0.84
Includes 0.00 103.00 103.00 0.85 3,240 1.36
PR-11-002 1.50 263.20 261.70 0.78 2,966 1.25
Includes 1.50 209.00 207.50 0.89 3,378 1.42
Includes 74.50 209.00 134.50 1.01 3,562 1.57
PR-11-003 4.00 327.30 323.20 0.41 1,843 0.70
Includes 4.00 150.50 146.50 0.65 2,742 1.08
Includes 150.50 293.00 142.50 0.22 1,197 0.41
Includes 293.00 327.20 34.20 0.13 683 0.24
PR-11-004         NSV** NSV**
PR-12-005 207.50 372.50 165.00 0.31 1,713 0.58
Includes 207.50 224.00 16.50 0.35 1,103 0.52
Includes 224.00 270.00 46.00 0.48 3,155 0.97
Includes 270.00 312.00 42.00 0.15 749 0.27
Includes 312.00 372.50 60.50 0.27 1,452 0.50
PR-12-006 12.00 102.00 90.00 0.21 1,315 0.42
PR-12-007 7.70 255.00 247.30 0.22 1,097 0.39
Includes 7.70 156.00 148.30 0.22 917 0.36
Includes 156.00 197.00 41.00 0.34 1,760 0.62
Includes 197.00 255.00 58.00 0.16 1,088 0.33
PR-12-008 107.65 280.00 172.35 0.48 2,401 0.86
Includes 107.65 131.50 23.85 0.32 1,478 0.55
Includes 131.50 187.00 55.50 0.67 3,507 1.222
Includes 187.00 280.00 93.00 0.41 1,978 0.72
Includes 280.00 382.50 102.50 0.23 1,139 0.41
Includes 393.00 430.50 37.50 0.14 1,005 0.30
PR-12-009         NSV** NSV**
PR-12-010 79.00 94.40 15.40 0.59 4,325 1.27
Includes 81.00 86.00 5.00 0.51 9,644 2.02
PR-12-011 6.95 166.48 159.53 0.46 2,008 0.77
Includes 6.95 95.65 88.70 0.53 2,225 0.88
Includes 166.48 215.50 49.02 0.21 977 0.36
Includes 262.00 285.15 23.15 0.19 1,306 0.39
PR-12-012 6.00 103.00 97.00 0.34 1,646 0.60
PR-12-013 24.00 46.50 22.50 0.44 2,090 0.77
Includes 46.50 87.00 40.50 0.25 1,150 0.43
PR-12-014 0.00 39.70 39.70 0.09 555 0.18
PR-12-014 269.00 275.00 6.00 0.61 212 0.64
PR-12-014 330.50 378.00 47.50 0.19 69 0.20
PR-12-014 415.30 461.80 46.50 0.16 496 0.24
PR-12-015 0.00 52.00 52.00 0.14 305 0.19
PR-12-015 241.50 275.00 33.50 0.12 1289 0.32
PR-12-015 365.00 397.50 32.50 0.11 489 0.19
PR-12-015 435.00 517.50 82.50 0.14 532 0.22
PR-12-016 0.00 201.35 201.35 0.77 3567 1.33
PR-12-016 25.20 88.65 63.45 1.09 4791 1.85
PR-12-016 315.00 325.30 10.30 1.26 25 1.26
PR-12-017 0.00 28.30 28.30 0.11 615 0.21
PR-12-018 63.30 93.60 30.30 0.07 743 0.19
PR-12-018 417.00 472.90 55.90 0.09 413 0.16
PR-12-019 2.05 181.50 179.45 0.17 1050 0.34
PR-12-019 103.50 177.00 73.50 0.22 1370 0.44
PR-12-019 295.00 420.00 125.00 0.16 795 0.29
PR-12-020 0.00 22.00 22.00 0.25 637 0.35
PR-12-020 365.00 410.00 45.00 0.11 448 0.18
PR-12-021 125.00 330.00 205.00 0.13 1007 0.29
PR-12-022 171.40 177.40 6.00 0.02 9139 1.47
PR-12-023 0.00 346.00 346.00 0.23 1269 0.43
PR-12-023 122.00 206.90 84.90 0.31 1591 0.56
PR-12-024 65.50 79.75 14.25 0.33 75 0.34
PR-12-024 496.55 536.55 40.00 0.21 656 0.31
PR-12-024 595.00 613.35 18.35 0.38 530 0.46
PR-12-024 653.20 656.70 3.50 6.90 404 6.96
PR-12-024 673.00 674.50 1.50 11.95 2373 12.33
PR-12-025 65.53 129.24 63.71 0.11 407 0.17
PR-12-025 104.45 129.54 25.09 0.16 407 0.22
PR-12-025 115.40 123.44 8.04 0.25 371 0.31
PR-12-025 320.20 325.00 4.80 0.19 540 0.28
PR-12-025 385.15 420.55 35.40 0.13 329 0.18
PR-12-025 409.20 411.60 2.40 0.54 989 0.70
PR-12-025 534.92 547.11 12.19 0.09 521 0.17
PR-12-025 560.83 566.93 6.10 0.18 1438 0.41
PR-12-026 18.29 28.96 10.67 0.24 290 0.29
PR-12-026 62.05 68.58 6.53 0.41 700 0.52
PR-12-026 92.40 110.20 17.80 0.28 441 0.35
PR-12-026 92.40 98.40 6.00 0.64 986 0.80
PR-12-026 265.30 267.00 1.70 2.45 404 2.51
PR-12-027 142.00 142.95 0.95 0.93 54 0.94
PR-12-027 161.50 167.50 6.00 0.19 561 0.28
PR-12-027 175.80 223.80 48.00 0.16 379 0.22
PR-12-027 175.80 203.25 27.45 0.11 334 0.16
PR-12-027 304.60 305.25 0.65 1.95 4285 2.63
PR-12-027 310.60 504.00 193.40 0.03 372 0.09
PR-12-027 535.00 554.50 19.50 0.04 564 0.13
PR-12-028 145.50 229.90 84.40 0.01 238 0.05
PR-12-028 310.75 312.42 1.67 2.74 3840 3.35
PR-12-028 332.35 447.00 114.65 0.01 195 0.04
PR-12-029 0.00 170.15 170.15 0.04 217 0.07
PR-12-029 32.00 55.15 23.15 0.10 283 0.14
PR-12-029 189.00 310.00 121.00 0.02 251 0.06
PR-12-030 0.00 142.60 142.60 0.05 354 0.11
PR-12-030 85.50 97.60 12.10 0.21 1016 0.37
PR-12-030 186.80 336.70 149.90 0.05 422 0.12
PR-12-030 186.80 204.30 17.50 0.13 666 0.24
PR-12-030 412.50 420.80 8.30 0.04 8083 1.32
PR-12-031 0.00 72.00 72.00 0.05 187 0.08
PR-12-031 176.75 253.00 76.25 0.04 359 0.10
PR-12-031 300.50 489.20 188.70 0.05 286 0.10
PR-12-031 363.70 452.63 88.93 0.09 376 0.15
PR-12-031 424.65 452.63 27.98 0.20 354 0.26
PR-12-032 163.00 377.05 214.05 0.11 177 0.14
PR-12-032 163.00 175.50 12.50 0.25 66 0.26
PR-12-032 232.00 263.65 31.65 0.24 160 0.27
PR-12-032 251.00 262.00 11.00 0.48 151 0.50
PR-12-032 254.20 254.85 0.65 2.14 279 2.18

*AuEq (g/t) Gold Equivalent calculated using 1,300/oz gold and 43.00/lb copper and metallurgicsal recoveries and net smelter returns are assumed to be 100%
**No significant values


The following images present an overview of the recently discovered geology, geochemistry, drilling and trenching maps and locations, and other details on the recently completed initial program at Primavera:

Click to Enlarge

Borosi Gold, Silver &
Copper Concessions -
"Mining Triangle

Primavera Gold/
Copper Project

Primavera Gold/Copper
Project Soil Geochemistry

Primavera Gold/Copper
Project Results

Primavera Gold/Copper
Project Drill Holes
PR 11-002, PR 12-008,
PR 12-011

Primavera Porphyry
Gold/Copper Mineralization --
District Potential

Selected Porphyry
Gold/Copper
Deposits/Mines

Trenching Results - Overview

PRTR11-011 intersected continuous gold and copper mineralization over the entire excavated length of the trench and returned a weighted average grade of 0.63 g/t Au and 997 ppm Cu over 179.4 metres (588 feet) with the mineralization being open for expansion in all directions. Trench PRTR11-011 was excavated in a north-easterly direction and is located approximately 200 metres south of Trench PRTR11-005 trending east-west that returned 1.53 g/t Au and 680 ppm Cu over 51.25 metres and 100 metres south of Trench PRTR11-010 which trends north-south and assayed 0.78 g/t Au and 980 ppm Cu over 107.0 metres. An area map of the trenches is provided below the summary table.

Trench PRTR11-014 (the final completed trench on the Primavera target) intersected continuous gold and copper mineralization over the entire excavated length of the trench and returned a weighted average grade of 0.42 g/t Au and 1286 ppm Cu over 51.7 metres (170 feet) with the mineralization being open for expansion in all directions (see Table below). Trench PRTR11-014 was excavated in a north-easterly direction and starts approximately 5.0 metres from the east end of trench TRPR11-012 which assayed 0.70 g/t Au and 1313 ppm Cu over 58.0 metres.

Mineralization in the trenches consists of stockwork veining in highly oxidized andesite and microdiorite. Sheeted and banded quartz-magnetite veins and veinlets have also been observed in multiple vein orientations. Textures and mineralization characteristics observed in the trenches are indicative of different zones within a gold porphyry system.

The table below summarizes the Primavera sampling trench results received to date:

Trench ID From (m) To(m) Interval (m) Gold (g/t ) Copper (ppm)
PRTR11-005* 0.00 51.25 51.25 1.53 680
PRTR11-010* 0.00 107.00 107.00 0.78 980
PRTR11-011* 0.00 179.40 179.40 0.63 997
PRTR11-012*
including
0.00
0.00
58.00
24.00
58.00
24.00
0.70
1.02
1,313
904
PRTR11-013*
including**
0.00
43.50
49.50
45.00
49.50
1.50
0.25
4.18
1,100
2,749
PRTR11-014
including
and
0.00
0.00
18.00
51.70
18.00
51.70
51.70
18.00
33.70
0.42
0.74
0.25
1,286
583
1,661
• Weighted averages calculated using uncut assays.

The recently excavated trenches are located within an 850 metre by 300 metre coincident gold-copper soil anomaly in a region with very limited rock exposure and no documented previous exploration. Mineralization in the trenches is characterized by abundant stockwork veining and the area is thought to be prospective for porphyry related gold-copper mineralization. The mineralized interval in the trenches is open in both directions.

Click to Enlarge

Primavera project Trenching Map 2011
Primavera Project Trenching Map 2011
 
Trench PRTR 11-005
PRTR 11-005
Stockwork quartz veining exposed in trench PRTR11-005
PRTR11-005
Stockwork quartz veining exposed in trench PRTR11-005
Stockwork quartz veining exposed in trench PRTR11-005


Click to Enlarge
FIG A - Primavera Geology
FIG A - Primavera Geology
FIG B - Primavera Pseudogravity
FIG B Primavera Pseudogravity
FIG C - Primavera Total Magnetics
FIG C - Primavera Total Magnetics
FIG D - Primavera Radiometrics Potassium
FIG D - Primavera Radiometrics Potassium
FIG E - Primavera Rock Samples
FIG E - Primavera Rock Samples
FIG H - Primavera North Grid Geology
FIG H - Primavera North Grid Geology