Selodong Intrusive Complex Synopsis

Location

The Selodong Intrusive Complex (SIC) is a gold-rich copper porphyry prospect located in the southwest corner of Lombok Island, 30 km SE of the administrative city of Mataram, West Nusa Tenggara Province, Indonesia. It is on the southeast part Southern Arc's West Lombok property (see Map of Selodong Prospect Location) at a mean elevation of 180 m.

History

The SIC covers an area of approximately 7 km by 3 km and is host to at least 15 distinct porphyry copper-gold targets and associated later high sulphidation epithermal gold mineralization.  Porphyry Cu-Au mineralization was discovered during drilling in the mid-1990s by Newmont, with 35 of 52 drill holes intersecting intervals of Cu-Au mineralized diorite-porphyry and volcanics.  Most of the Newmont holes were relatively shallow (less than 100 m depth). Exploration activities ceased in 1996 because Newmont had to focus on the development of the Nearby Batu Hijau porphyry Cu-Au deposit on west Sumbawa Island, and only commenced again in early 2007 following acquisition of the property by Southern Arc.

In April 2007, Southern Arc commenced an intensive definition drilling program of two to four drill holes per target to establish the size, geometry and potential grade of the porphyry Cu-Au mineralization. Nearly 18,000 m of diamond drilling were completed by early September 2008. Drilling was carried out using man-portable drilling rigs. Two medium drilling rigs capabale of reaching a little over 600 m were used together with a deep drill capable of reaching a length of 1,100 m. Thirty holes were completed and assayed. The first seven holes and holes SLD013, SLD023 and SLD026 showed significant Cu-Au mineralization over very long intervals.

Selodong Geology

The SIC lies at the southern end of a 13-km long, northwest trending structural corridor of mineralisation and alteration along which also lie the Pelangan Gold Prospect and the Mencanggah Epithermal/Porphyry District, both also within Southern Arc's West Lombok Property (See West Lombok Geology Compilation Map). The geology of the area is characterized by a Late Oligocene to Middle Miocene low-K, calc-alkaline to alkaline andesitic volcanic and interbedded volcaniclastic rock sequence, associated low-K intermediate intrusions and minor shallow-water marine sedimentary rocks. A series of dioritic intrusive phases and later diatreme breccias are host to copper and gold mineralization.  Porphyry Cu-Au targets tend to be aligned along secondary N to NNW and E-W structures.

The SIC prospect is large and covers an unprecedented 21 km² of hydrothermal alteration, comprising 15 porphyry copper-gold drilling targets, six of which were previously drill-tested by Newmont with a further nine targets having been identified by Southern Arc. (See Map of Selodong Complex Porphyry Cu-Au Targets). Independent 3-D geophysical modeling confirms the potential for significant depth and size of the 15 drilling targets.

Definition Drill Testing of Porphyry Targets

Southern Arc carried out definition diamond drilling using man-portable rigs, with the aim to test-drill all 15 porphyry targets. Drilling was completed in 30 holes for a total drilling length of 17,859.30 m. Historical higher grade Cu-Au occurrences (Montong Botek, Blongas I, Blongas II, Kekalik, Belikat and Kedaro) were drill-tested. In addition to the deep drill, Southern Arc concurrently also had two man-portable drilling rigs capable of easily reaching a length of 600 m and theoretically somewhat deeper, depending on downhole conditions. Generally, the use of the smaller man-portable rigs made the mobilization-demobilization of the rigs between drilling sites easier, made more economic and efficient use of shareholders' funds, and minimized negative impacts on both the environment and local communities.

Drilling intersected several broad zones (up to 442.2 m) of significant Cu-Au mineralization (>0.3% Cu and 0.4 g/t Au). Within these intervals significant widths (up to 168.2 m) of high grade Cu-Au values (>0.6% Cu and 0.8 g/t Au) were intersected from intense stockworking of early A-veinlets and transitional B-veinlets, along with contact intrusive breccias. Copper sulfide mineralization is predominantly chalcopyrite, with minor bornite and chalcocite present at depth. An alteration progression shows a central K-feldspar-biotite-magnetite and chlorite-magnetite assemblages, through proximal chlorite-sericite-magnetite-clay assemblage and a distal chlorite-epidote-calcite assemblage. Later structurally-controlled phyllic assemblages and high sulfidation epithermal veins overprint the earlier porphyry Cu-Au event.

All of the first seven holes (SLD001 - SLD007) showed very encouraging and significant mineralization over long intervals. The first six holes tested three of the 15 porphyry Cu-Au targets (Montong Botek, Blongas I and Blongas II, which are three of the 15 targets identified in the Selodong porphyry complex), and all seven holes intersected broad zones (363.5 m to 442.2 m) of significant Cu-Au mineralization.

Another three holes (SLD008 - SLD010) were subsequently completed with less encouraging results (see News Release 08-02).

Hole SLD011 in north Montong Botek revealed erratic lower grade Cu-Au mineralization (see News Release 08-04), however a 25-metre intercept was encountered with a grade of 0.34 g/t Au. Results confirmed both the extensive and complicated geometry of the Montong Botek porphyry stock and interpreted subsequent diatreme breccia, which stoped out northern portions of the mineralized intrusive body. It also provided important information on the physical model of the Motong Botek intrusion close to the surface and to the north of Motong Botek.

Hole SDL012 and SLD014 were completed at Belikat, with less than encouraging results although SLD014 did return some erratic lower-graded gold intercepts [see News Release No. 08-06].

Hole SLD013 in northwest Montong Botek returned the longest intercept to date of 576.95 m averaging 0.12% Cu and 0.25 g/t Au from 0.00 m to 576.95 m. Three sub-intercepts of hole SLD013 returned much higher Au grades [see News Release No. 08-06]. 

Hole SLD015 further towards Kekalik and located 160 m west of SLD013, drilled to further test inferred NW extensions of Montong Botek Cu-Au mineralization, returned two zones of lower-grade Cu and Au mineralization [see News Release No. 08-06].

SLD016 was collared 120 m northwest of the historic Newmont drill hole PSG037 (North Kekalik target) to test moderate density porphyry quartz stockwork hosted in magnetite+chlorite±tourmaline altered diorite intrusives, coincident with a 200 by 350 m ovoid magnetic high. Aside from narrow gold intercepts (maximum 4.0 metres at 0.45 g/t Au from 42.85 to 46.85 metres) relating to narrow quartz-sulfide veins, no other significant intersections were reported.

Drill hole SLD017 was the first of two planned deep holes at Montong Botek to test the conventional vertical “beer bottle shape” concept characterized by an increase in diameter and grade of porphyry Cu-Au mineralization with depth. Analytical results of SLD017 reported a shallow intersection of 208.10 m at 0.12% Cu and 0.22 g/t Au from 0.00 m to 208.10 m, which included 13.00 m at 0.38% Cu and 0.54 g/t Au from 8.50 m to 21.50 m.

SLD018 and SLD020 were drilled to define the south and north shallow extensions of the Montong Botek porphyry.  Drill Rig No. 1 drilled the holes to approximately 450 m vertical depth and targeted shallow to medium extensions of anomalous Cu-Au intersections identified in previous Newmont and later SA drill holes.  No significant intersections were reported from either hole. Phyllic and propylitic altered diorite and porphyry equivalents, along with polymictic breccias and volcanics were intersected in both drill holes.

SLD019 was drilled in the centre of the Kedaro target and successfully intersected Cu and Au mineralized QD1, the diorite phase analogous to high-grade Cu-Au mineralization already drilled at the Montong Botek and Blongas II targets, 1.5 km to the southeast. Analytical results reported a moderate intersection of 126.45 m at 0.16% Cu and 0.23 g/t Au from 193.60 m to 320.05 m, which included 44.00 m at 0.22% Cu and 0.34 g/t Au from 195.60 m to 239.60 m. Several phases of variably altered and locally mineralized diorite were logged from surface to a depth of 578 m. The mineralized interval from 193.6 to 320.1 m corresponds with variable density quartz-stockwork ± chalcopyrite hosted within intrusive quartz diorite (QD1). Phyllic altered volcanics were logged from 578 m to the end of the hole.

SLD021 was the first hole drilled at Lapangan Geres and was completed at a length of 521 m. SLD021 returned a low tenor Cu-Au intersection of 142.55 m at 0.07% Cu and 0.14 g/t Au from 0.00 m to 142.55 m.

Hole SLD022 was drilled to test for porphyry mineralization at the southern periphery of Blongas II. It was completed at a length of 567.7 m. No significant mineralisation was intersected in the drill hole.

Hole SLD023 was the second deep hole testing for porphyry mineralization at depth on the northern periphery of Montong Botek. It was completed at a length of 871 m. This hole returned the longest drill intercept on the property as of July 10, 2008 with 855.10 m at 0.10% Cu and 0.22 g/t Au from 0.00m to 855.10 m, including 242.00 m at 0.18% Cu and 0.41 g/t Au from 210.00 m to 452.00 m and 100.00 m at 0.26% Cu and 0.70% g/t Au from 278.00 m to 378.00 m.

Hole SLD024 was targeted to test for a potential NW extension linking Montong Botek to the Kekalik target, 600 m to the northwest. It was completed at a length of 414.5 m. Only a narrow zone of low-grade gold mineralization, 20.00 m @ 0.24 g/t Au from 290.65 m was intersected within a zone of mineralized breccia clasts.

Hole SLD025 at Lapangan Geres was completed at a length of 550.1 m.  Located 160 m north of SLD021, it was drilled to test the north-trending zone of anamalous quartz stockworks at this target, which when previously sampled at the surface had reported significantly anomalous results, including 35 m @ 0.12 g/t Au. This hole returned an intercept of 132.60 m @ 0.08% Cu and 0.14 g/t Au from the surface, including 80.60 m @ 0.10% Cu and 0.16 g/t Au from 10.00 m.

Hole SLD026, the first deep hole to test the Blongas II target, was located about mid-way between SGD002 and SLD005. It intersected mineralization analagous to that observed in hole SLD004.  SLD026 mineralization from the surface comprising 334.35 m @ 0.17% Cu and 0.31 g/t Au from 0.00 m, including 104.0 m @ 0.23% Cu and 0.50 g/t Au from 222.35 m and 34.00 m @ 0.29% Cu and 0.86 g/t Au from 278.35 m. SLD026 confirms continuity of Cu-Au mineralization previously intercepted in SLD004 on the eastern side of a N-S trending post-mineralization diorite dyke. Mineralization on the western side of the dyke was not tested as bad ground conditions necessitated abandoning the hole at 756 m, short of the planned 1000-m target depth.

SLD027 was the second hole to test the Kedaro area target. It was at a length of 523.6 m. This hole was positioned to test for potentially higher-grade mineralized extensions of SLD019 and to see if significant mineralization was associated with the large irregular 400 m by 200 m magnetic anomaly lcated immediately west of the drill collar. SLD02 successfully intersected a southerly extension of mineralization returning an intercept of 174.90 m @ 0.12% Cu and 0.25 g/t Auu from 15.50 m, including 54.00 m @ 0.18% Cu and 0.37 g/t Au from 87.05 m.

Hole SLD028 at Lapangan Geres was located a further 200 m north of SLD025. It was completed at a length of 429.6 m. Although micro-diorite with localized zones of moderately developed quartz stockwork were intersected from the surface to a depth of 214 m, no significant results were reported.

Hole SLD029 at the south of Motong Botek about 220 m south-southwest of SLD003, was completed at a length of 595.2 m. It was designed to test possible southward extensions and limits of higher grade Cu-Au mineralization defined in previous holes drilled into the target. Drilling returned a mineralized intercept of: 504.65 m at 0.13% Cu and 0.16 g/t Au from 0.00 to 504.65 m including: 127.95 m at 0.14% Cu and 0.26 g/t Au from 156.70 to 284.65 m, and 100.00 m at 0.16 % Cu and 0.20 g/t Au from 404.65 to 504.65 m.

Hole SLD030, located in the northern half of the Blongas II target midway along the 200-m interval between SLD004 and SLD006, was completed at a length of 585.3 m. The hole was designed to test the continuity of moderate to high grade Cu-Au mineralization between the two previously drilled holes, together with a coincident 3D magnetic anomaly modeled at moderate depths. Drilling returned a mineralized intercept of: 472.6 m @ 0.16% Cu / 0.28 g/t Au from 98.2 to 570.8 m, which includes higher grade intervals of: 284.95 m @ 0.20% Cu / 0.35 g/t Au from 172.20 to 457.15 m, and 101.00 m @ 0.28% Cu / 0.56 g/t Au from 276.70 to 377.70 m, and 47.00 m @ 0.34% Cu / 0.74 g/t Au from 276.70 to 323.70 m.

Also:
[see Selodong Drilling & Assay Statistics Summary]
[see Montong Botek-Blongas II-Kekalik Diamond Drilling Compilation map]
[see Kedaro-Blongas I Diamond Drilling Compilation map]
[see Selodong Intrusive Complex Cross-Sections]

Confirmation of targets as one large, continuous mineralized zone