Arc Exploration reports Indonesian mining ops
Tuesday, April 22 2014 - 12:54 AM WIB
ARX is exploring for gold and base metal deposits along Indonesia?s highly prospective magmatic arcs and associated geological terranes. The primary exploration targets are porphyry-related copper-gold and high-grade epithermal gold-silver veins.
Trenggalek Project, East Java (95% ARX)
Arc Exploration Limited (ARX) has a joint venture with PT. Sumber Mineral Nusantara (?SMN?), an Indonesian company which holds the Trenggalek Exploration IUP tenement that covers an area of approximately 300 km2 in the Southern Mountains of East Java.
Anglo American has entered into an agreement with ARX and SMN to farm into the Trenggalek Project. Details of this agreement were presented in the December 2012 quarterly report. Formal legal documentation in support of the Joint Venture between ARX and Anglo American was signed on 22 August 2013. Exploration activities at Trenggalek are currently managed by ARX but fully funded by Anglo American.
SMN holds a Pinjam-Pakai (?Borrow Use?) Forestry Permit for the Trenggalek IUP which is valid until the 3 November 2015 and allows the company to conduct exploration work on several targets in production forestry areas within the tenement.
Targets
The focus of early exploration work by ARX on the tenement was on gold. Several shallow intermediatesulphidation epithermal quartz vein systems associated with hydrothermal breccias and silica cappings in volcanic rocks and limestones were identified and had limited drill testing.
A new phase of exploration commenced in late 2011 for porphyry copper-gold targets. This followed the discovery of a high-sulphidation epithermal alteration system at Sumber Bening on the western side of the IUP. Other similar alteration systems have since been identified in the project area and these could be linked to porphyry gold-copper targets at depth.
Potential for major porphyry copper-gold deposits in the region is highlighted by the discovery of the Tumpangpitu deposit in the Tujuh Bukit district, located some 200 km to the east of Trenggalek. Tumpangpitu is in the same belt of rocks hosting the giant Batu Hijau and Elang copper-gold deposits on Sumbawa within the Sunda-Banda magmatic arc. Trenggalek contains a similar package of rocks to those hosting these three major porphyry deposits.
The Joint Venture with Anglo American announced in 2012 provides an opportunity to test the porphyry potential of the Trenggalek tenement.
Work Activities
Work activities during the quarter were focussed on prospects identified within the Buluroto Block Area in the southeast corner of the IUP.
Jerambah Prospect
Jerambah is located about 5 km west of the porphyry target identified at Singgahan Prospect and about 2 km west of the Buluroto Prospect.
Jerambah was originally identified as a geophysical target from the airborne magnetics survey. Subsequent prospecting and mapping highlighted extensive silica-clay-pyrite alteration occurring within a 2 km by 1.5 km area and showed indications of higher temperature clays (dickite and pyrophyllite). The presence of these higher temperature clays indicated the occurrence of a high-sulphidation epithermal footprint and therefore potential fora porphyry system at depth.
A single diamond hole (TRDD054) was drilled to test this target late last year. The hole intersected a thick package of extensively altered but weakly mineralized hydrothermal and diatreme-intrusion breccias cutting multiple igneous intrusive phases (andesite porphyry, diorite, quartz diorite and quartz-feldspar porphyry), bedded volcaniclastic and calcareous sedimentary rocks.
A petrological study was completed on a suite of 26 core samples collected from TRDD054 during the quarter.
This was done by Anthony Coote of Applied Petrologic Services & Research in New Zealand with the aim of characterising the rock types, alteration-mineralisation assemblages, and evaluating the position that the hole may have intersected a potential porphyry system.
The results of the study confirmed that the drill hole intersected diatreme intrusion breccias and calcareous volcaniclastic rocks that are texturally and compositionally similar to the rocks hosting the Tumpangpitu porphyry copper-gold deposit located to the east of Trenggalek.
The study also highlighted evidence for porphyry-related alteration minerals in some of the drill core including garnet, vesuvianite, secondary albite, K-feldspar, biotite, magnetite, epidote, actinolite/tremolite and tourmaline.
Porphyry-veined breccia intraclasts, extensive anhydrite veining, common traces of disseminated chalcopyrite and molybdenite mineralisation, and narrow structurally controlled zones of overprinting high-sulphidation epithermal alteration (pyrophyllite-dickite-rich) carrying traces of enargite and tennantite/tetrahedrite mineralisation, were also identified and indicate proximity to a porphyry system.
It was concluded from the petrological work that the results are highly encouraging and were interpreted to indicate that the hole intersected a peripheral position in a potential mineralised porphyry system.
Only one hole (TRDD054) has been drilled on this large target to date. More detailed mapping and surface sampling are in progress ahead of further drill hole planning.
Singgahan Prospect
Singgahan is located about 3km east of Buluroto Prospect. It was originally highlighted by a goldcopper drainage anomaly and as a target generated from the airborne magnetics survey.
Grid-based soil geochemical sampling and mapping completed here in the last quarter produced several geochemical anomalies within the grid area, the most significant of which was an approximately 500-m wide and 1,000-m long coincident gold-copper-molybdenum anomaly underlain by a silica-chlorite-clay-pyrite altered diorite intrusion and volcaniclastic rocks. The soil anomaly occurs within a prominent northwest-trending structural corridor that extends across the IUP and includes several other major prospects including Sentul, Buluroto, Jerambah and Sumber Bening.
Benching, continuous-chip sampling, additional mapping and one scout drill hole were completed at Singgahan during the quarter.
Benching
Contour benches were manually cut around the ridgeline to expose the source of the coincident copper-goldmolybdenum soil anomaly. A total of 1,320 m was completed in three benches (SGB01 ? SGB03). Each bench was continuously rock chip sampled and assayed for gold and a multielement package including copper and molybdenum.
Long intercepts of anomalous gold-copper-molybdenum geochemistry were returned in quartz-limonite stockworked diorite and volcaniclastic rocks.
The bench results confirmed that the coherent copper-gold-molybdenum anomaly persists in bedrock over at least 500m strike-length. The width and intensity of the mineralisation at depth is currently being investigated by scout diamond drilling.
Drilling
Scout drilling at Singgahan commenced late in the quarter. The drilling is under contract to PT. Maxidrill Indonesia using a MXD-420 man-portable diamond drill rig with a depth capacity of up to about 1,000 metres.
The first scout hole (TRDD055) was completed during the quarter and tested a coherent copper-goldmolybdenum anomaly highlighted by soil and bench sampling. The hole was drilled to a final depth of 331.7m. It intersected an altered diorite intrusion beneath a capping of locally silicified and skarnified calcareous volcaniclastic rocks. A quartz-magnetite-pyrite-anhydrite stockworkcontaining traces of disseminated chalcopyrite and molybdenite mineralisation was intersected from about 117 to 288 m down hole in the altered diorite intrusion, providing a good indication of porphyry-style veining in this prospect area. Splitting and sampling of the drill core was completed and assay results are awaited.
Buluroto Block Area
Further encouraging copper soil results were received from a large grid-based sampling program covering multiple targets in the Buluroto Block Area. In particular, a new cluster of coincident spotty copper-goldmolybdenum anomalies reporting up to 348 ppm Cu, 0.095 ppm Au and 59 ppm Mo was highlighted to the north of Jerambah Prospect. These anomalies are similar to those obtained at Jerambah and Singgahan and will be followed-up by prospecting and benching in the coming months.
Exploration expenditure at Trenggalek for the quarter totalled US$470,421, which was wholly funded by Anglo American.
Strategic Alliance with Anglo American in Papua
The Company holds a 20% interest in a Strategic Alliance with Anglo American and Indonesian parties to explore for copper-gold deposits in Papua and West Papua provinces.
The Alliance currently holds three Exploration IUP tenements owned by Indonesian parties pursuant to the Strategic Alliance. These cover nearly 3,000 km2 at the centre of the Bird?s Head peninsula in West Papua Province which cover prospective ground in the same region that hosts Grasberg - Indonesia?s largest porphyry copper-gold deposit.
Anglo American is responsible for managing and funding all exploration activities in West Papua.
No work was undertaken during the quarter. (end of excerpt)