Geology and mineralisation of the Mewet Vein, Jelai Gold Project ...

PT GMT Indonesia
Mewet Vein : Jelai Gold Project
5
5.1
HISTORY
Pre-Indochina Exploration
Before 1994, there was little sustained systematic exploration of the region by mining
companies. Much of Northeast Kalimantan was designated a Reserved Area (CTA 39A) and
was not available for mineral exploration.
CTA 39A was the reserve for a joint exploration and mapping programme at 1:250,000 scale
and a stream sediment geochemical survey conducted by a joint French-Indonesia research
team (Bureau de Recherché Geologiques et Mineres and Direktorat Jenderal Pertambang
Umum (BRGM/DSDM) during 1979-1986 (reports by Lefevre et al., 1982, Le Bel et al., 1985 &
1986 and Nagel et al., 1987). The BRGM/DSDM regional stream sediment geochemical survey
resulted in the discovery of an intrusive-skarn metallogenic province in the Long Laai area
(south of Jelai-Mewet). The skarns contain base metal-silver mineralisation associated with tinbearing
intrusives. No systematic sampling was undertaken for gold, apart from pan concentrate
analysis.
Follow up stream sediment sampling in 1:50,000 scale geological mapping were undertaken by
the BRGM/DSDM over the Long Laai region (Le Bel et al., 1986) and the Long Bia region (Nael
et al., 1987). Drilling was conducted at the Mamak prospect, but the results were disappointing.
The epithermal gold potential of north east Kalimantan was first discussed by Mr. D. Kirwin and
Mr. A. Beaudoin in 1985 (Kirwin, 1993).
RTZ (Rio Tinto) conducted a three month prospecting survey in 1990. The investigation
included stream sediment, panned concentrate, stream float, channel sampling and some tape
and compass mapping. Drainages investigated included the Sungai Turau, Mewet and Jelei.
The results were not considered encouraging at that time for RTZ
In 1993, PT Macan Mas Minerindo (Fleming, 1993) conducted a selective reconnaissance
survey over areas considered prospective based on the BRGM/DSDM survey results. The
reconnaissance survey located epithermal vein quartz in the Sungai Jelei area, silica-pyrite
breccias in the Sungai Makjun and Sungai Pangean drainages, presumably base-metal gossan
at Gunung Kelapis and confirmed the presence of base metal-silver mineralized skarns at Long
Laai.
Fleming (1993) indicated that some small scale hard rock gold mining activities were occurring
in the Bukit Pondok area associated with previously worked (1902) lead-silver veins. Episodic
local alluvial god panning was occurring in the Sungai Makjum, Saling, Betal, Geh, Malinau,
Pangean, Segah, Yin and Ptong.
5.2
Indochina Goldfields Exploration
A technical recommendation to systematically prospect the region for epithermal gold by Kirwin
(1993) was the basis for Indochina committing to exploration in Indonesia.
A geological assessment (Sennitt & Kirwin, 1994) and an aerial reconnaissance survey (Kirwin
& Sennitt, 1994) were undertaken over parts of the region, in order to confirm the prospectivity
for significant precious metal mineralisation. In July, 1994, Indochina Goldfields Ltd. entered into
a joint venture agreement, covering three CoW blocks totaling 3 million hectares, in order to
explore the region for precious metal mineralization.
Work commenced in Sungai Jelai as early as 1995 but it was not until 1995/1996 that the focus
shifted to the Sungai Mewet area, where epithermal quartz vein float was found in many
streams in the area and precipitated a full detailed geological survey of the area including
0065 JCM/GEO/2009.04 Page 15