Indonesian Journal on Geoscience

5

Authors: DANNY ZULKIFLI HERMAN

When tailing of a mining activity is discharged into either landscape or river body, the pollutan element wastes are possible to disperse within those areas and may cause pollution on environment. The environment pollution hazards of arsenic (As), mercury (Hg), lead (Pb) and cadmium (Cd) probably occurred if tailing with the content of those elements is not handled properly. Particularly in the tropical regions, higher rates of chemical weathering and bio-chemical activity will contribute a rapid mobilization of the most potentially toxic elements. One of adverse health effects from arsenic to human life is in the case of arsenic-contained drinking waters exceed the threshold limit value. As a result, it will create chronic symptoms of toxicity within the human body such as gastro-intestinal irritation, nerve damage and tissue wastage. Tailing originated from amalgamation processing of gold ore enables its mercury waste to disperse in the vicinity of mining area and may form environment pollution by either organic or inorganic mercury. The pollution would be more hazardous to human health if mercury element in the water body transform biochemically into a compound of methylmercury. There is a variety of mechanisms by micro-organism which can bring about the formation of the very toxic methylmercury species, particularly with regard to its uptake by fish. Effects to the human health from the organic mercury include the blood-brain barrier and upsetting the metabolism of the nervous system. Whilst the main toxic effect of inorganic mercury is disruption the functions of kidneys and liver within human body. Most mining activity of base metal may discharge tailing with a significant lead (Pb) content. Lead is a cumulative poison, hence absorbing this element by human body with particularly exceeding its threshold limit value will bind strongly to a large number of molecules such as amino acids, haemoglobin, many enzymes, RNA and DNA. Then it will bring into disruption of many metabolic pathways, blood hypertension, hyperactivity and brain damage. Problems of cadmium could arise from a lead-zinc mining and smelting operation, from where pollution due to cadmium-contained tailing with additional aerial pollution associates with cadmium-contained fumes and particles. The toxic effects of cadmium to human health are suffering from lumbago-type pains, bone damage with multiple fractures of the softened bones and kidney failure. Keywords: pollution on environment, tailing, ore processing

8

Authors: IGAN SUPRIATMAN SUTAWIDJAJA, HARALDUR SIGURDSSON, and LEWIS ABRAMS

The eruption of Tambora volcano on the island of Sumbawa in 1815 is generally considered as the largest and the most violent volcanic event in recorded history. The cataclysmic eruption occurred on 11 April 1815 was initiated by Plinian eruption type on 5 April and killed more than 90,000 people on Sumbawa and nearby Lombok. The type plinian eruptions occurred twice and ejected gray pumice and ash, to form stratified deposits as thick as 40-150 cm on the slopes and mostly distributed over the district west of the volcano. Following this, at about 7 pm, on 11 April the first pyroclastic surge was generated and progressively became greater extending to almost whole direction, mainly to the north, west, and south districts from the eruption center. The deadliest volcanic eruption buried ancient villages by pyroclastic surge and flow deposits in almost intact state, thus preserving important archaeological evidence for the period. High preservation in relatively stable conditions and known date of the eruptions provide approximate dating for the archaeological remains. Archaeological excavations on the site uncovered a variety of remains were relieved by ground penetrating radar (GPR) to map structural remains of the ancient villages under the pyroclastic surge and flow deposits. These traverses showed that GPR could define structures as deep as 10 m (velocity 0.090 m/ns) and could accurately map the thickness of the stratified volcanic deposits in the Tambora village area. Keywords: plinian eruption type, pyroclastic surge, pyroclastic flow, pyroclastic airfall, geoarchaeology, GPR, ancient village SARI

11

Authors: NANA SUWARNA, BAMBANG HERMANTO, TORKIS SIHOMBING, and KUSDJI DARWIN KUSUMAH

A geological research was performed in the Berau Basin, to provide a better understanding on the potential and resources of coalbed methane (CBM) in Berau Regency, East Kalimantan Province, particularly in the Lati Coalfield. Field observation conducted in the coalfield, shows that the banded to bright banded Lati coal is dominated by the bright banded one. Petrographically, the coal consists of vitrinite comprising typical telocollinite and desmocollinite; with rare to sparse exinite, and minor inertinite, and mineral matter. Geochemical analysis shows the range of volatile matter content is from 32.65–39.60%, total sulfur from 0.35–3.04%, ash varies between 2.78–14.50%, and moisture from 12.23–19.98%. Vitrinite reflectance values (Rv), varying from 0.42–0.57%, tend to indicate that the Lati coal rank ranges from sub-bituminous B to high volatile bituminous C category, with low ash content in general. Moreover, the coal maturity level, thermally immature to early mature, leads to the assumption that the expected gas present is suggested to be of biogenic origin. The fairly well cleated Lati coal shows cleat orientations trending north - northeastward, perpendicular to nearly oblique to the syncline axis. Furthermore, coal microcleat occurs as open tensional, sub-curved to curved lines microcracks, diagonally to perpendicular to bedding plane, but some are parallel to the bedding plane. An in-situ coal gas calculation tends to indicate a low to moderate methane content level, with a value of 44.20–47.08 scf/t. However, the Q1 plus Q2 calculation exhibits the gas content ranging from 41.69 to 78.71 scf/t. Moreover, total calculated gas in-place of the P, Q, and R Seams = 5.33 m3/t = 191.56 scf/t. Keywords: coalbed methane (CBM), Lati Coalfield, Berau Basin, East Kalimantan