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Koichiro Watanabe

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Author-ID : 4242864

Civil Engineering, Building, Construction & Architecture Earth & Planetary Sciences Energy Engineering Environmental Science

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Articles

Petrogenetic interpretation of granitoid rocks using multicationic parameters in the Sanggau Area, Kalimantan Island, Indonesia Kyaw Linn Zaw; Lucas Donny Setijadji; I Wayan Warmada; Koichiro Watanabe
Journal of Applied Geology Vol 3, No 1 (2011)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Granitoid rock compositions from a range of tectonic environments are plotted on a multicationic diagram, based on major and trace element geochemistry and K-Ar dating. This shows that there is a different tectonic nature, rock affinity and suites. The basement granitoid rocks are ranging from diorite to granite composition. They appear to the products of crystallization differentiation of a calc-alkaline magma of island affinity and range to metaluminous granites, granodiorite and tonalite. The tectonic setting has two kinds which are subduction and post-subduction. The geochemical interpretation, origin and melting of mechanism and tectonic setting shows the types of granitoid are M and I-M type. The basement of granite and granodiorite are a segment of island arc that were happened the Sintang Intrusion as post subduction or syn-collision tectonic setting. Keywords: Petrogenetic, tectonic, affinity, Sintang Intrusion, Kalimantan

Lateritization process of peridotites in Siruka, Choiseul, Solomon Islands Christopher V. Sagapoa; Akira Imai; Takeyuki Ogata; Kotaro Yonezu; Koichiro Watanabe
Journal of Applied Geology Vol 3, No 2 (2011)
Publisher : Geological Engineering Department Universitas Gadjah Mada

The lateritic weathering crusts exposed in Siruka, Choiseul Islands, Solomon Islands, were developed on the expense of serpentinized peridotite underlain by Siruka schists and Voza lavas with a subhorizontal contact. The lateritic profiles consist of three generalized zones: bedrock, saprolitic zone (weathered and decomposed zone) and the limonitic zones. The profiles demonstrate variations in depths and continuity but illustrate mineralogy and geochemical affinity down profile and are analogous to saprolitic nickel laterite deposits. Silica and magnesia in the bed rock and the saprolitic zones have been removed and only the residual elements (iron, chromium, aluminium, manganese, cobalt and nickel) remain in the limonitic zone. These elements are relatively concentrated as a result of the removal of the soluble elements. Nickel is associated with silica and magnesia, as lizardite ormixed gels (garnierite nickel ore) at the weathering fronts. On the other hand, nickel, with generally low concentrations (

MERCURY AND ARSENIC CONTAMINATION FROM SMALL SCALE GOLD MINING ACTIVITIES AT SELOGIRI AREA, CENTRAL JAVA, INDONESIA Agung Harijoko; Tin May Htun; Rodhie Saputra; I Wayan Warmada; Lucas Donny Setijadji; Akira Imai; Koichiro Watanabe
Journal of Applied Geology Vol 2, No 1 (2010)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Small scale gold mines discussed here are located at Selogiri area, Central Java, Indonesia which was mined by local community mainly during gold rush in 1990s. This Selogiri gold deposit genetically is characterized by porphyry mineralization overprinted by epithermal system. The ore minerals assemblage consists of pyrite, sphalerite, chalcopyrite, galena, chalcocite and rare arsenopyrite. Chemical analysis of soil and stream sediment sampled over 1.5 km across at the Selogiri gold extraction site indicates that the site has been contaminated with mercury due to mining activities. The mercury concentrations in soil and stream sediments collected during dry season range from 0.01 to 481 ppm and 0.01 to 139 ppm, respectively, higher than background value of 0.05 ppm. In contrast, mercury concentration in stream sediments collected during rainy season from the same location as dry season sampling ranges from 0.01 to 13.42 ppm, and one sample has anomalous value of 331 ppm. This result show that rain water may disperse and decrease mercury concentration in stream sediments. In case of arsenic, although the ore contains rare arsenic minerals, arsenic concentration in bulk rock and ore is high ranging from 8 to 59 ppm, while the arsenic concentration in tailing is much higher ranging from 5.8 to 385 ppm. Chemical analyses on pyrite reveal that the pyrite grains contain arsenic and might be the source of arsenic in Selogiri mine site. However, analysis of dug-well water demonstrates that the mercury and arsenic content is still lower than the maximum allowable concentration. Keywords: Mercury, arsenic, contamination, Selogiri, gold mine

THE USE OF FORAMINIFERA FOSSILS FOR RECONSTRUCTING THE YOGYAKARTA GRABEN, YOGYAKARTA, INDONESIA Didit Hadi Barianto; Pentatok Kuncoro; Koichiro Watanabe
Journal of Applied Geology Vol 2, No 2 (2010)
Publisher : Geological Engineering Department Universitas Gadjah Mada

The Yogyakarta region is located in the southeastern part of Central Java, Indonesia. The region forms an elongated northeast – southwest-trending central depression bordered by two parallel faults in the west and east. These major faults divided the area into three parts, including the western, central and eastern parts. Herein, we investigate the relative uplift rate of the each part by using planktonic and benthonic foraminiferas. The foraminifera will show the initial position/datum of each part before uplift. Over sixty samples (primarily limestones and marls) were taken for this research. The uplift rates of each part were different and created a depressed block control by way of parallel faults. Based on foraminifera fossil observations, each block was in the same depositional environment (inner neritic) during N9. The present positions indicate that the western part was uplifted higher than the others, with this part being uplifted more than 590 meters. The central part was uplifted less than 120 meters, and the eastern part was uplifted above an altitude of 170-300 meters. Keywords: Foraminifera fossil, planktonic, benthonic, graben, uplift

Co-Authors Agung Harijoko Akira Imai Christopher V. Sagapoa Didit Hadi Barianto I Wayan Warmada Kotaro Yonezu Kyaw Linn Zaw Lucas Donny Setijadji Pentatok Kuncoro Rodhie Saputra Takeyuki Ogata Tin May Htun

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