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INDONESIA
Indonesian Journal on Geoscience
ISSN : 23559314     EISSN : 23559306     DOI : -
Core Subject : Science,
The spirit to improve the journal to be more credible is increasing, and in 2012 it invited earth scientists in East and Southeast Asia as well as some western countries to join the journal for the editor positions in the Indonesia Journal of Geology. This is also to realize our present goal to internationalize the journal, The Indonesian Journal on Geoscience, which is open for papers of geology, geophysics, geochemistry, geodetics, geography, and soil science. This new born journal is expected to be published three times a year. As an international publication, of course it must all be written in an international language, in this case English. This adds difficulties to the effort to obtain good papers in English to publish although the credit points that an author will get are much higher.
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Search results for , issue "Vol 2, No 1 (2007)" : 10 Documents clear
Evolusi pengendapan sedimen Kuarter di daerah utara Air Musi, Kota Palembang - Sumatera Selatan Moechtar, Herman
Indonesian Journal on Geoscience Vol 2, No 1 (2007)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (748.723 KB) | DOI: 10.17014/ijog.2.1.1-13

Abstract

http://dx.doi.org/10.17014/ijog.vol2no1.20071In the studied area, the sedimentary Quaternary facies consists of fl uvial channel separated by fl oodbasin, swamp, and fl oodplain deposits. Changes in channel style from channel 1, 2, and to 3 are interpreted as the result of a change in the type of river discharge from low to high sinuosity channels. Vertical changes in the character of these fl uvial channels can be related to changes in humidity. The lateral and vertical succession of the fl oodbasin and swamp environments shows evidence of decreasing and increasing of these facies. They are the result of changes in climate. Vertical changes of the Quaternary deposit successions can be related to changes in climate. It is concluded that the subinterval facies I.a to I.c as form of channel 2 and fl oodplain facies (subinterval facies I.b) refl ects a continuosly increase in climate from minimum to climatic maximum. Whereas, from the subinterval facies I.c to II.c during deposition of the subinterval facies II.b by the occurrence of fl oodbasin facies 2, the humid climate decreased from climatic maximum to minimum. Probably, this can be called as astrostratigraphy or orbital stratigraphy.    
Hydrothermal system of the Papandayan Volcano, West Java, Indonesia and its geochemistry evolution of thermal water after the November 2002 eruption Mazot, Agnes; Bernard, Alain; Sutawidjaja, Igan Supriatman
Indonesian Journal on Geoscience Vol 2, No 1 (2007)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1346.064 KB) | DOI: 10.17014/ijog.2.1.15-29

Abstract

http://dx.doi.org/10.17014/ijog.vol2no1.20072Papandayan is a strato volcano situated in West Java, Indonesia. After the last magmatic eruptionin 1772, only few phreatic explosions have been occurring. At the present time, the activity is centeredin the northeast crater manifested by the presence of fumaroles and hot springs. In November 2002an explosive eruption occurred and ejected ash and altered rocks. Study of the altered rocks revealedthat an advanced argillic alteration took place in the hydrothermal system by an interaction betweenacid fl uids and rocks. Four zones of alteration have been formed as a limited extension along faults oracross permeable structures at different levels beneath the active crater of the volcano.Two types of acid fl uids are distinguished in the crater of the Papandayan Volcano: (1) acidsulphate-chloride water with pH values between 1.6 and 4.6, and (2) acid sulphate water with pHvalues between 1.2 and 2.5. The samples collected after the eruption revealed an increase in the SO4/Cl and Mg / Cl ratios. This evolution is likely explained by an increase in the neutralization of acidfl uids which tends to show that water-rock interactions were more signifi cant after the eruption. Thechanges in chemistry observed in 2003 were the consequence of the opening of new fractures whereunaltered or less altered volcanic rocks were in contact with the ascending acid water. The high δ34Svalues (9-17‰) observed in the acid sulphate-chloride water before the November 2002 eruptionsuggest that dissolved sulphates were mainly formed by the disproportionation of magmatic SO2. Onthe other hand, the low δ34S values (-0.3-7 ‰) observed in acid sulphate-chloride water sampled afterthe eruption suggest that the origin of dissolved sulphates for these waters is the surfi cial oxidation ofhydrogen sulphide.
Mekanisme erupsi ignimbrit Kaldera Maninjau, Sumatera Barat Pribadi, Agung; Mulyadi, Eddy; Pratomo, Indyo
Indonesian Journal on Geoscience Vol 2, No 1 (2007)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (823.541 KB) | DOI: 10.17014/ijog.2.1.31-41

Abstract

http://dx.doi.org/10.17014/ijog.vol2no1.20073Maninjau is a large collapsed caldera that was resulted from a large eruption of silicic pyroclastic material (220-250 km3), and was distributed to more than 75 km away from the source. Field observations have provided a good understanding to the eruptive mechanism of the Maninjau caldera formation, in respect to their stratigraphy, sedimentology and geochronology of the eruptive products. Two formations have been identifi ed, those are: the Maninjau Formation, comprising a sequence of ignimbrite and surge units erupted from the Maninjau Caldera, and the Malalak Formation as a prominent andesitic fall unit likely derived from the Singgalang - Tandikat Volcano that overlies the Maninjau Formation. The variable velocity of the fl ows suggests that the Maninjau eruption initiated by violent. The later phases of the eruption became more violent and associated with caldera collapse.  
Gunung api maar di Semenanjung Muria Bronto, Sutikno; Mulyaningsih, Sri
Indonesian Journal on Geoscience Vol 2, No 1 (2007)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (874.556 KB) | DOI: 10.17014/ijog.2.1.43-54

Abstract

http://dx.doi.org/10.17014/ijog.vol2no1.20074Three maars are well identifi ed in the Muria Peninsula, i.e. Bambang Maar, Gunungrowo Maar, and Gembong Maar. The maars were formed by monogenetic volcanic eruptions due to the interaction between heat source (magma), groundwater and calcareous basement rocks. This interaction is able to produce very high pressure of gas and steam causing phreatic explosions, followed by phreatomagmatic- or even magmatic explosions and ended by a lava extrusion. Satellite image analyses have recognized twelve circular features, comprising Bambang Maar, Gunungrowo Maar, and Gembaong Maar. Phisiographically, these maars are characterized by circular depressions which are surrounded by hills that are gently sloping down away from the crater or having a radier pattern morphology. Outcrops and drilling core in the circular areas that are considered as volcanic maars are lava fl ows, pyroclastic breccias, lapillistones, and tuffs, located far away from the eruption centres of Muria and Genuk Volcanoes. One of the circular features, i.e. Jepara Circular Feature, is also supported by negative anomaly (<30 mgal) showing a circular pattern. In the future, a maar volcano could possibly erupt depending on the tectonic reactivity in the region.  
Indikasi mineralisasi epitermal emas bersulfi da rendah, di Wilayah Kecamatan Bonjol, Kabupaten Pasaman, Sumatera Barat Abidin, Hamdan Z.; Harahap, Bhakti H.
Indonesian Journal on Geoscience Vol 2, No 1 (2007)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (730.785 KB) | DOI: 10.17014/ijog.2.1.55-67

Abstract

http://dx.doi.org/10.17014/ijog.vol2no1.20075Bonjol gold prospect, known as Old Dutch Gold mine, consists of several ore bodies (Malintang, Balimbing, Lubang Sempit, Lubang Belanda and Lubang Perak). The deposit hosts within the altered volcanic rocks known as Gunung Amas Formation of Early Miocene age (9.3 ± 0.4 - 11.9 ±1.0 Ma). This formation consists of various rock types such as rhyolitic tuff, volcanic breccia, dacitic tuffs and rhyolites. These rocks are moderate to strongly alter. Mineralogy of the deposit consists of gold and silver with minor pyrite, sphalerite and galena. Besides this, hematite, jarosite and manganese are also present as supergene minerals. Ore minerals are found within quartz veins ranging from few centimetres to tens of metres thick. The veins are characterized by crustiform, comb, vuggy, botroyidal, layering and bladed. Quartz is a dominant mineral as hydrothermal alteration in addition to illite, dickite, monmorillonite, kaolinite, chlorite, smectite, natrolite, nontronite, calcite, halloysite, palygorskite, muscovite, sepiolite, analcime, heulandite, clino-chlor, zircon, zoisite, laumontite, alunite, biotite and erionite. The presence of these secondary minerals could be classifi ed into prophylitic, argillic and advanced argillic types. Analytical result of gold–bearing quartz vein indicates higher content of gold (0.3%) and silver (400 ppm). In contrast, the content of sulphide minerals (Cu, Pb, and Zn) is very low (< 100 ppm). Combined geology, mineralogy, textures and alteration minerals, it is concluded that gold deposit in the area shows an indication of a low sulphidation epithermal type within Gunung Amas Formation.  
Evolusi pengendapan sedimen Kuarter di daerah utara Air Musi, Kota Palembang - Sumatera Selatan Moechtar, Herman
Indonesian Journal on Geoscience Vol 2, No 1 (2007)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (748.723 KB) | DOI: 10.17014/ijog.2.1.1-13

Abstract

http://dx.doi.org/10.17014/ijog.vol2no1.20071In the studied area, the sedimentary Quaternary facies consists of fl uvial channel separated by fl oodbasin, swamp, and fl oodplain deposits. Changes in channel style from channel 1, 2, and to 3 are interpreted as the result of a change in the type of river discharge from low to high sinuosity channels. Vertical changes in the character of these fl uvial channels can be related to changes in humidity. The lateral and vertical succession of the fl oodbasin and swamp environments shows evidence of decreasing and increasing of these facies. They are the result of changes in climate. Vertical changes of the Quaternary deposit successions can be related to changes in climate. It is concluded that the subinterval facies I.a to I.c as form of channel 2 and fl oodplain facies (subinterval facies I.b) refl ects a continuosly increase in climate from minimum to climatic maximum. Whereas, from the subinterval facies I.c to II.c during deposition of the subinterval facies II.b by the occurrence of fl oodbasin facies 2, the humid climate decreased from climatic maximum to minimum. Probably, this can be called as astrostratigraphy or orbital stratigraphy.    
Hydrothermal system of the Papandayan Volcano, West Java, Indonesia and its geochemistry evolution of thermal water after the November 2002 eruption Mazot, Agnes; Bernard, Alain; Sutawidjaja, Igan Supriatman
Indonesian Journal on Geoscience Vol 2, No 1 (2007)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1346.064 KB) | DOI: 10.17014/ijog.2.1.15-29

Abstract

http://dx.doi.org/10.17014/ijog.vol2no1.20072Papandayan is a strato volcano situated in West Java, Indonesia. After the last magmatic eruptionin 1772, only few phreatic explosions have been occurring. At the present time, the activity is centeredin the northeast crater manifested by the presence of fumaroles and hot springs. In November 2002an explosive eruption occurred and ejected ash and altered rocks. Study of the altered rocks revealedthat an advanced argillic alteration took place in the hydrothermal system by an interaction betweenacid fl uids and rocks. Four zones of alteration have been formed as a limited extension along faults oracross permeable structures at different levels beneath the active crater of the volcano.Two types of acid fl uids are distinguished in the crater of the Papandayan Volcano: (1) acidsulphate-chloride water with pH values between 1.6 and 4.6, and (2) acid sulphate water with pHvalues between 1.2 and 2.5. The samples collected after the eruption revealed an increase in the SO4/Cl and Mg / Cl ratios. This evolution is likely explained by an increase in the neutralization of acidfl uids which tends to show that water-rock interactions were more signifi cant after the eruption. Thechanges in chemistry observed in 2003 were the consequence of the opening of new fractures whereunaltered or less altered volcanic rocks were in contact with the ascending acid water. The high ?34Svalues (9-17?) observed in the acid sulphate-chloride water before the November 2002 eruptionsuggest that dissolved sulphates were mainly formed by the disproportionation of magmatic SO2. Onthe other hand, the low ?34S values (-0.3-7 ?) observed in acid sulphate-chloride water sampled afterthe eruption suggest that the origin of dissolved sulphates for these waters is the surfi cial oxidation ofhydrogen sulphide.
Mekanisme erupsi ignimbrit Kaldera Maninjau, Sumatera Barat Pribadi, Agung; Mulyadi, Eddy; Pratomo, Indyo
Indonesian Journal on Geoscience Vol 2, No 1 (2007)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (823.541 KB) | DOI: 10.17014/ijog.2.1.31-41

Abstract

http://dx.doi.org/10.17014/ijog.vol2no1.20073Maninjau is a large collapsed caldera that was resulted from a large eruption of silicic pyroclastic material (220-250 km3), and was distributed to more than 75 km away from the source. Field observations have provided a good understanding to the eruptive mechanism of the Maninjau caldera formation, in respect to their stratigraphy, sedimentology and geochronology of the eruptive products. Two formations have been identifi ed, those are: the Maninjau Formation, comprising a sequence of ignimbrite and surge units erupted from the Maninjau Caldera, and the Malalak Formation as a prominent andesitic fall unit likely derived from the Singgalang - Tandikat Volcano that overlies the Maninjau Formation. The variable velocity of the fl ows suggests that the Maninjau eruption initiated by violent. The later phases of the eruption became more violent and associated with caldera collapse.  
Gunung api maar di Semenanjung Muria Bronto, Sutikno; Mulyaningsih, Sri
Indonesian Journal on Geoscience Vol 2, No 1 (2007)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (874.556 KB) | DOI: 10.17014/ijog.2.1.43-54

Abstract

http://dx.doi.org/10.17014/ijog.vol2no1.20074Three maars are well identifi ed in the Muria Peninsula, i.e. Bambang Maar, Gunungrowo Maar, and Gembong Maar. The maars were formed by monogenetic volcanic eruptions due to the interaction between heat source (magma), groundwater and calcareous basement rocks. This interaction is able to produce very high pressure of gas and steam causing phreatic explosions, followed by phreatomagmatic- or even magmatic explosions and ended by a lava extrusion. Satellite image analyses have recognized twelve circular features, comprising Bambang Maar, Gunungrowo Maar, and Gembaong Maar. Phisiographically, these maars are characterized by circular depressions which are surrounded by hills that are gently sloping down away from the crater or having a radier pattern morphology. Outcrops and drilling core in the circular areas that are considered as volcanic maars are lava fl ows, pyroclastic breccias, lapillistones, and tuffs, located far away from the eruption centres of Muria and Genuk Volcanoes. One of the circular features, i.e. Jepara Circular Feature, is also supported by negative anomaly (<30 mgal) showing a circular pattern. In the future, a maar volcano could possibly erupt depending on the tectonic reactivity in the region.  
Indikasi mineralisasi epitermal emas bersulfi da rendah, di Wilayah Kecamatan Bonjol, Kabupaten Pasaman, Sumatera Barat Abidin, Hamdan Z.; Harahap, Bhakti H.
Indonesian Journal on Geoscience Vol 2, No 1 (2007)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (730.785 KB) | DOI: 10.17014/ijog.2.1.55-67

Abstract

http://dx.doi.org/10.17014/ijog.vol2no1.20075Bonjol gold prospect, known as Old Dutch Gold mine, consists of several ore bodies (Malintang, Balimbing, Lubang Sempit, Lubang Belanda and Lubang Perak). The deposit hosts within the altered volcanic rocks known as Gunung Amas Formation of Early Miocene age (9.3 ± 0.4 - 11.9 ±1.0 Ma). This formation consists of various rock types such as rhyolitic tuff, volcanic breccia, dacitic tuffs and rhyolites. These rocks are moderate to strongly alter. Mineralogy of the deposit consists of gold and silver with minor pyrite, sphalerite and galena. Besides this, hematite, jarosite and manganese are also present as supergene minerals. Ore minerals are found within quartz veins ranging from few centimetres to tens of metres thick. The veins are characterized by crustiform, comb, vuggy, botroyidal, layering and bladed. Quartz is a dominant mineral as hydrothermal alteration in addition to illite, dickite, monmorillonite, kaolinite, chlorite, smectite, natrolite, nontronite, calcite, halloysite, palygorskite, muscovite, sepiolite, analcime, heulandite, clino-chlor, zircon, zoisite, laumontite, alunite, biotite and erionite. The presence of these secondary minerals could be classifi ed into prophylitic, argillic and advanced argillic types. Analytical result of gold?bearing quartz vein indicates higher content of gold (0.3%) and silver (400 ppm). In contrast, the content of sulphide minerals (Cu, Pb, and Zn) is very low (< 100 ppm). Combined geology, mineralogy, textures and alteration minerals, it is concluded that gold deposit in the area shows an indication of a low sulphidation epithermal type within Gunung Amas Formation.  

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