Ildrem Syafri
Faculty of Geology, Padjadjaran University Jln. Raya Bandung Sumedang Km 21, Jatinangor 45363

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The origin of Cihara granodiorite from South Banten Syafri, Ildrem; Ardiansyah, Reza; Hartono, Udi
Indonesian Journal on Geoscience Vol 3, No 2 (2008)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (556.417 KB) | DOI: 10.17014/ijog.v3i2.52

Abstract

http://dx.doi.org/10.17014/ijog.vol3no2.20085Petrographical and geochemical characteristics of the Late Oligocene Cihara Granodiorite from South Banten are presented. Data show that the rock was originated from magma of a continental origin formed at a subduction zone environment. Fractional crystallization involving plagioclase, hornblende, pyroxene, and magnetite was the main process responsible for the geochemical variation of the rocks from the Cihara Granodiorite. There are two possibilities of parental magmas to the Cihara Granodiorite, i.e. the basaltic/ or andesitic magma of the Cikotok Formation or crustal melting magma from a subduction process. Some trace element data of the basaltic rocks from the Cikotok Formation are needed to support the first interpretation. Alternatively, heating of the Jawa lower crust by magma from either mantle or subducted slab melting caused the crustal melting to produce intermediate parent magma. Some degree of mixing between those two differ- ent magma sources during the fractionation may be involved in the petrogenesis.    
Gumuk gunung api purba bawah laut di Tawangsari - Jomboran, Sukoharjo - Wonogiri, Jawa Tengah Sudrajat, Adjat; Hartono, Gendoet; Syafri, Ildrem
Indonesian Journal on Geoscience Vol 3, No 1 (2008)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (738.494 KB) | DOI: 10.17014/ijog.v3i1.46

Abstract

http://dx.doi.org/10.17014/ijog.vol3no1.20084This paper discusses the study on the basalt volcanic rocks and the volcano morphology indicating the existence of an ancient submarine volcano in Tawangsari-Jomboran sub-regency, Sukoharjo- Wonogiri, Central Java. In general, this basalt volcanic rocks were identified as andesite breccia which might be grouped into the Mandalika Formation of Oligosen-Miosen age (Surono et al., 1992). The origin of the Mandalika Formation in relation to the classic sedimentation process and the submarine volcanism is still needed to be evaluated. The present study was based on the detailed descriptions of the rocks both in the field and in the laboratory. The autoclastic basalt outcrops consisting of breccias show the characteristics of the igneous rock fragment component embedded in the groundmass with the same composition, namely igneous rock, dark grey to black in colour; porphyritic texture, rough surface, brecciated; pillow structures, massive, fine vesicularities, amygdaloidal filled with calcite, and radial fractures; calk-alkaline andesite composition ( SiO = 54.71% , K O = 1.15% ). This rock body attains the  dimension of 2 - 5 m length, and 40 cm - 1 m in diameter with the direction of the deposition varies following the direction of the eruption source. Brecciated structures on the surface was controlled by the high cooling rate and the low flow, while the interior of the rock is massive because it was not in a direct contact to the cooler mass outside. Autoclastic basalt breccias and or the pillow basalt lava was interpreted to be formed by the undulating low gradient of morphology with the average angle of <10o. On the other hand, the low basaltic magma viscosity produced the effusive eruption related to the formation of the low angle morphology. The distance between the hills generally composed of pillow basalt is between 500 m - 1 km. The typical pillow structure of the igneous rock as described above is interpreted to be the product of the lava flow related to the effusive eruption  from a submarine volcano located under or close to the seawater surface.   
The Evolution of Gajahmungkur Paleovolcano, Wonogiri, Central Java, as A Reference to Revize the Terminology of “Old Andesite Formation” Sulaksana, Nana; Hartono, G.; Sudradjat, A.; Syafri, Ildrem
Indonesian Journal on Geoscience Vol 5, No 4 (2010)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1060.567 KB) | DOI: 10.17014/ijog.v5i4.109

Abstract

DOI: 10.17014/ijog.v5i4.109Gajahmungkur is a Tertiary paleovolcano located in Wonogiri Regency, Central Java. The volcanic product of this volcano are widely distributed and composed of important elements of the stratigraphic sequence in the Southern Mountain area. The volcanic products so far have been simply classified as “Old Andesite Formation” which apparently is not in line with the stratigraphic code and the Indonesian Stratigraphic Code. The description of paleovolcano therefore might contribute to the revision of the “Old Andesite Formation”. The evolution of Gajahmungkur paleovolcano commenced with the formation of a submarine volcano, and then at the second phase a composite volcano emerged above sea level forming a volcano island. The third phase was the self destruction resulting in a formation of a caldera. Pumiceous components dominated the products. At the fourth phase, the activities began to decline producing more basaltic rocks. The statistical analysis of the interrelation between various physical properties of the clastic rocks leads to the identification of volcanic facies and the location of the paleovolcano vent.
The Characteristics of Lahar in Merapi Volcano, Central Java as the Indicator of the Explosivity during Holocene Sudradjat, Adjat; Syafri, Ildrem; Paripurno, E. T.
Indonesian Journal on Geoscience Vol 6, No 2 (2011)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1903.942 KB) | DOI: 10.17014/ijog.v6i2.116

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DOI: 10.17014/ijog.v6i2.116Merapi Volcano in Central Java has been the most active volcano during Holocene time. As a strato volcano, Merapi exhibits alternating volcanic activities of effusive and explosive characters and self destruction. The explosivity index has evolved during the last ten thousand years. The effusive activities were characterized by the occurrence of lava flows, the development of lava dome, and the production of the “nuee ardente d’avalanche” called Merapi type. The explosive stage is frequently accompanied by the occurence of pyroclastic flows. The present investigation is attempted to reveal the relationship between the characteristics of lahar and the evolution of the activity of Merapi Volcano. The quantitative analysis was focused on the size and shape of the lahar components particularly that of pumice as the main indicators in 73 measured stratigraphic columns of lahar deposits. In addition, the main chemical element rim structures of hornblende identified in lahar components indicate the different lahar units. There are five lahar units and five groups of Merapi activities which can be distinguished. It can be concluded that the characteristics of lahar reflect the evolution of the activities in the past. The risk analyses of Merapi Volcano therefore can be enlarged to cover the possible hazard based on the lahar characteristics.
Geotectonic Configuration of Kulon Progo Area, Yogyakarta Budiadi, E.; Sudradjat, A.; Syafri, Ildrem
Indonesian Journal on Geoscience Vol 8, No 4 (2013)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (931.251 KB) | DOI: 10.17014/ijog.v8i4.168

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DOI: 10.17014/ijog.v8i4.168Kulon Progo Mountain, located west of Yogyakarta, is known as a unique morphological expression of an elongated dome frequently called “oblong dome”. The structural elements occurring in Kulon Progo Mountain were predominated by a radial pattern. Applying a quantitative method to measure various morphometric elements however, revealed that the regional geotectonic pattern apparently controlled the development of Kulon Progo Mountain. A general picture of the tectonics showed that the mountain building of Kulon Progo was not solely predominated by a vertical undation force; instead it was closely related to the general geotectonics operating in the area. The macro morphological analysis using various types of satellite imageries augmented with field visits unraveled three regional tectonic stages controlled the development of Kulon Progo Mountain. Those are Meratus, Sunda, and Java trends, operating in SW-NE, NNW-SSE, and E-W directions respectively.
Facies and Diagenetic Level of the Upper Cibulakan and Parigi Formation, in Randegan and Palimanan Area Jambak, Moeh. Ali; Syafri, Ildrem; Isnaniawardhani, Vijaya; Benyamin, Benyamin; Rodriguez, Hilarius
Indonesian Journal on Geoscience Vol 2, No 3 (2015)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (767.933 KB) | DOI: 10.17014/ijog.2.3.157-166

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DOI:10.17014/ijog.2.3.157-166This research aims to determine the facies and diagenetic level of limestone of the Upper Cibulakan and Parigi Formations, and also aims to determine the structural correlation between surface and subsurface limestones. Based on thin section analyses taken from the core and outcrop samples, there are four types of lithofacies on the Upper Cibulakan Formation, i.e. mudstone-wackestone, wackestone-packstone, packstone-grainstone, and grainstone facies, and also four types of lithofacies on the Parigi Limestone Formation, i.e. mudstone-wackestone, wackestone-packstone, packstone-grainstone, and lower mudstone-wackestone facies. The analysis of surface and subsurface limestone facies of the Upper Cibulakan and Parigi Formations led to the knowledge of the proportionality and variation of the limestone characteristics on both positions. Limestone of the Upper Cibulakan Formation was deposited locally and discontinuously, whilst the Parigi Formation limestone was deposited evenly and continuously. The structural correlation between the surface and subsurface limestone indicates that these formations were uplifted/exposed due to a local force, likely caused by the intrusion of igneous rocks, as happened in the Kromong Complex. The presence of residual hydrocarbon on the surface of the limestone samples suggests the possibility of potential hydrocarbon trapped in the limestone beneath the surface.
REE Comparison Between Muncung Granite Samples and their Weathering Products, Lingga Regency, Riau Islands Hutabarat, Johannes; Syafri, Ildrem; Irzon, Ronaldo; Sendjaja, Purnama
Indonesian Journal on Geoscience Vol 3, No 3 (2016)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.3.3.149-161

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DOI:10.17014/ijog.3.3.149-161The increasing demand for Rare Earth Elements (REE) is related to the continous development of technology, and these elements are used in modern equipments. REE can occur in igneous and sedimentary rocks in significant amounts as primary deposits, whereas the secondary REE deposit can be produced by intensive lateritic weathering of bedrocks under the tropical or subtropical climate. Lateritic process can increase REE concentration from sub-economic levels in host rocks to be more valuable. Muncung Granite is located in a tropical area of Lingga Regency, Riau Islands Province. REE occurs in the Muncung Granite and in weathered layers (saprolite, laterite, and soil). ICP-MS was applied to measure the REE content in all samples of this study. The average REE content of the Muncung Granite is 265 ppm with Eu anomaly in REE’s spider diagrams. Lateritization process has increased REE content by more than four times compared to that in the Muncung Granite. Ce and Eu anomalies in weathered layers can be associated with weathering process and initial REE contents in the host rock. Ce anomaly in a laterite layer is found to have a negative correlation to REE total enrichment. The REE level in the Muncung Granite is higher than the content in the soil and saprolite layers, but lower than that in the laterite.
Stable Isotopes and Hydrochemistry Approach for Determining the Salinization Pattern of Shallow Groundwater in Alluvium Deposit Semarang, Central Java Satrio, Satrio; Prasetio, Rasi; Hadian, Muhamad Sapari Dwi; Syafri, Ildrem
Indonesian Journal on Geoscience Vol 4, No 1 (2017)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.4.1.1-10

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DOI: 10.17014/ijog.4.1.1-10A groundwater study has been conducted in the Semarang City in August 2014, aiming to determine the source of shallow groundwater salinization using stable isotopes (18O, 2H) and water chemistry approach, and supported by local hydrogeological data. A number of shallow groundwater samples were taken at several locations with a depth of 0 - 35 m. Based on geological data, shallow groundwater of Semarang alluvium is dominated by insertion of sand-gravel and sandy-clay with average porosity of around 56.0 %. This layer is thinning towards the south and then increasingly thickening to the north and north-east of the studied area. The results of the analyses show that the characteristics of shallow groundwater, i.e. approximately 51% of groundwater, still have the original composition as meteoric water and the remaining approximately 49% obtained a shift in the isotopic composition as caused by interaction with seawater and the little influence of evaporation. The results of chemical analysis of water indicates that in dry seasons, shallow groundwater aquifers in the Semarang City is dominated by chloride (Cl-) with NaCl of water type. While the parameters of bicarbonate, chloride, and Na/Cl ratio, shallow groundwater can be classified into two groups, namely unintruded groundwater around 51% spread from the foot hills to the south towards the hills with elevations of 9 - 142 m above sea level and intruded groundwater around 49% spread from the coastline to the urban direction.
Stratigraphy Seismic and sedimentation Development of Middle Baong Sand, Aru Field, North Sumatera Basin Arfiansyah, Kurnia; Alfadli, Muhammad Kurniawan; Syafri, Ildrem; Natasia, Nanda
Journal of Geoscience, Engineering, Environment, and Technology Vol 1 No 1 (2016): JGEET Vol 01 No 01 : December (2016)
Publisher : UIR PRESS

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1297.511 KB) | DOI: 10.24273/jgeet.2016.11.7

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This paper defines the stratigraphic sequence focused on Middle Baong Sand. The analyses aim to understand the sedimentation pattern regarding to sequence stratigraphy model including its lateral and vertical succession based on seismic and well data. The study can be used in ranking the prospect for new oil field. Based on the analyses in 39 seismic sections and 2 wireline log, the area are consist of three depositional sequences, namely sequence I (consist of HST I) Sequence II (consist of TST II and LST II), and Sequence III (consist of TST III).  Baong Formation are deposited when the sea level are rising regionally at Middle Miocene (N7-N15) makes the sediment deposited in deep water environment. while Middle Baong Sand are deposited in the minor falling stage placed at N13 (Middle of Middle Miocene). In this episode, there is a change in depositional setting from bathyal to middle neritic. Clastic origin of this deposits were interpreted came from South-South West direction or from Bukit Barisan where at that time is started to uplift.
Characterization of Basement Fracture Reservoir In Field ‘X’, South Sumatera Basin, Based On The Analysis of Core And FMI Log Natasia, Nanda; Ismawan, Ismawan; Syafri, Ildrem; Riskha, Hartawi
Journal of Geoscience, Engineering, Environment, and Technology Vol 2 No 2 (2017): JGEET Vol 02 No 02 : June (2017)
Publisher : UIR PRESS

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (3544.342 KB) | DOI: 10.24273/jgeet.2017.2.2.196

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Basement reservoir is a reservoir that is located in the basement rock, comprised of either igneous rock or metamorphic rock that has secondary porosity, resulting in its capability to store oil and gas. The research was conducted at field X that is located at South Sumatra basin and it is a part of Jambi Sub-Basin. The study was focused on discussing hydrocarbon potential in Fields X, particularly at the basement metamorphic rock. The study was conducted at two wells in the field. The secondary porosity system of the basement is fracture porosity. Fracture analysis as secondary porosity system was performed on two wells, HA-1 and HA-2, by using FMI log interpretation. Based on the analysis of fracture on HA-1 well, the trend of fracture system is Northeast - Southwest (NE-SW) with a fracture porosity of 1.49%. On a different note, the trend of fracture system on HA-2 wells is East Northeast - West Southwest (ENE-WSW) with a fracture porosity of 0.888%. The effect of rock properties itself has little influence on the number of fractures as opposed to the effect of surrounding tectonic forces. The fractures are controlled by geological structures following Jambi pattern that has an orientation of Northeast - Southwest (NE-SW). Although the fracture porosity is relatively small, it is enough to storing hydrocarbons in economical quantity.