I Wayan Lugra
Marine Geological Institute of Indonesia, Jl. DR. Junjunan No. 236, Telp. 022 603 2020, 603 2201, Faksimile 022 601 7887, Bandung

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INDICATION OF GOLD AND SILVER OCCURRENCE AT SAMPIT BAY, KOTA WARINGIN TIMUR DISTRICT, CENTRAL KALIMANTAN PROVINCE I Wayan Lugra; Udaya Kamiludin
BULLETIN OF THE MARINE GEOLOGY Vol 28, No 1 (2013)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (830.816 KB) | DOI: 10.32693/bomg.28.1.2013.50

Abstract

The study area is fluviatile deposit which consists of yellow to light gray loose sand, iron oxide, and kaoline spreading from the land shallowing to sea direction. Concentration grade for determining of gold and silver content used a total analysis of the hot mixture HF-HNO3-HClO4 with measurements "Atomic Absorption Spectrofotometry".(AAS). Highest concentration of gold and silver found at sample GCTS-31 that gold 0.096 ppm and silver 2.284 ppm, in muddy sand type sediment, at 3.1 meters depth and arround 1,250 meter length from coast line. While the lowest concentration of the gold was 0.025 ppm found at sample GBTS 14 in very fine sand type sediment located at 1.07 meter depth and approximately 320 meters length from coast line. The lowest concentration of the silver was founded at sample GBTS 25 that is 0.860 ppm in sandy mud sediment type located at 2.49 meters depth and approximately 3,000 meters length from the coast line. The gold placer is may derived from weathering of Pambuang Formation which spreads in the west and north of Sampit Bay, and transported by Mentaya River and longshore current system. Key word : sediment samples, laboratory analyses, gold, silver and Sampit Bay. Daerah penelitian merupakan endapan fluviatil terdiri dari pasir lepas berwarna kuning muda sampai abu-abu pucat, oksida besi, dan kaolin yang memiliki sebaran makin mendangkal ke arah laut. Kadar konsentrasi untuk menentukan kandungan emas dan perak menggunakan analisis total campuran HF-HNO3-HClO4 dengan metoda AAS. Analisa besar butir digunakan untuk memisahkan sedimen fraksi kasar sedangkan analisa pipet dilakukan terhadap sediment fraksi halus. Kadar emas dan perak tertinggi terdapat pada contoh GCTS -31, yaitu emas 0,096 ppm dan perak 2,284 ppm, pada jenis sedimen lumpur pasiran, di kedalaman 3,1 meter dan sekitar 1.250 meter dari garis pantai. Sedangkan kadar emas terendah yaitu 0,025 ppm terdapat pada contoh GBTS 14 pada jenis sedimen pasir sangat halus di kedalaman 1,07 meter dan sekitar 320 meter dari garis pantai. Kadar perak terendah dijumpai pada contoh GBTS 25 yaitu 0,860 ppm dengan jenis sedimen pasir lumpuran pada kedalaman 2,49 meter dan sekitar 3.000 meter dari garis pantai. Sumber emas plaser diperkirakan dari lapukan Formasi Pembuang yang memiliki sebaran cukup luas di sebelah barat dan utara Teluk Sampit dan ditransportasi oleh Sungai Mentaya dengan anak-anak sungainya, serta sistem arus memanjang pantai. Kata kunci : contoh sedimen, analisis laboratorium, emas, perak dan Perairan Teluk Sampit.
HEAVY MINERAL DISTRIBUTION PATTERNS AND CHARACTERISTICS OF SEA FLOOR SURFICIAL SEDIMENT AT EAST BALI WATERS, BALI PROVINCE I Wayan Lugra
BULLETIN OF THE MARINE GEOLOGY Vol 26, No 2 (2011)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (352.573 KB) | DOI: 10.32693/bomg.26.2.2011.38

Abstract

Analyses result of the heavy minerals that was took from beach sediments and sea floor surficial sediments was founded ten heavy minerals namely hematite, magnetite, limonite and rutile from oxide and hydroxide group, pyroxene, amphibol and zircon from silicate group, biotit from mica group, barite from sulfide group and dolomite from carbonate group. From 10 minerals identified, only magnetit distributes in the whole area, with the highest percentage of 34,15% in the sea and 35,14 % on beaches. Other heavy minerals distribute locally with the percentage of less than 0,01 %. Grain size analyses result of sea floor surficial sediment had identified six units sediment such as sand, sand with few gravel, sandy gravel, gravely sand, gravel and reef. Distribution area of the six units sediment as follows sand and sandy gravel are occupied 25 % respectively of the study area, reef 20%, sand 15 %, gravel 10 % and gravely sand occupied 5%. The best sediment for making art goods is sand sizes which is rich of heavy minerals such as magnetite, hematitre, limonite, zircon, pyroxene and amphibol. If will be exploited of the sand sediment on beach or sea floor surficial sediment, should be considering of the environment sustainable. Keyword: grain size analyses, heavy mineral, seafloor surficial sediment, besach sediment, Karang Asem Hasil analisis mineral berat dari sedimen pantai dan permukaan dasar laut dijumpai sepuluh jenis mineral berat yaitu magnetit, hematit, limonit, rutil dari kelompok oksida & hidroksida, piroksen, ampibol, sirkon dari kelompok silikat, biotit dari kelompok mika, barit dari kelompok sulfida dan dolomit dari kelompok karbonat. Dari sepuluh jenis mineral berat yang teridentifikasi hanya magnetit yang sebarannya merata di seluruh daerah penyelidikan baik di laut maupun di pantai dengan persentase tertinggi 34,15 % di laut dan 35,14% di pantai, sedangkan sembilan mineral lainnya sebarannya tidak merata atau setempat-setempat dengan persentase umumnya di bawah 0,01 %. Hasil analisis besar butir sedimen permukaan dasar laut dapat di bedakan menjadi 6 satuan yaitu pasir, pasir sedikit krikilan, pasir krikilan, krikil pasiran, krikil dan terumbu karang. Luas sebaran ke enam jenis sedimen tersebut terhadap luas daerah penelitian adalah pasir sedikit krikilan menempati 25%, pasir krikilan 25%, terumbu karang 20%, pasir 15%, krikil 10% dan menempati pasir krikilan 5%. Jenis sedimen yang baik untuk pembuatan benda seni adalah sedimen berukuran pasir dengan kandungan mineral berat yang tinggi seperti magnetit, hematit, limonit, sirkon, piroksen, dan ampibol. Bila akan dilakukan eksploitasi terhadap sedimen jenis pasir baik di laut maupun di pantai, harus memperhatikan kelestarian lingkungan. Kata kunci: analisis besar butir, mineral berat, sedimen permukaan dasar laut, sedimen pantai, Karang Asem
CHARACTERISTIC OF RARE EARTH ELEMENT IN SEDIMENT AT COASTAL AND OFFSHORE AREA OF KUNDUR ISLAND, RIAU PROVINCE Deny Setiady; I Wayan Lugra
BULLETIN OF THE MARINE GEOLOGY Vol 28, No 2 (2013)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1373.426 KB) | DOI: 10.32693/bomg.28.2.2013.57

Abstract

The study area is located at coastal and offshore Kundur and Adjacent Area, geographically located at coordinates of 0º 39'00 "0º 50'00" N and 103º 10'00 "103º 25 '00" S. Rare earth elements are found in seven seafloor surfacial sediment and 3 core samples are Cerium (15.41 to 16.88 ppm), Lanthanum (5.40 to 6.80 ppm), Ytrium (5.18 to 5, 58 ppm), Zirconium (5.05 to 5.95 ppm) and Neodymium 20.25 to 20.95 ppm). The minerals that containing of rare earth elements at the study area are apatite, zircon, monazite, and pyrochlore and xenotime. Seafloor surfacial sediment at Kundur are composed by silt (Z), sandy silt (sZ), sandy gravel, mud and sand. Silt unit covering nearly 55% of the study area and followed by sandy gravel, sand, silt and sandy silt. Seafloor morphology varies those are flat morphology with gradually depth changes and a regularly shaped identation curves and holes likely a result of sand mining. Coastal characteristics consists of: sandy and muddy beach. Sandy beach has medium relief (5° - 8°), composed by medium to coarse sand, brownish yellow. The muddy beach has low relief (1° - 5°) where the edges of the beach is mangroves planted by the local peoples. Key words : rare earth elements, seabed sediments, sea floor morphology, and Kundur Island Daerah penelitian terletak di kawasan pantai dan lepas pantai perairan Pulau Kundur dan Sekitarnya. Secara geografis terletak pada koordinat 0º 39’00” - 0º 50'00” LU dan 103º 10'00”- 103º 35' 00”BT. Mineral di daerah penelitian yang mengandung unsur tanah jarang adalah mineral apatit, zirkon, monazit, dan mineral pyrochlore. Unsur tanah jarang yang dijumpai pada tujuh contoh sedimen permukaan dasar laut dan 3 contoh bor inti adalah Cerium (15,41 – 16,88 ppm), Lanthanum (5,40 – 6,80 ppm), Ytrium (5,18-5,58 ppm), Zirkonium ( 5,05-5,95 ppm) dan Neodimium 20,25 – 20,95 ppm). Sedimen permukaan dasar laut di perairan Kundur tersusun oleh lanau (Z), lanau pasiran (sZ), kerikil pasiran, lumpur dan pasir. Satuan lanau menutupi hampir 55% dari seluruh daerah penelitian diikuti oleh krikil pasiran , pasir, lumpur dan lanau pasiran. Morfologi permukaan dasar laut sangat bervariasi ada yang landai dengan perubahan kedalaman yang teratur ada juga yang berbentuk lekukan lekukan dan lubang lubang besar kemungkinan akibat dari penambangan pasir. Karakteristik pantainya terdiri dari : pantai berpasir dan pantai berlumpur.   Pantai berpasir, berelief sedang (5° - 8°), tersusun oleh pasir ukuran butir sedang sampai kasar, berwarna kuning kecoklatan. Pantai berlumpur berelief rendah berkisar antara  (1° - 5°) dimana pada bagian tepinya ditanami bakau oleh penduduk setempat. Kata kunci: unsur tanah jarang, sedimen permukaan dasar laut, morfologi permukaan dasar laut, dan Pulau Kundur
THE CHARACTERISTIC OF RECENT SEDIMENT IN SEGARA ANAKAN LAGOON, CIAMIS REGENCY, WEST JAVA I Wayan Lugra; Hananto Kurnio
BULLETIN OF THE MARINE GEOLOGY Vol 24, No 2 (2009)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1403.789 KB) | DOI: 10.32693/bomg.24.2.2009.16

Abstract

The high intensity of erosions at the rivers upstream which are rivermouthed into the Segara Anakan Lagoon, as sources of the materials which are causing the sedimentation on the lagoon systematically. Based on smear slide analyses and major element contents, source of the sediment which is deposited in the lagoon floor, was predicted as the volcanic products. This condition is supported by the existence of non biogenic materials such as quartz, mica, ferro-oxides, manganese oxides and tuff in the lagoon. Beside that, the existence of major elements such as SiO2 (36,6 – 51,4%) Al2O3 (13,38 – 24,70%), and Fe2O3 (8,69 – 30,6%), is particular element indicators of volcanic products. The lithology in the survey area are volcanic products such as Jampang Formation and Panutuan Formation. Jampang Formation consist of volcano breccia, tuff intercalated with lava and sandstone, claystone, napal intercalated with conglomerate. Panutuan Formation consist of sandstone, napal and tuff, Formation Members of Tuff Napalan, Panutuan Formation, which are spread on the basinal area of Citanduy, Cibeureum, and Ciseel rivers which are rivermouthed into Segara Anakan Lagoon. Key words : smear slide, major element, Segara Anakan. Intensitas erosi yang tinggi di daerah hulu sungai-sungai yang bermuara di Segara Anakan sebagai sumber material yang mengakibatkan sedimetnasi laguna secara sistematis. Sumber pasokan sedimen yang diendapkan di dasar laguna berdasarkan analisis sayatan oles, dan unsur utama mineral diperkirakan merupakan produk vulkanik yang bersifat basa. Hal ini didukung oleh terdapatnya mineral non biogenik seperti mineral kuarsa, mika, oksida besi, oksida mangan yang dijumpai tersebar secara merata, adalah produk vulkanik, berupa tuff. Disamping itu keterdapatan unsur utama mineral seperti SiO2 dengan kisaran 36,6 – 51,4%, kemudian Al2O3 dengan kisaran 13,38 – 24,70% sedangkan Fe2O3 dengan kisaran 8,69 – 30,6%, merupakan mineral khas hasil produk vulkanik yang bersifat basa. Litologi daerah penelitian merupakan produk gunungapi, seperti Formasi Jampang yang tersusun oleh breksi gunungapi tuff dengan sisipan lava, berselingan dengan batupasir, batulempung napal dengan sisipan konglomerat. Formasi Panutuan yang tersusun batupasir, napal dan tuff, Anggota Tuff Napalan formasi Panutuan, dan berada di daerah rendahan sungai Citanduy, Cibeureum, Ciseel beserta anak anak sungainya yang bermuara di Segara Anakan. Kata kunci : sayatan oles, unsur utama, Segara Anakan
NEW LAND ACCRETION FROM 2000-2003 AT SEGARA ANAKAN LAGOON, SOUTH COAST OF WEST AND CENTRAL JAVA I Wayan Lugra; Deny Setiady
BULLETIN OF THE MARINE GEOLOGY Vol 27, No 2 (2012)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (3078.468 KB) | DOI: 10.32693/bomg.27.2.2012.49

Abstract

Segara Anakan Lagoon is an unique lagoon , where a lot of rivers enter into the lagoon such as Citanduy, Cibeureum, Cijolang, Cikawung and Ciseel Rivers. These rivers bring the sediment materials from upstream to the lagoon areas and resisted by Nusa Kambangan Island. The rate of sediment transportation every year occurred continuously and significantly. Its caused the creation of new land at eastern part of Segara Anakan Lagoon was about 376.69 hectares which is located at Cilacap District, while in the western part is about 15,78 hectares which is located at Ciamis District. Since 1999 to 2003 land accretion at Segara Anakan Lagoon was about 392.47 hectares with the rate of accretion around 78.50 hectares/year. In 1999 the area of the Segara Anakan Lagoon approximately 1,595 hectares. Based on the averages of rate land accretion, its predicted that in the middle of the 2019 whole of Segara Anakan will be land. The study had been done in 2003 by using hand drilling up to 2 meters depth, grab sampler and GPS Garmin 250 Map. The hand drilling result at accretion area, show that at eastern part of study area is composed of silt and cly, while at Nusawere Bay and Solok Jero is characterized by fine to coarse sand. Keywords : sediment materials, accretion area, and Segara Anakan Segara Anakan merupakan sebuah laguna yang unik dimana banyak sungai yang bermuara di perairan tersebut seperti Citanduy, Cibeureum Cimuntur, Cijolang, Cikawung, dan Ciseel. Sungai-sungi tersebut membawa material sedimen dari daerah aliran hulu ke kawasan laguna yang tertahan oleh Pulau Nusa Kambangan. Transportasi sedimen berlangsung terus menerus dengan laju pertambahan dari tahun ke tahun cenderung meningkat secara signifikan. Akibatnya terjadi pertambahan daratan di perairan Segara Anakan bagian timur sekitar 376,69 hektar yang termasuk wilayah Kabupaten Cilacap dan di bagian barat sekitar 15,78 hektar yang terletak di wilayah Kabupaten Ciamis. Sejak 1999 – 2003, total luas pertambahan daratan di perairan Segara Anakan sekitar 392,47 hektar dengan perkiraan laju pertambahan daratan sekitar 78,50 hektar/tahun. Tahun 1999 luas Perairan Segara Anakan kurang lebih 1.595 hektar. Berdasarkan laju pertambahan daratan rata-rata tersebut, maka diperkirakan pada pertengahan tahun 2019 Perairan Segara Anakan seluruhnya menjadi daratan. Pada tahun 2003, telah dilakukan penelitian dengan menggunakan bor tangan sampai kedalaman 2 meter, pemercontoh comot dan GPS Garmin 250 Map. Hasil pemboran di lokasi pertambahan daratan tersebut menunjukkan di bagian timur tersusun dari lanau dan lempung, sedangkan di Teluk Nusawere dan Solok Jero disusun oleh pasir berbutir halus sampai sangat kasar. Kata kunci : material sedimen, pertambahan daratan, dan Segara Anakan