Keterdapatan Emas Letakan dan Ikutannya di Perairan Delta Kapuas, Pontianak, Kalimantan Barat

Perairan Delta Kapuas merupakan tempat yang baik bagi akumulasinya endapan letakan asal Sungai Kapuas. Permukaan dasar lautnya ditutupi oleh sedimen pasir, pasir lanauan, lanau pasiran dan lanau. Sedimen ini mengandung logam emas (Au) dan ikutannya, yaitu perak (Ag), tembaga (Cu), timbal (Pb), seng (Zn) dan timah (Sn). Kadar terendah yaitu emas berkisar 2 - 92 ppb dan tertinggi Sn < 10 - 320 ppm. Keterdapatan emas secara lateral relatif membesar ke arah bagian hulu dan secara vertikal membesar ke bagian bawah permukaan. Keterdapatan emas dan ikutannya tersebut tidak satupun dijumpai pembawa mineral bijihnya. Namun secara kualitatif keterdapatan unsur-unsur logam ini sesuai dengan hasil analisis geokimia dari percontohan "stream sediment" dan "pan concentrate" di Sungai Delta Kapuas. Primernya diduga berkaitan dengan peristiwa Batuan Terobosan Sintang yang dijumpai secara setempat di sebelah timur daerah penelitian. Delta Kapuas Waters are a good place for placer deposits accumulation originally from Kapuas River. The seafloor sediment surface are covered by sand, silty sand, sandy silt and silt. These sediments content of gold (Au) and its associate metal, such as silver (Ag), copper (Cu), lead (Pb), zinc (Zn) and tin (Sn). The lowest content of gold is approximately between 2 - 92 ppb and the highest content of tin is approximately between < 10 - 320 ppm. Laterally, the occurrence of gold is relatively higher to the upstream part and vertically higher to the deeper part of the sediment. The existence of gold (Au) and its associate metal as mentioned above could not be traced to its ore mineral. But qualitatively the existence of these metal elements are in accordance with the result of geochemical analysis of the stream sediments and concentrate pan samples in the Delta Kapuas river. Its primary source is anticipated relate to the Sintang intrusion event which occurred locally in eastern of research area

Penelitian Lingkungan Pantai dan Logam Berat Perairan Pariaman– Padang-bungus Teluk Kabung Sumatera Barat

Kawasan pesisir Padang merupakan salah satu kawasan andalan yang menjadi prioritas untuk dikembangkan oleh Pemerintah Provinsi Sumatera Barat. Kawasan pesisir Pariaman - Padang merupakan daerah pantai abrasi, disusun oleh endapan alluvial berupa kerikil, pasir, dan lempung membentuk pantai lurus dan landai. Kawasan pesisir Padang – Bungus Teluk Kabung berupa pantai teluk, stabil, disusun oleh batuan volkanik membentuk bentang alam perbukitan dan pantai terjal. Abrasi terjadi di daerah telitian sebagai dampak Perubahan iklim global dan aktivitas manusia (anthropogenic) seperti dampak kerusakan terumbu karang terutama terjadi di kawasan pantai Pariaman - Padang. Di Padang – Bungus Teluk Kabung sedimentasi terjadi akibat dampak Perubahan rona lingkungan di kawasan hulu sungai (hinterland) yang membawa sedimen ke perairan. Mangrove dengan luasan kecil terdapat di kawasan Padang – Bungus Teluk Kabung,. Terumbu karang masih banyak dijumpai di kawasan Bungus Teluk Kabung dan sekitarnya dalam kondisi 50% rusak akibat pemboman dan Perubahan kondisi air laut yang disebabkan oleh pencemaran dari limbah kapal, industri dan rumah tangga. Kandungan Logam berat Hg sebagai zat pencemar yang terdapat pada sedimen perairan Bungus Teluk Kabung mencapai 3500 ppb di atas baku mutu sedimen (410 ppb). Kandungan logam lainnya yang punya nilai ekonomis yang terdapat di daerah telitian yaitu emas, Au (4ppb – 22ppb) dan perak, Ag (1ppm – 2ppm). Kata kunci: lingkungan pantai, pencemaran, logam berat, mineral ekonomis, Pariaman, Padang, Bungus Teluk Kabung The coastal area of Padang is one of the target coastal areas that have been prioritised to be developed by the West Sumatra Government. The coastal area of Pariaman – Padang is an erosion coast of alluvial deposits consisted of gravel, sand, and clay which form straight and gentle slope beaches. The coastal area of Padang – Bungus Kabung Bay is a stable embayment coast consisted of volcanic rocks which form undulated hilly land and cliff. Erosion occurred at the research area as impact of the global climate changes and human activities (anthropogenic) for example impact of coastal reef destruction at the area of Pariaman – Padang. At the coastal area of Padang – Bungus Kabung Bay sedimentation occurred as impact of change environments in the hinterland, which transport sediment loads to the coast. Mangroves of small square areas are distributed at the coastal area of Padang – Bungus Teluk Kabung. While coral reef distributed in large area at the coast of Bungus Kabung Bay and adjacent area in 50% condition impacted from explosion and change of sea water quality due to waste disposal from boats, industries, and houses. Heavy metal content of mercury (Hg) as a toxic element in sediment of Bungus Kabung Bay reach 3500 ppb over the sediment quality standard (410 ppb). Economic native metals found at the research area are gold, Au (4ppb – 22 ppb), and silver, Ag (1ppm – 2ppm). Key words: coastal environments, pollution, heavy metals, valuable minerals, Pariaman, Padang, Bungus Teluk Kabun

Keterdapatan Emas dan Perak dalam Sedimen Permukaan Dasar Laut di Perairan Bayah dan Cihara, Banten Selatan

Sedimen permukaan dasar laut di daerah penyelidikan lebih dari 95 % terdiri atas material sedimen klastik hasil rombakan dari batuan di daratan (terrigenous sediment). Berdasarkan teksturnya, sedimen daerah telitian dapat diklasifikasikan menjadi 4 jenis : pasir lanaun, pasir, lanau pasiran, dan pasir sedikit kerikilan. Secara lateral, pasir lanauan merupakan sedimen yang paling luas sebarannya. Berdasarkan ukuran butirannya, komposisi sedimen di daerah telitian didominasi oleh ukuran pasir halus, pasir sangat halus dan lanau. Di blok timur, kadar emas dalam sedimen berkisar antara 0,1 – 0,54 ppm, namun umumnya 0,3 ppm. Kadar perak antara 7,43 – 28,35 ppm, namun umumnya > 15 ppm. Emas dan perak dalam sedimen terutama diperkirakan berasal dari mineralisasi primer yang terdapat di daerah hulu S. Cimadur dan daerah hulu S. Cihara. Kata Kunci : Emas, perak, sedimen, Bayah & Cihara. Submarine surficial sediments of the investigated area consist of more than 95 % land derived sediments. Based on textural classification the sediments are divided into 4 units: silty sand, sand, sandy slit and slightly gravelly sand. Laterally silty sand are the widest distribution. Based on grain size analyses, the composition of the sediment consists of fine sand, very fine sand and silt grain sizes. The Gold (Au) content within the sediment of the east block area ranges beetwen 0,1 – 0,54 ppm, but generally less than 0.3 ppm. The Silver (Ag) content ranges between 5,62 - 30,85 ppm, but generally less than 15 ppm. In west block area, Au content within sediment ranges between 0,11 – 0,57 ppm, but generally > 0,3 ppm. The Ag content ranges between 7,43 – 28,35 ppm, but generally > 15 ppm. The occurrence of Au and Ag within sediments of the investigation area are mainly estimated from primary gold mineralization areas which are located in upstream areas of Cimadur and Cihara Rivers. Keyword : Gold, silver, sedimen, Bayah & Cihar

Lingkungan Pengendapan Sedimen Perangkap Gas Biogenik di Delta Sungai Kapuas Kalimantan Barat

Lingkungan pengendapan delta Sungai Kapuas di Kalimantan Barat terdiri dari dataran delta atas, dataran delta bawah dan lingkungan marin. Pada wilayah pesisir, dataran delta bawah terdiri dari kanal cabang (distributary channels), rawa (swamp) pada pulau-pulau delta dan pantai. Lingkungan pengendapan marin terdiri muka delta (delta front) dan prodelta; dengan lingkungan muka delta sedimen bersifat pasiran karena mengendapkan muatan sedimen (bed load) dari sungai, sedangkan pada lingkungan prodelta, sedimen yang diendapkan bersifat suspensi pada paparan dengan pengaruh proses marin lemah. Reservoar pasir pada kanal cabang dan pantai purba delta Sungai Kapuas merupakan tempat akumulasi gas biogenik. Kata kunci: lingkungan pengendapan delta, gas biogenik, Sungai Kapuas Deltaic deposition environment of Kapuas River in Western Kalimantan is consisted of upper delta plain, lower delta plain and marine environment. Within coastal zone, lower delta plain can be classified into distributary channels, swamp, deltaic islands and coasts. Marine environment is composed of delta front and prodelta; with delta front environment characterized by sandy sediments derived from river bed load. While prodelta sediments are suspension materials deposited in shelf of weak marine influences. Sand reservoirs at paleo distributary channels and paleo coasts of Kapuas River delta is the media for biogenic gas accumulations. Key words: deltaic deposition environments, biogenic gas, Kapuas Rive

Coastal Dynamics Of Singkawang, West Kalimantan

Morphologically, Singkawang and adjacent area consist of zones beaches, undulating hills, and steep hills. Granitic rocks and alluvium as a based rock of Singkawang coasts. Generally, Singkawang coasts was developed for coastal farms, fishery pond, and beach resorts, where most of these area have been eroded. Geological and physical oceanography condition are the aspects that build the characteristics of Singkawang coast. Human activities also play an important role in managing the equilibrium and dynamics of this coastal region. This research is to determine the dynamics and coastline changes of Singkawang coasts based on the characteristics of the coastal element and sediment. The high erosion was occurred at Semalagi–Cape Bajau. The Cape Bajau - Cape Banjar is relatively stable due to headlands of this coast is characterized by igneous rocks which resistant to the erosion. The Cape Banjar – South Coasts is very intensive erosion coast. Modern shorelines of the Singkawang coast might be as a shallow marine environment which were occurred thousands years ago (pre-Recent). The high of sedimentation process is generated by global sea level change, where was occurred at that time, and might be changed the area become part of the mainland coast of Singkawang. Keywords: coastal dynamics, erosion, sedimentation, Singkawang, West Kalimantan Secara morfologi, Singkawang terdiri atas daerah patai, perbukitan bergelombang, dan perbukitan curam. Batuan granit dan alluvium mengalasi kawasan pesisir Singkawang. Pesisir Singkawang sebagian besar berupa daerah pertanian, tambak ikan, dan tempat wisata yang umumnya merupakan kawasan pantai erosi. Geologi dan oseanografi fisika merupakan aspek yang membentuk karakteristik pantai Singkawang. Aktifitas manusia juga memainkan peranan penting di dalam mengelola kesetimbangan dan dinamika pesisir daerah ini. Penelitian ini untuk mengetahui dinamika dan Perubahan garispantai Singkawang berdasarkan karakteristik dan sedimen pantai. Pantai Semalagi – Tanjung Bajau merupakan kawasan pantai erosi kuat. Tanjung Bajau – Tanjung Banjar merupakan kawasan pantai nisbi stabil ujung-ujung TanjungTanjungnya dicirikan oleh batuan beku yang tahan terhadap erosi. Tanjung Banjar – Pantai Selatan merupakan kawasan pantai erosi sangat kuat. Garispantai Singkawang pada saat ribuan tahun sebelum sekarang (pra-Recent) diperkirakan berupa kawasan lingkungan laut dangkal. Karena proses sedimentasi cukup kuat yang ditimbulkan oleh Perubahan muka laut global pada saat itu mengubah kawasan tersebut menjadi daratan pantai Singkawang. Kata kunci: Dinamika pantai, erosi, sedimentasi, Singkawang, Kalimantan Barat

Kandungan Konsentrat Emas Plaser di Perairan Bayah Kabupaten Lebak

Ekstraksi emas berdasarkan hasil amalgamasi terhadap konsentrat gisik pasir (sand beach) pada muka gisik (beach face) menunjukan bahwa di pantai Bayah dan sekitarnya mengandung emas (Au) lantak (bullion) berkisar 6 – 71 ppb dan ikutannya, perak (Ag) 4 – 47 ppb. Kadar tertinggi kandungan emas ditemukan pada muka gisik di daerah pantai Bayah dan terendah di Cihara. Hasil penambangan memperlihatkan semakin besar jumlah berat contoh asal maka kandungan emas dan ikutan yang didapat semakin besar walaupun dalam berat konsentrat yang relatif sama. Adanya penyimpangan kadar emas di pantai Bayah, selain hasil rombakan sumber batuan yang dibawa oleh aliran sungai Cimandur, diduga berasal pula dari lautan dekat pantai yang dibawa oleh gelombang laut. Daerah mineralisasi batuan berupa urat kuarsa, bijih silika dan skarn merupakan komplek Kubah Bayah yang terletak di sebelah utara daerah penelitian. Kata kunci : Gisik berpasir, muka gisik, emas letakan, amalgamasi, hasil penambangan, urat kuarsa, pantai Bayah dan sekitarnya. Gold extractions based on the amalgamation process resulted from the sand beach concentrate of the Bayah beach and its vicinity, contain gold (Au) bullion 6 - 71 ppb and its association, silver (Ag) 4 - 47 ppb. The highest and the lowest of gold content in each samples are found at the Bayah and Cihara beach areas. Result of the traditional gold mining show that the greater bulk sample, hence the greater gold content and its association eventhough in the same weight of concentrate. The occured gold anomalies in Bayah coast is resulted of source rock brought by Cimandur stream, probably deposited in the marine environment brought by wave near the coast. Rock mineralization took the form as quartz veins, ore silica and skarn represent Dome Bayah complex located in the north of research area. Keyword: Sand beach, beach face, gold placer, amalgamation, result of mining, quartz veins, Bayah and its vicinity