Heavy Metals Distribution in the Artisanal Gold Mining Area in Wonogiri

Artisanal and small gold mining activity in Wonogiri Regency has long been done with problems on environmental quality. This study was aimed to analyze the levels and spatial distribution of heavy metals in the mining area. Survey of  mining and amalgamation sites, sampling the soil and tailings had been conducted. There were 66 samples of soil and tailing were collected, analysis of heavy Fe, Mn, Pb, Hg, As and Co, using X-ray fluorescence (XRF). Normal distribution test of data was conducted using the Kolmogorov-Smirnov and Shapiro Wilk.  The spatial distribution of heavy metals was described using Krigging method. Contents of most heavy metals in the area studied were high, except for Co. According to the distribution pattern of heavy metals indicated that the contamination caused by the mining

Studi Petrografi Batuan Beku dan Sinter Silika di Kecamatan Alam Pauh Duo, Kabupaten Solok Selatan

Telah dilakukan analisis petrografi terhadap batuan beku dan sinter silika di Kecamatan Alam Pauh Duo, Kabupaten Solok Selatan. Penelitian ini bertujuan untuk mengetahui kenampakan mikroskopik batuan meliputi struktur dan tekstur, komposisi mineral penyusun batuan, jenis, dan nama batuan.  Batuan diambil pada empat titik di Kecamatan Alam Pauh Duo, sedangkan sinter silika diambil di sekitar mata air panas Sapan Maluluang. Batuan dan sinter silika dipreparasi menjadi sayatan tipis. Analisis dilakukan menggunakan mikroskop polarisasi dan X-Ray Diffractometer (XRD). Hasil analisis menunjukkan bahwa batuan pada Kecamatan Alam Pauh Duo didominasi oleh batuan beku basalt. Batuan ini menunjukkan struktur masa batuan yang seragam. Batuan beku basalt ini disusun oleh mineral primer dan sekunder. Mineral primer berupa plagioklas, piroksen, dan hornblen. Mineral sekunder berupa klorit, kalsit, dan kuarsa. Mineral sekunder ini mengindikasikan bahwa temperatur reservoir panas bumi di Kecamatan Alam Pauh Duo berkisar antara 120ºC-320ºC. Nilai estimasi ini berada dalam kisaran nilai estimasi temperatur reservoir yang diperoleh oleh PT. Supreme Energy yaitu 210ºC - 320ºC.Kata kunci: batuan beku basalt, petrografi, temperatur reservoi

Temporal variations of petrological characteristics of Tangkil and Rajabasa volcanic rocks, Indonesia

Tangkil and Rajabasa Volcanoes are neighbouring subduction-zone volcanoes located on the southeast tip of Sumatra Island (Sunda Strait, Indonesia). Stratigraphic correlation of lavas in Tangkil-Rajabasa volcanic area was established from field observations, morphological analysis, and K-Ar dating analysis. Detailed petrography and geochemical data of two and eleven lava units from Tangkil and Rajabasa, respectively, were then integrated with the stratigraphy to show the temporal variations. Early stage (> 4.3 Ma) effusives of Tangkil Volcano are dacitic to rhyolitic (67-71 wt. % SiO2; Tklf), whereas the later (c. 4.3 Ma) rocks are basalt to basaltic andesite (c. 52 wt. % SiO2; Tklm). Tangkil shows bimodal magmatism, of which the felsic endmember is > 71 wt. % SiO2 and < 0.1 wt. % MgO. Lavas of Rajabasa Volcano are comparatively younger (c. 0.3 to 0.1 Ma) with compositions ranging from basalt to andesite (51-62 wt. % SiO2; Rbs). Chemical variations of Rajabasa accounts for the interactions of at least three endmembers: Mg-rich medium-K basalt magma, low-Mg medium-K basalt magma, and high-K andesitic magma. During the long evolution of Rbs magma system, the temporal chemistry shows rising-falling variation in SiO2 and MgO indicating the three magmas were active. The felsic endmember magma of Rajabasa is fixed in composition (at ~62 wt. % SiO2; ~2.2 wt. % MgO). The rocks from the last Tklf and Rbs indicate open system processes by containing plagioclase and pyroxene phenocrysts that show resorption of evolved core and overgrowth of less evolved mantle. The multiple zones of dissolution-overgrowth in plagioclase crystals and the fluctuating trend in temporal whole-rock variation suggest that the changes of magmatic condition in temperature, H2O, or chemical composition were repetitive

Mapping recent shoreline changes spanning the lateral collapse of Anak Krakatau Volcano, Indonesia

We use satellite imagery to investigate the shoreline changes associated with volcanic activity in 2018–2019 at Anak Krakatau, Indonesia, spanning a major lateral collapse and period of regrowth through explosive activity. The shoreline changes have been analyzed and validated through the adaptation of an existing methodology based on Sentinel-2 multispectral imagery and developed on Google Earth Engine. This work tests the results of this method in a highly dynamic volcanic environment and validates them with manually digitized shorelines. The analysis shows that the size of the Anak Krakatau Island increased from 2.84 km2 to 3.19 km2 during 15 May 2018–1 November 2019 despite the loss of area in the 22 December 2018 lateral collapse. The lateral collapse reduced the island area to ~1.5 km2 but this was followed by a rapid increase in area in the first two months of 2019, reaching up to 3.27 km2. This was followed by a period of little change as volcanic activity declined and then by a net decrease from May 2019 to 1 November 2019 that resulted from erosion on the SW side of the island. This history of post-collapse eruptive regrowth and coastal erosion derived from the shoreline changes illuminates the potential for satellite-based automated shoreline mapping to provide databases for monitoring remote island volcanoes

GEOLOGI DAN STUDI LOGAM TANAH JARANG DAERAH KACANG BOTOR DAN SEKITARNYA, KECAMATAN BADAU, KABUPATEN BELITUNG, PROVINSI KEPULAUAN BANGKA BELITUNG

Banyaknya intrusi granit berumur Trias hingga Kapur di Kepulauan Bangka Belitung berpotensi untuk dilakukan penelitian batuan dan endapan yang mengandung unsur tanah jarang. Unsur tanah jarang merupakan unsur yang sangat langka atau ditemukan sangat sedikit di alam, berupa senyaw a kompleks umumnya senyawa fosfat dan karbonat. Seiring dengan perkembangan teknologi, unsur tanah jarang semakin dibutuhkan dan umumnya pada industri teknologi tinggi. Penelitian ini berada di daerah Kacang Botor Kecamatan Badau Kabupaten Belitung Provinsi Kepulauan Bangka Belitung dengan metode geokimia soil. Hasil dari pemetaan geologi didapatkan dua satuan geomorfologi, yaitu Satuan Perbukitan Intrusi (S11) dan Satuan Dataran Denudasional Peneplains (D5). Sedangkan untuk satuan geologi didapatkan Satuan Granit dari Formasi Tanjung Pandan dan Satuan Batupasir Kuarsa dari Formasi Tajam. Berdasarkan analisis ICP-MS (Inductively Coupled Plasma-Mass Spectrometry) sebanyak 115 conto soil diperoleh 16 unsur dan hanya 8 unsur yang dilakukan pengolahan data. Kisaran kadar kedelapan unsur tersebut antara lain 82,79-188 ppm Ce; 23,24-66 ppm La, 17,05-66 ppm Nd, 8-89 ppm Pr, 26,93-81 Li, 16-126 ppm Y; 8-51 ppm Gd; 16-140 ppm Sn. Pola sebaran unsur tanah jarang yang didapatkan yaitu berarah barat daya - timur laut. Pola sebaran ini mengikuti pola kontur litologi granit sebagai batuan sumber dan endapan residu dengan butiran halus–kasar sebagai perangkap terendapkannya mineral tanah jarang. Unsur tanah jarang saling berasosiasi dengan unsur Sn (timah), Uranium, dan Thorium

Rock Magnetic, Petrography, and Geochemistry Studies of Lava at the Ijen Volcanic Complex (IVC), Banyuwangi, East Java, Indonesia

Lava has complex geochemical characteristics based on differences in eruption centers, eruptive events, and flow emplacement. Characterization of lava is useful for understanding the geological conditions of a volcanic region. To complement geochemical methods, rock magnetic methods are being used to analyze lava. To explore the potential uses of rock magnetic methods for lava characterization, a series of magnetic measurements were completed in lava samples from eight locations in the Ijen Volcanic Complex (IVC) in Banyuwangi, East Java, Indonesia. These locations were grouped into two eruption centers: Ijen Crater and Mount Anyar. The magnetic measurements included frequency-dependent magnetic susceptibility, thermomagnetic, anhysteretic remanent magnetization (ARM), isothermal remanent magnetization (IRM), and hysteresis curve analyses. These measurements were supplemented using X-ray fluorescence, petrography analyses, and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS). Based on their lithology, lava samples were categorized into basalt, basaltic andesite, and basaltic trachyandesite. The dominant magnetic mineral contained in the sample was iron-rich titanomagnetite and titanium-rich titanomagnetite with a magnetic pseudo-single-domain and small amounts of superparamagnetic grain minerals in some samples. The significant difference in mass specific susceptibility (&chi;LF) is caused by differences in the crystallization process. The differences in susceptibility frequency dependence (&chi;FD) highlighted the differences in the magma cooling rate, demonstrated by the differences in the percentage of opaque mineral groundmass. The rock magnetic method was proven to support the geochemistry and petrography methods used to characterize lava and identify the causes of differences in lava characteristics

Geochemistry and Structure of Krakatoa Volcano in the Sunda Strait, Indonesia

The violent eruption of Krakatoa Volcano located in the Sunda Strait, Indonesia, in 1883 represents one of the deadliest eruptions in human civilization. Although lots of data have been reported, the trajectory of the subducted slab and the upper mantle structure beneath this volcano are still rather poorly known. We combined geochemical data, major, trace and rare earth elements with seismic tomograms to characterize the deep structure of Krakatoa Volcano at the junction of Sumatra and Java subduction systems. Geochemical data are in agreement with the partial melting of mantle wedge in these subduction systems, based on previous studies, and this conclusion is also supported by inferences from P-wave tomographic model. Whereas, the tomographic image of S-wave suggests that subducted slab has been intruded by hot material of mantle upwelling. The presence of both partial melting of mantle wedge and mantle upwelling in the upper mantle might be caused by the thinning of subducted slab beneath Krakatoa Volcano

Simple Statistical Testing on Existing Data of Core 39 KL SO189/2 to Reveal its Correlation Towards Sea Surface Temperature Variation

Several paleotemperature proxies using marine core sediment data have been developed and well-proven, but they need excellent laboratory handling and destructive tools. Spectrophotometer and Multi-Sensor Core Logger (MSCL) is considered rapid and non-destructive tools compared to other climate proxies. This paper enhances the correlation between existing data of spectrophotometer, MSCL, and sea surface temperature (SST) of the sediment core 39 KL from SO189/2 through a statistical test. The dataset is processed using interpolation, Pearson correlation, and K-means clustering. Pearson correlation reveals a strong correlation between spectrophotometer, MSCL, and SST. K-means clustering points out that SST is shifting from relatively colder to warmer. This study also tries to understand the source of four tephra and one terrigenous layer. It can be concluded that the spectrophotometer and MSCL have a positive correlation to SST variation. Keywords: statistical approach, existing data of SO189/2, spectrophotometer, Multi-Sensor Core Logger, sea surface temperatureBeberapa proksi paleotemperature menggunakan sedimen inti laut telah dikambangkan dan terbukti baik, namun membutuhkan penanganan laboratorium yang bagus dan bersifat destruktif. Spektrofotometer dan Multi Sensor Core Logger (MSCL) relatif lebih cepat dan tidak destruktif. Makalah ini membahas hubungan antara spektrofotometer, MSCL, dan temperature muka laut (SST) berdasarkan data sedimen inti 39 KL dari SO189/2 melalui pendekatan statistik. Data diolah menggunakan metode interpolasi, korelasi Pearson, dan kluster K-means. Korelasi Pearson menunjukkan korelasi kuat antara spektrofotometer, MSCL, dan SST. Kluster K-means menunjukkan pergeseran SST dari kondisi yang lebih dingin ke lebih hangat hubungan Stufi ini juga mencoba untuk memahami sumber 4 lapisan tefra dan 1 lapisan mineral terrigenous. Melalui studi ini, dapat disimpulkan bahwa spektrofotometer dan MSCL mempunyai korelasi positif terhadap variasi SST.Kata Kunci: Pendekatan statistik, Data existing SO189/2, spektrofotometer, Multi Sensor Core Logger, Suhu Permukaan Lau