DOI:10.17014/ijog.2.3.139-156This paper presents metamorphic evolution of metamorphic rocks from the Meratus Complex in South Kalimantan, Indonesia. Eight varieties of metamorphic rocks samples from this location, which are garnet-bearing epidote-barroisite schist, epidote-barroisite schist, glaucophane-quartz schist, garnet-muscovite schist, actinolite-talc schist, epidote schist, muscovite schist, and serpentinite, were investigated in detail its petrological and mineralogical characteristics by using polarization microscope and electron probe micro analyzer (EPMA). Furthermore, the pressure-temperature path of garnet-bearing epidote-barroisite schist was estimated by using mineral parageneses, reaction textures, and mineral chemistries to assess the metamorphic history. The primary stage of this rock might be represented by the assemblage of glaucophane + epidote + titanite ± paragonite. The assemblage yields 1.7 - 1.0 GPa in assumed temperature of 300 - 550 °C, which is interpreted as maximum pressure limit of prograde stage. The peak P-T condition estimated on the basis of the equilibrium of garnet rim, barroisite, phengite, epidote, and quartz, yields 547 - 690 °C and 1.1 - 1.5 GPa on the albite epidote amphibolite-facies that correspond to the depth of 38 - 50 km. The retrograde stage was presented by changing mineral compositions of amphiboles from the Si-rich barroisite to the actinolite, which lies near 0.5 GPa at 350 °C. It could be concluded that metamorphic rocks from the Meratus Complex experienced low-temperature and high-pressure conditions (blueschist-facies) prior to the peak metamorphism of the epidote amphibolite-facies. The subduction environments in Meratus Complex during Cretaceous should be responsible for this metamorphic condition.

This paper explores the experiment of Deep Learning method using Mask Region-Convolutional Neural Network (Mask R-CNN) to identify rock-forming minerals on thin section images from petrographic observation in igneous rocks, which are plagioclase, quartz, K-feldspar, pyroxene, and hornblende. Train and validation dataset consisted of 2 quartz diorites and 1 granodiorite from Monterado, West Kalimantan, 1 quartz diorite and 1 granite from Nangapinoh, West Kalimantan, and 7 andesite and 2 basalts from Bangli, Bali, while test dataset consisted of 3 quartz diorites from Monterado, West Kalimantan. This study uses 4 Mask R-CNN models, which is influenced by the lighting on polarizing microscope and using ResNet-50 architecture (Model A) or ResNet-101 (Model B), and the models that is not affected by the lighting on polarizing microscope and using ResNet-50 architecture (Model C) or ResNet-101 (Model D). From Average Precision scores, it was found that Model B has the highest score (58.0%), followed by Model A (57.8%), Model C (45.8%), and Model D (43.6%). In conclusion, the lighting of polarizing microscope is a major factor to give a better performances of Mask R-CNN models by 12%-14.4%, while the type of backbone architecture on Mask R-CNN models was not too consequential.

Guci Hot Spring is one of the tourist destinations in Central Java Province renowned for its beautiful scenery as well as its health-healing benefit. In 2016, this touristic destination attracted more than 650.000 visitors, this number is growing each year. However, this touristic spot has its hidden hazard and risk of the Slamet Volcano eruption. The historical eruptions of this volcano, recorded since the 18th century, have shown that this volcano is known for its explosive type of eruption. Despite its potential hazard and risk, this hot spring area is growing continuously as a touristic spot. Therefore, this study aims to understand tourists’ perception on volcanic hazard and risk in this area, by interviewing 31 respondents using questionnaires. The results show that 74% of respondents are aware that Slamet Volcano has different potential hazards such as volcanic ashfall, lahars, lava and pyroclastic flows. Although Guci Hot Spring is located in Slamet volcanic hazard area, only a few tourists know this information (42%). Majorities of the respondents did not have any experience on volcanic disaster (68%). Most of the respondents did not get any information on Slamet volcanic hazard (58%), while others only get information through television and/or social media. Nevertheless, almost all of the respondents claimed that they will follow any instructions given by government or related institutions if any volcanic eruption occurs (97%). Therefore, awareness program towards tourists in the volcanic touristic spot should be strengthened through different means to give information on volcanic hazard, its risk as well as mitigation and crisis management.

This paper explains the first report in metamorphic evolution of pelitic schist from Barru Complex in South Sulawesi, Indonesia. Garnet-biotitemuscovite schist was examined petrologically to assess the metamorphic evolution history, which has implications on tectonic condition of this region. The rock mainly composed of garnet, biotite, muscovite, epidote, quartz, rutile, hematite, and plagioclase. Inclusions in the garnet preserve records of prograde stage of this rock, which are epidote, titanite, quartz, and apatite. Garnet, biotite, muscovite, quartz, rutile, and plagioclase are concluded as equilibrium assemblages at peak P-T condition of this rock, which estimated at 501–562 ºC and 0.89–0.97 GPa. The result is still on the ranges of the estimated geothermal gradient P-T path of eclogite from Bantimala Complex. Similar geothermal gradients of metamorphisms might be indicated that these metamorphic rocks were metamorphosed on the similar tectonic environments. Keywords: Pelitic schist, Barru Complex, South Sulawesi, metamorphic evolution.

Bayat Ceramic Home Industry in Klaten, Central Java, Indonesia is produced from three primary locations of Melikan, Paseban, and Ndolon. The clay-sources of the ceramic were mined from Bayat and surrounding areas, which is geologically named Jiwo Hills. Characterization and identification of clay material sources of the ceramic products from these areas were done in to understand the correlation between provenance and production processes. This paper presents the first contribution on Bayat ceramic by investigating the mineralogical composition using petrography and X-Ray Diffraction (XRD) analyses. Understanding the characteristics and compositions of clay material source of ceramic in Bayat can be used to determine other clay source locations or quarry that have the similar characteristics to current clay-materials. The clay minerals of ceramic products from Melikan and Paseban are halloysite, smectite, and kaolinite, while from Ndolon are smectite and kaolinite. Monoand poly-crystalline quartz with the lithic fragments of phyllites were found in Melikan and Paseban ceramics. Ceramic from Ndolon is rich in plagioclase and lithic andesite. Clay provenance of ceramic products from Melikan and Paseban might be derived from weathered low-grade metamorphic and igneous rocks from West Jiwo Hills. While from Ndolon might be derived from weathered igneous or volcanic rocks from Kebo-Butak Formation. The amorphous silica found in the ceramic from Melikan, Paseban, and Ndolon suggests the firing process between 700–800 °C. Thus, our results provide the database of clay source characteristics to determine the following possible clay-quarry location for the raw materials of ceramic products in this location.