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The Kyaukmyet prospect is one of the principal epithermal gold prospects in the Monywa District, Central Myanmar; its gold- and base metal-bearing quartz veins contain around 3 g/t gold. Ore minerals are mainly hosted by volcanic and volcaniclastic rocks of the Late Oligocene to Middle Miocene Magyigon Formation. The distribution of magmatic intrusions in the area is controlled by ENE-WSW trending faults; these faults are likely related to ore mineralization. Common ore minerals at the Kyaukmyet prospect include pyrite, sphalerite, galena, chalcopyrite, and electrum. They occur in mineralized crustiform-textured brecciated quartz veins and banded (colloform) and massive quartz veins. Mineralized rock is accompanied by silicification and propylitic and argillic alterations. The alteration mineral assemblages include quartz, adularia, calcite, chlorite, illite/smectite, sericite, and illite. Fluid inclusions in the quartz veins have homogenization temperatures ranging from 148 °C to 304 °C and salinities from 0.35 wt % to 2.75 wt % NaCl equiv. The quartz in the mineralized quartz veins was most likely precipitated at a depth ranges165-256 m below the paleosurface. The precipitation of gold at the Kyaukmyet prospect may have been formed by mixing large amounts of meteoric fluid with small amounts of magmatic fluid. The coexistence of liquid-rich and vapor-rich inclusions and presence of adularia and bladed calcite indicate that fluid boiling is caused the main mechanism of ore formation. The vein textures, ore mineral assemblages, alteration minerals and fluid inclusion data suggest that the Kyaukmyet prospect is a polymetallic low-sulfidation epithermal gold deposit.

Gravity satellites are one of the alternatives to conducting preliminary surveys because the cost of exploring a large area using conventional gravity methods is very expensive and takes a lot of time. Therefore, this study on Sulawesi Island uses a gravity satellite to identify fault contact boundaries. The methodology in this study consists of several steps, starting with a literature study, data collection through ICGEM, and then processing and analysis by compiling the gravity anomaly with the Sulawesi regional geological structure map, further interpreted using the classification of rock density variations from a geological perspective. The regional gravity anomaly values for Sulawesi Island and its surroundings range from -270.9 mgal to 320.8 mgal, averaging 78.99 mgal. High anomalies are estimated to be between 180 mgal and 360 mgal, dominated by land with a lithology predominance of igneous rocks, while low anomaly areas are identified in the Batui thrust subduction zone. This study concludes that the convergence of high and low gravity anomalies characterizes the fault contact boundary in the study area. This has implications for the geothermal system on Sulawesi Island, which has a significant impact as a medium for the release of hot fluids from the subsurface.

This paper aims to propose a methodology to interpret electrical resistivity tomography (ERT) in an andesitic volcanic context and to feed hydrogeological conceptual model of the structure of the aquifers in volcanic context. The study takes place in Pandaan, in the northeastern part of Arjuno Welirang volcano, Indonesia. The district relies on the groundwater supply to sustain its needs (industries, agriculture, domestics). Therefore, characterizing the aquifers boundaries and functioning is important to apply sustainable groundwater management. The methodology is in two steps, first geological and hydrogeological mapping, leading to the ERT location identifications. And second, interpretation of electrical resistivity tomography profiles with the subsurface hydrogeological dataset. In this paper, the relationships between volcanic facies and aquifer properties are well described through 15 ERT profiles, calibrated with geological outcrops, borehole logs, and hydrogeological data. The geophysical signature shows that, in the proximal–medial zone of the Arjuno Welirang volcano, major springs are located where the lava flows end (lava tip) and are in contact with a clayey layer/lahars. In the medial zone, below and above the clayey/lahars layer, the volcanic sandstone and tuff breccia respectively support unconfined and confined aquifers, with the evidence of artesian boreholes for the latter and dug wells for the former. These results lead to an improved hydrogeological conceptual model for this research area. [ABSTRACT FROM AUTHOR]

Lasem and Senjong Volcanic Complex (LSVC) is one of four Quaternary volcanic complexes with high-K magmatism distributed in the northern coast of Central Java. This research aims to understand the magmatic evolution of the volcanic complex. Morphostratigraphy analysis and field observation show twelve pyroclastic density flow units in Lasem Volcano, distributed mainly in the northern to eastern flanks, but minor occurrences in the southern and western flanks. Meanwhile, nine lava flow units of Lasem are concentrated on the south flank of the volcano. Lasem stratovolcano is attributed to four lava domes distributed on the northern and southern flanks. Senjong Volcano comprises one lava flow and four lava domes. Rocks of LSVC are composed of plagioclase, K-feldspar, hornblende, clinopyroxene, and opaque minerals embedded in the groundmass of volcanic glass and microlite. These calc-alkaline rocks range from basaltic trachyandesite to trachyte in composition. The magma of LSVC can further be grouped into High K/Rb and Low K/Rb types, which dominate the Lasem and Senjong Volcano products, respectively. These two magma types consistently show divergent trends in K/Rb and Rb/Nb plots against increasing silica, indicating distinct differentiation processes of similar magma source. [ABSTRACT FROM AUTHOR]