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The 6th LP-SAM and the 2nd PBL

Audience listening to a presentation

 

Kristine Taguibao (D3)

 

Patchewee Nualkao (D3)

 

Syahreza S. Angkasa (D2)

 

Short presentation in the PBL

 

The 6th LP-SAM* and 2nd PBL** were held on November 29th 2017, and coordinated by Assistant Professor Kofi Adomako-Ansah. Three LP students presented the status of their research works in the LP. In the PBL, the two groups (Group A and Group B) introduced their selected topics to the audience and gave a two-minute presentation on why and how they chose those topics. Below are the summaries for the LP-SAM:

Presenter 1: Kristine Taguibao (D3)
Her PhD research seeks to generate a geological model for the tectonic evolution of the Co-O epithermal gold deposit in Mindanao Island of the Philippines. She described the main geological units in the region and, conducted petrographic and geochemical studies on samples from volcanics, intrusives, and polymictic breccia in the mine area. Discrimination diagrams indicated andesite and basaltic-andesite to sub-alkaline and alkali basalt composition having a tholeiitic affinity, which contrasted the previous data of calc-alkaline affinity suggested by Sonntag et al. (2011). Gold-bearing quartz±calcite veins are hosted in chloritic to weakly argillic-altered volcanic and intrusive rocks. Vein quartz is white to purplish (amethyst) and smoky; massive or banded; and exhibits comb or crustiform, and mosaic textures. Structural data indicated that these veins, trending E-W to NNW-SSE and dipping steeply to the N and ENE, are cut by faults that are generally trending NE-SW to NNW-SSE and dipping steeply to the NW and W. Fluid inclusions in vein quartz and calcite crystals are dominantly two-phase liquid-rich inclusions. Homogenization temperatures (mainly to liquid) were mostly in the range of 200 to 240°C. Variations in the homogenization temperature-salinity space reveal isothermal mixing as a possible forming process for the quartz veins. For calcite, additional measurements are required to obtain a more coherent trend. Light δ18O compositions of the vein-forming solutions, calculated from mineral-water equilibrium fraction equations, and δ18O values of vein quartz and calcite at the homogenization temperatures, indicate a major contribution of meteoric water; and could still imply a mixed meteoric-magmatic origin for the water; a process that would be consistent with the interpretation of the fluid inclusion data. In order to finalize the time constraints on evolution of the deposit and associated geological events, two samples have been sent to the laboratory to obtain absolute ages by the K-Ar dating method.

Presenter 2: Patchewee Nualkao (D3)
The objectives of her PhD research are to understand the geology, petrochemistry and geochemistry of granitoids along the Loei Fold Belt and to clarify the tectonic setting for the distribution of various hydrothermal deposit-types (skarn, vein-type gold, and porphyry-type base metal deposits) that appear to be associated with the granitic intrusive rocks. In contrast to previous works, her study shows that the granitoids are dominantly I-type intrusive rocks with an adakitic affinity. Based on magnetic susceptibility, granitoids from five areas were classified into the ilmenite series (<1 x 10-3 SI unit: Phu Thap Fah-Phu Thep and Rayong-Chantaburi areas) and magnetite series (>1 x 10-3 SI unit: Muang Loei, Phetchabun and Nakon Sawan areas). Gold-Cu-Fe deposits correlate with the magnetite-series granitoids in Phetchabun and Nakon Sawan-Lobburi areas whereas the Sb-Au deposit correlates with the ilmenite-series granitoids in Rayong-Chantaburi area. Combination of tectonic discrimination diagrams and new age data acquired by K-Ar dating method indicate that Nakon Sawan-Lobburi volcanic arc formed during Late Triassic (221 and 219 Ma), whereas Muang Loei volcanic arc formed later, in Middle Jurassic (171 Ma). These data suggest a continuity of magmatism and volcanism, and implies an extended period of magmatic activity that was not previously recognized in the Loei Fold Belt. Most of δ34SCDT of pyrite separated from the I-type granitoids range from -1.3 to +2.2‰. The negative δ34SCDT values suggest contamination of the I-type magma by biogenic sulfur from local country rocks. Future works to be conducted will include EPMA and fluid inclusion analyses on the granitoids. At present, her data suggest that the metallogeny along Loei Fold Belt is related I-type granitoids of both magnetite and ilmenite series showing adakitic rock signatures and, these granitoids were generated over an extended period in a volcanic arc setting that was related to the subduction of Paleo-Tethys.

Presenter 3: Syahreza S. Angkasa (D2)
His PhD research on the Tangkuban Parahu volcano, Indonesia, is rooted in the understanding of the difference between phreatic (hydrothermal) eruptions and magmatic-hydrothermal eruptions, which is based on the presence of magmatic-juvenile or pyroclastic materials of the volcanic products. Analytical methods to be employed include SEM-EDS, EPMA, XRD, and stable isotope measurements (e.g., O and S). From his preliminary study, the sampled materials from his recent field survey were classified as volcanic ash from the phreatomagmatic and phreatic eruption of the Young Tangkuban Parahu. Alteration of the volcanic products comprised silica-alunite and silica+kaolinite minerals. In weak alteration zones, the alunite grains occurred as replacement of pre-existing minerals such as feldspar or glass. Textural features in pervasive-to-moderate silica-alunite alteration, along with pyrite indicates that a sulfate stage initiated the alteration mechanism and, followed by a sulfide stage. He will continue with the detail characterization of mineralogy and petrological variation of the volcanic products in an attempt to identify and constrain the condition(s) of the sub-volcanic hydrothermal system of Mt. Tangkuban Parahu (e.g., temperature and the variability of hydrothermal events). Ultimately, the study will produce a schematic model of the sub-volcanic hydrothermal system and the implication to the catastrophic climate change (e.g., SO2 flux to the troposphere).

*LP-SAM: Leading Program Student Activity Meeting
LP-SAM provides a platform for students of different research backgrounds and professors to interact.It is aimed at developing and sharpening students organization and communication skills in a global environment. At such meetings students share the activities that they are/were engaged in during the course of the academic year. These activities include reports on research progress, field survey, conferences and field trips etc.

**PBL: Project Based Learning
It is compulsory course for doctoral students. In the PBL, students are put into groups of two to five members each and tasked to identify relevant topics of global interest related to the objectives of the LP. Students in each group will construct and propose solutions to problem(s) that they identified within their topic of choice. In the discussions, students are expected to show conscious efforts at exhibiting leadership qualities to solve a common problem. Their proposed solutions are then presented in a forum at the end of the academic year.