Presentation Information
[R7-07]Identification of solid inclusions in tin, columbite-tantalite, REE granite-pegmatite of the Kivu Belt through Petrography, Raman Spectroscopy, and Microthermometry.
*MUSA Kam's SAIDI1, MADHUSOODHAN Satish Kumar2 (1. Graduate School of Science and Technology, Niigata Univ., 2. Faculty of Science and Technology, Niigata Univ.)
Keywords:
Solid inclusions,microthermometry,critical mineral,Raman spectroscopy,dissolution temperature.
The global transition to renewable energy has intensified demand for critical minerals, including lithium (rechargeable batteries), tantalum (capacitors and aerospace components), rare earth elements (advanced electronics), and tin (electric vehicle batteries, sodium-ion batteries, and soldering). Tin occurs as cassiterite (SnO2) in hydrothermal deposits, granites, and alluvial ores. In the Democratic Republic of Congo, the Kibaran belt hosts numerous industrial minerals—tin, tungsten, niobium, tantalite, lithium, rare earth elements (REE), and gold—but fluid inclusion studies have revealed extreme supersaturation in many systems, with numerous unidentified solid phases. This research identifies solid inclusions in four Kibaran lithotypes (REE granite, tourmaline pegmatite, greisen, and tin quartz vein) using integrated petrographic microscopy, Raman spectroscopy, and microthermometry. Petrographic observation classified eight morphological solid types: S1 (euhedral cubic) as halite, S2 (subhedral cubic) as sylvite, S3 (rectangular) as a captive mineral, S4(anhedral/euhedral grain), S5 (prismatic), S6 (hexagonal), S7 (rhombic) as carbonate, and S8 (oval grain) as a metallic mineral. Raman spectroscopy revealed: (1) carbonate-sulfate daughter minerals with reduced gases (CH4, H2S, H2O) in tin quartz veins; (2) graphite, carbonate, complex hydrocarbons, and Raman-inactive phases in REE granite; (3) carbonates, boron species (HBO2), and Raman-inactive phases in tourmaline pegmatite; and (4) a carbonate-sulfate system with reduced carbon in greisen. Semi-quantitative molar fraction calculations show water (liquid + vapor) is the most abundant gas phase across all systems—highest in greisen (94 mol%) and lowest in tourmaline pegmatite (where H2S dominates). Reduced sulfur gases (H2S) occur in all systems, most prominently in tourmaline pegmatite. In Microthermometry, under vapor-saturated conditions, some solid phases dissolved before the bubble homogenization temperature, while others dissolved after it, and some did not dissolve. The microthermometry measurement has revealed that: S1 (halite) dissolved at 132 °C (REE granite), 216–260 °C (pegmatite), and 96–170 °C (tin vein), but was most stable in greisen (251–375 °C). S3 (Na/Ca carbonate) dissolved at 264–380°C (REE granite) and 515 °C (greisen). S5 (acicular tourmaline) did not dissolve, confirming its refractory nature. S8 was most stable in REE granite (550 °C). These results provide a petrogenetic framework for ore deposits in this mobile belt. Further analysis is ongoing to understand the mineralization in this formation.
