Javier Eduardo Bustamante Pablos, MSc

In Quebec, the James Bay region is well known for the hard-rock Li-bearing deposits hosted called LCT pegmatites, which are crucial for transitioning to greener energy. Within this region lies the Trieste Project, where the swarm of spodumene-bearing pegmatites is hosted in the Neoarchean Salomon River Formation of the La Grande Subprovince, Superior Province. This research is focused on an outcrop called Dyke 1, where assay intervals, such as 28.8 meters at 1.1% Li₂O (including 6.2 meters at 2.3%) from hole DIS23-006, highlight the area’s potential as a significant lithium resource. It also provides insights into the spatial distribution of spodumene, its overgrowths, the emplacement of veinlets, alteration patterns, and the distribution of gangue minerals. During fieldwork, spatial mineralogical relationships were carefully documented through photographs and complemented by detailed field sketches. Surface rock samples and drill core samples were collected for petrographic analysis, followed by whole-rock geochemical interpretation of drill hole data. The pegmatite is composed of very coarse-grained spodumene, the primary Li-bearing mineral, along with albite ± K-feldspar ± muscovite, and accessory minerals such as apatite, beryl, and tantalite. Textures such as graphic (plagioclase + quartz intergrowths) and symplectite (spodumene + quartz intergrowths) are observed. The host rock, a pelitic schist from amphibolite facies of the Salomon River Formation, is composed of quartz ± biotite ± muscovite ± cordierite ± staurolite ± plagioclase ± tourmaline. Alteration is characterized by moderate albitization, chloritization, and sericitization in the exocontact zone, while the endocontact zone exhibits weak sericitization. The pegmatite’s whole-rock geochemical analysis indicates a high hydrothermal evolution, based on low K/Rb <90 and Nb/Ta <5 ratios, which is geochemically favorable for Li mineralization. In addition, cesium functions as a geochemical vector due to its high mobility into the country rock following the pegmatite emplacement. The integration of systematic photographs, sketches, geochemical data, and petrographic analysis will play a crucial role in understanding pegmatite formation processes, further contributing to lithium exploration efforts in the James Bay region.