CO2 degassing and metal enrichments during magma-carbonate interactions in the Jurassic Bonanza Arc
| dc.contributor.author | Arndt, Graham | |
| dc.date.accessioned | 2025-08-08T17:30:47Z | |
| dc.date.available | 2025-08-08T17:30:47Z | |
| dc.date.issued | 2024 | |
| dc.description.abstract | The long term (>1 Myr) atmospheric carbon budget is dominated by the carbon cycle and has great implications on habitability. One potential source of degassed carbon can be derived from the overlying continental plate where CO2 is produced from magma-carbonate interactions. Limestone assimilation is a local process that is relegated to the vicinity of the sidewall around a magma chamber (Iacono Marziano et al., 2008). As such, the network of dykes and sills offer more surface area to interact with carbonate rock opposed to voluminous plutons. Meter-scale dyke and sill samples from the Jurassic Bonanza Arc were collected from the Merry Widow Mountain region to quantify the degree of limestone assimilation. Two types of samples were investigated: (1) bulk rock samples and (2) milli-slices sampled from a single 25 cm cross-section of dyke 79B. Major and trace element chemistry was gathered by LA-ICP-MS. We discovered that the dykes show anomalous elemental abundances for Sr, U, MnO2, and Na2O. In particular, the dykes appear super-enriched in Sr opposed to their parent basalt and limestone endmembers. The enriched Sr concentrations can be explained using a binary mixing model which indicates that the dykes assimilated up to 80 wt% limestone from a primitive carbonate source. This magnitude of limestone assimilation could generate up to 35 wt% CO2 during the decarbonization of limestone into basaltic dykes. Furthermore, limestone assimilation causes desilication and calcium enrichment of the basaltic melt adjacent to the contact region (Barnes et al., 2005; Iacono Marziano et al., 2008,). Consequently, this change in melt chemistry enhances the dyke’s sulfur saturation limit and therefore its capacity to transport sulfur species. SCSS calculations indicate that the dyke contact may hold up to three times more sulfur than the dyke interior as the result of partial assimilation by limestone. An increase in sulfur saturation has important implications because it can assist in the partitioning of chalcophile elements out of a silica-rich melt, and the dissolved sulfur species can later be degassed at volcanic arcs which impacts global climate (McLinden et al. 2016; D’Souza & Canil, 2018). Overall, sulfur saturation can help model the process by which sulfide immiscibility melts form in a magma body which is a critical step in the development of ore deposits (Haldar, 2018). Supervisors: Dante Canil and Rebecca Morris | |
| dc.description.reviewstatus | Reviewed | |
| dc.description.scholarlevel | Undergraduate | |
| dc.identifier.uri | https://hdl.handle.net/1828/22572 | |
| dc.language.iso | en | |
| dc.publisher | University of Victoria | |
| dc.subject.department | School of Earth and Ocean Sciences | |
| dc.title | CO2 degassing and metal enrichments during magma-carbonate interactions in the Jurassic Bonanza Arc | |
| dc.type | Honours thesis |