Exploring Garnet’s Geochemical Variations: Insights into Base Metal Deposits

This study addresses a significant gap in the geochemical literature by systematically investigating garnet compositions within and around base metal deposits -- a topic that remains relatively understudied, despite the mineral's known significance in various geological contexts. Garnet, traditionally associated with diamond exploration and recognized for its potential as an indicator mineral for deposits like skarns,emerges in our research as a key geochemical tracer in the context of base metal exploration.

Focusing on the Eastern Succession of the Mount Isa Inlier in Australia, a globally significant mineral province, we characterized the major and trace element compositions of garnets associated with diverse base metal systems. Our new dataset, containing more than 2500 datapoints, was complemented by literature data compiled from a range of mineral systems including skarns, IOCGs, subaqueous volcanic-related (VMS, Broken Hill, sedimentary-exhalative), porphyry-epithermal and granite-related pegmatite systems. Comparative analyses with background metamorphic/igneous garnets reveal distinct trends in Mn-Fe and Ca-Mg space in ore-associated garnets, along with unique trace element patterns (e.g., Eu anomalies) and chalcophile element variations (e.g., Zn, Cd, Ga) in diverse ore systems.

To clarify the importance of these anomalous compositions, we refined our dataset by considering specific garnet associations and their related geological context. Garnets in the database were categorized depending on their occurrence within the ore bodies, the alteration haloes, or the background lithologies. Additionally, we carried out a multivariate statistical analysis through a principal component analysis (PCA) and subsequent cluster analysis, to identify hidden spatial patterns. Our results shed light on the geochemical variations in garnet composition across various ore systems and provide new insights into the sources of these variations.

This research not only contributes valuable geochemical data for base metal exploration but also establishes the efficacy of multivariate statistical analyses in deciphering complex garnet data structures. The implications of our findings extend beyond the Eastern Succession of the Mount Isa Inlier, fostering a broader understanding of the geochemical dynamics associated with base metal deposits globally.