Insight into building a classification sequence for defining monogenetic volcanic field allocations: The case of Negros de Aras and El Negrillar in northern Chile

The distinction between nearby groups of volcanic monogenetic centers (MCs) is often unclear, yet it is crucial for understanding the formation and evolution of monogenetic volcanic fields (MVFs). This uncertainty is illustrated by the Negros de Aras and El Negrillar volcanic groups—located south of the Salar de Atacama (northern Chile)—that have been variously identified as a single MVF or two separate ones. This issue becomes especially significant when MC groups show contrasting features—such as distribution patterns, eruptive timelines, or morphological and geochemical traits—that make it difficult to define clear volcanic field allocations. We analyzed the spatial distribution patterns of 88 MCs over an area of 187 km2, along with morphometric parameters, structural controls, and whole-rock geochemistry (165 samples) associated with Negros de Aras and El Negrillar groups, to determine whether they form a single MVF or two different fields. Multiple factor analysis results reveal differences between the two groups. Based on these findings, we define two distinct MVFs: the Negros de Aras MVF and the El Negrillar MVF. Our results emphasize the importance of using a multi-parameter approach when mapping MVF allocations, especially in tectonically active regions. This case study and our integrated approach help advance efforts to better define MVF allocations at both local and regional levels, opening the challenge of the concept of monogenetic, or distributed, volcanic fields for future research.