Which tectonic setting is least likely to host magmatic segregation deposits?

• A. Divergent margins
• B. Convergent margins
• C. Transform margins
• D. Passive continental margins

Answer: (D)

Magmatic segregation deposits form when metals partition into ore minerals as a silicate magma crystallizes and separates into distinct magmas or melts within a large intrusive body. That requires substantial, long-lived magmatic activity and the presence of sizable intrusions where metals can concentrate as they crystallize.

Divergent margins provide magma during rifting, creating mafic intrusions that can crystallize into layered bodies capable of concentrating ore minerals. Convergent margins generate magmas related to subduction, producing sizeable intrusive rocks and associated ore deposits. Transform margins may have some magmatic activity in pull-apart basins, but it’s less common and less extensive than at ridges or subduction zones.

Passive continental margins, by contrast, are tectonically quiet after breakup and largely dominated by sedimentation rather than new, large-scale magmatic intrusions. Without the sustained magmatic emplacement needed to concentrate metals, they are the least likely setting for magmatic segregation deposits.