is a sensitive method for tracing halogen provenance and evolution in magmatic systems  Rum halogens exhibit a broad scatter between mantle-and sedimentary-like halogens  PGE-rich chromitites preserve evidence of a high-I (sedimentary) component *Highlights (for review) Halogen cycling and precious metal enrichment in sub-volcanic magmatic systems: insights from the Rum layered intrusion, Scotland

The activity of volatile-rich fluids may be important in the evolution of basaltic magmatic systems and associated precious metal ore formation. There is evidence for Cl-rich fluids within the Stillwater Complex (Montana, USA), which have been linked to platinum and palladium mineralisation in the economically important J-M Reef ore body. We present the first dataset for heavy halogens (Cl, Br and I) and natural noble gas isotopes in bulk rock and mineral separates from the Peridotite Zone and the Olivine-Bearing Zone I of the Stillwater Complex, including samples from the J-M Reef and G Chromitite bodies. Our data reveal concentrations of 4 to 13500 ppm for Cl, 26 ppb to 360 ppm for Br and <1 ppb to 9 ppm I over This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America.The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.