TY - JOUR

T1 - Fluids as primary carriers of sulphur and copper in magmatic assimilation

AU - Virtanen, Ville J.

AU - Heinonen, Jussi S.

AU - Molnár, Ferenc

AU - Schmidt, Max W.

AU - Marxer, Felix

AU - Skyttä, Pietari

AU - Kueter, Nico

AU - Moslova, Karina

N1 - Funding Information: Dean Peterson and the staff of the Hibbing Drill Core Library of the Minnesota Department of Natural Resources, Lands, and Minerals Division are acknowledged for helping in acquiring the black shale sample. Giuliano Krättli, Radoslaw Michallik, and Heikki Suhonen are thanked for helping with sample preparations, Severi Juttula, Markus Metsälä, Christoph Beier, and Adam Abersteiner for helping with the analytical procedures, and Fabio Cafagna, James Connolly, and Sanni Turunen for discussions. The LA-ICP-MS data are contribution #1 from the Environmental and Mineralogical Laboratories (Hellabs) of the Department of Geosciences and Geography, University of Helsinki. The study was funded by the Academy of Finland Grants 295129 (J.S.H.), 306962 (V.J.V. and J.S.H.), and 327358 (V.J.V.). Open access funded by Helsinki University Library.

PY - 2021/12

Y1 - 2021/12

N2 - Magmas readily react with their wall-rocks forming metamorphic contact aureoles. Sulphur and possibly metal mobilization within these contact aureoles is essential in the formation of economic magmatic sulphide deposits. We performed heating and partial melting experiments on a black shale sample from the Paleoproterozoic Virginia Formation, which is the main source of sulphur for the world-class Cu-Ni sulphide deposits of the 1.1 Ga Duluth Complex, Minnesota. These experiments show that an autochthonous devolatilization fluid effectively mobilizes carbon, sulphur, and copper in the black shale within subsolidus conditions (≤ 700 °C). Further mobilization occurs when the black shale melts and droplets of Cu-rich sulphide melt and pyrrhotite form at ∼1000 °C. The sulphide droplets attach to bubbles of devolatilization fluid, which promotes buoyancy-driven transportation in silicate melt. Our study shows that devolatilization fluids can supply large proportions of sulphur and copper in mafic–ultramafic layered intrusion-hosted Cu-Ni sulphide deposits.

AB - Magmas readily react with their wall-rocks forming metamorphic contact aureoles. Sulphur and possibly metal mobilization within these contact aureoles is essential in the formation of economic magmatic sulphide deposits. We performed heating and partial melting experiments on a black shale sample from the Paleoproterozoic Virginia Formation, which is the main source of sulphur for the world-class Cu-Ni sulphide deposits of the 1.1 Ga Duluth Complex, Minnesota. These experiments show that an autochthonous devolatilization fluid effectively mobilizes carbon, sulphur, and copper in the black shale within subsolidus conditions (≤ 700 °C). Further mobilization occurs when the black shale melts and droplets of Cu-rich sulphide melt and pyrrhotite form at ∼1000 °C. The sulphide droplets attach to bubbles of devolatilization fluid, which promotes buoyancy-driven transportation in silicate melt. Our study shows that devolatilization fluids can supply large proportions of sulphur and copper in mafic–ultramafic layered intrusion-hosted Cu-Ni sulphide deposits.

UR - http://www.scopus.com/inward/record.url?scp=85119147961&partnerID=8YFLogxK

U2 - 10.1038/s41467-021-26969-3

DO - 10.1038/s41467-021-26969-3

M3 - Article

VL - 12

JO - Nature Communications

JF - Nature Communications

SN - 2041-1723

IS - 1

M1 - 6609

ER -