Abstract
Ferropericlase [(Mg,Fe)O] is one of the major constituents of Earth's lower mantle and the most abundant mineral inclusion in sub-lithospheric diamonds. Although a lower mantle origin for ferropericlase inclusions has often been suggested, some studies have proposed that many of these inclusions may instead form at much shallower depths, in the deep upper mantle or transition zone. No straightforward method exists to discriminate ferropericlase of lower-mantle origin without characteristic mineral associations, such as co-existing former bridgmanite. To explore ferropericlase-diamond growth relationships, we have investigated the crystallographic orientation relationships (CORs), determined by single-crystal X-ray diffraction, between 57 ferropericlase inclusions and 37 diamonds from Juina (Brazil) and Kankan (Guinea). We show that ferropericlase inclusions can develop specific (16 inclusions in 12 diamonds), rotational statistical (9 inclusions in 7 diamonds) and random (32 inclusions in 25 diamond) CORs with respect to their diamond hosts. All measured inclusions showing a specific COR were found to be Fe-rich (XFeO > 0.30). Coexistence of non-randomly and randomly oriented ferropericlase inclusions within the same diamond indicates that their CORs may be variably affected by local growth conditions. However, the occurrence of specific CORs only for Fe-rich inclusions indicates that Fe-rich ferropericlases have a distinct genesis and are syngenetic with their host diamonds. This result provides strong support for a dual origin for ferropericlase in Earth's mantle, with Fe-rich compositions likely indicating redox growth in the upper mantle, while more Mg-rich compositions with random COR mostly representing ambient lower mantle trapped as protogenetic inclusions.
Original language | English (US) |
---|---|
Article number | 118081 |
Journal | Earth and Planetary Science Letters |
Volume | 608 |
DOIs | |
State | Published - Apr 15 2023 |
Funding
FN thanks the European Research Council (grant agreement n. 307322 ). MGP thanks the European Union's Horizon 2020 research and innovation programm (Marie Sklodowska-Curie grant, grant n. 796755 ). DN thanks the Rita Levi Montalcini programme (Italian Ministry of University and Research) for support. This study was also supported in part through the U.S. National Science Foundation (NSF) grant EAR-1853521 to SDJ. Portions of this work were performed at GeoSoilEnviroCARS (The University of Chicago, Sector 13), Advanced Photon Source (APS), Argonne National Laboratory. GeoSoilEnviroCARS is supported by NSF grant EAR-1634415 . This research used resources of the APS, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357 . Experiments at beamline 13-BM-C used the PX̂2 facility, supported by COMPRES under NSF Cooperative Agreement EAR-1661511 . We thank Mike Walter, whose the constructive suggestions helped to improve the manuscript, and Rajdeep Dasgupta for careful editorial handling. FN thanks the European Research Council (grant agreement n. 307322). MGP thanks the European Union's Horizon 2020 research and innovation programm (Marie Sklodowska-Curie grant, grant n. 796755). DN thanks the Rita Levi Montalcini programme (Italian Ministry of University and Research) for support. This study was also supported in part through the U.S. National Science Foundation (NSF) grant EAR-1853521 to SDJ. Portions of this work were performed at GeoSoilEnviroCARS (The University of Chicago, Sector 13), Advanced Photon Source (APS), Argonne National Laboratory. GeoSoilEnviroCARS is supported by NSF grant EAR-1634415. This research used resources of the APS, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. Experiments at beamline 13-BM-C used the PX̂2 facility, supported by COMPRES under NSF Cooperative Agreement EAR-1661511. We thank Mike Walter, whose the constructive suggestions helped to improve the manuscript, and Rajdeep Dasgupta for careful editorial handling.
Keywords
- crystallographic orientation relationship
- diamond
- ferropericlase
- growth relationship
- protogenesis
- syngenesis
ASJC Scopus subject areas
- Geophysics
- Geochemistry and Petrology
- Space and Planetary Science
- Earth and Planetary Sciences (miscellaneous)