ORCID Profile
0000-0001-9249-843X
Current Organisation
Baylor College of Medicine
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: Sociedad Geologica Mexicana
Date: 28-11-2020
DOI: 10.18268/BSGM2020V72N3A110620
Abstract: The Havana–Matanzas Ophiolite contains one of the few ex les of ophiolitic platinum group minerals (PGM)-rich chromitites associated with orthopyroxenites in the mantle section of ophiolitic complexes. The chromitites occur as veins hosted by orthopyroxenite bands within mantle peridotites. The peridotites are mostly harzburgites and their accessory chromite shows high-Al compositions (Cr# [Cr/(Cr+Al), atomic ratio] = 0.39–0.50), which are typical of spinels in abyssal peridotites. Conversely, chromite from the chromitite veins and their host orthopyroxenite are high-Cr (Cr# = 0.72–0.73 and 0.62–0.69, respectively), with lower Mg# [Mg/(Mg+Fe2+), atomic ratio]. This suggests that both the chromitite and the orthopyroxenite formed from melts with boninitic affinity. The abundant PGM inclusions found in the chromitites are mainly Os-rich laurite grains, which is also characteristic of chromitites formed from magmas with boninitic affinity. Therefore, we propose that the chromitite veins and the orthopyroxenite bands probably formed contemporaneously in the fore-arc setting of an intra-oceanic arc during subduction. The chromitite-orthopyroxenite pair of the Havana-Matanzas Ophiolite could form after the reaction of a Si-rich melt with boninitic affinity and mantle harzburgite, with the orthopyroxenite bands preserving fingerprints of the infiltration of boninitic-affinity melts within the mantle. The small volume of forming chromitite could maximize the efficiency for the mechanical collection of the PGM forming in the parental melt of these rocks, resulting in the anomalous enrichment of primary PGM in the chromitites.
Publisher: Elsevier BV
Date: 11-2020
Publisher: Elsevier BV
Date: 09-2023
Publisher: Oxford University Press (OUP)
Date: 23-10-2017
DOI: 10.1093/NAR/GKX963
Publisher: Geological Society of America
Date: 07-12-2019
DOI: 10.1130/G45640.1
Publisher: Elsevier BV
Date: 12-2017
Publisher: Mineralogical Association of Canada
Date: 11-2021
Abstract: This paper focuses on a nanoscale study of nano- and micrometer-size Os-rich mineral particles hosted in a Ni-Fe-Cu sulfide globule found in an olivine megacryst from the Udachnaya pipe (Yakutia, Russia). These platinum-group element mineral particles and their host sulfide matrices were investigated using a combination of techniques, including field emission gun electron probe microanalyzer, field emission scanning electron microscopy, and focused ion beam and high-resolution transmission electron microscopy. The sulfide globule is of mantle origin, as it is hosted in primitive olivine (Fo90–93), very likely derived from the crystallization of Ni-Fe-Cu sulfide melt droplets segregated by liquid immiscibility from a basaltic melt in a volume of depleted subcontinental lithospheric mantle. Microscopic observations by means of field emission scanning electron microscopy and single-spot analysis and mapping by field emission gun electron probe microanalyzer reveal that the sulfide globule comprises a core of pyrrhotite with flame-like exsolutions (usually & μm thickness) of pentlandite, which is irregularly surrounded by a rim of granular pentlandite and chalcopyrite. Elemental mapping by energy dispersive spectroscopy (acquired using the high-resolution transmission electron microscopy) of the pyrrhotite (+ pentlandite) core reveals that pentlandite exsolution in pyrrhotite is still observable at the nanoscale as fringes of 100 to 500 nm thicknesses. The sulfide matrices of pyrrhotite, pentlandite, and chalcopyrite contain abundant nano- and micrometer-size platinum group element mineral particles. A careful inspection of eight of these platinum group element particles under focused ion beam and high-resolution transmission electron microscopy showed that they are crystalline erlichmanite (OsS2) with well-developed crystal faces that are distinctively oriented relative to their sulfide host matrices. We propose that the core of the Ni-Fe-Cu sulfide globule studied here was derived from a precursor monosulfide solid solution originally crystallized from a sulfide melt at & °C, which later decomposed into pyrrhotite and the pentlandite flame-like exsolutions upon cooling at & °C. Once solidified, the solid monosulfide solid solution reacted with non-equilibrium Cu-and Ni-rich sulfide melt(s), giving rise to the granular pentlandite in equilibrium with chalcopyrite now forming the rim of the sulfide globule. Meanwhile, nano- to micron-sized crystals of erlichmanite crystallized directly from or slightly before monosulfide solid solution from the sulfide melt. Thus, Os, and to a lesser extent Ir and Ru, were physically partitioned by preferential uptake via early formation of nanoparticles at high temperature instead of low-temperature exsolution from solid Ni-Fe-Cu sulfides. The new data provided in this paper highlight the necessity of studying platinum group element mineral particles in Ni-Fe-Cu sulfides using analytical techniques that can image nanoscale textural features in order to better understand the mechanisms of platinum group element fractionation in magmatic systems. These processes may play a crucial role in controlling the background geochemical budgets for siderophile and chalcophile elements in a wide range of mantle-derived magmas.
Publisher: Elsevier BV
Date: 11-2020
Publisher: Geological Society of America
Date: 08-2019
DOI: 10.1130/G46602Y.1
Publisher: Springer Science and Business Media LLC
Date: 15-10-2021
Publisher: Sociedad Geologica Mexicana
Date: 30-05-2019
Publisher: Elsevier BV
Date: 2021
Publisher: Elsevier BV
Date: 09-2022
Location: United States of America
No related grants have been discovered for Júlia Farré-de-Pablo.