Trace-Element Geochemistry of Sulfides in Upper Mantle Lherzolite Xenoliths from East Antarctica

Abstract

Sulfides in upper mantle lherzolite xenoliths from Cretaceous alkaline-ultramafic rocks in the Jetty Peninsula (East Antarctica) were studied for their major and trace-element compositions using SEM and LA-ICP-MS applied in situ. Modal abundance of sulfides is the lowest in Cpx-poor lherzolites ≤ Spl-Grt lherzolites << Cpx-rich lherzolites. Most sulfides are either interstitial (i-type) or inclusions in rock-forming minerals (e-type) with minor sulfide phases mostly present in metasomatic veinlets and carbonate-silicate interstitial patches (m-type). The main sulfide assemblage is pentlandite + chalcopyrite ± pyrrhotite; minor sulfides are polydymite, millerite, violarite, siegenite, and monosulfide solution (mss). Sulfide assemblages in the xenolith matrix are a product of the subsolidus re-equilibration of primary mss at temperatures below ≤300 °C. Platinum group elements (PGE) abundances suggest that most e-type sulfides are the residues of melting processes and that the i-type sulfides are crystallization products of sulfide-bearing fluids/liquids. The m-type sulfides might have resulted from low-temperature metasomatism by percolating sulfide-carbonate-silicate fluids/melts. The PGE in sulfide record processes are related to partial melting in mantle and intramantle melt migration. Most other trace elements initially partitioned into interstitial sulfide liquid and later metasomatically re-enriched residual sulfides overprinting their primary signatures. The extent of element partitioning into sulfide liquids depends on P, T, fO2, and host peridotite composition.

A New Mapping Protocol for Laser Ablation (withFast‐Funnel) Coupled to aTime‐of‐FlightMass Spectrometer (LA‐FF‐ICP‐ToF‐MS) for the Rapid, Simultaneous Quantification of Multiple Minerals

“…2020, Andronikov et al . 2021). Calibration using a variety of matrix RMs has the advantage of producing an extended coverage of the elements because no single reference material can cover all (see online supporting information Table S1).…”

Major and Trace-Element Chemistry of Cr-Spinel in Upper Mantle Xenoliths from East Antarctica

“…The Jetty Peninsula upper mantle xenoliths display evidence for multiple episodes of metasomatic enrichment through silicate, carbonate and sulfide melts [2,4,7,16,17]. The existence of such melts is confirmed by the presence of glasses along grain boundaries, inside resorbed Cpx and Spl rims and as interstitial patches and interstitial carbonate patches and small (<10 µm) sulfide blebs occurring as inclusions in spinels.…”

“…Small Late Jurassic to Early Cretaceous intrusions of alkaline-ultramafic rocks in Jetty Peninsula (northern Prince Charles Mountains; East Antarctica; Figure 1) contain multiple upper mantle xenoliths [1][2][3][4][5][6][7]. These xenoliths, derived from the subcontinental lithospheric mantle (SCLM), carry information about mineral and geochemical changes in the mantle.…”

“…Briefly, the studied area lies on the flank of the small rift system formed ca. 650 Ma and presently is located on the western side of the larger Lambert-Amery rift system which was active from the Mesozoic to Cenozoic [6,7]. Tectonically, amalgamation of East Antarctica is believed to have taken place either ca.…”

“…We conducted in situ scanning electron microscopy (SEM) and laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) analyses of spinel in peridotite xenoliths from Jetty Peninsula in order to constrain mantle processes such as melting and mantle rock to melt interaction. The present work was based on the xenolith samples previously studied for bulk rock, rock-forming mineral and sulfide geochemistry [2][3][4]7,16]. Spinel is a common phase in mantle rocks and is mostly represented by its Cr-rich variety (e.g., [18][19][20] and references therein).…”