The origin of low-Ca olivine from ultramafic xenoliths and host basaltic lavas in a back-arc setting, James Ross Island, Antarctic Peninsula

Altunkaynak, Şafak; Ünal, Alp; Howarth, Geoffrey H.; Aldanmaz, Ercan; Nývlt, Daniel

doi:10.1016/j.lithos.2019.05.039

Cited by 8 publications

(2 citation statements)

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“…The compositions of the Terina olivine macrocrysts correspond to the pyroxenite trend (Figure 12a). However, the increase in Zn content may be related not to the melting of pyroxenite but instead may be linked to the metasomatism of the mantle source [75,79]. This may explain the gentler trend for olivine macrocrysts of the Terina complex compared to the pyroxenite source trend.…”

Section: Contribution Of Various Mantle Sources To the Formation Of Olivine Macrocrystsmentioning

confidence: 99%

“…Many researchers use the compositional features of olivine as an early liquidus phase to define the contribution of mantle and crustal material. Mn/Fe, Ni/Mg, as well as trace elements such as Mn, Li, Zn, Co, and Ti are used to determine the type of mantle metasomatism (e.g., carbonate, silicate) during the formation of deep melts [24,46,66,[75][76][77][78].…”

Section: Contribution Of Various Mantle Sources To the Formation Of Olivine Macrocrystsmentioning

confidence: 99%

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Polygenic Nature of Olivines from the Ultramafic Lamprophyres of the Terina Complex (Chadobets Upland, Siberian Platform) Based on Trace Element Composition, Crystalline, and Melt Inclusion Data

et al. 2021

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Olivine from the deep mantle-derived rocks, such as ultramafic lamprophyres, carries important information about the composition of the mantle source, the processes of mantle metasomatism, the origin of specific silicate-carbonate melts, as well as the composition and mechanisms of crystallization of these rocks. Textures and compositions of olivine from the carbonate-rich ultramafic lamprophyres (aillikites) of the Terina complex, along with their mineral and melt inclusions, exposed that olivines have different sources. Two populations of olivines were considered: macrocrysts (>1 mm) and groundmass olivines (<1 mm). Groundmass olivines are phenocrysts and characterized by weak variations in Mg# (84–86.5), a sharp increase in Ca and Ti contents, and a decrease in Ni and Cr from core to rim. They have higher concentrations of Li, Cu, Ti, and Na compared to macrocrysts. Among the macrocrysts, the following populations are observed: (1) high-Mg olivines (Mg# 89–91) with high Ni and low Ti contents, which are interpreted as xenocrysts from the slightly depleted lherzolite mantle; (2) high-Ca olivines (Mg# 84–88, CaO 0.13–0.21 wt %), which have patterns similar to groundmass olivines and are interpreted as cumulates of early portions of aillikite melt; (3) macrocrysts with wide variations in Mg# (73–88), low CaO contents (0.04–0.11 wt %), and positive slope in Ca vs. Al and negative slope in Ca vs. Mn, which are interpreted as disintegrated megacrysts from the Cr-poor megacryst suite. The megacryst suite could have been formed in the pre-trap period during the melting of the metasomatized subcontinental lithospheric mantle (SCLM). The aillikite melt evolution is traced by secondary melt inclusions in olivine macrocrysts: early phlogopite-diopside-calcite-apatite association, containing Ti-magnetite and ilmenite, is followed by an association with magnetite and sulfides (pyrrhotite and pentlandite); finally, at a late stage, inclusions with a predominance of Ca-Na-carbonates and sulfates and enriched in U, Th, Y, REEs, Sr, and Ba were captured.

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Section: Contribution Of Various Mantle Sources To the Formation Of Olivine Macrocrystsmentioning

confidence: 99%

Section: Contribution Of Various Mantle Sources To the Formation Of Olivine Macrocrystsmentioning

confidence: 99%

Polygenic Nature of Olivines from the Ultramafic Lamprophyres of the Terina Complex (Chadobets Upland, Siberian Platform) Based on Trace Element Composition, Crystalline, and Melt Inclusion Data

et al. 2021

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Effects of Mantle Hybridization by Interaction with Slab Derived Melts in the Genesis of Alkaline Lavas across the Back-Arc Region of South Shetland Subduction System

Altunkaynak

Aldanmaz

Nývlt

2022

Journal of Petrology

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Late Miocene to Late Pleistocene alkaline lavas in the northernmost part of the Antarctic Peninsula and its off-lying islands are the latest stage of magmatic activity that took place in response to lithospheric extension in the back-arc region of the South Shetland subduction system. The alkaline magmatism occurred much later than the main pulse of Cretaceous arc magmatism and generated basaltic extrusive rocks during several sub-aqueous/sub-glacial and sub-aerial eruption periods. The suite consists primarily of alkali olivine basalts with oceanic island basalt (OIB)-like trace element signatures, characterized by elevated highly to less incompatible element ratios compared to MORB. The samples have higher 87Sr/86Sr (0.70301–70365), and lower 143Nd/144Nd (0.51283–0.51294) and 176Hf/177Hf (0.28291–0.28298) than depleted MORB mantle. Their lead isotope ratios vary within a limited range with 206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb ratios of 18.797–18.953, 15.577–15.634, and 38.414–38.701, respectively. Sr, Nd, Hf and Pb isotope systematics suggest involvement of diverse source materials in the genesis of the alkaline magmas. Evaluation of radiogenic isotope and trace element data indicates that the source of the alkaline melts had a complex petrogenetic history, reflecting the effects of mantle hybridization along the slab mantle interface through interaction of mantle wedge peridotites with volatile-bearing, siliceous melts produced by melting of subducted sediments and basaltic oceanic crust. Hf-Nd isotope and trace element projections further demonstrate that the metasomatizing melt was likely generated by eclogite partial melting at sub-arc to post-arc depths, in equilibrium with a garnet-bearing residue and involved breakdown of high field strength elements (HFSE) retaining phases. Consumption of metasomatic amphibole during partial melting of hybridized peridotite at the wet solidus appears to have had a significant effect on the final melt compositions with high HFSE, Na and H2O contents.

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Slab window–related magmatism as a probe for pyroxenite heterogeneities in the upper mantle

Hole

Gibson

Morris

2023

Geology

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New high-precision trace-element analyses of magmatic olivines point to a pyroxenite-dominated source for recent alkali basalts erupted above slab windows formed along the Antarctic Peninsula. Melting occurred at ambient mantle temperature, and basalts have geochemical compositions that are indistinguishable from ocean-island basalts (OIBs). We propose that the pyroxenite component originally resided in the upper mantle beneath the subducted slab; formation of a slab window allowed limited decompression and the generation of melts of garnet-pyroxenite, but little or no melting of mantle peridotite. The pyroxenite component in the mantle formed ca. 550 Ma, an age that does not require long-term recycling of subducting slabs to the core-mantle boundary. Enriched mid-ocean ridge basalt (E-MORB) from the adjacent extinct Phoenix Ridge owes its enriched trace-element compositions to mixing between small melt fractions of pyroxenite and peridotite during a period of decreased spreading rate prior to the death of the ridge ca. 3.3 Ma. It is likely that the variable trace-element enrichment seen in East Pacific Rise E-MORB distal from hotspots results from the same process of interactions between small-melt-fraction (<~5%) melts of pyroxenite and peridotite.

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The origin of low-Ca olivine from ultramafic xenoliths and host basaltic lavas in a back-arc setting, James Ross Island, Antarctic Peninsula

Cited by 8 publications

References 64 publications

Polygenic Nature of Olivines from the Ultramafic Lamprophyres of the Terina Complex (Chadobets Upland, Siberian Platform) Based on Trace Element Composition, Crystalline, and Melt Inclusion Data

Polygenic Nature of Olivines from the Ultramafic Lamprophyres of the Terina Complex (Chadobets Upland, Siberian Platform) Based on Trace Element Composition, Crystalline, and Melt Inclusion Data

Effects of Mantle Hybridization by Interaction with Slab Derived Melts in the Genesis of Alkaline Lavas across the Back-Arc Region of South Shetland Subduction System

Slab window–related magmatism as a probe for pyroxenite heterogeneities in the upper mantle

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