Osmium behavior in a subduction system elucidated from chromian spinel in Bonin Island beach sands

AbstractThe Sungun copper–molybdenum porphyry deposit is located in the north of Varzaghan, northwestern Iran. The Sungun quartz-monzonite is the oldest mineralized intrusive body in the region and was emplaced during the Early Miocene. Eight categories of the late and unmineralized dykes, which include quartz diorite, gabbrodiorite, diorite, dacite, microdiorite and lamprophyre (LAM), intrude the ore deposit. The main mineral phases in the dykes include plagioclase, amphibole and biotite, with minor quartz and apatite and secondary chlorite, epidote, muscovite and sericite. The composition of plagioclase in the quartz diorite dykes (DK1a, DK1b and DK1c) varies from albite-oligoclase to andesine and oligoclase to andesine; in the diorite, it varies from andesine to labradorite; in the LAM, from albite to oligoclase; and in the microdiorite (MDI), it occurs as albite. Amphibole compositions are consistent with classification as hornblende or calcic amphibole. Based on their AlIV value (less than 1.5), amphibole compositions are consistent with an active continental margin affinity. The average percentage of pistacite (Ps) in epidotes formed from alteration of plagioclase and ferromagnesian minerals is 27–23% and 25–30%, respectively. Thermobarometric studies based on amphibole and biotite indicate approximate dyke crystallization temperature of 850–750℃, pressure of 231–336 MPa and high fO2 (>nickel-nickel-oxide buffer). The range of mineral compositions in the postmineralization dyke suite is consistent with a genetic relationship with the subduction of the Neotethys oceanic crust beneath the continental crust of the northwest part of the Central Iranian Structural Zone. Despite the change from calc-alkaline to alkaline magmatism, the dykes are likely related to the late stages of magmatic activity in the subduction system that also generated the porphyry deposit.

Download Full-text

Mineralogy, Geochemistry and Provenance of Coastal Sands from Greece: New Insights on the REE Content of Black Coastal Sands from Aggelochori Area, N.-Greece

Minerals ◽

10.3390/min11070693 ◽

2021 ◽

Vol 11 (7) ◽

pp. 693

Author(s):

Argyrios Papadopoulos ◽

Stylianos Lazaridis ◽

Afroditi Kipourou-Panagiotou ◽

Nikolaos Kantiranis ◽

Antonios Koroneos ◽

...

Keyword(s):

Major And Trace Elements ◽

Heavy Minerals ◽

Sea Waves ◽

Complex Flow ◽

Fine Grained ◽

Microscopy Analysis ◽

Beach Sands ◽

Geochemical Analyses ◽

The One ◽

Black Color

Beach sands from Aggelochori coast line are investigated for their geochemistry and REE content, mineralogy and their provenance. These fluvial sands bear heavy minerals enriched horizons (containing minerals such as magnetite, zircon, ilmenite, hematite, rutile and titanite) that can be distinguished due to their black color and are formed usually due to the action of sea waves that deposit the heavy minerals and remove the lighter ones. After a suitable processing (washing, sieving, drying and magnetic separation) of the samples, the mineral constituents and their presence (wt.%) were estimated by XRD. Among the samples, the one being simultaneously the more fine grained and the more zircon-enriched (as suggested by XRPD data and optical microscopy analysis) has been selected for further geochemical analyses. The major and trace elements contents were compared to previously studied REE enriched beach sands from Kavala and Sithonia. Beach sands from Aggelochori area appear to have relatively low REE contents. Considering the provenance of these sediments, we suggest that these sands, are a product of the erosion of multi-sources, including the near-by Monopigado granite, as well as metamorphic rocks, as indicated by the presence of rutile and both ilmenite and magnetite in some samples. Therefore, there are indications of a complex flow pattern that existed at the paleo-catchment area of the deposition.

Download Full-text

Chromian spinel neomineralisations and the microstructure of plastically deformed ophiolitic peridotites (Kraka massifs, Southern Urals, Russia)

Mineralogy and Petrology ◽

10.1007/s00710-021-00748-w ◽

2021 ◽

Author(s):

Dmitry E. Saveliev ◽

Vladimir V. Shilovskikh ◽

Semen N. Sergeev ◽

Anton V. Kutyrev

Keyword(s):

Southern Urals ◽

Chromian Spinel

Download Full-text

Large-scale variation in seismic anisotropy in the crust and upper mantle beneath Anatolia, Turkey

Communications Earth & Environment ◽

10.1038/s43247-021-00142-6 ◽

2021 ◽

Vol 2 (1) ◽

Author(s):

Cédric P. Legendre ◽

Li Zhao ◽

Tai-Lin Tseng

Keyword(s):

Upper Mantle ◽

Large Scale ◽

Seismic Anisotropy ◽

Crust And Upper Mantle ◽

Wave Splitting ◽

Mantle Processes ◽

Open Question ◽

Subduction System ◽

Anisotropic Phase ◽

Regional Tectonics

AbstractThe average anisotropy beneath Anatolia is very strong and is well constrained by shear-wave splitting measurements. However, the vertical layering of anisotropy and the contribution of each layer to the overall pattern is still an open question. Here, we construct anisotropic phase-velocity maps of fundamental-mode Rayleigh waves for the Anatolia region using ambient noise seismology and records from several regional seismic stations. We find that the anisotropy patterns in the crust, lithosphere and asthenosphere beneath Anatolia have limited amplitudes and are generally consistent with regional tectonics and mantle processes dominated by the collision between Eurasia and Arabia and the Aegean/Anatolian subduction system. The anisotropy of these layers in the crust and upper mantle are, however, not consistent with the strong average anisotropy measured in this area. We therefore suggest that the main contribution to overall anisotropy likely originates from a deep and highly anisotropic region round the mantle transition zone.

Download Full-text

Detrital Chromian Spinel Compositions Used to Reconstruct the Tectonic Setting of Provenance: Implications for Orogeny in the Canadian Cordillera

Journal of Sedimentary Research ◽

10.1306/d4268509-2b26-11d7-8648000102c1865d ◽

1997 ◽

Vol Vol. 67 ◽

Cited By ~ 6

Author(s):

H. O. Cookenboo (1), R. M. Bustin (

Keyword(s):

Tectonic Setting ◽

Chromian Spinel ◽

Canadian Cordillera

Download Full-text

Mineral ages and zircon Hf isotopic composition of the Andong ultramafic complex: implications for the evolution of Mesozoic subduction system and subcontinental lithospheric mantle beneath SE Korea

Geological Magazine ◽

10.1017/s0016756813000757 ◽

2013 ◽

Vol 151 (5) ◽

pp. 765-776 ◽

Cited By ~ 5

Author(s):

GI YOUNG JEONG ◽

CHANG-SIK CHEONG ◽

KEEWOOK YI ◽

JEONGMIN KIM ◽

NAMHOON KIM ◽

...

Keyword(s):

Lithospheric Mantle ◽

Tectonic Setting ◽

Eastern China ◽

Mantle Xenoliths ◽

Late Triassic ◽

Magmatic Differentiation ◽

Suprasubduction Zone ◽

Ultramafic Complex ◽

Yeongnam Massif ◽

Subduction System

AbstractThe Phanerozoic subduction system of the Korean peninsula is considered to have been activated by at least Middle Permian time. The geochemically arc-like Andong ultramafic complex (AUC) occurring along the border between the Precambrian Yeongnam massif and the Cretaceous Gyeongsang back-arc basin provides a rare opportunity for direct study of the pre-Cretaceous mantle wedge lying above the subduction zone. The tightly constrained SHRIMP U–Pb age of zircons extracted from orthopyroxenite specimens (222.1±1.0 Ma) is indistinguishable from the Ar/Ar age of coexisting phlogopite (220±6 Ma). These ages represent the timing of suprasubduction zone magmatism likely in response to the sinking of cold and dense oceanic lithosphere and the resultant extensional strain regime in a nascent arc environment. The nearly coeval occurrence of a syenite-gabbro-monzonite suite in the SW Yeongnam massif also suggests an extensional tectonic setting along the continental margin side during Late Triassic time. The relatively enriched ɛHf range of dated zircons (+6.2 to −0.6 at 222 Ma) is in contrast to previously reported primitive Sr–Nd–Hf isotopic features of Cenozoic mantle xenoliths from Korea and eastern China. This enrichment is not ascribed to contamination by the hypothetical Palaeozoic crust beneath SE Korea, but is instead attributable to metasomatism of the lithospheric mantle during the earlier subduction of the palaeo-Pacific plate. Most AUC zircons show a restricted core-to-rim spread of ɛHf values, but some grains testify to the operation of open-system processes during magmatic differentiation.

Download Full-text