Szczegóły publikacji

Opis bibliograficzny

Autorzy (4)

• AGHDumańska-Słowik Magdalena
• AGHPowolny Tomasz
• AGHNatkaniec-Nowak Lucyna
• Stankiewicz Krzysztof

Słowa kluczowe

Dane bibliometryczne

ID BaDAP	138524
Data dodania do BaDAP	2022-01-11
Tekst źródłowy	URL
DOI	10.1016/j.oregeorev.2021.104684
Rok publikacji	2022
Typ publikacji	artykuł w czasopiśmie
Otwarty dostęp
Creative Commons
Czasopismo/seria	Ore Geology Reviews

Abstract

Dianite represents a unique amphibole–rich rock of ambiguous origin that has been reported from the alkaline Murun Complex in eastern Siberia (Russia). The mineral composition of the rock is dominated by four types of amphibole species including i.e.: (I) magnesio-hastingsite (Na0.64K0.23)(Ca1.94Na0.06)(Mg2.97Fe2+1.01Fe3+0.62Al0.32Ti0.04Mn2+0.03)[Si6.16Al1.84O22](OH1.81F0.19), (II) pargasite – magnesio-hastingsite (Na0.68K0.21)Ca2.04(Mg3.81Al0.47Fe3+0.59Fe2+0.07Ti0.05Mn2+0.02)[Si5.86Al2.14O22](OH1.55F0.45), (III) potassic-richterite (K0.93Na0.07)(Na1.45Ca0.53Sr0.02)(Mg4.63Fe3+0.33Mn3+0.04)[Si7.95Ti0.03Fe0.03O22](OH1.70F0.30), and (IV) potassic-magnesio-arfvedsonite (K0.94Na0.04)(Na1.72Ca0.23Sr0.01)(Mg4.62Fe3+0.30Mn3+0.03Ti0.02)[Si8.09O22](OH1.79F0.21). Magnesio-hastingsite and pargasite – magnesio-hastingsite species form intergrowths and/or individual crystals with a tabular-like habit, and are partially replaced by minor (III) colourless potassic-richterite marked by slight Sr impurity (up to 0.42 wt% of SrO). Magnesiohastingsite-pargasite minerals possibly crystallized at relatively low oxidation conditions, from Ca- and Al-rich melt contaminated by adjacent skarn-type deposits. Later, as a result of a dissolution-precipitation process, they were partially replaced by potassic-richterite. The most abundant type of amphibole species recognized in dianite is represented by amphibole (IV) potassic-magnesio-arfvedsonite that not only envelops abundant anhedral K-feldspars, but also appears to be associated with clustered and nest-like micaceous aggregates. Felted/fine-fibrous fabrics of the potassic-magnesio-arfvedsonite along with (K, Na) ↔ NH4+/H3O+ substitution revealed by Raman bands at 2434 and 2334 cm−1, suggest it crystallized in a water-rich environment. The origin of this amphibole is likely related to the crystallization from highly-evolved Na-, Si-rich peralkaline magma at the higher oxidation conditions, although post-magmatic formation from hydrothermal fluids cannot be excluded. Accessory, hydrothermal phases of dianite comprise barite and sphalerite, which both indicate S-bearing fluid influx. Whole-rock major and trace element data indicate i.e. perpotassic and peralkaline nature of dianite, as well as the presence of rare composite M- and W-type tetrad effect. M−type curves were recognized La-Nd and Er-Lu segments whilst W-type prevails in the Gd-Ho segment of the chondrite-normalized REE patterns. Thus, dianite could form in a complex magmatic-hydrothermal system, where i.e. both fluids-melts interactions and/or post-magmatic high-temperature fluid imprint could be involved. Sr-enrichment of the rock samples, coupled with only minor negative Eu anomaly (Eu/Eu*: 0.52–0.78), further suggests that early-stage separation of plagioclases has not significantly contributed to the magma evolution. Thus, Sr was capable of entering the structure of alkali-amphiboles.

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