Age and genesis of the largest Phanerozoic Mn deposits in the Paratethys: Inferences from 40Ar/39Ar and U/Pb ages in NE Bulgaria and NW Turkey

IF 3.4 2区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Journal of Geochemical Exploration Pub Date : 2025-03-25 DOI:10.1016/j.gexplo.2025.107764

Peter Marchev , Raya Raicheva , Rositsa Ivanova , Brian Jicha , Irena Peytcheva

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引用次数: 0

Abstract

The early Oligocene manganese (Mn) deposits around the Black Sea represent the second largest accumulation of Mn in the world (600 × 10⁶ tons). Various hypotheses have been offered to explain the genesis of these deposits. However, very few can explain all the major characteristics of the Mn deposits, in particular: 1) their contemporaneity and short depositional time; 2) vast covered territory; 3) the source of the great volume of metals (Mn, Fe, P and Si) and 4) the mechanisms of metal precipitation and concentration. Most of the former hypotheses assume the source for the Mn is the local crystalline rocks, ignoring or misinterpreting the involvement of volcanic material. Here, we propose a volcanic-derived model sourced from a 33.2 ± 0.1 Ma supereruption from the Rhodope Massif, Bulgaria, which covers large areas of the Central, Southern and Eastern Europe with ash. The model is based on radioisotopic age data of the volcanic material from two of the Mn deposits, located on the western shore of the Black Sea. Our model implies that the Mn (along with other metals, Fe, P, Si) have been transported by the large amount of erupted dust and aerosols with absorbed soluble fluoride, chloride, and sulfate metals. The fast dissolution of gases and aerosols into restricted or shallow Paratethys sea basins produced anoxic-euxinic conditions, which in turn promoted high concentration and deposition of the Mn. Final structuring of the zonation of the deposits was the result of the restoration of the normal sea redox-stratification after the end of the volcanic influence.

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来源期刊

Journal of Geochemical Exploration 地学-地球化学与地球物理

CiteScore

7.40

自引率

7.70%

发文量

148

审稿时长

8.1 months

期刊介绍： Journal of Geochemical Exploration is mostly dedicated to publication of original studies in exploration and environmental geochemistry and related topics. Contributions considered of prevalent interest for the journal include researches based on the application of innovative methods to: define the genesis and the evolution of mineral deposits including transfer of elements in large-scale mineralized areas. analyze complex systems at the boundaries between bio-geochemistry, metal transport and mineral accumulation. evaluate effects of historical mining activities on the surface environment. trace pollutant sources and define their fate and transport models in the near-surface and surface environments involving solid, fluid and aerial matrices. assess and quantify natural and technogenic radioactivity in the environment. determine geochemical anomalies and set baseline reference values using compositional data analysis, multivariate statistics and geo-spatial analysis. assess the impacts of anthropogenic contamination on ecosystems and human health at local and regional scale to prioritize and classify risks through deterministic and stochastic approaches. Papers dedicated to the presentation of newly developed methods in analytical geochemistry to be applied in the field or in laboratory are also within the topics of interest for the journal.