Mercury Anomaly in Oligocene–Miocene Maykop Group Sediments (Caucasus Continental Collision Zone): Mercury Hosts, Distribution, and Sources
| Autor: | Ella V. Sokol, Svetlana N. Kokh, M. A. Gustaytis |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Caucasus
010504 meteorology & atmospheric sciences Sulfide chemistry.chemical_element engineering.material 010502 geochemistry & geophysics 01 natural sciences mud volcano Organic matter 0105 earth and related environmental sciences organic matter chemistry.chemical_classification Total organic carbon sulfidic mercury Heavy mineral cinnabar Geology Geotechnical Engineering and Engineering Geology Mineralogy Anoxic waters pyrite Mercury (element) magmatic activity Maykop Group sediments Cinnabar chemistry Environmental chemistry engineering Pyrite total mercury QE351-399.2 |
| Zdroj: | Minerals, Vol 11, Iss 751, p 751 (2021) Minerals Volume 11 Issue 7 |
| Popis: | The Oligocene–Miocene Maykop Group sediments, mainly composed of illite–smectite, store mercury in strongly variable concentrations from 10 to 920 μg/kg. Extremely high Hg levels (98–920 μg/kg) coupled with abnormal mercury-to-total organic carbon (TOC) ratios (Hg/TOC = 109 to 3000 μg/kg/wt% TOC = 0.2 wt% to 1.2 wt%) were measured in the Middle Maykop marine shales that were deposited in the deepwater Indol–Kuban Basin under anoxic conditions. The Middle Maykop shales contain up to 70% of total mercury in sulfide form. In heavy mineral fractions, abundant Hg-bearing pyrite (with up to 4810 µg/kg Hg in hand-picked concentrates) is accompanied by sporadic cinnabar. Relative to the Middle Maykop sediments, the Upper Maykop shales have much lower Hg concentrations and Hg/TOC ratios: 10 to 63 μg/kg (34 μg/kg on average) and 7.7 to 137 μg/kg/wt% (39 μg/kg/wt% on average), respectively. Mercury sequestration is inferred to occur mostly by binding in sulfide hosts in the Middle Maykop anoxic deep-sea sediments and in organic matter, Fe3+-(oxy)hydroxides, and clay particles in the Upper Maykop shales which were deposited in a more oxygenated environment. Mercury inputs to the marine shales during Maykopian sedimentation were possibly associated with local Oligocene–Lower Miocene volcanic activity in the Caucasus Continental Collision Zone. At the same time, the mode of Hg binding in sediments was controlled by redox conditions which changed from anoxic to disoxic and suboxic at the Middle-to-Upper Maykop transition. |
| Databáze: | OpenAIRE |
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