Mineralogical and geochemical characteristics of hydrothermal clay minerals beneath active hydrothermal fields at the Iheya North Knoll, Middle Okinawa Trough
Abstract
Many of active hydrothermal fields in the Okinawa Trough are located in sediment-rich environment. Terrigenous sediment derived probably from the Asia continent as well as volcaniclastic material originated from adjacent felsic submarine volcanoes often pile up around the hydrothermal fields. In these sediments around a hydrothermal field, intense hydrothermal alteration was often recognized. Occurrence of clay minerals provides an important key to understand hydrothermal interactions beneath the seafloor. We studied clay minerals in the core samples recovered by scientific drilling campaigns of D/V Chikyu, which were performed in 2014-2016 under the framework of the Next-generation Technology for Ocean Resources Exploration Project.
Hydrothermal alteration recognized at Aki Site at the Iheya North Knoll showed similar aspects to that observed at Original Site located 3 km north, where IODP Expedition 331 were performed in 2010. At Site C9023 where drilled into a hydrothermal mound associated with high temperature fluid venting, hydrothermal alteration characterized by abundant occurrence of chlorite and anhydrite was recognized below a sulfide mineral-bearing zone. In the deeper zone, illite was dominant clay mineral displacing chlorite. At Site C9016 where drilled in an area of low temperature shimmering, focused formation of kaolin minerals was recognized in rather shallow depth (from 8.5 to 11.0 meters below the seafloor). Change of dominant kaolin minerals along the depth from halloysite, kaolinite to dickite is notable, because it could reflect temperature gradient.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.V43F0181I
- Keywords:
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- 0930 Oceanic structures;
- EXPLORATION GEOPHYSICSDE: 1034 Hydrothermal systems;
- GEOCHEMISTRYDE: 3616 Hydrothermal systems;
- MINERALOGY AND PETROLOGYDE: 8424 Hydrothermal systems;
- VOLCANOLOGY