15:45 〜 16:00
[MIS18-14] Mado Megamullion: a potential new target for IODP drilling to understand backarc basin lithosphere
キーワード：マドメガムリオン、国際深海科学掘削計画、海洋コアコンプレックス、背弧海盆
Oceanic core complexes (OCCs) or megamullions are domal bathymetric highs with axis-normal corrugations, and with exposure of serpentinized peridotite and gabbroic rocks, interpreted as exhumed footwalls of low-angle detachment faults. OCCs are the only places at which the petrological crust/mantle boundary can be reached by ocean drilling with current technology.
A significant fraction of the ocean floor is created in backarc basins where water plays a major role in magmatic processes, leading to an accretionary style potentially contrasting to that of normal mid-ocean ridges. A better understanding the architecture and composition of backarc basins is therefore important to understand the oceanic crustal accretion process globally. However, there has been no single core of lower oceanic crust or uppermost mantle located at backarc basin to characterize this important tectonic setting. On this rationale, we have been proposing an IODP proposal to drill Godzilla Megamullion, the largest known OCC on Earth, located in an extinct backarc basin, the Parece Vela Basin, in the Philippine Sea.
Here, we introduce our intention to drill another OCC located in a backarc setting, Mado Megamullion, in the Shikoku Basin, located ~1100 km north of Godzilla Megamullion. Mado Megamullion is the OCC that is most easily accessible OCC from major city; it is located only ~1200 km from Tokyo. Importantly, it has a ~20 km square corrugated surface, comparable in areal size to typical OCCs in the Mid-Atlantic Ridge, such as Atlantis Massif and Kane Megamullion. It thus represents an ideal case to make a comparative study with well-known OCCs exposed at the slow-spreading Mid-Atlantic Ridge. This will provide useful information to understand the fundamental differences of the lithospheric characteristics between the two major oceanic settings.
We believe that IODP drilling of Godzilla Megamullion will provide important datasets to understand the long-term evolution of this unique OCC. On the other hand, IODP drilling of Mado Megamullion will provide complimentary data, necessary to understand the difference of the lithospheric characteristics between the two major oceanic settings. In this contribution, we will summarize the dataset available to a preliminary IODP drilling proposal, and discuss its scientific framework.
A significant fraction of the ocean floor is created in backarc basins where water plays a major role in magmatic processes, leading to an accretionary style potentially contrasting to that of normal mid-ocean ridges. A better understanding the architecture and composition of backarc basins is therefore important to understand the oceanic crustal accretion process globally. However, there has been no single core of lower oceanic crust or uppermost mantle located at backarc basin to characterize this important tectonic setting. On this rationale, we have been proposing an IODP proposal to drill Godzilla Megamullion, the largest known OCC on Earth, located in an extinct backarc basin, the Parece Vela Basin, in the Philippine Sea.
Here, we introduce our intention to drill another OCC located in a backarc setting, Mado Megamullion, in the Shikoku Basin, located ~1100 km north of Godzilla Megamullion. Mado Megamullion is the OCC that is most easily accessible OCC from major city; it is located only ~1200 km from Tokyo. Importantly, it has a ~20 km square corrugated surface, comparable in areal size to typical OCCs in the Mid-Atlantic Ridge, such as Atlantis Massif and Kane Megamullion. It thus represents an ideal case to make a comparative study with well-known OCCs exposed at the slow-spreading Mid-Atlantic Ridge. This will provide useful information to understand the fundamental differences of the lithospheric characteristics between the two major oceanic settings.
We believe that IODP drilling of Godzilla Megamullion will provide important datasets to understand the long-term evolution of this unique OCC. On the other hand, IODP drilling of Mado Megamullion will provide complimentary data, necessary to understand the difference of the lithospheric characteristics between the two major oceanic settings. In this contribution, we will summarize the dataset available to a preliminary IODP drilling proposal, and discuss its scientific framework.