Nagatoro, Chichibu District, Saitama Prefecture, Japani

Regional Level Types
Nagatoro	Town
Chichibu District	District
Saitama Prefecture	Prefecture
Japan	Country

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Nagatoro (長瀞町, Nagatoro-machi) is a town located in Saitama Prefecture, Japan. The total area of the town is 30.43 square kilometres (11.75 sq mi). The Nagatoro River is well known for its rapids and whitewater rafting and boating, and the entire town is designated as a prefectural nature park and preserve.

Muscovite-quartz schist in Sanbagawa metamorphic belt.

The Nagatoro area is in the eastern Kanto Mountains, central Japan, and belongs to the eastern end of the Sanbagawa metamorphic belt. In addition to the schists mentioned above, small rock bodies of piemontite schist, stilpnomelane schist, and serpentinite crop out in this area. Hematite-quartz schist is also associated with these basic rocks. The Sanbagawa metamorphic rocks in the eastern Kanto Mountains are generally divided into zones I, II, and III based on the metamorphic mineral parageneses and the degree of graphitization of pelitic and psammitic schists. The P-T conditions of these zones are equivalent to the chlorite, garnet, and albite-biotite zones on Shikoku Island, respectively. The area around the sampling point in this study is part of Zone I (chlorite zone) and corresponds to pumpellyite-actinolite facies (300–360 °C, 5.5–6.5 kbar). A recent study demonstrated metamorphic temperatures of 358 °C and 368 °C for the chlorite zone of the Sanbagawa metamorphic complex in the eastern Kanto Mountains by applying Raman spectroscopy to carbonaceous material. The metamorphic grade of studied area is relatively lower within the high P/T Sanbagawa belt. However, it clearly differs from other localities where the umbers were previously reported (e.g. Chichibu and Shimanto belts).
Although few studies have been published on the chronology of the Nagatoro area, radiolarians and foraminifers of Early Jurassic to Early Cretaceous age were found in a hematite-quartz schist. Furthermore, the accretionary age of Zone I of the Sanbagawa schists in the Kanto Mountains has been estimated to be Late Cretaceous (95.3 ± 1.5 Ma) based on the detrital zircon U-Pb ages of the psammitic schist. Late Cretaceous (84–72 Ma) phengite K-Ar ages have also been reported and are interpreted as the cooling and exhumation ages of the Sanbagawa schists in the Kanto Mountains.

Mineral List

Mineral list contains entries from the region specified including sub-localities

18 valid minerals.

Rock Types Recorded

Rock list contains entries from the region specified including sub-localities