| East Diamante | |
| Depth: | -1270NaN0 |
| Pushpin Map: | Northern Mariana Islands#North Pacific |
| Location: | Northern Mariana Islands |
| Coordinates: | 15.93°N 145.67°W |
| Country: | United States |
| Type: | Submarine volcano |
| Volcanic Group: | Izu–Bonin–Mariana Arc |
| Last Eruption: | Unknown[1] |
East Diamante is a submarine volcano located 43km (27miles) south of Anatahan in the Northern Mariana Islands of the northwestern Pacific Ocean. It forms part of the Izu–Bonin–Mariana Arc and is hydrothermally active, containing a complex, elongated caldera at its summit.
East Diamante is one of two submarine volcanoes in the southern Izu–Bonin–Mariana Arc that have erupted felsic magmas, the other being Zealandia Bank.[2] Dacite is the primary rock type and generally has a porphyritic texture, with phenocrysts embedded in a matrix of quartz, plagioclase, clinopyroxene, orthopyroxene and iron-titanium oxides.[1] [2] The phenocrysts account for up to 41% of the total rock volume.[2]
The summit of East Diamante lies 127m (417feet) below sea level and is truncated by an elongated, northeast–southwest-trending caldera. Formation of the caldera was followed by the emplacement of a central dome complex and the construction of a volcanic cone on the southwest caldera rim. The central dome complex displays hydrothermal activity, including black smokers.[1]
Argon–argon dating of dacite from inside the caldera has given an age of 20,000 ± 4000 years, indicating that the volcano was active in the Late Pleistocene.[3] Volcanism continued into the Holocene, but the age of the last eruption is unknown.[1]