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The oldest seafloor massive sulfide deposits at the Mid - Atlantic Ridge: 230th/u chronology and composition

Kuznetsov V., Tabuns E., Kuksa K., Cherkashov G., Maksimov F., Bel’Tenev V., Lazareva L., Zherebtsov I., Grigoriev V., Baranova N.

Geochronometria

2015

Vol. 42, no.1

100--106

A geochronological and geochemical study on 10 samples of seafloor massive sulfides (SMS) from the inactive Peterburgskoye hydrothermal field at the Mid-Atlantic Ridge (MAR) was carried out. The 230Th/U ages of the SMS are the oldest for the Quaternary hydrothermal ores ever found at the ocean floor. According to them the hydrothermal activity at Peterburgskoye field started at least 170 ka and continued down to 63 ka. The oldest hydrothermal ores from this field consist mainly of pyrite and chalcopyrite and have geochemical properties typical for SMS associated with basalts.

230Th/U chronology of ore formation within the Semyenov hydrothermal district (13°31' n) at the Mid-Atlantic Ridge

Kuznetsov V., Maksimov F., Zheleznov A., Cherkashov G., Bel’tenev V., Lazareva L.

Geochronometria

2011

Vol. 38, no. 1

72-76

A radiochemical study was carried out on massive sulfides from Semyenov hydrothermal district at the Mid-Atlantic Ridge. New and published results provide evidence that 230Th/U ages obtained for massive sulfides are reliable. The sulfide deposits from the West, North-West, North-East, and East hydrothermal sites at the Semyenov hydrothermal district were formed between ~124 ka and ~37 ka ago. The hydrothermal activity might have started in the eastern part of the district and moved to the west by episodic ore formation.