Alexey Martynov (Russia)

Email: amartynov　@lycos.com

Thesis title:  Evolution of basalts on Kunashir and Iturup islands from Miocene to Quaternary.

Supervisor:  Prof. Jun-Ichi Kimura (2005-2007).

The Kuril Arc is traditionally considered to be part of the geodynamic system consisting of the Kuril-Kamchatka Trench, the Bolshaya Kuril volcanic chain and, in the rear section, the Kuril Basin (Sergeev, Krasny, 1987).

Formation of the Bolshaya Kuril volcanic chain began in the Early Miocene or in the Oligocene. The chain has a length of 1150 km, and the volcanic zone is as wide as 100-200 km. The depth of the subducted oceanic slab varies between 120-150 km. The Bussol’ and Kruzenshtern Straits divide the arc into South, Central and North chains. The thickness of the earth’s crust varies only slightly along the arc, being 28-33 km in the southern sector, 25-30 km in the central part, and 32-36 km in the northern segment (Zlobin, 1987). The exposed part of the islands consists of volcanic and volcanic-sedimentary rocks that are divided into two structural units. The lower unit forming the arc pedestal is composed of moderately deformed Neogene deposits, while the upper unit is virtually all undeformed Quaternary volcanics.

The Neogenic volcanic and sedimentary rocks are divided into “green tuff”, and “vocanogenic sedimentary” formations. The early – middle Miocene "green-tuff" formation, up to 4000 m thickness, is extensively exposed on Urup and Paramushir Islands, and less so on Kunashir and Iturup. The "vocanogenic sedimentary" formation is poorly studied. On Kunashir Island is is divided into the Alekhinskay and Golovninskaya suites.

The Late Neogene - Quaternary volcanics are typically subdivided into a Late Pliocene – Pleistocene plateau-basalt complex and a Holocene andesitic formation. Both are exposed on almost all islands of the Bolshaya Kuril volcanic chain.

The goal of my present research is the petrology and geochemistry of the Late Miocene – Pleistocene lavas from Kunashir, Iturup, Urup and Simushir Islands, to improve understanding of the processes of the island arc formation and magma evolution.

I will carry out major and trace element analyses of by XRF and ICP-MS. I will also determine the ages and petrogenesis of the volcanic rocks using Sr, Nd, Hf, Pb isotopic analyses by TIMS and MC-ICPMS.