Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (12) Citing Articles via Google Scholar Google Scholar Articles by Hourigan, J. K. Articles by Akinin, V. V. Search for Related Content GeoRef GeoRef Citation

Tectonic and chronostratigraphic implications of new ⁴⁰Ar/³⁹Ar geochronology and geochemistry of the Arman and Maltan-Ola volcanic fields, Okhotsk-Chukotka volcanic belt, northeastern Russia

Jeremy K. Hourigan^,1 and Vyacheslav V. Akinin^,2

¹ Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305, USA
² North East Interdisciplinary Scientific Research Institute, Far East Branch, Russian Academy of Sciences, Magadan, Portovaya Ulitsa, 16, 685000, Russia

The Okhotsk-Chukotka volcanic belt is part of an extensive late Early to Late Cretaceous Andean-style magmatic arc that spans the entire eastern margin of the Asian continent. The belt itself stretches 3000 km from the Chukotka Peninsula to the Uda River and comprises 1.2 x 10⁶ km³ of volcanic rock over a 500,000 km² area. Despite its size and regional tectonic significance, the time span of magmatic activity is poorly constrained and the subject of significant debate, mostly in the Russian literature. In this paper, we provide new geochronologic control on the timing of inception and cessation of magmatism for the Arman and Maltan-Ola volcanic fields. These field localities were chosen because they are well studied, relatively accessible, and contain floral assemblages that have been used to correlate volcanic sequences at the regional scale. The majority of the volcanic sequence was emplaced between 85.5 ± 1.3 Ma and 74.0 ± 1.2 Ma, as shown by 17 new ⁴⁰Ar/³⁹Ar ages. The Coniacian– Santonian to Campanian age range indicated is 15 m.y. younger than the Albian to early Cenomanian age range given by a synthesis of floral stratigraphic, K-Ar, and Rb-Sr geochronologic data. The calc- alkaline part of the volcanic section spans an apparent age range of 85.5 ± 1.3 Ma to 80.7 ± 0.8 Ma. Capping basalts were emplaced between 77.5 ± 1.1 Ma and 74.0 ± 1.2 Ma and exhibit a within-plate geochemical signature, which we attribute to a temporally and geochemically distinct, possibly extension-related, phase of magmatism. The apparent northwestward migration of the arc front from the interior (seaward) zone (Taigonos Peninsula, Magadan batholith) in Albian–Cenomanian time to the Arman and Maltan-Ola volcanic fields in Coniacian–Santonian to Campanian time may be explained by shallowing of the subducting paleo-Pacific (Kula?) oceanic plate.

The flat-lying nature of these volcanic rocks and the within-plate geochemical affinity of the capping basalt unit are inconsistent with prevailing tectonic models for the cessation of arc magmatism and formation of the Sea of Okhotsk which require the collision of a microcontinental block or oceanic plateau with the northeast Asian margin in the Late Cretaceous.

Key Words: Okhotsk-Chukotka volcanic belt • northeast Russia • geochronology • Cretaceous • subduction-related magmatism

This article has been cited by other articles:

				J. K. Hourigan, M. T. Brandon, A. V. Soloviev, A. B. Kirmasov, J. I. Garver, J. Stevenson, and P. W. Reiners Eocene arc-continent collision and crustal consolidation in Kamchatka, Russian Far East Am J Sci, May 1, 2009; 309(5): 333 - 396. [Abstract] [Full Text] [PDF]

				T. Ntaflos, C. Tschegg, M. Coltorti, V. V. Akinin, and J. Kosler Asthenospheric signature in fertile spinel lherzolites from the Viliga Volcanic Field in NE Russia Geological Society, London, Special Publications, January 1, 2008; 293(1): 57 - 81. [Abstract] [Full Text] [PDF]