Pallasite / Iron IIE
|Find: 1967, Russia, Seymchan, Magadan district. This meteorite
was not observed to fall.
Coordinates: 62° 54' N 152° 26' E
Class: Iron, coarse octahedrite, or IIE (NHM ) or Iron-ung ( met base) Group: IIE, bandwidth 2.0 mm (officially) or Pallasite
TKW: 322,3 kg in 1967 and more than 50 kg in 2004
Chemical class: Group IIE, 9.15% Ni, 24.6 ppm Ga, 68.3 ppm Ge, 0.55 ppm Ir.
Meteoritical Bulletin, no. 43, Moscow (1968) reprinted Met. 5, 85-109 (1970)
Circumstances of the discovery:
Falling in prehistoric times, this meteorite was first reported in 1967. The original Seymchan 300 kilogram meteorite was found by a geological survey party in the bed of a brook flowing into the Hekandue, a tributary of Jusachnaja River in Magadan District, Russia. A smaller 51 kilogram mass was later found with use of a metal detector about 20 meters from the location of the main mass. Metal detectors are currently being used to find additional fragments of this meteorite. As reported by Mednikov (1967), Zvetkov (1967), and Tsvetkov (1969), a large mass was found in a stream bed of the Yasachnaya River (flowing into the river of Hekandue, a left tributary of the river of Jasachnaja) by a geologist, F. A. Mednikov, about 150 km from Seymchan, in the Magadan Region of the USSR (V. Buchwald, 1975). The thumbprinted, triangular-shaped mass weighed 272.3 kg. In October of that year, a further search of the area by I. H. Markov, utilizing a mine detector, resulted in the recovery of an additional mass weighing 51 kg. The large mass was provided to the Academy of Sciences, USSR. A small section of the iron was analyzed by J. Wasson (1974) and it was determined to be a member of chemical group IIE. Subsequently, a more precise elemental analysis of the IIE iron group members by J. Wasson and J. Wang (1986) found that Seymchan (and another IIE member, Lonaconing) had many elemental trends which deviated strongly from typical IIE group members, and therefore, Seymchan (and Lonaconing) was reclassified as an ungrouped iron. During a 2004 expedition to the original Seymchan discovery site, D. Kachalin found additional masses having a combined weight of ~50 kg. Remarkably, many of the new masses contain silicates with a pallasitic texture, something not discovered previously during studies of only small sections of the original mass. This compositional mixture - portions composed of only FeNi-metal, along with portions containing silicates forming a pallasitic texture - is similar to the iron-pallasite mixture found previously in both the Brenham and Glorieta Mountain pallasites.
Source: Ivan Koutyrev