#Isale impacts code#
#Isale impacts series#

The Neumann band has been known to be a deformation twin (Uhlig 1955) formed by the intracrystalline plastic deformation in many metals. Because of such importance, we made experimental simulations of the formation and disappearance of the Neumann band. Therefore, the formation and disappearing conditions of the Neumann band are useful to identify unaltered or less-altered iron meteorites after their formation in the early solar system. According to them, the Neumann band is a prominent signature of stage 1, which shows the records of relatively weak collisions, and it can be removed by annealing caused by the later heating events. ( 2011) made an effort to classify the four shock stages for IVA, IVB, and some ungrouped iron meteorites based on various shock textures. 1991), there are few systematic classifications of shock stages in iron meteorites. Therefore, if we accurately understand the impact conditions required for producing the shock features in iron meteorites, we would be able to decode the impact environment in the early solar system.Īlthough magnitudes of the shock events in ordinary chondrites have been classified as the shock stage from S1 to S6 based on their shock textures (Stöffler et al. Many iron meteorites, however, have experienced textural deformation because of mutual collisions, which would modify the original information. Therefore, iron meteorites possess information on their early differentiated planetesimals. Such early metal–silicate fractionation occurred perhaps because of melting caused by the radiogenic heating by extinct radiogenic elements such as 26Al (e.g., Goldstein et al. 2011).īoth carbonaceous chondritic (CC)-type and non-carbonaceous (NC)-type iron meteorites fractionated in their parent bodies in the early stage of formation of the solar system, perhaps within 1–3 My after the formation of calciumaluminum-rich inclusions in the solar nebula (Kruijer et al. The Neumann band has been observed in kamacite (body-centered cubic phase) separated as the Widmanstätten pattern in most groups of iron meteorites such as Goose Lake IAB (Scott 2020) and IVA, IVB, and ungrouped iron meteorites such as Hammond and Babb’s Mill (Blake’s Iron and Troost’s Iron) (Yang et al. Based on these analyses, iron meteorites have been divided into 13 groups according to their chemical compositions (Goldstein et al. ( 1998) analyzed 700 iron meteorites, initially for Ni, Ga, Ge, and Ir and later for Cr, Co, Cu, As, Sb, W, Re, Pt, and Au, using instrumental neutron activation analyses. The iron meteorites with Neumann bands were shocked at this pressure range and temperatures at least up to 670 K, and were not heated to the temperatures above 1070 K after the Neumann band formation. The twin in iron almost disappeared by annealing at 1070 K. The present experiments combined with the numerical simulations revealed that the twin was formed by impacts with various shock pressures from 1.5–2 GPa to around 13 GPa. The twin was formed in the run products of the experiments conducted at room temperature and 670 K, whereas it was not observed in the run product formed by the impact at 1100 K. The effects of pressure and temperature on the formation and disappearance of the twins (Neumann band) were explored based on laboratory and numerical experiments.

#Isale impacts code#

We also conducted numerical simulations with the iSALE-2D code to investigate peak pressure and temperature distributions in the nontransparent targets.

#Isale impacts series#

We conducted a series of shock recovery experiments on bcc iron with the projectile velocity at 1.5 km/s at various initial temperatures, room temperature, 670 K, and 1100 K, and conducted an annealing experiment on the shocked iron. Neumann band in iron meteorites, which is deformation twins in kamacite (Fe–Ni alloy), has been known to be a characteristic texture indicating ancient collisions on parent bodies of meteorites.