Meteoritic component in impact breccias of the Jeokjung-Chogye structure, South Korea: Evidence from the HSE abundances and Re-Os isotopic systematics
Sung Hi Choi, Jeong-Hyun Lee, Seung-Sep Kim, Jaehyung Yu, Igor S. Puchtel
In Press, Journal Pre-proof, Available online 1 October 2022
• We report HSE and Re-Os isotope data for impactites from the JC structure in Korea.
• The impactites have 5 times higher abundances of PGE compared to the target rocks.
• The impactites have 187Os/188Os ratios relatively lower than the target rocks.
• Endogenic or chondritic relative HSE abundances argue against irons as impactor.
• Chondritic contribution to the impact breccias is estimated to be ~0.05% or less.”
“Geochemical compositions, including highly siderophile element (HSE) abundances and Re-Os isotope compositions, of 9 polymict impact breccias in two drill cores and 3 target rocks from the Jeokjung-Chogye structure, South Korea, have been investigated to test the impact origin of the structure, and to infer the potential projectile type for the formation of the crater. The impactites have around 5 times higher abundances of platinum group element (PGE) compared to target rocks, and two orders of magnitude higher Re abundances. The weighted mean for 187Os/188Os ratios of impactites is 0.806, which is lower than this value for the target rocks (1.049), suggesting the presence of a meteoritic contribution. The PGE abundances and a broad negative correlation between Os contents and 187Os/188Os ratios show that the impactites incorporated ~0.05 wt% of a chondritic component. The endogenic or chondritic relative abundances of the HSE argue against iron meteorites as impactor for the Jeokjung-Chogye structure. Yet, the present data do not allow to unambiguously identify the projectile type (i.e., chondrite class) in the impactites because of the high proportion of the indigenous component.”