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DISENTANGLING CRATERING PROCESSES USING NON-TRADITIONAL ISOTOPE RATIOS ON CORE M0077A OF THE IODP-ICDP EXPEDITION 364 IN THE CHICXULUB IMPACT STRUCTURE

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Introduction: The Chicxulub impact structure, located on the Yucat√°n peninsula of Mexico, has been drilled by the IODP-ICDP Expedition 364 in 2016. A continuous sequence of the upper peak-ring has been retrieved from Site M0077A. This core is from top to bottom composed of ~110 m of Paleogene sediments, ~130 m of suevite and impact melt rocks, and ~590 m of crystalline and metamorphic basement lithologies [1]. The suevite complex deposition is the result of several processes, including the fall-back of material ejected by the impact, slump and avalanches on the peak-ring, and wash-back by tsunami waves within the crater [2]. Therefore, the suevite was likely exposed to different thermodynamic processes during its deposition, as was the case for the impact melt rocks. In addition, the whole core has been the subject of severe hydrothermal alteration, potentially overprinting any primary compositional and isotopic signatures [3].
This abstract examines the Fe, Zn, and Cu isotopic composition of 27 samples from various units within core M0077A, and combines these with major and trace element data and petrographic observations. The main objectives are to disentangle the different processes affecting the various units of the upper peak-ring, such as mixing of distinct target lithologies, tracing potential volatilization or condensation effects (as observed for sulfur [4]), and determining the degree of post-impact hydrothermal alteration.
The choice of the Fe, Zn, and Cu stable isotope systems here is motivated by the relative abundance of these elements in the samples, their distribution among different mineral phases, and their difference in volatility with a 50% condensation temperature of 1334K for Fe (medium refractory), 1037K for Cu (semi-volatile), and 726K for Zn (highly volatile) [5 ; 6]. Because of these different condensation temperatures, the isotopic ratios of these elements may exhibit variations inherited from distinct thermodynamic environments and time intervals during crater formation.
Boek: Large Meteorite Impacts VI 2019 (LPI Contrib No. 2136)
Volume: 6
Pagina's: 1-2
Aantal pagina's: 2
Jaar van publicatie:2019