The samples are from drill core of IODP-ICDP Expedition 364 'Drilling the K-Pg boundary impact', which is the 66 Ma Chicxulub crater, Mexico. This meteorite impact event wiped out about the 75 % of the species that existed at that time, including the dinosaurs. The samples analysed with micro-CT were taken from the so called suevite, a unit that consists of highly fragmented rock covering solidified impact melt, and from granitoid rocks, that form the basement to the crater and which were uplifted during the cratering from mid-crustal depths. The granitoid rocks are shock-metamorphosed and show a number of deformation structures. More information in Riller, U., et al., 2018, Rock fluidization during peak-ring formation of large impact structures. Nature 562. The purpose of the CT-analysis was to display fragment and mineral fabrics as well as quantifying the porosity in both rock units. In terms of mineral fabrics, we were not very lucky, as the rocks consist mostly of feldspar and quartz, which have similar densities. We were, therefore, unable to quantify preferred orientations of the two mineral phases. We were the more happy to display and quantify porosity of these rocks, which are unusually high, up to about 15 %, compared to equivalent and unshocked rocks outside the crater. The high porosities account nicely for the low seismic velocities that were measured in these rocks. A very nice result in this regard is also, that the porosities are very low in zones, where the rock was fractured to a very small grain size, but rather high in fractured rock hosting the ultra-cataclasite. This result is very surprising to us, as porosity in brittle rocks usually increases with fracturing intensity. The shocked granitoid rocks show the opposite. Either there is a threshold in grain size, below which CT does not detect porosity well, because open spaces are so small, in which case the porosity estimates may be incorrect, or porosity is indeed that low. To get this dataset, please contact fairdata-pas@gtk.fi. Preview dataset found at http://urn.fi/urn:nbn:fi:att:6f14a13f-200d-47b5-80c9-f86a98e6482d

2019