Chicx-03A drilling report
Source: ESO - Chicxulub K-Pg Impact Crater Expedition 364

Norbert Brügge Germany
Dipl.-Geol.

Update: 01.01.201
7

What can we say:
The Chicxulub crater is smaller than predicted (see above). It is more like a huge volcanic vent with about 70 km diameter. The expected peak or peak ring in the "impact-crater" does not exist.
The indifferent seismic profiles were unfortunately misinterpreted because they were accompanied by a wishful thinking. The ever-used gravity anomaly map shows neither a crater nor a paek ring, but is only the reflection of a former magma chamber.
The "Chicxulub-impact" is a great error. The compact crystalline basement is encountered here in an exceptionally high postion (similar as in the
Chesapeake Bay structure). Enclosed mafic dykes are intrusions from the dioritic magma chamber. There are even indications that the so-called "impact melt" in the cores is partly a pure andesite rock. But that must be verified. It should also be verified whether all the granites have the same age.
The Lamprophyre dykes are the oldest hypabyssal intrusions and were created long times before the event.

First Results:
Paper "Science" vol. 354, issue 6314, pp. 878-882 (2016, Nov.16)
"The uppermost peak ring is composed of ~130 m of breccia, with impactmelt fragments that overlie clastpoor impact melt rock.We encountered felsic basement rocks between 748 and 1334.7 mbsf that were intruded by preimpact mafic and felsic igneous dikes as well as impact-generated dikes.
We recovered one particularly thick impact breccia and impact melt rock sequence between 1250 and 1316 mbsf. The entire section of felsic basement exhibits impact-induced deformation on multiple scales. There aremany fractures (Fig. 3A), foliated shear zones (Fig. 3B), and cataclasites (Fig. 3C), as well as signs of localized hydrothermal alteration (Fig. 3D). The felsic basement is predominantly a coarse-grained, roughly equigranular granitic rock (Fig. 3E) that is locally aplitic or pegmatitic and, in a few cases, syenitic.
The basement rocks in the peak ring differ from basement in nearby drill holes encountered immediately below the Mesozoic sedimentary rocks, suggesting a source of origin that was deeper than 3 km (???).
Evidence of shock metamorphism is pervasive throughout the entire basement, with quartz crystals displaying up to four sets of decorated planar deformation features. We observed shatter cone fragments in pre-impact dikes between 1129 and 1162 mbsf, as well as within the breccia. Jointly, the observed shock metamorphic features suggest that the peak ring rocks were subjected to shock pressures of ~10 to 35 GPa (?) . No clear systematic variation in shock metamorphism was observed with depth. Impact-melt, which is formed at shock pressures of >60 GPa (?), is also a component of the peak ring.
The formation of the Chicxulub peak ring from felsic basement confirms that crustal rocks lie directly above Mesozoic sedimentary rocks, which is consistent with the dynamic collapse model of peak-ring formation (???).
The drilling data confirm that the peak-ring rocks have low densities and seismic velocities, as suggested by geophysical models. The density of the felsic basement varies between 2.10 and 2.55 g cm−3, with a mean of 2.41 g cm−3, and P wave velocities vary between 3.5 and 4.5 km s−1, with a mean of 4.1 km s−1. These values are unusually low for felsic basement, which typically has densities of >2.6 g cm−3 (correct is: 2.5 to 2.7 !) and seismic velocities of >5.5 km s−1 (correct is: 4.0 to 6.0)."

It is claimed that the condition of the drilled felsic basement rocks provide the evidence for the existent of a "peak ring" in the Chicxulub crater. These parts of this crystalline basement were shifted several kilometers towards the surface during impact and lie directly above Mesozoic sedimentary rocks. These rocks are cross-cut by dikes and shear zones and have an unusually (?) low density and seismic velocity. Analysis shows that impact generated vertical fluxes and increased porosity.

Again only wishful thinking ! Model simulations are for the trash. Nothing was uplifted and the shear zones etc. can  have emerged during the explosion of the supervolcano, or of times long before the event.
"Shatter cone fragments in pre-impact dikes" in amphibolite facies are even a clear indication that they were created by shock waves in the magma-chamber long time before the event. But, no of the existing hypotheses for the formation of shatter-cones currently is able satisfactory explain the characteristics of this fracturing phenomenon.
I refer in this context to the mysterious angular sandstone columns in Jebel Uweinat (Egypt), and Israel, Scotland, Germany, Australia and Paraguay, which were clearly created by subvolcanic shock waves.


My new geological section through the Chicxulub crater


Here some pictures that I found in publications in the net
 

                

Felsic basement rock types

Shatter-cone fragment from an amphibolite clast in the breccia (708.5 mbsf)



Above the crystalline basement: "Green melt" with crystal grains (?)
Photo published on May 10


Breccia in condition of solution-penetration (690 mbsf ?)



Breccias



 



Filled fissure in the granite



Melt rock with granitic clasts



"Granite cut by mixture of impact melt (green vs black)"


Seems to be black andesite melt !? (depth unknown)



Core 104R: Granite with melt filled fissures



Crystalline basement rock, and lots of it



Different "granite"


          
Dark mafic melt (andesite ?) and pink granitic basement rock


     
Pre-event welded shear-fissure in the basement rock


About 1165 mbsf: Pre-"impact" dyke filled with crystals and clasts, perhaps Lamprophyre
 (finds of shatter-cone fragments in amphibolite facies)


"In two days of drilling (24th - 25th) we recovered a complicated sequence of melt breccia. This sequence has some physical properties that are different to the previous melt breccias found further up the hole"



About 1265 mbsf : No "impact" melt breccia
perhaps
amphibolite clast of Lamprophyre dyke