Chicx-03A (M0077A) drilling results
ESO - Chicxulub K-Pg Impact Crater Expedition 364

Norbert Brügge Germany

Update: 08.04.2018


What can we say when we analyze the ECORD drilling report, which presents unexpected results for all and brings the impact-theory advocates in difficult situation:

The Chicxulub crater is smaller than predicted (see below). 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 (granite) is encountered here in an exceptionally high position. Dykes therein could be intrusions from the dioritic magma chamber and/or older intrusions, create long times before the event. There are strong indications that the so-called "impact melt" above the granite in their origin is an
 andesitic melt  .
If the so-called "impact melt" is indeed a glassy andesitic melt, the entire impact theory collapses like a "house of cards", finally.

Note:  In the meantime we know that a granitoide intrusion from the Carboniferous period was drilled and the dykes are different in composition. The composition of the granitoide intrusion point to syenite and granite origin. The composition of the dikes varies in felsic as well as in a range from  small quartz content to high content of foids (Phonothephrite, basanite, foidite). The composition of the "dark melt" above the granite-intrusion  (720 to 745 mbfs) as well as deeper (1250 to 1310 mbsf), in the granite itself, has not yet been published ...... that is more than strange !

New geological section through the Chicxulub crater as well as of the creation of the structure

First published Results of Research

Paper "Science" vol. 354, issue 6314, pp. 878-882 (2016, Nov.16)
"The uppermost peak ring is composed of ~130 m of breccia, with impact melt 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, foliated shear zones, and cataclasites, as well as signs of localized hydrothermal alteration. The felsic basement is predominantly a coarse-grained, roughly equigranular granitic rock 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.

Anyone "brain" have come to the conclusion that the detection of shatter-cones, PDFs in quartz grains, "suevite" and glassy melt, as well as iridium and other extraordinary inclusions (e.g., diamond) can only be related to an extraterrestrial event. Again and again such finds in classic "impact craters" are used for the proof. But these are mostly of volcanic origin. Therefore, the criteria used are unsuitable.

Further published Results

Site M0077: Lower Peak Ring
S. Gulick, J. Morgan and others --  IODP Publications 2017;  (+PDF)

"Hole M0077A was drilled through a long succession of mainly felsic basement rocks of granitoid composition from 747.02 mbsf (Section 95R-3, 117 cm) to the bottom of the hole.
These rocks are petrographically characterized as coarse-grained granite to syenite hosting aplite and pegmatite dikes. Moreover, granitoid rocks are intruded by three types of subvolcanic dikes or dike swarms that are macroscopically classified as felsite, dacite, and diabase/dolerite. An approximately 100 m thick unit of  suevite and impact melt rock (edited: melt rock and clast bearing melt rock) occurs at 1215–1316 mbsf.
The dominant basement lithology is macroscopically classified as a granitoid. Overall, the rock is coarse grained and consists of red to pink alkali-feldspar, white to light yellowish plagioclase, and gray to white quartz, with some biotite and, locally, accessory minerals.
Alteration of granitoids is mostly observed near contact zones with faults,  melt rock, breccias, and intrusive dikes. Granitoids here display color variations that could be caused by thermal or shock alteration or a combination of both. Feldspars often show discoloration to green or variable shades of yellow, orange, and red, whereas quartz may turn milk-white or rarely pale red. Mafic minerals locally appear midgray instead of black.

Coarse-grained granite (97R-3) Dark green altered granite (168R-3) Altered granite with pink quartz (272R-1) Red alkali-feldspar granite (296R-2)

Aplite and pegmatite
Aplite and pegmatite dikes were commonly observed within the granitic host rock and commonly occur together. These dikes range in thickness from ~10 to 80 cm. Aplite is characterized by fine-grained zones of diffusely distributed feldspar minerals andranges from orange to dark pink. Apart from alkali-feldspar, concentrations of other minerals vary. Plagioclase, quartz, and biotite are strongly reduced or absent. Pegmatite is composed of large alkali-feldspars, plagioclase, quartz, and minor biotite. Contact boundaries between the dikes and the host granitic rock are commonly sharp and do not show metamorphism or alteration zones.
Three grayish brown dikes were found within the granitoid rocks in Sections 164R-3, 238R-1, 238R-2, and 246R-3 through 247R-2 and were macroscopically described as dacites. These dacite dikes have a porphyritic texture with euhedral plagioclase phenocrysts as large as 3.5 cm, alkali-feldspar phenocrysts as large as 2 cm, and minor quartz and biotite. Alkali-feldspar locally displays reaction rims and may therefore be clasts derived from the granitoid country rock. The groundmass is medium-grained with plagioclase, alkali-feldspar, and amphibole. Dike thicknesses are between 0.6 and 2.7 m.
Three very fine grained, homogeneous, midbrown to gray dikes within the granitoid rocks in Sections 234R-2 through 235R-2, 236R-3 through 237R-1, and 238R-3 through 239R-2 were macroscopically described as felsites. Larger phenocrysts seen in the dacite are lacking here. Felsite dike thicknesses range from 1.5 to 2.5 m. Xenoliths occur and sometimes include the local granitic host rock but otherwise are deep-sourced gneiss or amphibolite that range in size from submillimeter to ~5 cm. Felsite has local white- or black-filled veins and rare quartz-filled vugs as large as 3 cm.

Aplite dike (147R-2)

Pegmatitic dike (114R-1)

Dacite (246R-3)

Dacite thin section (246R-3)

Felsite (239R-2)

Felsite thin section (234R-3)

Diabase/dolerite and porphyritic diabase/dolerite
Several mafic dikes were observed in the upper portion of the granitoids and were macroscopically described as diabase/dolerite. They have two textures; the more common one is porphyritic, composed of a dark gray to black aphanitic groundmass containing characteristic ~1–10 mm needle-shaped white-green, partially altered plagioclase phenocrysts and 1 mm long mafic phenocrysts. The other consists of a dark gray to black aphanitic groundmass without plagioclase phenocrysts. The groundmass is composed of mafic and felsic mineral constituents and iron sulfide mineral phases. Rarely, there are granitic fragments within the matrix (on average less than 1 fragment per section) that appear partially digested. Dike thicknesses range from a few centimeters to 5 m.



Porphyritic diabase/dolerite (169R-2)
 with large plagioclase and pyroxene (169R-3)

Aphanitic diabase/dolerite (162R-1) with
submillimeter-sized plagioclase (221R-3)

My summery of the preliminary important results

Suevite and impact melt rock (edited in: Melt rock and clast bearing melt rock)
An approximately 100 m thick unit of suevite and impact melt rock occurs from 1215 to 1316 mbsf (Cores 265R–298R), with suevite as the dominant lithology. In Cores 277R–298R, suevite and impact melt rock form a nearly continuous, 58 m thick interval, with only a few decimeter- to meter-scale occurrences of granite, some of which may be suevite within the impact melt rock.
Flow banding occurs in both. The clasts entrained in the units have angular to rounded shapes and consist of melt rock, granitic rock (including aplite), granodiorite, felsite, diabase/dolerite, another unidentified mafic lithology, gneiss, mylonite, schist, and quartzite. These rocks do not have visible carbonate clasts or clasts of other sedimentary rocks. The largest clast logged was 100 cm (a gneiss in Section 281R-2). Some clasts are mantled by impact melt rock. Other clasts are partially resorbed or digested within the melt rock.
The impact melt rock and suevite are locally altered. White and green veins were observed, and diffuse green mineralization is common. Dissolution vugs occur in both intervals and are in some cases partially filled with a green mineral. Red and yellow mineralization is also present but less frequent than green mineralization."

Andesite intrusion into Granite

Andesite in schlieren configuration

Clast rich andesite melt (268R)

Large clasts in black/brown andesite melt

Large clast in andesite melt rock

About the composition of the "impact melt" only this is in the article:
The major element compositions of 194 samples from cores 96R-303R (747.02-1334.69 mbsf) were determined.
Compared to the granitoids, the pre-impact dike lithologies (felsite, dacite, and diabase/dolerite) have much lower SiO2 and K2O contents than the granitic rocks, whereas MgO, FeO, CaO, MnO, and TiO2 are typically significantly enriched. A dacite sampled at 1160.9 mbsf exhibits a moderate enrichment in TiO2 and a moderate depletion in SiO2. Suevite and impact melt rock intercalations show variable compositions but tend to be relatively depleted in K2O and enriched in TiO2, FeO, MgO, and MnO compared to the granitoids. The Na2O concentrations from 948.39 and 1332.75 mbsf (average 6.12 ± 1.12 wt%) are slightly higher than those between 748.89 to 948.39 mbsf (average 3.92 ± 0.59 wt%).

Site M0077: Upper Peak Ring

S. Gulick, J. Morgan and others --  IODP Publications 2017;  (+PDF)

"Upper Peak Ring interval lithologies are divided into Units 2 and 3. Unit 2 is polymict breccia with impact melt rock fragments and is thus suevite. Unit 3 is impact melt rock with occasional (<25%) clasts. Units 2 and 3 are divided into Subunits 2A–2C, 3A, and 3B based on sedimentary features and matrix or groundmass characteristics.

Unit 2
The upper surface of Unit 2 in the lithologic sequence is defined by the sharp stylolitized contact at the top of the cross-bedded suevite in Section 40R-1, 109.4 cm (617.33 mbsf). Unit 2 is an approximately 104 m thick suevite (interval 40R-1, 109.4 cm, to 87R-2, 90 cm; 617.33–721.62 mbsf) and is predominantly composed of various types of green to black impact melt rock clasts, as well as to a lesser degree lithic fragments, including Mesozoic sedimentary rocks and crystalline basement rocks. The maximum clast size, defined here as the long axis length of the largest clast in each section, varies from 0.2 cm to more than 25 cm. Overall, the unit has a fining-upward trend, although upward coarsening or grain size oscillations in maximum clast size are locally observable, especially in the upper part of Subunit 2A.

Unit 3
The second principal lithology of the Upper Peak Ring interval consists of a ~25 m thick succession of impact melt rocks. It is dominantly clast-poor impact melt rock, but clast-rich intervals occur locally.
Subunit 3A
Subunit 3A is ~16 m thick (interval 87R-2, 90 cm, to 92R-3, 17 cm; 721.62–737.56 mbsf) and is characterized by a mixture of dark green and black clast-poor impact melt rocks. The first occurrence of the dark green melt rock marks the top of the subunit. The green melt rock often forms a matrix with angular fragments of black melt rock. These black melt rock fragments commonly entrain various mineral fragments and <1 mm to ~1 cm lithic fragments and also can contain vesicles and flow lines. The green melt rock reacts to HCl and thus may be altered through hydrothermal processes. The green melt rock was also found to be intimately intermixed with black melt rock, forming multiple millimeter to centimeter thin schlieren of green material within the black melt rock.
Black impact melt rock also occurs in larger regions up to 0.5 m in size. These regions include centimeter- to decimeter-sized clasts of target material. The smaller clasts are partially resorbed and in some cases heavily shocked, making lithologic identification difficult. Larger clasts in the impact melt rock are composed of metamorphic and igneous target lithologies, including decimeter-sized clasts of granodiorite (Sample 91R-1, 44–68 cm) and gneiss (Sample 91R-1, 94–110 cm) and rare clasts of red sandstone (e.g., Sample 90R-3, 8–15 cm).
One thin section was available for this subunit (Sample 89R-3, 39–43 cm). The impact melt rock in this sample is variably altered, with some parts consisting of microcrystalline melt rock with tiny phenocryst laths in an aphanitic groundmass (with partly digested clasts and blebs of opaque minerals), green domains consisting of smectite (likely a secondary alteration product from a formerly glassy melt), zeolite, silica, and chloritoid/chlorite. Up to ~0.5 cm angular to subrounded clasts in the melt rock are variably assimilated, some with reaction coronas. A few silica clasts with ballen quartz occur, and one clast of quartz with decorated planar deformation features was noted.
Subunit 3B
Subunit 3B occurs below the green schlieren-bearing black impact melt rock and is a ~9 m thick, black, coherent, clast-poor impact melt rock (interval 92R-3, 17 cm, to 95R-3, 117 cm; 737.56–747.02 mbsf). The contact occurs at the lowest occurrence of green schlieren. Although the green schlieren are absent, the black melt rock still contains observable flow banding and vesicles. It also entrains a variety of mineral and lithic clasts. In some parts, the clasts are evenly distributed. Other areas contain clusters and subtle alignments of clasts. As in Subunit 3A, clasts are composed of metamorphic and igneous target lithologies, but Subunit 3B lacks visible clasts of sedimentary lithologies. Granitoid clasts dominate and increase in abundance toward the base of the subunit, reaching 42 cm in size before the base. Subunit 3B contains clasts of previously solidified impact melt rock that seem to have separated, and the gaps are filled with melt rock. The lower surface of this subunit is the top of the shocked granitoid target in Section 95R-3 at 747.02 mbsf.
One thin section was available for this subunit (Sample 93R-3), revealing that this impact melt rock is composed of a fine-grained matrix made of tiny plagioclase laths and opaque minerals (magnetite) in a melt (now altered to clay minerals). Mineral clasts including quartz, alkali-feldspar, and plagioclase occur, as well as partially assimilated mineral and rock (mainly granitoids) clasts and some melt rock fragments. Quartz grains display planar deformation features and are in some cases toasted. Plagioclase grains with possible planar deformation features were also noted."



Variety of mineral and lithic clasts (?) in "impact melt" rock from Subunit 3A (93R-3)


"Impact melt" rock sample from Subunit 3A.
A. Intermix of green and black "impact melt" rocks with angular to subrounded clasts (89R-3).
B. Microcrystalline black melt rock and green domains of smectite.
C.  Melted silica clast (?) in black melt rock.


About the composition of the "impact melt" in Unit 3 only this is in the article:
"The lowermost portion, which is dominated by impact melt rock, is chemically distinct with higher concentrations of SiO2, TiO2, Al2O3, FeO, and, notably, oxide totals that are on average 20 wt% higher than those of the suevite above."
"In Core 87R through Section 95R-2 (719.54–744.88 mbsf), the mineralogical assemblage is mainly composed of albite and anorthite (average = 30%), as well as quartz (average = 10%). Here, calcite is almost completely absent in the samples. The clay fraction is dominated by smectite (average = 20% of saponite) and traces of mica (phlogopite and glauconite), chlorite (clinochlore), vermiculite, clinoptilolite, and serpentine (lizardite and antigorite). Accessory minerals are again highly variable, including feldspar (sanidine, orthoclase, bassanite, and nepheline), zeolite (microcline and andesine), silicates (talc, forsterite, sodalite, diopside, and ferrosilite), evaporite (gypsum), and oxides (corundum and magnetite). Of particular note is the occurrence of coesite, a high-pressure polymorph of quartz, in Core 87R at 719.99 mbsf, near the top of Unit 3."

Constraints for Enplacement Conditions of the Chicxulub Impact Crater's Upper Peak Ring Section (747-617 mbfs) in IODP Expedition 364 Drill Cores
Axel Wittmann, Arizona State University -- 49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083), 2994.pdf

Content: "The dark vitric melt rock shows variable amounts of liquidus phase phenocryst plagioclase and pyroxene. It contains greenish-brown swirls of assimilated debris and exhibits brecciation. The groundmass of these brecciated melt rocks contains secondary (?) sparitic calcite, phyllosilicates, titanite, and garnet with andradite-rich cores and grossular-rich rims.
In the 15 thin sections 147 zircon crystals occur 3 to 174 μm in size; 35% of these ZrSiO4 grains are components of crystallized melt clasts and one third belongs to lithic clasts; less than 3% of these grains occur in a clastic groundmass. Some zircons that occur in a mafic clast exhibit planar features and ZrO2 domains. Also, zircons associated with garnet-bearing brecciation zones in melt rock exhibit unusually delicate decomposition features.
Preliminary Raman spectroscopic analyses on some of these zircons did not identify the presence of the high-pressure polymorph reidite. Some zircons crystals exhibit features that are unusual and may relate to alteration conditions instead of reactions to high pressures and/or temperatures.
The unusual decomposition texture and the presence of Ca-rich garnet records an unusual high temperature process.
Experimental studies of melts with similar composition to those of Chicxulub found rapid quenching from >1200°C to below 650°C stunts the crystallization of pyroxene and plagioclase phenocrysts."

Chicxulub Impact Structure - Study of Large Impact Formation and Effects (conference talk and tutorial video)
Sean Gulick --
Scientific Computing with Python, Austin, Texas, July 10-16, 2017


Macro- and microscopic Evidence of impact Metamorphism in Rocks from the Chicxulub peak ring
L. Ferričre et al. -- Lunar and Planetary Science XLVIII (2017); 1600.pdf

"The M0077A core was subdivided into three main lithological units: a (post-impact) section (from 505.7 to 617.3 mbsf), an upper (peak ring) section of "suevite" and melt rocks (from 617.3 to 747.0 mbsf), and a lower (peak ring) section mainly consisting of granitoid rocks (with aplite and pegmatite dikes) intruded by different types of subvolcanic dikes, and intercalations of millimeter to decameter thick "suevite" and  melt rock units (from 747.0 to 1334.7 mbsf).
The upper (peak ring) section consists of 104 m of  "suevite"  (polymict lithic breccia with mm to over 25 cm in size melt clasts and lithic mineral and rock fragments) on top of ~25 m  melt rock (dominantly clast-poor but with clast-rich intervals). The matrix of the "suevite" is calcitic (ranging from micritic to sparitic). Clasts include a variety of more or less shocked mineral and rock fragments (sedimentary [including isolated fossils], metamorphic, and igneous lithologies, with carbonate and granitoid being the most abundant rock types) and melt fragments withaltered (green to brown in color in plane-polarized-light; clay minerals) glassy to microcrystalline textures. Many of the melt fragments have flow textures and are occasionally vesicular. They often contain relic mineral clasts (dominated by feldspars and quartz) and shocked lithic rock fragments, or are, themselves, coated with an additional layer of melt. Quartz grains show planar fractures (PFs) and/or (decorated) planar deformation features (PDFs), with up to 3 sets. A few toasted quartz grains were noted. Silica glass, generally recrystallized, with a chert-like appearance (and with ballen silica also occur. Other minerals also exhibit shock features, especially plagioclase and alkali-feldspar (with PFs and PDFs). Possible coesite (??) was observed in a large silica-rich melt fragment. The melt rock from the lower part of the upper (peak ring) section is green to black in color, with flow banding, and in some cases vesicular. The green and black melts are locally intermixed, forming schlieren of green material (altered melt?) in a black-colored melt. A large variety of clasts are present (as in "suevite", with the exception of sedimentary rock clasts that were not found), in some cases so heavily shocked and/or hydrothermally altered that it was difficult to identify them. Shock features similar to those in "suevite" were observed in the melt rocks, such as PFs and PDFs in quartz, toasted quartz, and a variety of shock features in other minerals.
The lower (peak ring) section consists mainly of pervasively deformed granitoid basement rocks (granite to syenite), overall coarse-grained, with locally cm to dm thick aplitic and pegmatitic sections. All main rock-forming minerals, i.e., alkali-feldspar, plagioclase, quartz, and biotite, show signs of shock deformation. In the case of quartz, locally PFs were even visible as a result of preferential hydrothermal alteration. Almost all quartz grains are shocked, with PFs, feather features (FFs), and/or (decorated) PDFs ; up to 4 sets of PDFs are seen. Kinkbanding was also observed for some quartz grains. Similar shock features were observed in alkali-feldspar and plagioclase. Biotites and chlorites are often kinked. Based on qualitative evaluation of the thin sections no noticeable shock attenuation with depth was observed. Preliminary quantitative results seem to indicate little or no shock attenuation with depth.
For the first time shatter cones were found at Chicxulub. They are well-developed in some of the subvolcanic dikes intruding the granitoid basement rocks, such as in aplite at 777.2 and 777.4 mbsf and in phonotephrite dikes at 1125.1, 1131.7, 1137.5, and 1138.3 mbsf. A possible poorly-developed shatter cone was also noted in a coarse-grained granitoid sample at 909.6 mbsf. Finally, "suevites"and melt rocks also occur in the lower (peak ring) section in the form of small dikes and large bodies, such as the ~100 m thick occurrence between 1215 and 1316 mbsf. Similar shock features as in "suevites" and melt rocks from the upper (peak ring) section were observed."

Emplacing impact melt in the Chicxulub peak ring
David A. Kring et al. -- Lunar and Planetary Science XLVIII (2017); 1213.pdf

"Distribution of Melt in the Core: After penetrating (post-impact) sediments (Unit 1), the top of the (peak ring) was encountered at 617.33 mbsf, beginning with a 104-m-thick polymict, melt-bearing breccia (Unit 2) with a calcitic matrix that may represent a plume of carbonate ash. The most abundant clasts in the breccia are melt fragments. That unit has been sub-divided (2A, 2B, 2C) based on sedimentary and matrix features. A melt rock, Unit 3, extends ~26 m to a depth of 747 mbsf. It is dominantly a clast-poor melt rock, but clast-rich intervals occur at ~722, ~732-734, and ~744 mbsf. It has been subdivided to reflect a change from green schlieren-bearing black melt (3A) to a basal ~9.5 m-thick coherent black melt unit (3B). Those units cover granite and related basement lithologies. Thin, <1 m-thick melt horizons were logged within the granite. A thicker (~4 m) series of melt and melt-bearing breccia horizons were logged at ~1000 mbsf and ~58 m of melt and melt-bearing breccias dominate the lower 100 m of core. The total thickness of the basement interval sampled by the borehole is 588 m.

Clast Content: There is a diverse array of sedimentary, metamorphic, and igneous clasts within those units. Sedimentary lithologies are carbonate, chert that in many cases is visibly associated with and derived from carbonate, shale, sandstone, and red silt-stone. Metamorphic lithologies are gneiss, mylonite, schist, amphibolite, and quartzite. Marble was also logged, but thin-section studies are needed to determine if it is a target unit or shock-modified carbonate. Igneous lithologies include granite, granodiorite, diorite, dacite, felsite, and mafic clasts that were variously logged as gabbro, diabase, and dolerite. Carbonate and granite are the most abundant lithologies.
Sedimentary, metamorphic, and igneous lithologies are found in the uppermost units, but carbonate was not logged in the bottom eight cores (from ~722 to ~747 mbsf) of the Unit 3 melt rock, and granite dominates the clast assemblage at the base of that interval. Thin melt horizons within the granite only have clasts of (locally derived) granite. However, the horizon at ~1000 mbsf contains clasts of melt, granite, granodiorite, dolerite, and gneiss. The basal interval of melt and melt-bearing breccias also has a diverse array of metamorphic and igneous clasts, but no sedimentary clasts.

Discussion: For the melt-bearing horizons within the granite, we consider four hypotheses. (1) The "impact" melts in the granite may have been injected into the walls of the transient crater and transported with the bounding granite during uplift and collapse into a peak ring. This seems unlikely, however, because the granite is heavily sheared while the impact melt rocks and melt-bearing breccias are not. The melts were introduced after most (albeit not all) of the deformation of the peak ring had occurred.
The "impact" melts in the granite may have instead been (2) produced by melting along shear planes and faults in the basement. That is a likely source of the thin, <1 m melt horizons, which only contain clasts of granite. However, there is a wide variety of clasts in the thicker melt-bearing units at ~1000 mbsf and at the base of the borehole that would require transport of multiple lithologies (granodiorite, gneiss, dolerite) an unknown distance along an intrusive conduit and emplacement in granite.
We cannot discount, however, (3) the infusion of melt from adjacent melt pools along open fractures in the peak ring. The melts at the base of the borehole lie at a greater depth than "impact" melt in the adjacent crater trough, although that source may require transport through fractures over a distanceof at least 2 km, without quenching, while mixing with clasts from multiple peak-ring lithologies.
An alternative (ludicrously) hypothesis (4) is prompted by the lack of sedimentary clasts in the deeper "impact" melts. If the dynamic collapse and Displaced Structure Uplift models are correct, then as the peak ring collapsed and deformed outward, it may have overrun and flowed over surficial melt-bearing components before the fallback breccia with its sedimentary clast components landed. The repetition of "impact" melts within the granitic sequence implies there was internal shearing within the granite as it displaced outward, allowing it to cover breccias at least twice."

Preliminary chemical Data for drill cores of the Chicxulub impact structure's peak ring
A. Wittmann et al. -- Lunar and Planetary Science XLVIII (2017); 2075.pdf

"Upper  Peak Ring
The 50 samples from the 130 m thick section of "suevite" and (impact) melt rocks between 618.22‒744.07 mbsf show pronounced vertical variation in their major and minor element concentrations. Based on these chemical variations, the upper (peak ring) section can be subdivded into an upper sorted "suevite" section from 617.34‒684 mbsf that is grossly chemically homogenous. A lower sorted "suevite"section from 687‒718 mbsf shows more chemical variation compared to the subsection above, while average concentrations are grossly similar.
The lowermost section between 720‒744 mbsf is dominated by  melt rocks and is chemically distinct with higher concentrations of SiO2, TiO2, Al2O3, FeO compared to the "suevite" subsections and notably, oxide totals that are typically 20 wt% higher than those of the "suevite" subunits above.

Lower Peak Ring:
We analyzed 194 samples from the 586 m thick section of granite, subvolcanic dikes, "suevite" and melt rocks between 747.89‒1332.75 mbsf. The granite lithologies in this section are remarkably similar in composition, suggesting compositions of granites and syenites in the TAS diagram and metasedimentary protoliths. Subtile differences are present, though, for example Na2O concentrations from 748.89‒948.39 mbsf are lower than in the section between 948.39 and 1332.75 m. Very low incompatible trace element compositions suggest a volcanic arc setting for the emplacement of these granites, which is also supported by their magnesian character.
Compared to the granitic rocks, the most common intrusive rock, a dark, aphanitic, subvolcanic lithology, has much lower SiO2 and K2O contents, while MgO, FeO, CaO, MnO, TiO2 are significantly enriched. A less common, brown, fine-grained subvolcanic lithology that exhibits shatter cones displays a chemical affinity to the dark subvolcanic dike lithology in that it shows similar depletion and enrichment trends for the major, minor and trace element concentrations compared to their granite host rocks. In the TAS diagram it plots in the field for phonotephrite, while the dark subvolcanic dikes plot in the fields for foidite and basanite.
Intercalcations of "suevite" and melt rocks show variable compositions but tend to be relatively depleted in K2O and enriched in TiO2, CaO, FeO, MgO, and MnO compared to the granitic rocks."

Ages and Geochemistry of the Basement Granites of the Chicxulub impact crater
L. Xiao et al. -- Lunar and Planetary Science XLVIII (2017); 1311.pdf

"The granitic rocks are intruded by three or more types of subvolcanic dikes or dike swarms including felsite/phonotephrite, dacite/trachyte and diabase/dolerite. Major rock-forming minerals of the granitoid are alkali feldspar, plagioclase, quartz and biotite. Accessory minerals observed in thin section include zircon, apatite, sphene, and opaques. Shock metamorphism is extensive throughout the core; planar deformation features developed in quartz and plagioclase at mineral scale.
Five samples taken from depths of 829mbsf, 927mbsf, 979mbsf, 1076mbsf and 1200 mbsf were dated. Their 206Pb/238U ages are 304+10Ma,321+7.7Ma, 313+14Ma, 325.9+7.5Ma and 340.8+9.9 Ma. A total of 147 analyses yielded major element oxide contents for SiO2 of 64wt% to 79wt%, Al2O3 of 10 to 17wt%, Na2O of 3.5wt% to 7wt%, and K2O of 2wt% to 8wt%. In the TAS diagram, most samples plot within the granite field, while some are in the quartz monzonite and syenite field.
The zircon dating results suggest that the granites were formed mostly around 300-340 Ma ago. This large age variation of the five samples may indicate that this was not a single granitic intrusion during the Carboniferous period."

Some published pictures


Felsic "basement" rock types

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

Transition between black melt (andesite ?) to green melt schlieren (~ 730 mbsf)

A: "Suevite" (~645 mbsf) / B: Melt rock with granite clasts (~745 mbsf)

C: Granite (~814 mbfs) / D: Melt rock with metamorphic and igneous clasts (~1268 mbfs)

A: "Suevite" (~703 mbsf) / B: Melt rock with green schlieren (~738 mbsf) / C: Granite (~1018 mbsf)

Above the granite: "Green melt" with phenocrysts

Shatter cone in a fine-grained phonotephrite dyke (1138.3 mbsf)


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

Filled fissure in the granite

Melt rock with granitic clasts

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

Seems to be the black (andesite?)  melt

Core 104R: Granite with melt filled fissures

Crystalline basement rock, and lots of it

Different "granite"

Contact of black melt and pink granitic rock

Pre-event welded shear-fissure in the granite

About 1160 mbsf: Dacite dyke with granitoide clasts

About 1265 mbsf : Probably amphibolite clast