High-Pressure Shock Metamorphism
| Additional photos for this section: Album 4 |
| Comet Impact Inquiry |
| "Science Related" not "Scientifically Related" |
According to current understanding, “only the presence of diagnostic shock metamorphic
effects” by itself “can provide unambiguous evidence for an impact origin” (French, 1998). It is
acceptable that numerous minerals found in and around impact structures show the effects
and changes due to sudden shock. High-pressure evidence - shock metamorphism, covering
impact critera no. 5, shows multiple sets of intersecting lines or shock lamellae, the shock-
induced micro twinning along with strong rhombohedral planar deformation features (PDFs) on
quartz blocks ranging in size from 25 - 35 mm. Also shown in microscopic view are planar
fractures (PFs) in quartz and shock deformation in mineral grains 2mm or less in size. Many
more photos applicable to this section available in Album 4!
effects” by itself “can provide unambiguous evidence for an impact origin” (French, 1998). It is
acceptable that numerous minerals found in and around impact structures show the effects
and changes due to sudden shock. High-pressure evidence - shock metamorphism, covering
impact critera no. 5, shows multiple sets of intersecting lines or shock lamellae, the shock-
induced micro twinning along with strong rhombohedral planar deformation features (PDFs) on
quartz blocks ranging in size from 25 - 35 mm. Also shown in microscopic view are planar
fractures (PFs) in quartz and shock deformation in mineral grains 2mm or less in size. Many
more photos applicable to this section available in Album 4!
These are some of the transparent to semi-transparent crystals found under the root-mat covering the point of impact or mid-
center of the small impact structure. As there as many faces of different sizes and shapes on each side of the crystals, it is
difficult to discern a basic shape on which to base the crystals’ structures.
center of the small impact structure. As there as many faces of different sizes and shapes on each side of the crystals, it is
difficult to discern a basic shape on which to base the crystals’ structures.
References:
Nicholas M. Short, Sr. - Remote Sensing Tutorial (Section 18, Basic Science II: Impact Cratering): Shock Metamorphism –
[http://rst.gsfc.nasa.gov/Sect18/Sect18_3.html]
[http://rst.gsfc.nasa.gov/Sect18/Sect18_3.html]
French B. M. (1998) Traces of Catastrophe: A Handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact
Structures. LPI Contribution No. 954, Lunar and Planetary Institute, Houston. 120 pp.
Structures. LPI Contribution No. 954, Lunar and Planetary Institute, Houston. 120 pp.
Nicholas M. Short, Sr. - Remote Sensing Tutorial (Section 18, Basic Science II: Impact Cratering): The Manson Impact
Crater [http://rst.gsfc.nasa.gov/Sect18/Sect18_3a.html]
Crater [http://rst.gsfc.nasa.gov/Sect18/Sect18_3a.html]
I think it is fair to say that I do not know my rock minerals. If it is white, milky with lovely sheen
and without planes... it is quartz. If it is white, milky, layered without sheen... it is calcite. Some
of the mineral blocks below show partial planes or layering, only, the planes may be deep
fractures. Although I have tried many image sources such as Cochise College’s Virtual
Geology Museum [http://skywalker.cochise.edu/wellerr/VGM/intro.htm] and our local library’s
rock collection, they are not easily identified. I believe that I am unable to identify them
because they have experience shock and heat change.
and without planes... it is quartz. If it is white, milky, layered without sheen... it is calcite. Some
of the mineral blocks below show partial planes or layering, only, the planes may be deep
fractures. Although I have tried many image sources such as Cochise College’s Virtual
Geology Museum [http://skywalker.cochise.edu/wellerr/VGM/intro.htm] and our local library’s
rock collection, they are not easily identified. I believe that I am unable to identify them
because they have experience shock and heat change.
For now they are being referred to as quartz. Many of the pieces show an intrusion of dark
mineral with those areas attracted to a magnet. In spite of my failure to identify them, they are
minerals, which show persistent planar deformation features.
mineral with those areas attracted to a magnet. In spite of my failure to identify them, they are
minerals, which show persistent planar deformation features.
Blocks ranges in size from 25 to 35 mm. Although the photos are macro mode photo shots, multiple sets of
intersecting lines or shock lamellae, the shock-induced micro twinning along with strong rhombohedral
planar deformation features (PDFs) can be seen without the aid of a magnifier. In photo 4, the blocks
appear to be much like quartz.
intersecting lines or shock lamellae, the shock-induced micro twinning along with strong rhombohedral
planar deformation features (PDFs) can be seen without the aid of a magnifier. In photo 4, the blocks
appear to be much like quartz.
Photo 1
Photo 4
Photo 3
Photo 2
Closely spaced alternate or Brazil twins deformation lines showing planar deformation features (PDFs) - similarity with image shown on
this page - N.M. Short [http://rst.gsfc.nasa.gov/Sect18/Sect18_3.html]. Seen also are planar fractures (PFs) below PDFs (photo 1).
Rhombohedral cleavage planar features and multiples sets of PDFs or shock lamellae (photo 2 & 3). Micro-twinning, seen only when
magnified, on fractured quartz surface (photo 4). Photos taken through a 30x magnifier with the camera set on macro-mode to
emphasize the parallel lines and rhombohedral cleavages.
this page - N.M. Short [http://rst.gsfc.nasa.gov/Sect18/Sect18_3.html]. Seen also are planar fractures (PFs) below PDFs (photo 1).
Rhombohedral cleavage planar features and multiples sets of PDFs or shock lamellae (photo 2 & 3). Micro-twinning, seen only when
magnified, on fractured quartz surface (photo 4). Photos taken through a 30x magnifier with the camera set on macro-mode to
emphasize the parallel lines and rhombohedral cleavages.
Photo 1
Photo 3
Photo 2
Microscopic view of four of the mineral grains, ranging in sizes from 1 to 1 1/2 mm, from the group shown on the far right. With no ability
to view thin sections or etch the grains, larger and more transparent grains were viewed at 300x. Quite possible some of the grains are
glasses. They are residue caught in the bottom of the bucket after washing the mud from the rocks picked up at the exact point of impact.
to view thin sections or etch the grains, larger and more transparent grains were viewed at 300x. Quite possible some of the grains are
glasses. They are residue caught in the bottom of the bucket after washing the mud from the rocks picked up at the exact point of impact.
Christian KOEBERL, Ao. Univ. Professor Dr., Impact Cratering: An Overview of Mineralogical and Geochemical Aspects
(after: Koeberl, C., 1997, Impact cratering: The mineralogical and geochemical evidence. In: Proceedings, "The Ames
Structure and Similar Features", ed. K. Johnson and J. Campbell, Oklahoma Geological Survey Circular 100, 30-54)
[http://www.univie.ac.at/geochemistry/koeberl/impact/]
(after: Koeberl, C., 1997, Impact cratering: The mineralogical and geochemical evidence. In: Proceedings, "The Ames
Structure and Similar Features", ed. K. Johnson and J. Campbell, Oklahoma Geological Survey Circular 100, 30-54)
[http://www.univie.ac.at/geochemistry/koeberl/impact/]
Throughout my research, I have read that the true nature of shock effect can only be resolved by
transmission electron microscopy (TEM). Also seen are numerous images labeled in the realm of
“photomicrographs; thin sections; cross polarizers or polarize lighting; width measurements in um
and etched with hydrofluoric acid to emphasize the planar deformation features.” Thankfully, the
materials at hand are large and PDFs are extremely straight with sharp parallel lamellae.
transmission electron microscopy (TEM). Also seen are numerous images labeled in the realm of
“photomicrographs; thin sections; cross polarizers or polarize lighting; width measurements in um
and etched with hydrofluoric acid to emphasize the planar deformation features.” Thankfully, the
materials at hand are large and PDFs are extremely straight with sharp parallel lamellae.
The multiple sets of sharp PDFs on the pieces of quartz and the clear planar fractures seen in
microscopic view below attest to the levels of shock sent through them. This is consistent with the
number of small impact structures seen on the sloping bench and outlined in the aerial
photograph shown as map 3 in Album 1. (Map 3 shows also numerous impact structures moving
in a North Eastern direction.) With no ability to do TEM work, produce thin sections or etched grains
with acid, I provided simple 30x micro photographs and 300x microscopic view photographs of
PDFs and PFs, respectively.
microscopic view below attest to the levels of shock sent through them. This is consistent with the
number of small impact structures seen on the sloping bench and outlined in the aerial
photograph shown as map 3 in Album 1. (Map 3 shows also numerous impact structures moving
in a North Eastern direction.) With no ability to do TEM work, produce thin sections or etched grains
with acid, I provided simple 30x micro photographs and 300x microscopic view photographs of
PDFs and PFs, respectively.
Photo 4
Photo 1
Photo 5
Photo 4
Photo 3
Photo 2
Quartz conglomerate with shock fractured milky and transparent quartz crystals. Bright points show within each crystals held together by
a fine-grain yellowish-white matrix (photos 1 - 3). Fractured quartz within magnetic impact breccia consisting of quartz and other
minerals held together by impact melt substance (photos 4 & 5). Photos showing crystal subject in their entirety are in the Album.
a fine-grain yellowish-white matrix (photos 1 - 3). Fractured quartz within magnetic impact breccia consisting of quartz and other
minerals held together by impact melt substance (photos 4 & 5). Photos showing crystal subject in their entirety are in the Album.
Photo 4
Photo 3
Photo 2
Photo 1
Planar deformation features on quartz grain transform to glass (diaplectic glass or thetomorph of quartz - photo 1). Polymorphs and
thetomorphs of quartz (photos 2 - 4). Shock-induced quartz crystal converted to glass (photo 5)
thetomorphs of quartz (photos 2 - 4). Shock-induced quartz crystal converted to glass (photo 5)
Photo 5
Transparent and semi-transparent crystals found at the point of impact or exact center of one of the small impact structures. Due to the
many faces and different shapes and sizes of those faces, it is difficult to discern the shape of the crystals structure. Not sure what to
make of the lines on the crystal in the photo to the utmost right.
many faces and different shapes and sizes of those faces, it is difficult to discern the shape of the crystals structure. Not sure what to
make of the lines on the crystal in the photo to the utmost right.
Shatter cones in Sedimentary target and other glasses (Special Evidence) such as tektites, carbon spherules and glass
spherules from the impact structure is covered in the next section!
spherules from the impact structure is covered in the next section!
The faces do have similarities in shape and being unfinished in form to the layers seen on the glass-like carbon. One of the
crystals has an indentation similar to those in the glass-like carbon. Quite possible, they are lonsdaleite__ the diamond that
form under extreme pressure and heat generated by an impact. A multitude of colors explodes from within the more
transparent crystals, some of which show signs of fracture. (More photos in Album 4)!
crystals has an indentation similar to those in the glass-like carbon. Quite possible, they are lonsdaleite__ the diamond that
form under extreme pressure and heat generated by an impact. A multitude of colors explodes from within the more
transparent crystals, some of which show signs of fracture. (More photos in Album 4)!
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Red & yellow colored
glasses in soil!