What is an example of shock metamorphism?
Nearly all meteorites of all types exhibit some evidence of shock metamorphism, ranging from deformation of olivine crystals to complete melting. Among the effects of impact, the most notable are brecciation and the formation of high pressure polymorphs.
How does shock metamorphism happen?
Shock metamorphism exclusively occurs locally around impact craters and possibly around some diatremes. It is characterized by extremely high P/T conditions (tens of hundred of kilobars) over very short time spans. These conditions result from the passing of a shock wave through the rocks.
What rocks form from shock metamorphism?
Such shock-metamorphic effects, in addition to the shatter cones and slickenslides, include brecciated rocks, suevites, impact melts and pseudotachylites.
What are shocked minerals?
Shocked quartz is a form of quartz that has a microscopic structure that is different from normal quartz. Under intense pressure (but limited temperature), the crystalline structure of quartz is deformed along planes inside the crystal.
What is impact or shock metamorphism?
Shock metamorphism or impact metamorphism describes the effects of shock-wave related deformation and heating during impact events.
Where is Stishovite found in nature?
Barringer Crater
The results are particularly exciting because stishovite is exactly the mineral found in shocked rocks at the Barringer Crater and similar sites across the globe. Indeed, stishovite (named after a Russian high-pressure physics researcher) was first found at the Barringer Crater in 1962.
What is burial metamorphism?
Burial Metamorphism (Fig. 8.3): occurs when sedimentary rocks that had undergone diagenesis are buried even deeper. Diagenesis grades into burial metamorphism, a relatively mild type of metamorphism resulting from the heat and pressure exerted by overlying sediments and sedimentary rocks.
What are the characteristic features of shock metamorphism?
Although the occurrence of planar fractures is relatively common in other deformed rocks, the development of intense, widespread, and closely spaced planar fractures is considered diagnostic of shock metamorphism.
What is prograde metamorphism?
Prograde metamorphism involves the change of mineral assemblages (paragenesis) with increasing temperature and (usually) pressure conditions. These are solid state dehydration reactions, and involve the loss of volatiles such as water or carbon dioxide.
Is stishovite a form of silica?
Stishovite is an extremely hard, dense tetragonal form (polymorph) of silicon dioxide. It is very rare on the Earth’s surface; however, it may be a predominant form of silicon dioxide in the Earth, especially in the lower mantle.
What is stishovite used for?
Chemistry: SiO2; Silicon Dioxide. Group: Rutile and Quartz. Uses: As an indicator of a meteor impact and as mineral specimens.
How is burial metamorphism recognized?
Burial metamorphism occurs when sediments are buried deeply enough that the heat and pressure cause minerals to begin to recrystallize and new minerals to grow, but does not leave the rock with a foliated appearance.
Which is the best description of shock metamorphism?
Shock metamorphism or impact metamorphism describes the effects of shock-wave related deformation and heating during impact events.
Can a kink band be a shock metamorphic effect?
Kink bands, although common in impact environments (Fig. 4.2), can also be pro- duced by normal tectonic deformation; they are not a unique criterion for shock metamorphism, and they will not be dis- cussed further.
Which is the largest shock metamorphic crater in the world?
The larger of the two, the 65-million-year-old Chicxulub crater, Yucatan, Mexico, is buried under more than 300 m of carbonate rocks, and was identified in 1981 by the recognition of circular patterns in gravity and magnetic field data. Shock metamorphic features in drill cores have confirmed the identification.
Why do some meteorites have 20 GPa shock metamorphism?
Thus, 20 GPa shock metamorphic effects found in some small meteorites may be interpreted as the result of impacts on a meteorite parent body. The exception to this general rule is when there is evidence that a small meteorite is a fragment of a much larger body that impacted the Earth at high velocity.