This handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures emphasizes terrestrial impact structures, field geology, and particularly the recognition and petrographic study of shock-metamorphic effects in terrestrial rocks. Individual chapters include: 1) Landscapes with Craters: Meteorite Impacts, Earth, and the Solar System; 2) Target Earth: Present, Past and Future; 3) Formation of Impact Craters; 4) Shock-Metamorphic Effects in Rocks and Minerals; 5) Shock-Metamorphosed Rocks (Impactities) in Impact Structures; 6) Impact Melts; 7) How to Find Impact Structures; and 8) What Next? Current Problems and Future Investigations.

/pdf/traces-of-catastrophe-a-handbook-of-shock-metamorphic-28xgtwpf9g.pdf

Traces of Catastrophe: A Handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures

Current equation-of-state formulations, used for finite-difference cratering flow calculations, are cast into a framework permitting comparison of peak pressures attained upon impact of a sphere, with a half-space, along the impact symmetry axis, to one-dimensional impedance match solutions. On the basis of this formulation and application of thermochemical data, the regimes of melting and vaporization are examined. For the purpose of identifying material which will, upon isentropic release from the impact-induced shock state, result in a solid just brought to its melting point, i.e., incipiently melted (IM), completely melted (CM), just brought to its boiling point, i.e., incipiently vaporized (IV), and completely vaporized (CV) state, the pressures at which the critical isentropes intersect the Hugoniots of iron and gabbroic anorthosite (GA) are examined in detail. The latter rock type is assumed to be representative of the lunar highlands. The Hugoniot pressures, for which IM, CM, IV, and CV will occur upon isentropic expansion, are calculated to range from 2.2 to
16.8 Mbar, respectively for iron. For the high-pressure phase (hpp) assemblage of GA, modelled as a mixture of plagioclase in the hollandite structure and pyroxene in the perovskite structure, IM, CM, IV, and CV are calculated to occur upon isentropic expansion from Hugoniot states ranging from 0.43 to 5.9 Mbar, respectively. The spatial attenuation of shock pressure along the impact axis is
found to be clearly represented by two regimes, if the peak pressure, P, and radius normalized to that of the projectile, r, are fitted to expressions of the form P ∝ r^α. At distances from 2.2 to 5.6 projectile radii into a GA target, the constant, a, is on the order of -0.2. This low-attenuation rate, near-field regime, extends further into the target at the slower impact velocities and arises because of
the slightly divergent flow associated with the penetration of a spherical projectile. For the near-field impact regime, an impact at 5 km/sec of an iron object with a GA surface will induce CM for GA but
the iron will remain solid. At 15 km/sec, partial vaporization (PV) occurs for both GA and iron, whereas at 45 km/sec, CV occurs in both materials. Similar calculations are summarized for a GA meteoroid striking a GA surface at velocities ranging from 5 to 45 km/sec. At greater radii, in thefar-field regime, the exponent, a, varies systematically from -1.45 to -2.15 for impacts of GA onto GA as the impact velocity is increased from 5 to 45 km/sec. For an iron projectile impacting at speeds of 5-45 km/sec, the exponent, a, varies from -1.67 to -2.95. By comparison, the equivalent value of a, reported for both contained and surface explosions in various rocks is ~ -2. It is suggested that, given field data on shock attenuation (based on identification of various shock metamorphic features versus distance), overall crater size, and some chemical data as to the type of meteoroid which produced a crater, quantitative bounds on the impact velocity of the meteorite may be obtained.

/pdf/equations-of-state-and-impact-induced-shock-wave-attenuation-4zbhefyljx.pdf

Equations of state and impact-induced shock-wave attenuation on the moon

Exogenic and endogenic breccias: a discussion of major problematics

[1] Shatter cones are rock discontinuities known only from sites of extraterrestrial impacts, and they are assumed to be formed by impact-induced shock waves. Here we characterize the structure of shatter cones by field and microanalyses and explain their formation by dynamic fracture mechanics. Our analyses reveal that shatter cones always occur as multilevel, three-dimensional networks, 0.01–100 m in size, with hierarchal branched fractures. A typical, individual shatter cone is a curved, oblate branch that bifurcates from its parent fracture (e.g., a larger shatter cone) and expands to form a spoon-like surface. The unique shatter cone striations are arranged in V-shaped pairs whose enclosed angle is constant for a given sample. We propose that shatter cones are the natural consequence of tensile rock fracturing at extreme velocities. First, the structure of shatter cone networks is strikingly similar to the structure of branched networks of experimental dynamic fractures that propagate at high velocities (velocities that approach the Rayleigh wave speed, VR). Second, “fracture front waves,” generated experimentally by the interaction of a rapidly moving tensile fractures and material inclusions, create tracks on the fracture surface that correspond to the V-shaped striations of shatter cones. Third, applying the front wave concept to our field measurements (Vredefort impact, South Africa) shows that the shatter cones propagated at velocities of 0.98–0.90VR, with a systematic velocity decrease from the impact center. These extreme asymptotic velocities require the intense energy flux of impacts. Our model explains all of the structural features of shatter cones (curved surfaces, cone directivity, unique striations, hierarchic, multilevel structure) and their exclusive occurrence at impact sites.

/pdf/shatter-cones-branched-rapid-fractures-formed-by-shock-ncbte4sm8k.pdf

Shatter cones: Branched, rapid fractures formed by shock impact

Shatter cones have been described from a number of circular and polygonal structures worldwide, the origin of which has been alternatively ascribed to the impacts of large extraterrestrial projectiles or to catastrophic endogenic processes. Despite their association with enigmatic, catastrophic processes, the nature of shatter cones and the physics involved in their formation have not been comprehensively researched. Results of detailed field and laboratory studies of shatter cones from three areas in the collar of the Vredefort Dome in South Africa are presented. Vredefort shatter cones are directly related to a widely displayed fracture phenomenon, termed “multiply striated joint sets (MSJS)”. MSJs are planar to curviplanar fractures occuring at spacings of < 1 to several millimeters. The joint sets have a fractal character. When a new measurement protocol is used in the field, involving study of all joint surfaces and all steps and striae exposed on these surfaces, new information is gained on the genesis and significance of the MSJS and on their relationship to striated conical fractures. The internal constitution of a rock specimen with MSJS was examined in detail, by documenting the precise geometry of many fractures in a suite of parallel thin sections transecting the specimen. The steps and striae on shatter cone surfaces have the characteristics of displacement fractures (microfaults), along which evidence of melting is observed. Shatter cone and MSJS surfaces are often covered with glassy films; we evaluate whether these fracture phenomena are linked to the formation of pseudotachylitic (friction) melt. Our field and petrographic observations can be interpreted as consistent with the generation of shatter cones/MSJS relatively late in the formation of the Vredefort structure. This scenario contrasts sharply with the widely held view that shatter cones are formed during the early “compression” phase of a shock event that affected horizontal strata.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/1998JB900068

Vredefort shatter cones revisited

The composition of spherules and other features on shatter cone surfaces from the Vredefort structure, South Africa

Popular Tasks used by Researchers

How can I help with your research?

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

We encountered an error while loading the panel. Please try refreshing the page.

Something went wrong

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

Anyone with the link can view this chat. You can switch it back to private anytime.

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

N.R. Comins

Author Tools

Chat about Author

Papers

The composition of spherules and other features on shatter cone surfaces from the Vredefort structure, South Africa