Impact Melting

Osinski, G. R.; Grieve, R. A. F.; Marion, C. L.; Chanou, A.

doi:10.1002/9781118447307.ch9

Cited by 15 publications

(13 citation statements)

References 98 publications

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“…These flows are interpreted to be impact melt, mixtures of clasts and melted material that are emplaced during the late stages of impact crater formation (Howard and Wilshire, 1975;Hawke and Head, 1977;Osinski et al, 2011). Melt generation is a fundamental part of the impact process and is influenced by a number of factors including impact velocity, impact angle and the composition of the impactor and the target (e.g., Grieve et al, 1977;Osinski et al, 2012). Thus, the origin and emplacement of impact melt flows may provide important insights into the impact cratering process in general.…”

Section: Introductionmentioning

confidence: 98%

Global distribution of lunar impact melt flows

Neish

Madden

Carter

et al. 2014

Icarus

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Section: Introductionmentioning

confidence: 98%

Global distribution of lunar impact melt flows

Neish

Madden

Carter

et al. 2014

Icarus

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“…; Osinski et al. ; Neish et al. ) would cause rapid changes in the overall melt composition but also promote turbulent mixing.…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, the fallback of material into the melt sheet means a compositional heterogeneity can also occur vertically as clasts are entrained and assimilated into the top of the melt (Osinski et al. ). An example of the heterogeneity that can be observed within impact melt rocks can be seen at the Mistastin Lake impact structure, Canada.…”

Section: Introductionmentioning

confidence: 99%

Through the impact glass: Insight into the evolution of melt at the Mistastin Lake impact structure

Hill

Osinski

Banerjee

2020

Meteorit & Planetary Scien

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By analyzing impact glass, the evolution of the impact melt at the Mistastin Lake impact structure was investigated. Impact glass clasts are present in a range of impactites, including polymict breccias and clast-rich impact melt rock, and from a variety of settings within the crater. From the glass clasts analyzed, three petrographic subtypes of impact glass were identified based on their clast content, prevalence of schlieren, color, texture, and habit. Several alteration phases were also observed replacing glass and infilling vesicles; however, textural observations and quantified compositional data allowed for the identification of pristine impact glass. Although the various types of glasses show significant overlap in their major oxide composition, several subtle variations in the major oxide chemistry of the glass were observed. To investigate this variation, a least-squares mixing model was implemented utilizing the composition of the glass and the known target rock chemistry to model the initial melt composition. Additionally, image analysis of the glass clasts was used to investigate whether the compositional variations correlated to textural difference in the lithologies. We propose that the textural and compositional dichotomy observed is a product of the evolution, assimilation, and emplacement of the glass. The dichotomy is reflective of the melt either being ballistically emplaced (group 2 glasses: occurring in melt-poor polymict breccias at lowermost stratigraphic position outside the transient crater) or the result of late-stage melt flows (group 1 glasses, occurring in meltbearing polymict breccias and impact melt rocks at higher stratigraphic positions outside the transient crater). P. J. A. Hill et al. Impact glass at Mistastin Lake

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“…Breccia dikes are a ubiquitous feature of impact craters that can be broadly characterized as injections of fragmented, and in some dikes molten, target rock into the crater subsurface during an impact event. These dikes are differentiated primarily by their matrix composition and include: (1) pseudotachylites (matrix dominated by impact melt glass generated in situ; Lambert, 1981;Stöffler and Grieve, 2007), (2) impact melt dikes (intrusion of impact melt from the crater melt sheet; Osinski et al, 2012), and (3) lithic breccia dikes (clastic matrix free of impact melt; Lambert, 1981). Pseudotachylites are emplaced during shock compression, whereas thicker lithic breccia dikes are interpreted to be emplaced after the passage of the shock wave, during dilatation of the target rock and excavation of the transient crater (Lambert, 1981;Masaitis, 2005).…”

Section: Introductionmentioning

confidence: 99%

A matter of minutes: Breccia dike paleomagnetism provides evidence for rapid crater modification

Fairchild

Swanson‐Hysell

Tikoo

2016

Geology

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During an impact event, a crater's transient structure adjusts gravitationally. Within medium-sized complex craters, a central uplift rises and collapses resulting in large-scale rotations of the target rock. Estimated crater modification rates from numerical models indicate that complex impact craters modify to a structurally stable state within tens of seconds to several minutes after excavation. However, there is little direct geologic evidence constraining these rates. We show how paleomagnetic measurements of lithic breccia dikes emplaced during crater excavation can be used to constrain the rate of crater modification within the central uplift of the ~34-km-diameter Slate Islands impact structure, Ontario, Canada. The uniformity and linearity of paleomagnetic directions among the clasts and matrix of breccia dikes throughout the impact structure indicate that breccia dikes were frictionally heated above the magnetite Curie temperature (580 °C) during their emplacement and subsequently cooled in situ through magnetic blocking temperatures. The tight grouping of these paleomagnetic directions implies that these breccia dikes cooled and locked in magnetic remanence over a time interval in which the impact structure was not experiencing structural rotations and had already reached a stable state. Conductive cooling of the thinnest sampled breccia dike would have led to the recording of magnetic remanence approximately six minutes after emplacement. This constraint necessitates a stable crater structure only minutes after impact and presents a rare case in which a geological process can be resolved on such a short time scale.

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Impact Melting

Cited by 15 publications

References 98 publications

Global distribution of lunar impact melt flows

Global distribution of lunar impact melt flows

Through the impact glass: Insight into the evolution of melt at the Mistastin Lake impact structure

A matter of minutes: Breccia dike paleomagnetism provides evidence for rapid crater modification

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