— Quartz, as a ubiquitous mineral constituent of the Earth's crust, displays the greatest variety of well-defined residual shock effects among all rock-forming minerals. It represents an important and most reliable shock barometer and thermometer for terrestrial impact formations. In this paper, the current status of knowledge about the nature, origin, and experimental pressure-temperature calibration of shock-induced deformations and phase transformations is reviewed for natural and experimental shock conditions.

Shock metamorphism of quartz in nature and experiment: I. Basic observation and theory*

The convincing identification of terrestrial meteorite impact structures: What works, what doesn't, and why

We reevaluate the systematics and geologic setting of terrestrial, lunar, Martian, and asteroidal “impactites” resulting from single or multiple impacts. For impactites derived from silicate rocks and sediments, we propose a unified and updated system of progressive shock metamorphism. “Shock-metamorphosed rocks” occur as lithic clasts or melt particles in proximal impactites at impact craters, and rarely in distal impactites. They represent a wide range of metamorphism, typically ranging from unshocked to shock melted. As the degree of shock metamorphism, at a given shock pressure, depends primarily on the mineralogical composition and the porosity of a rock or sediment sample, different shock classification systems are required for different types of planetary rocks and sediments. We define shock classification systems for eight rock and sediment classes which are assigned to three major groups of rocks and sediments (1) crystalline rocks with classes F, M, A, and U; (2) chondritic rocks (class C); and (3) sedimentary rocks and sediments with classes SR, SE, and RE. The abbreviations stand for felsic (F), mafic (M), anorthositic (A), ultramafic (U), sedimentary rocks (SR), unconsolidated sediments (SE), and regoliths (RE). In each class, the progressive stages of shock metamorphism are denominated S1 to Sx. These progressive shock stages are introduced as: S1–S7 for F, S1–S7 for M, S1–S6 for A, S1–S7 for U, S1–S7 for C, S1–S7 for SR, S1–S5 for SE, and S1–S6 for RE. S1 stands for “unshocked” and Sx (variable between S5 and S7) stands for “whole rock melting.” We propose a sequence of symbols characterizing the degree of shock metamorphism of a sample, i.e., F-S1 to F-S7 with the option to add the tabulated pressure ranges (in GPa) in parentheses.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/maps.12912

Shock metamorphism of planetary silicate rocks and sediments: Proposal for an updated classification system

Single crystals of sanidine, orthoclase, microcline, oligoclase, and labradorite as well as polycrystalline bytownite were shocked from 10.5 to 45 GPa and recovered. The direction of shock wave propagation in single crystals was always parallel to the crystallographic a-axis. Optical observations reveal a continuous sequence of shock effects: fracturing starts to develop at <10.5 GPa, planar elements develop at 10.5–14 GPa, mosaicism at 18–26 GPa, transformation of the crystal into diaplectic glass begins at 26–34 GPa, and formation of melt glass is observed at ∼42 GPa. Microcline, however, remains weakly birefringent even at 45 GPa. Refractive indices of diaplectic glass drop sharply at shock pressures between 30 and 40 GPa. Xray investigations reveal only a minor expansion of the unit cell of sanidine, whereas the other feldspars display no systematic change of lattice constants. The structural state (Al,Si-distribution) of feldspars is not affected by shock. EPR analyses reveal the disordering of the crystal structure and the formation of a short-range order phase in feldpars at pressures as low as 10.5–14 GPa. The beginning of the formation of diaplectic glass in the range from 18–22 GPa is evident from IR-spectra of shocked samples. It is assumed that diaplectic glass is an arrangement of grossly unchanged crystalline material and a glassy phase that is structurally indistinguishable from fusion-formed glass. The influence of the chemical composition and initial structural state of feldspars on the development of shock effects is believed to be less than the influence of exsolution lamellae and alteration products. Based on the results of these investigations, pressure ranges are given for the lower and upper boundary of the mixed-phase regime of the pV Hugoniot (p = shock pressure; V = specific volume) for all samples. Two independent methods for the determination of shock pressures from residual shock effects are proposed based on optical and IR-spectroscopic analyses.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/JB088iS01p0B364%4010.1002/%28ISSN%292169-9356.LPSC14

Shock experiments on feldspar crystals

Refractive index, density, and infrared absorption studies of naturally and experimentally shocked-produced glasses formed from quartz, plagioclase, and alkali-feldspar confirm the existence of two main groups of amorphous forms of the framework silicates: solid-state and liquid-state glasses. These were apparently formed as metastable release products of high-pressure-phases above and below the glass transition temperatures. Solid-state glasses exhibit a series of structural states with increasing disorder caused by increasing shock pressures and temperatures. They gradually merge into the structural state of fused minerals similar to that of synthetic glasses quenched from a melt. Shock-fused alkali feldspars can, however, be distinguished from their laboratory-fused counterparts by infrared absorption and by higher density.

Quartz and feldspar glasses produced by natural and experimental shock

T e m p e r a t u r i n t e r v a l l au f e inen gewissen Homogen i t~ t sbe re i ch h indeu te t . I n al ien S y s t e m e n weis t die P h a s e L P d , [2~ ein I t omogen i t~ t s gebiet auf, das sich yon der s t6eh iomet r i schen Z u s a m m e n s e t z u n g zur Pd-Se i te h i n ers t reckt . Die in der Tabel le gegebenen L6s l ichke i t sgrenzen w u r d e n fflr die eu tek t i sche T e m p e r a t u r aus d e m G i t t e r k o n s t a n t e n v e r l a u f extrapol ier t , der auge r bet Gd l inear m i t der A t o m k o n z e n t r a t i o n bis 75 At . -% P d a n g e n o m m e n werden konn t e (s. auch [3~).

Elektronenmikroskopischer Nachweis amorpher Bereiche in stoßwellenbeanspruchtem Quarz

A characteristic structure in the apical junctional belt of the olfactory epithelium in Rana temporaria is visible in freeze-fracture preparations. This structure is described as a “funnel with channel across the junctional belt”. It is supposed to represent a possible way for “discarding used molecules” after stimulation, and to allow the stimulation of free nerve endings in the depth of olfactory epithelia.

Cell junctions with funnels in the olfactory mucosa of frogs (Rana temporaria L.).

Experimental techniques for the investigation of spatial structure formation in semiconductor systems are limited in spatial resolution and will eventually change the intrinsic system behavior drastically Scanning probe techniques can probably overcome these constraints We present first experimental results of Low-temperature Scanning tunneling microscopy on current filaments in p-Germanium Possible applications of related probe techniques are briefly discussed

Wolfgang Müller

Papers

Elektronenmikroskopischer Nachweis amorpher Bereiche in stoßwellenbeanspruchtem Quarz

Cell junctions with funnels in the olfactory mucosa of frogs (Rana temporaria L.).

Scanning probe microscopy of self-organized structure formation in semiconductor systems