scholarly journals Shock‐induced formation of wüstite and fayalite in a magnetite‐quartz target rock

2019 ◽  
Vol 55 (1) ◽  
pp. 56-66
Author(s):  
Leonard F. Henrichs ◽  
Agnes Kontny ◽  
Boris Reznik ◽  
Uta Gerhards ◽  
Jörg Göttlicher ◽  
...  
Keyword(s):  
Target Rock

scholarly journals Ocean resurge-induced impact melt dynamics on the peak-ring of the Chicxulub impact structure, Mexico

2021 ◽  
Author(s):  
Felix M. Schulte ◽  
◽  
Axel Wittmann ◽  
Stefan Jung ◽  
Joanna V. Morgan ◽  
...  
Keyword(s):  
Impact Structure ◽  
Physical Processes ◽  
Hydrothermal Conditions ◽  
Chemical Examination ◽  
Impact Melt ◽  
Target Rock ◽  
Single Process ◽  
Chicxulub Impact ◽  
The Impact

AbstractCore from Hole M0077 from IODP/ICDP Expedition 364 provides unprecedented evidence for the physical processes in effect during the interaction of impact melt with rock-debris-laden seawater, following a large meteorite impact into waters of the Yucatán shelf. Evidence for this interaction is based on petrographic, microstructural and chemical examination of the 46.37-m-thick impact melt rock sequence, which overlies shocked granitoid target rock of the peak ring of the Chicxulub impact structure. The melt rock sequence consists of two visually distinct phases, one is black and the other is green in colour. The black phase is aphanitic and trachyandesitic in composition and similar to melt rock from other sites within the impact structure. The green phase consists chiefly of clay minerals and sparitic calcite, which likely formed from a solidified water–rock debris mixture under hydrothermal conditions. We suggest that the layering and internal structure of the melt rock sequence resulted from a single process, i.e., violent contact of initially superheated silicate impact melt with the ocean resurge-induced water–rock mixture overriding the impact melt. Differences in density, temperature, viscosity, and velocity of this mixture and impact melt triggered Kelvin–Helmholtz and Rayleigh–Taylor instabilities at their phase boundary. As a consequence, shearing at the boundary perturbed and, thus, mingled both immiscible phases, and was accompanied by phreatomagmatic processes. These processes led to the brecciation at the top of the impact melt rock sequence. Quenching of this breccia by the seawater prevented reworking of the solidified breccia layers upon subsequent deposition of suevite. Solid-state deformation, notably in the uppermost brecciated impact melt rock layers, attests to long-term gravitational settling of the peak ring.

Anisotropy of magnetic susceptibility (AMS) of impact melt breccia and target rocks from the Dhala impact structure, India

2021 ◽  
Author(s):  
Anuj Kumar Singh ◽  
Jayanta Kumar Pati ◽  
Shiva Kumar Patil ◽  
Wolf Uwe Reimold ◽  
Arun Kumar Rao ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Anisotropy Of Magnetic Susceptibility ◽  
Impact Structure ◽  
Magnetic Phases ◽  
Impact Melt ◽  
Rock Samples ◽  
Average Value ◽  
Magnetic Fabrics ◽  
Target Rock ◽  
The Impact

ABSTRACT The ~11-km-wide, Paleoproterozoic Dhala impact structure in north-central India comprises voluminous exposures of impact melt breccia. These outcrops are discontinuously spread over a length of ~6 km in a semicircular pattern along the northern, inner limit of the monomict breccia ring around the central elevated area. This study of the magnetic fabrics of impact breccias and target rocks from the Dhala impact structure identified a weak preferred magnetic orientation for pre-impact crystalline target rocks. The pre- and synimpact rocks from Dhala have magnetite and ilmenite as common magnetic phases. The distributions of magnetic vectors are random for most impact melt breccia samples, but some do indicate a preferred orientation. Our anisotropy of magnetic susceptibility (AMS) data demonstrate that the shape of susceptibility ellipsoids for the target rocks varies from prolate to oblate, and most impact melt breccia samples display both shapes, with a slight bias toward the oblate geometry. The average value for the corrected degree of anisotropy of impact melt rock (P′ = 1.009) is lower than that for the target rocks (P′ = 1.091). The present study also shows that both impact melt breccia and target rock samples of the Dhala structure have undergone minor postimpact alteration, and have similar compositions in terms of magnetic phases and high viscosity. Fine-grained iron oxide or hydroxide is the main alteration phase in impact melt rocks. Impact melt rocks gave a narrow range of mean magnetic susceptibility (Km) and P′ values, in contrast to the target rock samples, which gave Km = 0.05–12.9 × 10−3 standard international units (SI) and P′ = 1.036–1.283. This suggests similar viscosity of the source magma, and limited difference in the degrees of recorded deformation. Between Pagra and Maniar villages, the Km value of impact melt breccias gradually decreases in a clockwise direction, with a maximum value observed near Pagra (Km = 1.67 × 10−3 SI). The poor grouping of magnetic fabrics for most impact melt rock samples implies local turbulence in rapidly cooled impact melt at the front of the melt flow immediately after the impact. The mean K1 for most impact melt samples suggests subhorizontal (<5°) flow in various directions. The average value of Km for the target rocks (4.41 × 10−3 SI) is much higher compared to the value for melt breccias (1.09 × 10−3 SI). The results of this study suggest that the melt breccias were likely part of a sheet-like body of sizeable extent. Our magnetic fabric data are also supported by earlier core drilling information from ~70 locations, with coring depths reaching to −500 m. Our extensive field observations combined with available widespread subsurface data imply that the impact melt sheet could have covered as much as 12 km2 in the Dhala structure, with an estimated minimum melt volume of ~2.4 km3.

Prototype Raman Spectroscopic Sensor for in Situ Mineral Characterization on Planetary Surfaces

1998 ◽  
Vol 52 (4) ◽  
pp. 477-487 ◽  
Author(s):  
Alian Wang ◽  
Larry A. Haskin ◽  
Enriqueta Cortez
Keyword(s):  
Raman Spectroscopy ◽  
Planetary Surfaces ◽  
Detailed Characterization ◽  
Raman Spectroscopic ◽  
Fine Grained ◽  
Target Rock ◽  
Reaction With Water ◽  
Probe Head

Raman spectroscopy has the potential to provide definitive identification and detailed characterization of the minerals that comprise rocks and soils on planetary surfaces. We have designed a probe head for Raman spectroscopy that is suitable for use on a spectrometer deployed by a rover or a lander on the surface of a planet such as Mars, the Moon, or an asteroid. The probe head is lightweight, low power, rugged, and simple. It is based on a tiny distributed feedback diode laser and volume holographic components. A protective shell surrounds the probe head and serves as a mechanical stop for the mechanical arm of a planetary rover or lander during placement of the probe head onto the surface of a rock or soil. Pressing the shell against the rough surface of a target rock or soil also places the sampling objective of the probe head in rough focus, and the probe head is designed to be tolerant of focusing errors of ∼5 mm. A breadboard version of the probe head gave spectra of high quality on clean crystals of diamond, sulfur, calcite, quartz, and olivine. The results are qualitatively comparable to those obtained by using a conventional micro-Raman spectrometer on fine-grained travertine and on difficult specimens of basaltic lavas and impactites whose original mineralogy had been altered by reaction with water and air.

scholarly journals Petrographic Investigation of Target Rock Transformation under High Shock Pressures from the Colônia Impact Crater, Brazil

2017 ◽  
Vol 7 (1) ◽  
pp. 13 ◽  
Author(s):  
Victor F. Velázquez ◽  
Rodrigo F. Lucena ◽  
Jose M. Azevedo Sobrinho ◽  
Alethéa E. Martins Sallun ◽  
William Sallun Filho
Keyword(s):  
Shock Waves ◽  
Impact Crater ◽  
Small Scale ◽  
Impact Melt ◽  
Basement Rocks ◽  
High Shock ◽  
Target Rock ◽  
Deformation Phase ◽  
Deformation Features ◽  
The Impact

The Colônia impact crater, developed on crystalline basement rocks, offers an excellent example of one of the most unique features of the impact process: the effects of shock waves on textural and mineralogical changes of the target rock. The impact melt-bearing impactites were derived essentially from the igneous and metamorphic rocks, including granite, mica schist, granitic gneiss, and quartzite. Investigations using optical microscopy indicate that the effect of shock waves on those lithologies caused a wide variety of deformation features and generation of new materials. The most common features include fluidal textures, unusual rearrangement patterns between grains, recrystallization, decomposition and precipitation of new phases, agglutination of glassy and crystalline spherules, and the mobilized melt formed different types of impact melt particles. These transformations cover processes that may involve a new grain growing at the expense of parental grains of the same species, or crystallization of different mineral types from component-providing grains until a complete textural and compositional change of the target rocks occurs. Small-scale structures in deformed rocks are particularly interesting for exploring elastic-plastic deformation, phase transformations, and generation of impact melt products.

Thermo‐mechanical interaction of a large impact melt sheet with adjacent target rock, Sudbury impact structure, Canada

2019 ◽  
Vol 54 (6) ◽  
pp. 1228-1245 ◽  
Author(s):  
Paul L. Göllner ◽  
Torben Wüstemann ◽  
Lisa Bendschneider ◽  
Sebastian Reimers ◽  
Martin D. Clark ◽  
...  
Keyword(s):  
Large Impact ◽  
Impact Structure ◽  
Mechanical Interaction ◽  
Impact Melt ◽  
Target Rock

scholarly journals Rho-Kinase/ROCK as a Potential Drug Target for Vitreoretinal Diseases

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Muneo Yamaguchi ◽  
Shintaro Nakao ◽  
Mitsuru Arima ◽  
Iori Wada ◽  
Yoshihiro Kaizu ◽  
...  
Keyword(s):  
Drug Target ◽  
Unmet Needs ◽  
Rho Kinase ◽  
Age Related Macular Degeneration ◽  
Effector Protein ◽  
Disease Treatment ◽  
Potential Therapeutic Target ◽  
Age Related ◽  
Target Rock ◽  
Vitreoretinal Diseases

Rho-associated kinase (Rho-kinase/ROCK) was originally identified as an effector protein of the G protein Rho. Its involvement in various diseases, particularly cancer and cardiovascular disease, has been elucidated, and ROCK inhibitors have already been applied clinically for cerebral vasospasm and glaucoma. Vitreoretinal diseases including diabetic retinopathy, age-related macular degeneration, and proliferative vitreoretinoapthy are still a major cause of blindness. While anti-VEGF therapy has recently been widely used for vitreoretinal disorders due to its efficacy, attention has been drawn to new unmet needs. The importance of ROCK in pathological vitreoretinal conditions has also been elucidated and is attracting attention as a potential therapeutic target. ROCK is involved in angiogenesis and hyperpermeability and also in the pathogenesis of various pathologies such as inflammation and fibrosis. It has been expected that ROCK inhibitors will become new molecular target drugs for vitreoretinal diseases. This review summarizes the recent progress on the mechanisms of action of ROCK and their applications in disease treatment.

scholarly journals Wettability of organic-rich source rocks: case study on Bazhenov Formation (Abalak-Bazhenov group)

2020 ◽  
Vol 54 ◽  
pp. 195-204
Author(s):  
Aliya Mukhametdinova ◽  
Tagir Karamov ◽  
Natalia Bogdanovich ◽  
Sergey Borisenko ◽  
Svetlana Rudakovskaya ◽  
...  
Keyword(s):  
Contact Angle ◽  
Organic Content ◽  
Wetting Angle ◽  
Source Rocks ◽  
Initial Assessment ◽  
Thin Sections ◽  
Bazhenov Formation ◽  
Wetting Contact Angle ◽  
Target Rock ◽  
Rock Eval

Abstract. In this work, we have investigated the wettability of Bazhenov Formation rock samples using a nuclear magnetic resonance (NMR), the methods of vapor adsorption, and wetting contact angle. We have conducted the petrographic description of rocks using ultra-thin sections and scanning electron microscopy (SEM). In addition, we used data on the organic content (TOC) obtained by the Rock-Eval method and the results of lithological typing on thin sections for detailed analysis of NMR and contact angle methods results. Thus, for target rock, the groups with a similar rock wettability were highlighted by the lithological description of thin sections. The calculation of the wetting angle provided an initial assessment of the surface wettability of the rock and made it possible to establish the relationship between the wetting angle and the TOC, which is relevant for rocks of the Abalak-Bazhenov group. The NMR method described the core plug wettability proved to be less sensitive to the rock lithotype and organic matter (OM) texture in the rock and, therefore, used for the integral characterization of core plugs. Correlations of calculated wetting angle and adsorption wettability index vs. TOC and OM texture illustrated the dependence of rock wettability behavior on both the lithological specifics and the OM properties.

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