Shock experiments on pre-heated α- and β-quartz: I. Optical and density data

Langenhorst, F.; Deutsch, Alexander

doi:10.1016/0012-821x(94)90229-1

Cited by 118 publications

(140 citation statements)

References 23 publications

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“…Our results suggest a deeper origin for peak-ring rocks, and thus are more in accordance with alternative models for the composition of a heterogeneous lunar crust in which an anorthositic layer extends regionally to deeper depths (40)(41). The dynamic collapse model and Expedition 364 results predict density reduction by shock and shear fracturing within the uplifted material (33), which is consistent with the recent Gravity…”

Section: Continental Scientific Drilling Program (Icdp)supporting

confidence: 89%

“…Dilation during brittle deformation is observed in central uplifts in other large terrestrial impact craters (30)(31), and dilatancy is predicted to increase fracture porosity in the peak-ring rocks by between 1 and 5% (32). Shock metamorphism can also reduce density, as shown in experiments (33) and in nature (34).…”

Section: Continental Scientific Drilling Program (Icdp)mentioning

confidence: 90%

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The formation of peak rings in large impact craters

Morgan

Gulick

Bralower

et al. 2016

Science

204

246

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Large impacts provide a mechanism for resurfacin g planets through mixing near-surface rocks with deeper material. Central peaks are formed from the dynamic uplift of rocks during crater formation. As crater size increases, central peak s transition to peak ri ngs. Without samples, debate surrounds the mechanics of peak-ring formation and their depth of origin. Chicxulub is the only known impact structure on Earth with an unequivocal peak ring, but it is buried and only accessible through drilling. Ex pedition 364 sampled the Chicxulub peak ring, which we found was formed from uplifted, fractured, shocked, felsic basement rocks. The peak-ring rocks are cross-cut by dikes and shear zones and have an unusually low density and seismic velocity. Large impacts therefore generate vertical fluxes and increase porosity in planetary crust

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Section: Continental Scientific Drilling Program (Icdp)supporting

confidence: 89%

Section: Continental Scientific Drilling Program (Icdp)mentioning

confidence: 90%

The formation of peak rings in large impact craters

Morgan

Gulick

Bralower

et al. 2016

Science

204

246

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“…They are generally found as small grains, 1-5 mm in size, and typically have 1 to 3 sets of PDFs (Fig. 9a) that are indicative of shock pressures of 15 to ~30 GPa (e.g., Stöffler 1974;Langenhorst and Deutsch 1994;Huffman and Reimold 1996). Point count analyses indicate that the proportion of quartz grains with multiple sets of PDFs appears to increase with depth in the impactite interval (Table 3).…”

Section: Shock Metamorphismmentioning

confidence: 99%

First petrographic results on impactites from the Yaxcopoil‐1 borehole, Chicxulub structure, Mexico

Tuchscherer¹,

Reimold²,

Koeberl³

et al. 2004

Meteorit & Planetary Scien

109

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Abstract-The ICDP Yaxcopoil-1 (Yax-1) borehole located 60 km south-southwest of the center of the Chicxulub impact structure intercepted an interval of allogenic impactites (depth of 795-895 m). Petrographic analysis of these impactites allows them to be differentiated into five units based on their textural and modal variations. Unit 1 (795-922 m) comprises an apparently reworked, poorly sorted and graded, fine-grained, clast-supported, melt fragment-bearing suevitic breccia. The interstitial material, similar to units 2 and 3, is permeated by numerous carbonate veinlets. Units 2 (823-846 m) and 3 (846-861 m) are groundmass-supported breccias that comprise green to variegated angular and fluidal melt particles. The groundmass of units 2 and 3 comprises predominantly fine-grained calcite, altered alkali element-, Ca-, and Si-rich cement, as well as occasional lithic fragments. Unit 4 (861-885 m) represents a massive, variably devitrified, and brecciated impact melt rock. The lowermost unit, unit 5 (885-895 m), comprises highly variable proportions of melt rock particles (MRP) and lithic fragments in a fine-grained, carbonate-dominated groundmass. This groundmass could represent either a secondary hydrothermal phase or a carbonate melt phase, or both. Units 1 and 5 contain well-preserved foraminifera fossils and a significantly higher proportion of carbonate clasts than the other units. All units show diagnostic shock deformation features in quartz and feldspar clasts. Our observations reveal that most felsic and all mafic MRP are altered. They register extensive K-metasomatism. In terms of emplacement, we suggest that units 1 to 3 represent fallout suevite from a collapsing impact plume, whereby unit 1 was subsequently reworked by resurging water. Unit 4 represents a coherent impact melt body, the formation of which involved a significant proportion of crystalline basement. Unit 5 is believed to represent an initial ejecta/ground-surge deposit.

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“…10), corresponding to the {10 3} crystallographic plane of quartz with 50% (9) of the measured PDF sets falling within ±5° of 23°. The presence of relatively abundant and p orientations indicate that moderate to high shock pressures, ranging between 20 and 25 GPa (Robertson and Grieve 1977;Langenhorst and Deutsch 1994;Stöffler and Langenhorst 1994), affected the target rocks of the central peak during formation of these PDFs. The crystallographic orientations distribution shown in Fig.…”

Section: Shock Metamorphismmentioning

confidence: 99%

Cloud Creek structure, central Wyoming, USA: Impact origin confirmed

Stone

Therriault

2003

Meteorit & Planetary Scien

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Abstract-The circular Cloud Creek structure in central Wyoming, USA is buried beneath ~1200 m of Mesozoic sedimentary rocks and has a current diameter of ~7 km. The morphology/morphometry of the structure, as defined by borehole, seismic, and gravity data, is similar to that of other buried terrestrial complex impact structures in sedimentary target rocks, e.g., Red Wing Creek in North Dakota, USA. The structure has a fault-bordered central peak with minimum diameter of ~1.4 km, composed predominantly of Paleozoic carbonates thickened by thrust faulting and brecciation, and is elevated some 520 m above equivalent strata beyond the outer rim of the structure. There is a ~1.6 km wide annular trough sloping away from the central peak (maximum structural relief, 300 m) and terminated by a detached, fault-bounded, rim anticline. The youngest rocks within the structure are Late Triassic (Norian?) clastics and these are overlain unconformably by post-impact Middle Jurassic (Bathonian?) sandstones and shales. Thus, the formation of the Cloud Creek structure is dated chronostratigraphicly as ~190 ± 20 Ma. Reported here for the first time are measurements of planar deformation features (PDFs) in shocked quartz grains in thin sections made from drill cuttings recovered in a borehole drilled at the southern perimeter of the central peak. Other, less definitive microstructures consistent with impact occur in samples collected from boreholes drilled into the central peak and rim anticline. The shockmetamorphic evidence confirms an impact origin for the Cloud Creek structure.

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Shock experiments on pre-heated α- and β-quartz: I. Optical and density data

Cited by 118 publications

References 23 publications

The formation of peak rings in large impact craters

The formation of peak rings in large impact craters

First petrographic results on impactites from the Yaxcopoil‐1 borehole, Chicxulub structure, Mexico

Cloud Creek structure, central Wyoming, USA: Impact origin confirmed

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