Estimating shock pressures based on high-pressure minerals in shock-induced melt veins of L chondrites

Xie, Z.; Sharp, T. G.; Carli, P. S. de

doi:10.1111/j.1945-5100.2006.tb00458.x

Cited by 37 publications

(38 citation statements)

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“…The latter, classified as "disequilibrium" effects (Stöffler et al 1991), are melt veins (shock veins) and melt pockets observed typically in mafic and ultramafic rocks. It should be emphasized that the high pressure polymorphs, which occur in or near to melt veins and melt pockets (e.g., Chen et al 1996;El Goresy et al 2000, 2003Beck et al 2002;Xie and Sharp 2004;Xie et al 2006aXie et al , 2006b, cannot be used as barometers of the "equilibration" shock pressure as they form in very localized, kinetically favored regions characterized by pressure-temperature spikes.…”

Section: Determination Of "Equilibration" Shock Pressuresmentioning

confidence: 99%

Helium loss from Martian meteorites mainly induced by shock metamorphism: Evidence from new data and a literature compilation

Schwenzer

Fritz

Stöffler

et al. 2008

Meteorit & Planetary Scien

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available online at http://meteoritics.org Helium loss from Martian meteorites mainly induced by shock metamorphism:Evidence from new data and a literature compilation Abstract-Noble gas data from Martian meteorites have provided key constraints about their origin and evolution, and their parent body. These meteorites have witnessed varying shock metamorphic overprinting (at least 5 to 14 GPa for the nakhlites and up to 45-55 GPa (e.g., the lherzolitic shergottite Allan Hills [ALH] A77005), solar heating, cosmic-ray exposure, and weathering both on Mars and Earth. Influences on the helium budgets of Martian meteorites were evaluated by using a new data set and literature data. Concentrations of 3 He, 4 He, U, and Th are measured and shock pressures for same sample aliquots of 13 Martian meteorites were determined to asses a possible relationship between shock pressure and helium concentration. Partitioning of 4 He into cosmogenic and radiogenic components was performed using the lowest 4 He/ 3 He ratio we measured on mineral separates ( 4 He/ 3 He = 4.1, pyroxene of ALHA77005). Our study revealed significant losses of radiogenic 4 He. Systematics of cosmogenic 3 He and neon led to the conclusion that solar radiation heating during transfer from Mars to Earth and terrestrial weathering can be ruled out as major causes of the observed losses of radiogenic helium in bulk meteorites. For bulk rock we observed a correlation of shock pressure and radiogenic 4 He loss, ranging between ~20% for Chassigny and other moderately shocked Martian meteorites up to total loss for meteorites shocked above 40 GPa. A steep increase of loss occurs around 30 GPa, the pressure at which plagioclase transforms to maskelynite. This correlation suggests significant 4 He loss induced by shock metamorphism. Noble gas loss in rocks is seen as diffusion due to (1) the temperature increase during shock loading (shock temperature) and (2) the remaining waste heat after adiabatic unloading (post shock temperature). Modeling of 4 He diffusion in the main U,Th carrier phase apatite showed that post-shock temperatures of ~300 °C are necessary to explain observed losses. This temperature corresponds to the post-shock temperature calculated for bulk rocks shocked at about 40 GPa. From our investigation, data survey, and modeling, we conclude that the shock event during launch of the meteorites is the principal cause for 4 He loss.

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Section: Determination Of "Equilibration" Shock Pressuresmentioning

confidence: 99%

Helium loss from Martian meteorites mainly induced by shock metamorphism: Evidence from new data and a literature compilation

Schwenzer

Fritz

Stöffler

et al. 2008

Meteorit & Planetary Scien

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“…Such phases include lingunite (the highpressure polymorph of NaAlSi 3 O 8 in the hollandite structure) (1,2); stishovite and poststishovite silica phases (3)(4)(5); wadsleyite (6) and ringwoodite (7), the high-pressure polymorphs of (Mg,Fe) 2 SiO 4 in a spinelloid (wadsleyite) and the spinel structure (ringwoodite), respectively; and (Mg,Fe)SiO 3 in the garnet [majorite (8,9)], ilmenite [akimotoite (10)], and arguably the perovskite structure (11,12). Pressures of formation have been estimated from static synthesis experiments of such phases and range up to 26 GPa (12)(13)(14)(15)(16). However, only stishovite has been recovered from shock experiments with very rapid quench and only in small amounts (17)(18)(19).…”

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confidence: 99%

Ultrafast growth of wadsleyite in shock-produced melts and its implications for early solar system impact processes

Tschauner

Asimow

Kostandova

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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We observed micrometer-sized grains of wadsleyite, a high-pressure phase of (Mg,Fe) 2SiO4, in the recovery products of a shock experiment. We infer these grains crystallized from shock-generated melt over a time interval of <1 s, the maximum time over which our experiment reached and sustained pressure sufficient to stabilize this phase. This rapid crystal growth rate (Ϸ1 m/s) suggests that, contrary to the conclusions of previous studies of the occurrence of high-pressure phases in shock-melt veins in strongly shocked meteorites, the growth of high-pressure phases from the melt during shock events is not diffusion-controlled. Another process, such as microturbulent transport, must be active in the crystal growth process. This result implies that the times necessary to crystallize the high-pressure phases in shocked meteorites may correspond to shock pressure durations achieved on impacts between objects 1-5 m in diameter and not, as previously inferred, Ϸ1-5 km in diameter. These results may also provide another pathway for syntheses, via shock recovery, of some high-value, high-pressure phases.meteorite ͉ recovery ͉ high-pressure phases ͉ planetesimal growth ͉ shock experiments A number of high-pressure silicate phases that stably occur only in the Earth's deep interior have documented natural occurrences, most commonly within shock-induced melt veins in L-and H-chondrites and Martian meteorites, notably the highly shocked (S6) Peace River, Tenham, Sixiangkou, and Yamato 791384 meteorites. Such phases include lingunite (the highpressure polymorph of NaAlSi 3 O 8 in the hollandite structure) (1, 2); stishovite and poststishovite silica phases (3-5); wadsleyite (6) and ringwoodite (7), the high-pressure polymorphs of (Mg,Fe) 2 SiO 4 in a spinelloid (wadsleyite) and the spinel structure (ringwoodite), respectively; and (Mg,Fe)SiO 3 in the garnet [majorite (8, 9)], ilmenite [akimotoite (10)], and arguably the perovskite structure (11,12). Pressures of formation have been estimated from static synthesis experiments of such phases and range up to 26 GPa (12-16). However, only stishovite has been recovered from shock experiments with very rapid quench and only in small amounts (17)(18)(19). None of the other dense silicate phases (wadsleyite, ringwoodite, majorite, lingunite, akimotoite, or perovskite) has been recovered from shock experiments conducted up to megabar pressures (20). These negative laboratory results in combination with observations of texture and paragenesis of high-pressure silicate polymorphs in meteorites have been used to infer the durations of shock-induced highpressure, high-temperature conditions to be on the order of seconds to minutes (15,(21)(22)(23)(24). In particular, this conclusion has been based on the grain size of these minerals (15), the width of lamellae within partly converted phases (21,22), and diffusion profiles of trace or major elements across phase boundaries (23, 24) between high-pressure minerals occurring within shockinduced melt veins of meteorites. Seconds-to minutes-lo...

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“…8. Additionally, it has been assumed that the maximum shock temperature in the vein rim was lower than that in the vein center (e.g., Xie et al. 2006a, 2006b).…”

Section: Discussionmentioning

confidence: 99%

“…Thereafter, majorites have been reported from the Suizhou L6 chondrite (Chen et al. 2004), the Tenham L6 chondrite (Xie and Sharp 2007; Xie et al. 2006a, 2006b) and from the Y‐75267 H6 chondrite (Kimura et al.…”

Section: Introductionmentioning

confidence: 99%

High-pressure polymorphs of magnesian orthopyroxene from a shock vein in the Yamato-000047 lherzolitic shergottite

Imae

Ikeda

2010

Meteoritics and Planetary Science

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Abstract-We found a simple thin shock vein, less than or equal to about 60 lm in width and 1.8 mm in length, in the poikilitic area in the Yamato (Y-) 000047 lherzolitic shergottite. The shock vein occurs only in magnesian Ca-poor clinopyroxene, which may have transformed from orthopyroxene during the pressure increase at the shock event. The shock vein consists of (Mg 0.8 ,Fe 0.2 )SiO 3 pyroxene polymorphs, such as columnar akimotoite, two kinds of pyroxene glasses, dendritic akimotoite, and framboidal pyroxene glass, in the order from the periphery to the center. The compositions and textures suggest that columnar akimotoite in the periphery of the shock vein crystallized from solid-state phase transition of clinopyoroxene during the cooling of the vein, and the remains in the shock vein solidified from shock-produced melt. The glass includes two kinds of massive glass in the vein and framboidal glass in the vein center. The framboidal glass is the most magnesian and may have been vitrified from perovskite crystallized from high-pressure melt produced at high temperature ‡3000°C and high-pressure 23-40 GPa. Dendritic akimotoites in the vein center metastably crystallized from residual shock melt. The formation sequences of the constituent phases in the shock vein happen in the following order: columnar akimotoites, rim glass, center glass, framboidal glass, and dendritic akimotoites. The increase of the Raman intensity of 660-670 cm )1 in the order of rim glass, center glass, and framboidal glass suggests that the formation of the pyroxene chain proceeds faster in the vein center than in the vein rim due to its slower cooling. The finding of the shock vein consisting merely of high-pressure polymorphs of pyroxene, akimotoite, and framboidal glass (vitrified perovskite) is the first reported among all Martian meteorites.

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Estimating shock pressures based on high-pressure minerals in shock-induced melt veins of L chondrites

Cited by 37 publications

References 56 publications

Helium loss from Martian meteorites mainly induced by shock metamorphism: Evidence from new data and a literature compilation

Helium loss from Martian meteorites mainly induced by shock metamorphism: Evidence from new data and a literature compilation

Ultrafast growth of wadsleyite in shock-produced melts and its implications for early solar system impact processes

High-pressure polymorphs of magnesian orthopyroxene from a shock vein in the Yamato-000047 lherzolitic shergottite

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