Zoned chondrules in Semarkona: Evidence for high‐ and low‐temperature processing

Grossman, J. N.; Alexander, Conel M. O'd.; Wang, Jingyuan; Brearley, Adrian J.

doi:10.1111/j.1945-5100.2002.tb00795.x

Cited by 98 publications

(95 citation statements)

References 38 publications

(51 reference statements)

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“…The X-ray mapping procedure used here was documented by Grossman et al (2000Grossman et al ( , 2002. Mapped samples included a wide variety of weakly metamorphosed chondrites of many groups, including H, L, LL, CO, CV, CR, and CI.…”

Section: Samples and Experimental Proceduresmentioning

confidence: 99%

“…All microprobe analyses of mesostasis were done using the methods outlined in Grossman et al (2002), making use of a 5 × 5 μm rastered beam, 20 nA beam current, 15 kV accelerating voltage, and completing the integration of the Na peak within 10 sec of unblanking the beam. All analyses were as free from small crystallites as possible, although in some chondrules it was not possible to avoid them all.…”

Section: Study Of Chondrule Mesostasismentioning

confidence: 99%

“…In the ordinary and CO chondrites, and probably the CVs as well, metamorphism always produces the same effects, indicating that the oxidation state and site occupancy of Cr in olivine was probably similar prior to metamorphism. If quenching from Fig 16. Comparison of the alkali element trends in zoned type I chondrules in Semarkona (arrows, after Grossman et al 2002) with mean type I chondrule mesostasis composition in types 3.0-3.2 chondrites (Tables 1 and 6). On a plot of K/Al versus Na/Al, the zoning trends follow the same path as the metamorphic trend defined by the chondrites and are probably due to the same process.…”

Section: Exsolution Features In Olivinementioning

confidence: 99%

“…The mesostasis in exterior portions of many type I chondrules in Semarkona is rich in alkalis and water; such mesostasis zoning is the result of metasomatism during aqueous alteration on the parent asteroid (Grossman et al 2002;Grossman and Alexander 2004). This aqueous alteration probably occurred during the incipient metamorphism that caused albite crystallization in some type II chondrules in Semarkona, with the entire process better characterized as "fluid-assisted metamorphism.…”

Section: Open System Behavior Of Alkalis In Chondrules During Metamormentioning

confidence: 99%

“…The Na lost from the matrix between types 3.0 and 3.1 can only go into chondrules, as X-ray maps do not reveal any other alkalibearing components (like the "white matrix" that is found in Tieschitz; Christophe Michel-Levy 1976; Hutchison et al 1998). It is likely that type I chondrules are one sink for excess matrix Na at these early stages of metamorphism, resulting in zoned or fully metasomatized chondrules (Grossman et al 2002). Glass in type II chondrules is another possible sink, as Na/Al does rise in this material in the correct sequence (Fig.…”

Section: Alkali Mobility In Matrixmentioning

confidence: 99%

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The onset of metamorphism in ordinary and carbonaceous chondrites

Grossman

Brearley

2005

Meteorit & Planetary Scien

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337

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Received May 18, 2004; revision accepted November 3, 2004) Abstract-Ordinary and carbonaceous chondrites of the lowest petrologic types were surveyed by Xray mapping techniques. A variety of metamorphic effects were noted and subjected to detailed analysis using electron microprobe, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and cathodoluminescence (CL) methods. The matrix in the least metamorphosed chondrites is rich in S and Na. The S is lost from the matrix at the earliest stages of metamorphism due to coalescence of minute grains. Progressive heating also results in the loss of sulfides from chondrule rims and increases sulfide abundances in coarse matrix assemblages as well as inside chondrules. Alkalis initially leave the matrix and enter chondrules during early metamorphism. Feldspar subsequently nucleates in the matrix and Na re-enters from chondrules. These metamorphic trends can be used to refine classification schemes for chondrites. Cr distributions in olivine are a highly effective tool for assigning petrologic types to the most primitive meteorites and can be used to subdivide types 3.0 and 3.1 into types 3.00 through 3.15. On this basis, the most primitive ordinary chondrite known is Semarkona, although even this meteorite has experienced a small amount of metamorphism. Allan Hills (ALH) A77307 is the least metamorphosed CO chondrite and shares many properties with the ungrouped carbonaceous chondrite Acfer 094. Analytical problems are significant for glasses in type II chondrules, as Na is easily lost during microprobe analysis. As a result, existing schemes for chondrule classification that are based on the alkali content of glasses need to be revised.

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Section: Samples and Experimental Proceduresmentioning

confidence: 99%

Section: Study Of Chondrule Mesostasismentioning

confidence: 99%

Section: Exsolution Features In Olivinementioning

confidence: 99%

Section: Open System Behavior Of Alkalis In Chondrules During Metamormentioning

confidence: 99%

Section: Alkali Mobility In Matrixmentioning

confidence: 99%

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The onset of metamorphism in ordinary and carbonaceous chondrites

Grossman

Brearley

2005

Meteorit & Planetary Scien

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337

441

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Metasomatism in the Early Solar System: The Record from Chondritic Meteorites

Brearley

Krot

2012

Lecture Notes in Earth System Sciences

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103

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Mineralogic, petrologic, and isotopic studies of chondritic meteorites have revealed a significant body of evidence of metasomatic processes during the earliest stages of Solar System evolution. The exact nature of these processes, as well as the conditions and environments where metasomatism occurred, are still the subject of vigorous debate. The interaction of aqueous fluids with early Solar System solids affected different chondrite groups to different degrees: even within a single chondrite group the effects of metasomatism can be highly variable. Among the carbonaceous chondrite groups, the CV (Vigarano-type) and CO (Ornans-type) chondrites show the best documented evidence of metasomatic effects. In the oxidized subgroup of the CV chondrites, Ca-Al-rich Inclusions (CAIs), Amoeboid Olivine Aggregates (AOAs), chondrules, and matrix have all been extensively affected by Fe-alkali-halogen metasomatism, that has resulted in the formation of a wide range of secondary, dominantly anhydrous minerals, including grossular, andradite, wollastonite, monticellite, anorthite, forsterite, ferroan olivine, corundum, Na-melilite, nepheline, sodalite, wadalite, Al-diopside, kushiroite, ferroan diopside À hedenbergite pyroxenes, ilmenite, phosphates, magnetite, awaruite, tetrataenite, and Fe,Ni sulfides. Hydrous phases are much rarer, but include, margarite, vesuvianite, and kaolinite. The mineral assemblages that form are highly dependent on the primary mineralogy of the host object: distinct mineral assemblages are produced by alteration of CAIs, chondrules, and matrix, for example. Nebular and asteroidal scenarios for these metasomatic effects have been extensively discussed in the literature for the metasomatism observed in the

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In situ SIMS oxygen isotope analyses: Evidence for the formation of aluminum-rich chondrules from ordinary chondrites

Jiang

Hsu

Guan

et al. 2015

Sci. China Earth Sci.

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Aluminum-rich chondrules (ARCs), which share mineralogic and chemical properties with both Ca, Al-rich inclusions (CAIs) and ferromagnesian chondrules, play an important role in revealing their temporal and petrogenetic relationships. In this work, seven ARCs were found in three ordinary chondrites GRV 022410 (H4), GRV 052722 (H3.7) and Julesburg (L3.6). They contain bulk Al 2 O 3 ~ 17%−33% and exhibit igneous textures composed of olivine, high-and low-Ca pyroxene, plagioclase, spinel and glass. In situ SIMS analyses show that ARCs have oxygen isotopic compositions (δ 18 O=-6.1‰-7.1‰; δ 17 O= -4.5‰-5.1‰) close to ferromagnesian chondrules but far more depleted in 16 O than CAIs (δ 18 O=−40‰; δ 17 O=−40‰). Most ARCs plot close to the terrestrial mass fractionation (TF) line, and a few between the TF and carbonaceous chondrite anhydrous mixing (CCAM) lines. Plagioclase, nepheline and glass suffered O-isotopic exchanges during the metamorphism processes in the parent body. Spinel, olivine and pyroxene represent the primary O-isotopic compositions of ARCs, and define a fitted line with a slope of ~ 0.7±0.1. Compared with the results of previous studies, shallower slope as well as more depleted 16 O compositions further demonstrates that ARCs in ordinary chondrites are not a simple mixing product of ferromagnesian chondrules and CAIs. Instead, they probably experienced higher-degree oxygen isotope exchange with a 16 O-poor nebular gas reservoir during multiple melting episodes. O-isotope, SIMS, Al-rich chondrule, ordinary chondrite, Antarctic meteorite Citation:Jiang Y, Hsu WB, Guan YB, et al. 2015. In situ SIMS oxygen isotope analyses: Evidence for the formation of aluminum-rich chondrules from ordinary chondrites. Science China: Earth Sciences,

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Zoned chondrules in Semarkona: Evidence for high‐ and low‐temperature processing

Cited by 98 publications

References 38 publications

The onset of metamorphism in ordinary and carbonaceous chondrites

The onset of metamorphism in ordinary and carbonaceous chondrites

Metasomatism in the Early Solar System: The Record from Chondritic Meteorites

In situ SIMS oxygen isotope analyses: Evidence for the formation of aluminum-rich chondrules from ordinary chondrites

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