The relative formation ages of ferromagnesian chondrules inferred from their initial aluminum‐26/aluminum‐27 ratios

Mostefaoui, S.; Kita, N. T.; Togashi, S.; Tachibana, Shogo; Nagahara, H.; Morishita, Y.

doi:10.1111/j.1945-5100.2002.tb00825.x

Cited by 99 publications

(131 citation statements)

References 18 publications

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“…The same observation holds for the Mg concentrations. 27Al/24Mg ratios in anorthite in CAIs range up to 1000; in plagioclase from chondrules they are usually much smaller (Russell et al, 1996;Hutcheon et al, 2000;Kita et al, 2000;Marhas et al, 2000;Srinivasan et al, 2000a;Huss et al, 2001;Mostefaoui et al, 2002). In contrast, the 27Al/24Al ratios in the plagioclase grains of this study range up to 5300 for SM, 10 200 for FV and 6700 for Quenggouk (Table 1 and Fig.…”

Section: Are the Plagioclase Measured Of Metamorphic Origin?mentioning

confidence: 55%

Aluminum‐26 in H4 chondrites: Implications for its production and its usefulness as a fine‐scale chronometer for early solar system events

Zinner

Göpel²

2002

Meteorit & Planetary Scien

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— In order to investigate whether or not 26Al can be used as a fine‐scale chronometer for early solar system events we measured, with an ion microprobe, Mg isotopes and Al/Mg ratios in separated plagioclase, olivine, and pyroxene crystals from the H4 chondrites Ste Marguerite (SM), Forest Vale (FV), Beaver Creek and Quenggouk and compared the results with the canonical 26Al/27Al ratio for calcium‐aluminum‐rich inclusions (CAIs). For SM and FV, Pb/Pb and Mn‐Cr ages have previously been determined (Göpel et al., 1994; Polnau et al., 2000; Polnau and Lugmair, 2001). Plagioclase grains from these two meteorites show clear excesses of 26Mg. The 26Al/27Al ratios inferred from these excesses and from isotopically normal Mg in pyroxene and olivine are (2.87 ± 0.64) × 10−7 for SM and (1.52 ± 0.52) × 10−7 for FV. The differences between these ratios and the ratio of 5 times 10−5 in CAIs indicate time differences of 5.4 ± 0.1 Ma and 6.1 ± 0.2 Ma for SM and FV, respectively. These differences are in agreement with the absolute Pb/Pb ages for CAIs and SM and FV phosphates but there are large discrepancies between the U‐Pb and Mn‐Cr system for the relative ages for CAIs, SM and FV. For example, Mn‐Cr ages of carbonates from Kaidun are older than the Pb/Pb age of CAIs. However, even if we require that CAIs are older than these carbonates, the time difference between this “adjusted” CAI age and the Mn‐Cr ages of SM and FV require that 26 Al was widely distributed in the early solar system at the time of CAI formation and was not mostly present in CAIs, a feature of the X‐wind model proposed by Shu and collaborators (Gounelle et al., 2001; Shu et al., 2001). From this we conclude that there was enough 26Al to melt small planetary bodies as long as they formed within 2 Ma of CAIs, and that 26Al can serve as a fine‐scale chronometer for early solar system events.

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Section: Are the Plagioclase Measured Of Metamorphic Origin?mentioning

confidence: 55%

Aluminum‐26 in H4 chondrites: Implications for its production and its usefulness as a fine‐scale chronometer for early solar system events

Zinner

Göpel²

2002

Meteorit & Planetary Scien

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“…Two aluminumrich chondrules from Acfer 094, an anomalous but primitive C chondrite, had ( 26 Al/ 27 Al) 0 ~1 × 10 −5 (Hutcheon, Krot, and Ulyanov 2000). Essentially, all aluminum-rich and ferromagnesian chondrules from Type 3.0-3.1 UOCs contained 26 Al with ( 26 Al/ 27 Al) 0 ratios between ~0.3 × 10 −5 tõ 2.3 × 10 −5 (Kita et al 2000;McKeegan et al 2000;Huss et al 2001;Mostefaoui et al 2002). Most recently, an anorthitebearing chondrule from the EH chondrite Sahara 97072 was shown to have formed with ( 26 Al/ 27 Al) 0 = (0.67 ± 0.27) × 10 −5 (Guan et al 2002).…”

Section: Ferromagnesian Chondrulesmentioning

confidence: 99%

Al‐Mg systematics of CAIs, POI, and ferromagnesian chondrules from Ningqiang

Hsu

Huss

Wasserburg

2003

Meteorit & Planetary Scien

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“…Because Semarkona, Bishunpur, Krymka, and Y81020 are among the least metamorphosed ordinary and carbonaceous chondrites, the observed ranges in initial ( 26 Al/ 27 Al) ratios have chronological significance for chondrule formation. The observed ratios suggest that chondrule forming events lasted at least for a few Myr at almost the same time within the formation regions of ordinary and carbonaceous chondrites and that chondrules with older ages did not experience the heating events that formed younger chondrules (Mostefaoui et al, 2002;Kurahashi et al, 2004;Kita et al, 2005a).…”

Section: Mgmentioning

confidence: 99%

“…The obtained initial , which is smaller than the canonical value for CAIs. Mostefaoui et al (2002) reported further resolvable 26 Mg excesses in 11 ferromagnesian chondrules in Bishunpur (LL3.1). Similar results were obtained from chondrules in Semarkona and Bishunpur by McKeegan et al (2000), and chondrules from Krymka (LL3.1) by Tomomura et al (2004) and Kita et al (2005b).…”

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confidence: 99%

Chondrule formation and evolution of the early solar system

Tachibana¹

2006

Journal of Mineralogical and Petrological Sciences

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Chondrules are millimeter to sub millimeter size silicate spherules that formed during localized and transient high temperature events in the early solar system. Although it is not yet understood how chondrules formed, recent studies have provided important clues in understanding the physical conditions of chondrule formation. In this paper I review recent developments in studies of chondrules to provide constraints on high temperature processes during the evolution of protoplanetary disks, including: (1) the timing and duration of the chondrule forming high temperature period, based on long lived and short lived chronometers; (2) the thermal history of chondrule melts during each chondrule forming event, as constrained from laboratory experiments and petrological and isotopic studies of chondrules, including shock wave heating as a plausible heat source for chondrule formation; and (3) sources for shock waves and chondrule forming regions in the protoplanetary disk. Given our current knowledge, I provide the following possible answers to the above four points: (1) the period of chondrule formation began shortly after the formation of calcium aluminum rich inclusions and lasted for a few million years; (2) chondrule precursors were heated at a rate of > 10 4 K/h in the temperature range of ~ 1400 1600 K, and melt droplets were cooled from a peak temperature of ~ 1800 2200 K at a rate of ~ 5 1000 K/h; (3) high velocity shock waves (> 20 km/s) in a low density gas region (< 10 19 particles/m 3 ) may be appropriate for localized transient heating events associated with chondrule formation; and (4) X ray flares from the young Sun in its T Tauri stage might be the source of the shock waves.

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The relative formation ages of ferromagnesian chondrules inferred from their initial aluminum‐26/aluminum‐27 ratios

Cited by 99 publications

References 18 publications

Aluminum‐26 in H4 chondrites: Implications for its production and its usefulness as a fine‐scale chronometer for early solar system events

Aluminum‐26 in H4 chondrites: Implications for its production and its usefulness as a fine‐scale chronometer for early solar system events

Al‐Mg systematics of CAIs, POI, and ferromagnesian chondrules from Ningqiang

Chondrule formation and evolution of the early solar system

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