Thermoluminescence characteristics of a chondrite (Holbrook) and an aubrite achondrite (Norton County) meteorites

Author’s Accepted Manuscript Thermoluminescence characteristics of a chondrite (Holbrook) and an aubrite achondrite (Norton County) meteorites Lily Bossin, Nikolaos A. Kazakis, George Kitis, Nestor C. Tsirliganis www.elsevier.com/locate/apradiso

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S0969-8043(16)30844-2 http://dx.doi.org/10.1016/j.apradiso.2017.05.002 ARI7881

To appear in: Applied Radiation and Isotopes Received date: 17 October 2016 Revised date: 14 March 2017 Accepted date: 4 May 2017 Cite this article as: Lily Bossin, Nikolaos A. Kazakis, George Kitis and Nestor C. Tsirliganis, Thermoluminescence characteristics of a chondrite (Holbrook) and an aubrite achondrite (Norton County) meteorites, Applied Radiation and Isotopes, http://dx.doi.org/10.1016/j.apradiso.2017.05.002 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Thermoluminescence characteristics of a chondrite (Holbrook) and an aubrite achondrite (Norton County) meteorites Lily Bossina, Nikolaos A. Kazakisb,c,*, George Kitisc, Nestor C. Tsirliganisb a

Department of Archaeology, Durham University, UK Laboratory of Archaeometry and Physicochemical Measurements, R.C. ‘Athena’, P.O. Box 159, Kimmeria University Campus, 67100 Xanthi, Greece c Nuclear Physics Laboratory, Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece [email protected] [email protected] * Corresponding author. tel.: +302541078787, fax.: +302541063656 b

Abstract The present study constitutes the first part of a meteorite project, currently in progress, towards the full and thorough dosimetric study (TL and OSL) of two different meteorites of recent fall, Norton County and Holbrook. Both meteorites exhibit strong TL sensitivity, linear dose response and no saturation for doses up to 2 kGy. However, the two meteorites exhibited a very dissimilar TL glow curve and behaviour regarding sensitization and fading. Notably, the Norton County aubrite achondrite was found to exhibit a strong fading of the high-temperature peak (~300 οC), attributed to anomalous fading, whereas Holbrook did not seem to show signs of anomalous fading. Since quantitative conclusions regarding the thermal and irradiation history of meteorites, require knowledge of the detailed peak structure of the glow curve and deeper understanding of the trapping mechanism, the glow curves, after irradiation in the range 102000 Gy, were deconvoluted using general order kinetics. The fitting parameters extracted point towards complex non-strictly first order mechanisms with a multitude of traps acting very differently. All the above, combined with future OSL measurements, currently in progress, are expected to shed light on the nature of the involved traps in both phenomena (energy depth, 1

light-resistance etc), which would allow to extract more concrete conclusions about their history. Keywords: Thermoluminescence; Meteorites; Norton County; Holbrook; Deconvolution; General Order Kinetics

1

Introduction The thermoluminescence of extra-terrestrial materials has been the subject of

extensive studies as it would provide a remarkable set of information on the history of the samples; their orbits, by deducing the temperature at perihelion (Melcher, 1981), terrestrial age (Sears and Durrani, 1980; Sears, 1988), cosmic ray exposure (Biswas et al., 2011) or even shock and metamorphism history (Sears et al., 1984; Guimon et al., 1984) could be obtained by a simple measurement of the natural TL. One of the most extensive studies on the TL properties of meteorites was carried by Sears et al. (2013), who investigated newly recovered Antartic meteorites for 14 years and gathered a remarkable set of data on the natural signal of meteorites of various types of chondrites in an effort to estimate their terrestrial age. More recently, TL measurements have also been conducted in a study by the Chelyabinsk Airburst Consortium (Popova et. al, 2013) in an effort to understand the recent meteoroid heating events and confirmed a perihelion of 0.6 to 0.8 AU. In addition, the TL dating of meteorites has been proven useful as well with the dating of the Morasko meteorite, providing an age of 4.5-5.0 ka, in agreement with other means of dating (Fedorowicz and Stankowski, 2016). More than focusing on the assessment of the natural dose, the approach adopted in the present study is of an integrated dosimetric study. Several researchers suggested in the past (e.g. Sears et al., 1991; Akridge et al., 2004) that the TL signal in chondrites arises from feldspars, minerals whose luminescence properties have been extensively studied for the past 2

decades. Thus, such a dosimetric study including a thorough investigation of the kinetics of two very different meteorites would allow their comparison with analogous behaviour of terrestrial material. The present study constitutes the first part of a going meteorite project, where a complete and thorough dosimetric study on the meteorites under investigation is being conducted. Both TL and OSL measurements are being conducted in order to enhance the knowledge of their luminescence behavior. The scope of the present work is to present the TL measurements with the corresponding detailed kinetic study and to provide more data in order to fully realize the luminescence behavior of these materials. The above will be compared at a later time with the OSL measurements and the OSL kinetic study, which are scarce in the literature, and will allow the investigation of possible correlations between the various traps involved in both phenomena, i.e., TL and OSL. In addition, although the Holbrook meteorite has been the subject of most of the literature on meteorites TL, very few information exists on the dosimetric properties of the Norton County meteorite. A comparative approach was hence adopted in the present study between Holbrook, a chondrite type meteorite, and Norton County, a rare aubrite achondrite, which would further advance our understanding regarding the luminescence behaviour of this type of meteorite.

2

Materials and methods The two meteorites of the study (Norton County and Holbrook) were selected for their

easiness to be crushed and their dissimilarity in type (chondrite/achondrite). Further information about these meteorites (date and place of fall, type etc) can be found elsewhere (e.g. LaPaz, 1949; Charalambus et al., 1969; Pillinger et. al., 2013).

2.1

Sample preparation Small pieces of each meteorite sample were gently crushed in light condition using an

agate mortar and then sieved to get different size fractions. Grains of 75-150 μm diameter 3

were used for the TL measurements, while aliquots were prepared by placing ~1.7 mg of grains in stainless steel cups.

2.2

Stereoscopic examination Stereoscopic study of the meteorite samples was achieved by means of a high-

performance stereoscopic microscope (Leica MZ-APO) with a maximum magnification of 80x. The entire imaging system was apochromatically corrected. A digital micro-camera (Leica DC 200) was also attached to the stereoscopic microscope and connected to a computer allowing the on-line viewing, processing and storage of the acquired images through an appropriate software. The micro-camera had an optical resolution of 1920 x 1536 (3.0 Mpixels), while illumination and colour correction of the images were also controlled through the software. The main bodies of the meteorites were used for the stereoscopic examination (i.e., before extraction and crushing of a piece) to gather a full understanding of their structure.

2.3

TL measurements TL measurements were carried out using a Risø TL/OSL reader (model TL/OSL-DA-

15) equipped with a

90

Sr/90Y beta particle source, delivering a nominal dose rate of 3.48

Gy/min at the time of the measurements, calibrated for quartz. A 9635QA photomultiplier tube with a combination of Pilkington HA-3 heat absorbing and a Corning 7-59 blue filter (320-440 nm detection window) were used for light detection. The above filter combination optimizes the signal and prevents the saturation of the PMT for high doses measurements. All measurements were performed in a nitrogen atmosphere with a constant heating rate of 2 oC/s up to a maximum of 660 oC (unless stated otherwise), while the counts were recorded every 1.0 s.

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3

Results

3.1

Stereoscopic investigation

3.1.1 Norton County Norton County stereoscopic examination reveals a complex heterogeneous structure with numerous white and black inclusions of various sizes in a grey matrix (Fig. 1). Due to the complexity and rarity of the materials, the type of mineral composing each inclusion was not identified here. However, previous studies on Norton County identified rare minerals not present on earth such as titanoan troilite or ferromagnesian alabandite (e.g. Keil and Fredriksson, 1963), although the main body is believed to be mainly composed of Fe-O free enstatite (Okada et al., 1988). A mineralogical study of the Norton County meteorite carried by Okada et al. (1988) suggested an igneous origin (i.e., the parent-body crystallized from a magma), from a variety of rocks agglomerated to form the final structure.

Figure 1

3.1.2 Holbrook Holbrook exhibits a white main body of heterogeneous structure as well, with various round grey inclusions, but of smaller size than that of Norton County's (Fig. 2a). These inclusions are called chondrules and classify the meteorite as a chondrite. Holbrook also presents a black crust of less than 0.1 mm thick (Fig. 2b), very likely due to the combustion when the meteorite entered into the atmosphere. Holbrook meteorite’s sample is therefore of the outer part of the meteorite and it is likely that the native dose has been erased in the fusion crust when the meteorite entered into the atmosphere in 1912. According to previous studies (e.g. Mason and Wiik, 1961), Holbrook meteorite’s composition is complex enough,

5

mainly consisting of olivine, hypersthene, plagioclase, troilite, nickel-iron, chromite, orthorombic pyroxene.

Figure 2

3.2

TL dose response and signal The natural TL was first measured to erase the stored signal and a dose in the range

10-2000 Gy was then administered before recording the induced TL glow curve. A residual TL glow curve was also acquired in order to use it as background. The acquired glow curves for both meteorites are presented in Fig. 3.

Figure 3

3.2.1 Norton County The glow curves for various beta doses for the case of Norton County are illustrated in Fig. 3a. The TL response to β irradiation is relatively strong and exhibits a TL glow curve with multiple peaks from relatively low temperature (≤ 200 οC) to high temperature. Three are the main peaks observed with the maximum intensities at temperature ~135, 250 and 360 o

C respectively. A natural TL signal with two or more high-temperature peaks (≥ 200 οC) was

surprisingly observed, even though the samples were prepared in light condition. This could be an indication of light-resistant traps and/or that the temperature at the main core of the meteorite (where the sample was extracted from) did not increase enough to erase the natural TL signal above 200 οC during its entrance in the atmosphere. On the other hand, the absence 6

of natural TL at lower temperature could probably allow an estimation of the maximum temperature of the meteorite’s body during its entrance in the atmosphere, but it could also suggest a thermal fading mechanism. As previously stated the TL dose response was investigated in the range 10-2000 Gy. Fig. 4 presents the integral of each peak of the glow curves obtained as a function of dose for both meteorites. The integral of each peak was calculated as the sum of the five channels before and after peak maximum. The solid lines in Fig. 4a and 4b are the fit of the experimental data with a function (

)

(

, which in log-scale becomes

(

)

). The value of the parameter a1 is a linearity index. Hence, when a1 = 1

the response is linear, when a1 < 1 the response is sub-linear and when a1 > 1 the response is supra-linear. The values of a1 for each individual peak for both meteorites are given in Table 1. It is interesting to observe that the a1 values are very close to the unity which means that Norton County has a linear dose response to a wide range of doses.

Figure 4

Moreover, another interesting observation is that, contrary to well-known minerals such as feldspars or quartz, the signal does not saturate even at relatively high doses (1000 and 2000 Gy), which is fortuitous as the ability to determine higher doses is essential for extra-terrestrial materials since doses in space are much higher than in earth.

Table 1

7

3.2.2 Holbrook In the same respect, Holbrook meteorite exhibits a strong response after β irradiation (Fig. 3b) with a main peak at relatively low temperature (~165 οC). Another broad peak at higher temperature (~370 οC) may be present but of much lesser intensity. This type of TL glow curve is typical of chondrites (McKeever, 1980) and the high intensity peak was attributed to feldspars emissions by Keck and Sears (1987). Holbrook presents a strong natural signal in the high temperature region with a single peak centered at ~400 οC. Similarly to Norton County, Holbrook’s natural TL signal at lower temperatures is also absent. As in the case of Norton County, a1 values of the fitting of each peak’s integral (experimental glow curve) are very close to the unity in the Holbrook as well (Table 1). Thus Holbrook also exhibits a linear dose response to a wide range of doses with no saturation observed for doses up to 2000 Gy.

3.3

Sensitization The sensitization has been tested by irradiating samples with a test dose of 50 Gy,

recording the TL glow curve and repeating the cycle three additional times. The acquired glow curves are illustrated in Fig. 5 for both meteorites.

Figure 5

3.3.1 Norton County Norton County exhibits a relatively weak linear sensitization (Fig. 5a), ~2.5% increase per cycle. This could suggest that not all traps are completely emptied after heating to 660 οC and a number of competitors still remain filled. 8

3.3.2 Holbrook On the other hand, Holbrook does not exhibit detectable sensitization (Fig. 5b), indicating that heating up to 660 οC is adequate to empty all traps for this dose (i.e., 50 Gy).

3.4

Fading Fading tests were also conducted for both meteorites giving a sample a dose of 100

Gy, then storing the sample in the dark for 1 and 7 days and recording the remaining TL glow curve (Fig. 6 & 7).

Figure 6

Figure 7 3.4.1 Norton County Norton County exhibits a consequent fading of all the TL peaks after 24 h and 7 days of storage in the dark (Fig. 6). The fading of the low temperature peaks could be interpreted as thermal fading. However, since even the high-temperature peaks (≥ 200 oC) fade this could be an indication of an anomalous fading mechanism involved. The phenomena of anomalous fading have been largely described in the literature and observed on multiple materials (e.g. Spooner, 1994; Wintle, 1973; Wintle, 1977; Visocekas, 1985) and was even reported on extra-terrestrial materials (e.g. Tsukamoto and Duller, 2008; Hasan et al., 1986; Tyler and McKeever, 1988). Besides, it should be noted that the peaks do not fade at the same rate: the second peak fades ~50% in 7 days while the third peak fades ~30% in the same period. The difference in fading rates points towards traps of different depth fading at different rates. This 9

fading rate can be considered as fast and could be a major backward for the studies of the meteorites history - as the scale considered would be from hundreds to millions of years. It also suggests that the natural dose initially recorded was underestimated due to fading (Fig. 3a). In addition, the maximum peak temperature is slightly shifted to higher temperature after fading which could also indicate a continuum distribution of energy levels.

3.4.2 Holbrook Fig. 7a presents the various glow curves for Holbrook’s fading study, while Fig. 7b illustrates the ratio of the same glow curves with the one acquired directly after irradiation. It seems that Holbrook exhibits fading of the low temperature peaks that could be due to the thermal elapsing of the charges. However, Holbrook does not display fading of the highest temperature region even after 7-day storage. The absence of fading of the higher temperature peak could explain the high natural dose recorded (Fig. 3b).

3.5

General kinetic order deconvolution The set of dose response TL glow curves were fitted using a Levenberg-Marquardt

algorithm with the analytical expression of the general order kinetics equation for TL developed by Kitis et al. (1998) such as:

( )

(

)

[(

)(

)

(

)

]

, (1)

where T (K) is the temperature, Im (a.u.) the intensity at the peak maximum, b the order of kinetics, E (eV) the activation energy, Tm (K) the position of the peak maximum, k the Boltzmann constant, Δ = 2kT/E, Δm = 2kTm/E and Zm = 1+(b-1)Δm. The fitting parameters are therefore Im, Tm, E and b. The goodness of the fit was tested using the well-known figure of merit (F.O.M) such as:

10

( )

∑ |

| ∑

,

(2)

where p stands for the number of the individual peaks. The deconvolutions obtained using Eq. 1 were considered as very good with a F.O.M. between 0.8-1.5% for the various doses. The glow curves of both meteorites are complex and consist of many overlapping peaks. As already discussed, both Norton County and Holbrook are heterogeneous materials consisting of different minerals, many of which could contribute to the TL emission. The questions immediately arising here are if the TL glow curve is (a) a sum of the individual glow curves of each mineral and (b) which one of the individual peaks related to a mineral would be the most sensitive. Resolving those questions is crucial to proceed to an accurate glow curve deconvolution (CGCD) analysis and the interpretation of its results. A first observation based on the experimental dose-response results is that the glow curve shows for both meteorites a remarkable stability over the dose range of 10 Gy up to 2 kGy. Furthermore, in the case of Norton County the shape of the glow curve clearly indicates the possibility of individual peaks, whereas this is not so clear in the case of Holbrook. Although the CGCD analysis of complex materials is not in principle relatively easy, however, very good fits with a few different arrangements of individual glow-peaks within the whole glow curve, especially in the case of Holbrook meteorite, were achieved. In order to decide which one of the possible arrangement would be the most representative, the following criteria were considered: a. the kinetic parameters of each individual peak must be similar within an acceptable error for all of the glow curves for doses in the range 10 Gy-2 kGy b. the integrated area of each glow peak should keep a very clear functional relationship with the dose All results of the CGCD analysis match very well the above criteria. 11

Fig. 8a shows an example of the CGCD analysis of the Norton County meteorite corresponding to a dose of 50 Gy. The resulting values of kinetic parameters are listed in Table 2. The value of each parameter is the mean of the values obtained from the glow curves of all doses. Results of Table 2 show that, in fact, the CGCD analysis of all glow curves was achieved with almost the same values of the kinetic parameters. In the same respect, Fig. 8b shows an example of the CGCD analysis of the Holbrook meteorite for a dose of 50 Gy. The resulting values of kinetic parameters are listed in Table 3. As previously, the value of each parameter is the mean of the values obtained from the glow curves of all doses. In the case of Holbrook the CGCD analysis was achieved with the values of the kinetic parameters varying in a short range (Table 3). Besides, the activation energies found are in agreement with the values ≥1.2 eV for the higher temperature peak found by Akridge et al. (2001).

Figure 8

Table 2

Table 3

The integrated area of each glow peak resulting from the CGCD analysis has a very good functional dependence on dose for both Norton County and Holbrook. Fig. 9a presents the dose response of those of the above individual peaks contributing to the natural TL signal of the Norton County meteorite. The corresponding results for Holbrook meteorite are also

12

shown in Fig. 9b. The values of a1 for each individual peak resulting from the CGCD analysis for both meteorites are given in Table 4, which are also very close to the unit.

Figure 9

Table 4

4

Discussion Although the shape of Holbrook’s TL glow curve is consistent with the existing

literature on chondrites (e.g. McKeever, 1980) and therefore well-understood (e.g., TL emission related to the amount and structural state of feldspars; Haq et al., 1988), the exact minerals that cause Norton County’s signal remain unknown. As stated in the stereoscopic examination, the main body is mainly composed of very bright enstatite, characteristic of the aubrites. Besides, as observed in the deconvolution process, the well-separated peaks suggest traps with very different characteristics within a wide range of activation energies (0.63–1.55 eV), supporting the hypothesis of the contribution of more than one type of mineral. Considering the identified minerals in Norton County (Table 3 of Keil and Fredriksson, 1963), the other materials are kamacite, troilite, olivine (Mg2SiO4) with a low Fe content (≤0.1% w.w.), metallic copper, ferromagnesian alabandite and daubreelite, most of which also found in chondrites and exhibiting a significant iron content not suitable for TL emission. However, though most of those minerals are also found in chondrites, they were found by Keil and Fredriksson (1963) to differ by their chemical composition, pointing toward a meteorite formation under extreme reducing conditions (i.e., in O2 free atmosphere). 13

Another known parallel that could be drawn between Norton County and some chondrites’ behaviour is the presence of anomalous fading. Although thermal fading is expected to occur for low-activation energy traps, since the expected lifetime of Norton County’s 371 K peak (peak #1) is ~20.3±0.2 min at room temperature, this should not be the case for the higher temperature/activation energy 644 K peak (peak #6) with a calculated lifetime at room temperature of ~4.50±0.02 ×107 years that clearly indicates anomalous fading. Hasan et al.’s (1986) work on the anomalous fading of meteorites proved the existence of this phenomenon in some ordinary chondrites, nevertheless, the Holbrook meteorite of the present study follows the example of most of the chondrites that do not exhibit anomalous fading. That difference was not attributed by Hasan et al. (1986) to significant variations in the composition, but to the presence of high temperature feldspars in the samples that do not fade. Hence it is likely that Holbrook is -at least partially- composed of those high temperature feldspars, giving rise to a very bright signal, no fading and no saturation above 1 kGy. It should also be noted that the sensitization observed in Norton County could perhaps indicate a reservoir of charges not completely emptied by a single TL measurement related to deeper traps. The above would be worth investigating as if the fading issue could be resolved, the Norton County aubrite achondrite would make a space dosimeter as efficient as the chondrites. Moreover broadening the range of those “space dosimeters” could also provide a useful set of information on their parent-body as well. In general, it seems that the history of the meteorite has influence on the TL properties along with its primary chemical composition, and a simple TL measurement reflects the diversity of scenarios in the formation of the meteorites and/or parent-bodies. Finally, the dose contained in the natural TL of Norton County was evaluated using the higher temperature peak at 644 K - supposedly the most stable over thermal fading - and 14

gave a natural dose of about 300 Gy. This high natural dose suggests that it is not only due to the earth β radioactivity as the meteorite is of recent fall (witnessed February 1948). Even though the signal is supposed to be bleached by heating when the meteorite enters into the atmosphere, it is more likely here that the bleaching was incomplete, considering the high level of dose. As already discussed, a possible explanation for this partial bleaching could be that the sample was extracted from an inner part of the meteorite, not directly exposed to the heat, where the temperature was not greatly increased (>200 oC). Hence, it is possible that the natural dose observed is a result of the following mechanism: when the meteorite is in space the traps are saturated because of the high radioactivity caused by cosmic rays. Once it falls on earth, the ambient radioactivity is lesser so each TL peak decays to a terrestrial level (Sears et al., 2013). For Holbrook, the dose equivalent of the natural signal compared to the β induced peaks would be of 1600 Gy. Similarly to Norton County, this suggests the presence of an extra-terrestrial TL signal decaying rather than a built up of the TL after the fall on earth (occurred July 19th 1912). Similar natural TL signals (with no peaks for temperatures below 200 οC) have been observed by other researchers as well (e.g. Melcher, 1981). In addition, Melcher (1981), in an effort to calculate the equivalent dose of a chondritic meteorite, found that the TL of the peaks above 350 οC was within 50% of the saturation value determined by the TL response of the sample when subjected to induced doses. On the other hand, the TL level at glow curve temperatures below 300 °C is far below the level exhibited by the high-temperature TL. This difference between the measured equivalent dose at temperatures below 300 °C and that at high temperatures is attributed to thermal draining. Moreover, the TL level <300 °C is best explained as a dynamic equilibrium between build up due to cosmic rays and thermal draining.

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Furthermore, such a natural TL signal indicates that the main core of the meteorite has not been subjected to high temperatures while entering the atmosphere. The above is also supported by other researchers (e.g. Melcher, 1979; Melcher, 1981; Sears, 1975; Vaz, 1971), who claim that the heating effects during passage through the atmosphere are confined only to the outer few millimetres of the meteorites.

5

Conclusion The present study constitutes the first part of an integrated and thorough investigation

of the full luminescence properties (TL and OSL) of two different meteorites, i.e., the Holbrook and the Norton County. Presently, the TL dosimetric properties and the detailed kinetics of the two meteorites are presented. Both meteorites exhibit characteristics suitable for dosimetry (strong TL sensitivity, linear dose response over a wide range of doses, no saturation of the signal detected up to 2000 Gy) those materials still have to be treated carefully. Norton County’s major disadvantage to be used as a space dosimeter would be its strong anomalous fading (50% loss for the lower temperature peaks after 7-day storage in the dark). This fading could induce false estimation of the natural dose and hence of the terrestrial age. The sensitization of Norton County is minor and correctable. Notwithstanding, the shape of the TL glow curve with multiple well-separated TL peaks enables an easy and accurate deconvolution with a CGCD analysis, separating the glow curve into the various components (stable and unstable). Holbrook’s case seems to be simpler since no anomalous fading and sensitization were detected. Even though the closely overlapping TL peaks make the signal harder to be deconvoluted, a good fit was also obtained using a general order kinetic equation.

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The values of the parameters found through CGCD were stable over the entire dose range studied for both meteorites, pointing towards non-first order kinetics and high activation energies, while the individual peak area confirmed the linear dose response. Additional studies, which are presently in progress, are focusing on the OSL dosimetric properties and the respective kinetics of the above meteorites, which do not exist in the literature. Comparison between their TL and OSL properties and kinetics are expected to shed light on the nature of the involved traps in both phenomena (e.g. energy depth and light-resistance), which would allow to extract more concrete conclusions about their history.

Acknowledgement Authors wish to thank the Emeritus Pr. Charalambus for providing the meteorites of the present study.

References Akridge, D., Akridge, J., Batchelor, J., Benoit, P., Brewer, J., DeHart, J., Keck, B., Jie, L., Meier, A., Penrose, M., et al., 2004. Photomosaics of the cathodoluminescence of 60 sections of meteorites and lunar samples. Journal of Geophysical Research: Planets 109(E7), 1-10. Akridge, J. M., Benoit, P. H., Sears, D. W., 2001. Determination of trapping parameters of the high temperature thermoluminescence peak in equilibrated ordinary chondrites. Radiation Measurements 33(1), 109-117. Biswas, R., Morthekai, P., Gartia, R., Chawla, S., Singhvi, A., 2011. Thermoluminescence of the meteorite interior: A possible tool for the estimation of cosmic ray exposure ages. Earth and Planetary Science Letters 304(1), 36-44.

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Charalambus, St., Goebel, K., Stötzel-Riezler W., 1969. Tritium and Argon-39 in Stone and Iron Meteorites. Z. Naturforsdi 24a, 234-244. Fedorowicz, S., Stankowski, W.T., 2016. Dating the Morasko meteorite fall by natural thermoluminescence of the fusion crust. Geologos 22(3), 251-258. Guimon, R., Weeks, K., Keck, B., Sears, D., 1984. Thermoluminescence as a palaeothermometer. Nature 311, 363-365. Haq, M., Hasan, F.A., Sears, D.W., 1988. Thermoluminescence and the shock and reheating history of meteorites: IV. The induced TL properties of type 4–6 ordinary chondrites. Geochimica et Cosmochimica Acta, 52(6), 1679-1689. Hasan, F.A., Keck, B.D., Hartmetz, C., Sears, D.W., 1986. Anomalous fading of thermoluminescence in meteorites. Journal of Luminescence 34(6), 327-335. Keck, B.D., Sears, D.W., 1987. Chemical and physical studies of type 3 chondrites|viii: Thermoluminescence and metamorphism in the CO chondrites. Geochimica et Cosmochimica Acta 51(11), 3013-3021. Keil, K., Fredriksson, K., 1963. Electron microprobe analysis of some rare minerals in the Norton County achondrite. Geochimica et Cosmochimica Acta 27(9), 939IN1943942IN6947. Kitis, G., Gomez-Ros, J., Tuyn, J., 1998. Thermoluminescence glow-curve deconvolution functions for first, second and general orders of kinetics. Journal of Physics D: Applied Physics 31(19), 2636. LaPaz, L., 1949. The achondritic shower of February 18, 1948. Publications of the Astronomical Society of the Pacific 61(359), 63-73. Mason, B., Wiik, H., 1961. The Holbrook, Arizona, chondrite. Geochimica et Cosmochimica Acta 21(3), 276-283. McKeever, S. W., 1980. On the analysis of complex thermoluminescence. glow-curves: Resolution into individual peaks. Physica Status Solidi (a) 62(1), 331-340. 18

Melcher, C., 1981. Thermoluminescence of meteorites and their orbits. Earth and Planetary Science Letters 52(1), 39-54. Melcher, C.L., 1979. Kirin meteorite temperature gradient produced during atmospheric passage, Meteoritics 14, 309-316. Okada, A., Keil, K., Taylor, G. J., Newsom, H., 1988. Igneous history of the aubrite parent asteroid: Evidence from the Norton County enstatite achondrite. Meteoritics, 23(1), 5974. Pillinger, C. T., Greenwood, R. C., Gibson, J. M., Pillinger, J. M., Gibson, E. K., 2013. The Holbrook Meteorite-99 Years Out in the Weather. 44th Lunar and Planetary Science Conference, March 18-23, The Woodlands, Texas. Popova, O.P., Jenniskens, P., Emel’yanenko, V., Kartashova, A., Biryukov, E., Khaibrakhmanov, S., Shuvalov, V., Rybnov, Y., Dudorov, A., Grokhovsky, V.I., Badyukov, D.D., Yin, Q.-Z., Gural, P.S., Albers, J., Granvik, M., Evers, L.G., Kuiper, J., Kharlamov, V., Solovyov, A., Rusakov, Y.S., Korotkiy, S., Serdyuk, I., Korochantsev, A.V., Larionov, M.Y., Glazachev, D., Mayer, A.E., Gisler, G., Gladkovsky, S.V., Wimpenny, J., Sanborn, M.E., Yamakawa, A., Verosub, K.L., Rowland, D.J., Roeske, S., Botto, N.W., Friedrich, J.M., Zolensky, M.E., Le, L., Ross, D., Ziegler, K., Nakamura, T., Ahn, I., Lee, J.I., Zhou, Q., Li, X.-H., Li, Q.-L., Liu, Y., Tang, G.-Q., Hiroi, T., Sears, D., Weinstein, I.A., Vokhmintsev, A.S., Ishchenko, A.V., Schmitt-Kopplin, P., Hertkorn, N., Nagao, K., Haba, M.K., Komatsu, M., Mikouchi, T. (the Chelyabinsk Airburst Consortium) 2013. Chelyabinsk airburst, damage assessment, meteorite recovery, and characterization. Science, 342(6162), 1069-1073. Sears, D. W., 1988. Thermoluminescence of meteorites: Shedding light on the cosmos. International Journal of Radiation Applications and Instrumentation. Part D. Nuclear Tracks and Radiation Measurements 14(1-2), 5-17.

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Sears, D. W., Bakhtiar, N., Keck, B. D., Weeks, K. S., 1984. Thermoluminescence and the shock and reheating history of meteorites ii: Annealing studies of the Kernouve meteorite. Geochimica et Cosmochimica Acta 48 (11), 2265-2272. Sears, D. W., Batchelor, J. D., Lu, J., Keck, B. D., 1991. Metamorphism of CO and CO-like chondrites and comparisons with type 3 ordinary chondrites. In: Proceedings of the NIPR Symposium on Antarctic Meteorites. Vol. 4., 319-343. Sears, D. W., Ninagawa, K., Singhvi, A. K., 2013. Luminescence studies of extraterrestrial materials: Insights into their recent radiation and thermal histories and into their metamorphic history. Chemie der Erde-Geochemistry 73(1), 1-37. Sears, D., Durrani, S., 1980. Thermoluminescence and the terrestrial age of meteorites: Some recent results. Earth and Planetary Science Letters 46(2), 159-166. Sears, D.W., 1975. Temperature gradients in meteorites produced by heating during atmospheric passage, Modern Geology 5, 155-164. Spooner, N. A., 1994. The anomalous fading of infrared-stimulated luminescence from feldspars. Radiation Measurements 23(2), 625-632. Tsukamoto, S., Duller, G., 2008. Anomalous fading of various luminescence signals from terrestrial basaltic samples as martian analogues. Radiation Measurements 43(2), 721725. Tyler, S., McKeever, S., 1988. Anomalous fading of thermoluminescence in oligoclase. International Journal of Radiation Applications and Instrumentation. Part D. Nuclear Tracks and Radiation Measurements 14(1), 149-154. Vaz, J.E., 1971. Lost City meteorite determination of the temperature gradient induced by atmospheric friction using TL. Meteoritics 6, 207-216. Visocekas, R., 1985. Tunnelling radiative recombination in labradorite: its association with anomalous

fading

of

thermoluminescence.

Nuclear

Tracks

and

Radiation

Measurements (1982) 10(4), 521-529. 20

Wintle, A. G., 1973. Anomalous fading of thermo-luminescence in mineral samples. Nature 245, 143-144. Wintle, A., 1977. Detailed study of a thermoluminescent mineral exhibiting anomalous fading. Journal of Luminescence 15(4), 385-393.

Figure 1. Norton County stereoscopic photomicrograph Figure 2. (a) Holbrook's main body stereoscopic photomicrograph and (b) photograph of the Holbrook’s piece, showing the evidence of a fusion crust (black upper part) Figure 3. Natural TL glow curve and induced TL glow curves for various β doses for (a) Norton County and (b) Holbrook; markers are used for illustration purposes. Figure 4. Dose response for doses 10-2000 Gy of the peaks observed in the experimental glow curves for (a) Norton County and (b) Holbrook; markers correspond to experimental data, line represents the linear fit Figure 5. TL glow curves for four consecutive cycles of irradiation (50 Gy) and TL measurement (sensitization of TL glow curve) for (a) Norton County and (b) Holbrook; markers are used for illustration purposes Figure 6. Fading study for Norton County: (a) Glow curves for various storage periods after irradiation (100 Gy) and (b) ratio of the same glow curves with the one acquired directly after irradiation; markers are used for illustration purposes Figure 7. Fading study for Holbrook: (a) Glow curves for various storage periods after irradiation (100 Gy) and (b) ratio of the same glow curves with the one acquired directly after irradiation; markers are used for illustration purposes Figure 8. TL glow curve deconvolution for (a) Norton County and (b) Holbrook; open circles correspond to the experimental TL glow curve (50 Gy), dotted lines are the individual glow peaks resulting from the CGCD analysis using Eq. 1, black solid line is their summation.

21

Figure 9. Dose response of the individual peaks contributing to the TL signal computed by integration of the peak obtained with CGCD for (a) Norton County and (b) Holbrook; lines represent the linear fit

Table 1. Values of the exponent a1 in equation used to fit the TL dose response of each TL peak of the experimental glow curves.

Peak

Norton County

Holbrook

1

1.195

1.140

2

1.257

1.100

3

1.165

-

Table 2. Values of the kinetics parameters of Norton County meteorite obtained by CGCD analysis using Eq. 1.

Peak

Tm (K)

E (eV)

b

1

371 ± 2

0.63 ± 0.04

1.95 ± 0.14

2

412 ± 1

0.86 ± 0.06

1.75 ± 0.19

3

472 ± 1

1.10 ± 0.09

1.85 ± 0.15

4

527 ± 2

1.17 ± 0.03

1.80 ± 0.15

5

604 ± 4

1.35 ± 0.14

1.50 ± 0.14

6

644 ± 2

1.55 ± 0.18

1.20 ± 0.14

Table 3. Values of the kinetics parameters of Holbrook meteorite obtained by CGCD analysis using Eq. 1.

Peak

Tm (K)

E (eV)

b

22

1

374 ± 4

0.80 ± 0.02

1.95 ± 0.15

2

418 ± 5

0.73 ± 0.04

1.97 ± 0.13

3

460 ± 3

0.85 ± 0.10

1.95 ± 0.15

4

511 ± 4

0.98 ± 0.03

1.97 ± 0.15

5

615 ± 5

0.97 ± 0.06

1.91 ± 0.21

6

659 ± 5

1.26 ± 0.08

1.78 ± 0.24

Table 4. Values of the exponent a1 in equation used to fit the TL dose response of each individual TL peak resulted from the CGCD analysis.

Peak

Norton County

Holbrook

2

1.194

1.033

3

1.118

1.172

4

1.276

1.300

5

1.000

1.066

6

1.195

1.132

23

24

25

26

27

28

29

30

31

Highlights 32



TL properties of two meteorites, Norton County and Holbrook, are investigated



CGCD analysis points towards the presence of multiple deep, potentially lightresistant, traps



Dose response data can be fitted with a linear function for doses up to 2 kGy



Results are promising and an OSL study should also be conducted

33