# Volatile loss under a diffusion-limited regime in tektites: Evidence from tin stable isotopes

John Creech, Frédéric Moynier, Christian Koeberl

► To cite this version:

John Creech, Frédéric Moynier, Christian Koeberl. in tektites: Evidence from tin stable isotopes. 10.1016/j.chemgeo.2019.119279. insu-02916813

Volatile loss under a diffusion-limited regime
Chemical Geology, 2019, 528, pp.119279.

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1 Volatile loss under a diffusion-limited regime in tektites:

2 evidence from tin stable isotopes

3 **John B. Creech**¹,²,*, **Frédéric Moynier**¹,³, and **Christian Koeberl**⁴,⁵

4 ¹Institut de Physique du Globe de Paris, Université de Paris, 1 Rue Jussieu, 75328 Paris
5 cedex 05, France

6 ²Department of Earth and Planetary Sciences, Macquarie University, NSW 2109, Australia

7 ³Institut Universitaire de France, 75005, Paris

8 ⁴Department of Lithospheric Research, University of Vienna, Althanstrasse 14, 1090 Vienna,
Austria

10 ⁵Natural History Museum, Burgring 7, 1010 Vienna, Austria

11 *Email address: john.creech@mq.edu.au

12 ABSTRACT

13 Tektites are glasses derived from near-surface continental crustal rocks that were
14 molten and ejected from the Earth's surface during hypervelocity meteorite impacts. They are
15 among the driest terrestrial samples, although the exact mechanism of water loss and the
16 behaviour of other volatile species during these processes are debated. Based on the
17 difference in magnitude of the Cu and Zn isotopic fractionations in tektites, and the difference
18 of diffusivity between these elements, it was suggested that volatile loss was diffusion-
19 limited. Tin is potentially well suited to testing this model, as it has a lower diffusivity in
20 silicate melts than both Cu and Zn, but a similar volatility to Zn. Here, we analysed the Sn
21 stable isotopic composition in a suite of seven tektites, representing three of the four known
22 tektite strewn fields, for which Zn and Cu isotopes were previously reported. Tin is enriched
23 in the heavier isotopes (≥2.5‰ on the ¹²²Sn/¹¹⁸Sn ratio) in tektites, correlated with the degree
24 of Sn elemental depletion in their respective samples as well as with Cu and Zn isotope ratios,
25 implying a common control. While the isotope fractionation of Sn, Cu and Zn is a result of
volatility, the magnitude of isotope fractionation is strongly moderated by their relative rates
of diffusion in the molten tektite droplets. An Australasian Muong Nong-type tektite analysed
has the least Sn depletion and Sn isotope fractionation, consistent with these samples being
more proximal to the source and experiencing a shorter time at high temperatures.

Keywords: tektites; volatiles; tin; stable isotopes; impacts

## INTRODUCTION

Tektites are distal impact glasses, typically up to a few cm in size, formed by rapid
melting of terrestrial upper crustal rocks during hypervelocity impacts on the Earth's surface
(e.g., Shaw and Wasserburg, 1982; Koeberl, 1986, 1990, 1994; Koeberl et al., 1996; Melosh
and Artemieva, 2004). Tektites have chemical and isotopic compositions similar to that of the
terrestrial upper crust, and thus are thought to have formed by fusion of the target
rocks/sediments rather than from the impactor itself (e.g., Shaw and Wasserburg, 1982;
Koeberl, 1986, 1994).

Although tektites are generally chemically and isotopically similar to the upper crust,
they are characterized by extremely low water contents (Beran and Koeberl, 2010; 0.002–0.02
wt.%; Koeberl, 1994), indicating a depletion of water (and potentially other volatiles) from
their precursor rocks (typically sediments, with >1% water) while the tektites were molten.
The mechanism for this depletion and, more broadly, the behaviour of volatile elements and
molecules during tektite formation is not well understood. Volatilization is known to
fractionate elemental and isotopic abundances of volatile elements, and isotopic fractionation
of moderately volatile elements has been recorded, for example, in lunar samples (e.g., Cl,
Ga, K, Zn, Rb; Sharp et al., 2010; Paniello et al., 2012; Kato et al., 2015; Boyce et al., 2015;
Kato and Moynier, 2017; Pringle and Moynier, 2017; Wang and Jacobsen, 2016). Recently,
even relatively refractory elements (e.g., Mg, Si, Ca, Ti) have been shown to have isotopic
variations that are attributed to high-temperature volatility-related processes in the early Solar
System (e.g., Richter et al., 2009; Pringle et al., 2014; Hin et al., 2017; Davis et al., 2018). As
such, developments of additional tools to investigate such processes are timely. Given that
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tektites were rapidly heated, molten, and quenched over timescales that are likely to capture
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kinetic effects related to volatility, stable isotopes of volatile elements are well-suited to
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studying tektite formation and the isotopic effects thereof.
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So far, studies of isotopic fractionation in tektites have yielded equivocal results.

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Studies of Mg (Esat and Taylor, 1987, 1986), K (Herzog et al., 2008; Humayun and Koeberl, 2004; Jiang et al., 2019), B (Chaussidon and Koeberl, 1995), and Li (Magna et al., 2011) in tektites found that vapour fractionation (at least for those elements) did not play an important role during tektite formation, and that isotope ratios reflect the compositions of their source materials. However, those elements lie towards the more refractory end of the moderately volatile elements. Among the more volatile of the moderately volatile elements, Cd is enriched in the heavy isotopes in one Muong Nong-type Australasian tektite, which could reflect evaporative loss of light Cd isotopes (Wombacher et al. 2003), although with only one sample, this finding is inconclusive. Moynier et al. (2010, 2009) reported Zn and Cu isotope compositions, respectively, for a suite of tektites from all strewn fields. These results were reaffirmed by a study of moldavites and sediments of the Ries crater (Rodovská et al., 2017).

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Both Cu and Zn show significant isotopic fractionation that correlates with their elemental depletions, consistent with preferential evaporative loss of light isotopes (Moynier et al., 2010, 2009), and the larger isotopic fractionation in Cu was attributed to the greater chemical diffusivity of Cu over Zn due to their differences in ionic charge (i.e., Zn²⁺ vs. Cu⁺; Moynier et al. 2010). However, this model is based on only two elements, and further testing is required to validate this hypothesis.

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Tin is amongst the more volatile of the moderately volatile elements, and is potentially
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more volatile than both Cu and Zn. No quantitative estimates exist for the temperature of
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volatilization of these elements in conditions relevant to tektite formation. Cosmochemical
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condensation temperatures, based on condensation from a gas of solar nebular composition at
77
a partial pressure of ~$10^{-4}$ atm. (Lodders, 2003), are often used as a first order estimate of volatility. These would suggest the relative volatilities of these elements increase in the order $Cu \ll Zn \le Sn$. Recent vaporization experiments of basalts at higher oxygen fugacities suggest that the relative volatilities of these elements increase in the order $Zn<Cu<Sn$ ($Zn$ is getting relatively less volatile under oxidizing conditions, while $Sn$ stays the most volatile element; Norris and Wood, 2017). However, another recent vaporization study under more oxidising conditions suggests that $Zn$ remains more volatile than $Cu$ (Sossi et al., 2019), although unfortunately Sossi et al. (2019) do not provide data for $Sn$. Here, we assume an order of volatility is maintained under tektite forming conditions whereby $Sn$ and $Zn$ have similar volatility, and $Cu$ is less volatile than $Sn$ and $Zn$.

Understanding the isotopic behaviour of $Sn$ during evaporation will be central to understanding isotopic data in planetary materials and in impact-related samples. Tin isotope cosmochemistry is a new field, and so far, published data have been limited to conference abstracts (Bourdon et al., 2017; Creech and Moynier, 2017; Fitoussi et al., 2017) and one paper (Creech and Moynier, 2019). However, the discovery of a light isotopic composition of $Sn$ in lunar samples compared to the Earth (Fitoussi et al., 2017) is unique amongst isotopic systems analysed so far. Tektites can be used as natural experiments to test the behaviour of $Sn$ during evaporation.

Here, we report the first $Sn$ stable isotope data in a suite of tektites from three of the four major tektite strewn fields in which $Cu$ and $Zn$ isotopic composition had been previously reported (Moynier et al., 2009, 2010). We use these data to investigate the processes leading to the chemical and isotopic compositions of tektites, and, in turn, the effect of volatility related processes on the isotopic composition of tin. By comparing the isotope fractionations of $Cu$, $Zn$, and $Sn$, as well as their relative diffusivities, we test the previous model of Moynier et al. (2009) of volatile loss in a diffusion-limited regime. These constraints on the isotopic behaviour of $Sn$ during evaporation will be central to understanding isotopic data in
104

planetary materials and in impact-derived samples, and will assist in interpretation of future
analyses of other cosmochemical samples, such as lunar rocks and chondrites.

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## MATERIALS AND METHODS

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### Sample descriptions

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The Sn isotopic composition of a total of seven tektites were analysed in this study, comprising all samples from previous Zn and Cu work with sufficient remaining sample material for Sn isotope analysis. Details of the samples are summarized in Table 1. These tektite samples represent three of the four identified tektite strewn fields, comprising:

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*Central European tektites:* Four moldavite tektites were studied, three of which are from the vicinity of Jankov (Jankov 1, Jankov 2, Jankov 3) and one is from the vicinity of Chlum (Chlum). Of these samples, three have been previously analysed for Zn isotope ratios by Moynier et al. (2009), and three for Cu isotope ratios by Moynier et al. (2010) – see Table 1.

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*North American tektites:* One North American tektite (BED 8402), which is from the bediasite sub-strewn field (Texas). This sample has been previously described in Weinke and Koeberl (1985), and analysed for Zn and Cu isotope ratios by Moynier et al. (2010, 2009).

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*Australasian tektites:* Two Australasian tektites, both indochinites, were analysed in this study. These comprise one Muong Nong type tektite from Thailand (MN 8309) and one splash-form tektite from Hainan, China (HSF1). Both of the Australasian tektites have been analysed for major and trace element compositions by Koeberl (1992) or Moynier et al. (2009); Cu and Zn isotope data have also been published by Moynier et al. (2009, 2010).

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For comparison with terrestrial compositions, isotopic and concentration data for four commonly used USGS terrestrial reference materials are also given in Table 1. Note that in the following discussion, a generic terrestrial upper crust $\delta^{122}/^{118}$Sn (the per mil deviation of the $^{122}$Sn/$^{118}$Sn ratio from the IPGP_Sn standard) composition is approximated as 0.00–0.50‰, with [Sn] of 0.65–2.50 µg g$^{-1}$, based on data from Creech et al. (2017) and

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Badullovich et al. (2017); the exact composition of the tektite source rocks may be further constrained in the future as Sn isotope data for more geological materials become available.

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**Analytical methods**

133

Tin purification and isotopic analysis were conducted using the same methods as described by Creech et al. (2017; 2019). Powders comprising 55–380 mg of tektite samples were digested in a mixture of concentrated HF:HNO₃ in closed teflon beakers on a hotplate at 120 °C. Dissolved tektite samples were evaporated to incipient dryness at 100 °C, taken up in a small volume of concentrated HCl and dried down again before being taken up in 2 mL of 0.5 M HCl for loading on to columns. Biorad columns were prepared with 1.5 mL per column of TRU resin and cleaned prior to sample loading by repeated rinsing with 0.5 M HNO₃, 0.5 M HCl and milli-Q water. After loading, matrix was rinsed off the column with 4 mL of 0.5 M HCl and 7 mL of 0.25 M HCl, and Sn was subsequently eluted in 10 mL of 0.5 M HNO₃.

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Prior to sample digestion, samples were doped with a ¹¹⁷Sn–¹²²Sn double-spike to give approximate proportions of 40% Sn from the double-spike and 60% from the sample, as detailed by Creech et al. (2017). Tin stable isotope measurements were carried out using a Thermo-Scientific Neptune Plus MC-ICPMS at the Institut de Physique du Globe de Paris, France, under analytical conditions identical to those described by Creech et al. (2017).

Isotope results are reported in δ¹²²/¹¹⁸Sn notation. Sufficient material was only available to measure each tektite sample once. Creech et al. (2017) reported an external reproducibility for this technique of (conservatively) ±0.065‰ on δ¹²²/¹¹⁸Sn, or ca. 0.016‰ on a per amu basis.

Uncertainties on figures represent either the internal error of the respective analysis or the external reproducibility, whichever is larger.

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Data reduction was conducted offline using the freely available double-spike data reduction tool IsoSpike (www.isospike.org; Creech and Paul, 2015).

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## 154 RESULTS

Tin isotopic and concentration data for tektites are presented in Table 1, along with literature data for Zn and Cu for the same tektite samples. Tektites are strongly fractionated towards heavy Sn isotopic compositions relative to those of terrestrial upper crust samples (Table 1; Fig. 1). Overall, the tektites span a range in $\delta^{122}/^{118}$Sn of ca. 2 ‰, which is significantly larger than any natural Sn isotopic variation so far reported for geological samples. The single North American tektite has a $\delta^{122}/^{118}$Sn = 1.40 ± 0.18‰, whereas the Central European tektites span a range from $\delta^{122}/^{118}$Sn = 1.35 ± 0.03‰ (Jankov 1) to 2.53 ± 0.15‰ (Chlum). The Australasian tektites are more variable; the splash form tektite from Hainan (HSF1) has a similar isotopic composition to the North American and Central European tektites ($\delta^{122}/^{118}$Sn = 1.60 ± 0.10‰), while the Muong Nong-type tektite MN8309 is less fractionated, with a composition more similar to terrestrial upper crust ($\delta^{122}/^{118}$Sn = 0.46 ± 0.18‰; basalt, Badullovich et al., 2017).

## 167 DISCUSSION

We observe a general shift towards heavy isotope compositions in tektites that is correlated with decreasing Sn content (Table 1, Fig. 1). This observation is consistent with evaporative loss of the light Sn isotopes during the molten phase of tektite formation, as previously observed for Cu and Zn (Moynier et al., 2010, 2009; Rodovská et al., 2017). In Figure 1 we show calculated isotopic compositions based on mass-dependent fractionation by Rayleigh distillation, which describes the isotopic evolution of a system from which a phase is continuously extracted. The isotopic composition of the tektites is well reproduced by a Rayleigh distillation, following a fractional distillation relationship for Sn as given in equation (1):

$$ \frac{^{122}_{118}Sn}{^{122}_{118}Sn_0} = \left( \frac{[Sn]}{[Sn]_0} \right)^{\alpha-1} \quad (1) $$

where $\alpha$ is the isotope fractionation factor, and the subscript 0 indicates initial values. The initial composition is an assumed terrestrial upper crust composition (note: on the scale of
180 isotopic fractionation observed in tektites, varying the initial composition within the range
181 observed in terrestrial samples has little effect on the shape of projection, although it does
182 change the relative position). In an ideal case, the kinetic fractionation factor, α, is dependent
183 on the square root of the ratio of the masses involved (i.e., αideal = √(M¹¹⁸Sn/M¹²²Sn),
184 where M¹¹⁸Sn and M¹²²Sn are the masses of ¹¹⁸Sn and ¹²²Sn, respectively; in the case of Sn,
185 αideal = 0.983), although in natural samples fractionation factors are found to deviate from this
186 ideal case (e.g., Moynier et al., 2009, 2010; Day and Moynier, 2014; Wimpenny et al., 2019).
187 Suitable natural samples can thus be used to derive empirical kinetic fractionation factors that
188 may be useful in interpreting volatility related isotope effects in other settings (with the caveat
189 that additional factors/reactions may also affect isotopic fractionation). Tektites are well
190 suited for this purpose.

191 As shown in Figure 1, the Sn isotopic compositions of most tektites are very close to
192 predicted compositions from fractional distillation, for α values of 0.998 (Central European
193 and North American tektites) or 0.999 (Australasian), and an initial composition of
194 δ¹²²/¹¹⁸Sn₀ = 0.13‰ and [Sn]₀ = 1.6 µg g⁻¹. This match between observed and predicted
195 isotope fractionation behaviour supports that during kinetic evaporation of a silicate melt the
196 lighter isotopes of Sn are preferentially lost in the vapour.

197 The Muong Nong-type tektite MN8309 is closest in composition to terrestrial upper
198 crust. This is consistent with previous observations that these tektites are less depleted in
199 volatiles than splash form tektites, contain mineral remnants of the target, and were possibly
deposited closer to the site of impact, having experienced lower formation temperatures
200 (Glass and Barlow, 1979; Koeberl, 1994, 1992). Muong Nong-type tektites were also found to
201 be less isotopically fractionated for Zn and Cu (Moynier et al., 2010, 2009). These results
202 reflect the temperature–time regime (i.e., likely shorter periods of melting and evaporation)
203 experienced by this group of tektites.
204
The Sn isotope data from tektites show strong correlations with Cu and Zn isotope data (Table 1, Fig. 2). The correlations between these different isotope systems suggest that they have been fractionated by a common process. Linear regressions through the data yield R² values of 0.94 and 0.73 for Sn vs. Cu and vs. Zn, respectively (note that the moldavite from Chlum appears to be an outlier in Cu isotope space, and was excluded from that regression). Considering the similar relative mass differences of the respective isotope ratios (i.e., 3.13% for ⁶⁶Zn/⁶⁴Zn, 3.17% for ⁶⁵Cu/⁶³Cu, and 3.39% for ¹²²Sn/¹¹⁸Sn), the slopes of the regressions in Figure 1 represent the relative rate of isotope fractionation for each element, which may result from e.g., volatility or diffusion rates, as discussed below. We find that the rate of Sn isotope fractionation in tektites is ca. 94% that of Zn isotopes (i.e., not significantly distinguishable within uncertainties), and ca. 17% that of Cu isotopes. If we assume volatilities decrease as Sn ≥ Zn > Cu, as described above, this fractionation must be partially moderated by another factor.

In the model of Moynier et al. (2010, 2009), molten tektite droplets are viscously stirred, with differential evaporation occurring at the surface. While the evaporation is controlled by volatility, the availability of elements at the surface for evaporation is governed by the rate of diffusion, which depends on many factors (e.g., T, melt composition, ionic radii). Where the diffusion rate of an element is slow, a diffusion-limited regime predominates, and evaporative loss of the element is restricted. Thus, elements that diffuse slowly in a melt are expected to be less isotopically fractionated, than elements that diffuse quickly, and for a fixed evaporation flux, the relative isotopic fractionation between volatile elements will be controlled by the diffusivity.

In anhydrous melts, the relative diffusivities of these elements increase in the order Sn < Zn << K, Cu (Behrens and Hahn, 2009; Zhang et al., 2010; Yang et al., 2016; Ni et al., 2017, 2018; see Supplementary Material for further discussion). Given the similar volatility of Sn relative to Zn, the larger relative fractionation in Zn is therefore likely a consequence of
231 the slower diffusion of Sn in molten droplets. The relatively large isotope fractionation
232 observed in Cu isotopes (Moynier et al., 2010), despite its lower volatility than Sn (and
233 possibly Zn), is largely due to the greater availability of Cu resulting from the faster diffusion
234 of Cu⁺.

235 **CONCLUSIONS**

236 Tektites are enriched in the heavier isotopes of Sn, and the isotopic composition
237 correlates with the degree of elemental Sn depletion in these samples. This is consistent with
238 evaporative loss of light Sn isotopes in to the vapour phase during tektite formation. The
239 observed Sn isotopic fractionation in tektites is consistent with calculations of fractional
240 distillation of Sn, with corresponding kinetic fractionation factors (α) of ca. 0.998–0.999. A
241 relationship is observed isotopic fractionation in Sn, Zn and Cu, suggesting a common
242 fractionation process. The smaller relative isotopic fractionation of Sn compared to Zn,
243 despite similar volatility, and the much larger isotopic fractionation of Cu reflects the
244 availability of these elements at the droplet surface, which is limited by the rate of diffusion.

245 **ACKNOWLEDGMENTS**

246 We are grateful to three anonymous reviewers for their detailed and constructive comments on the
247 manuscript, and to Don Porcelli for his editorial handling. F.M. acknowledges funding from the European
248 Research Council [ERC Starting grant agreement 637503-Pristine] to as well as the financial support of the
249 UnivEarthS Labex program at Sorbonne Paris Cité [ANR-10-LABX-0023 and ANR-11-IDEX-0005-02] and a
250 chaire d'excellence ANR-Idex Sorbonne Paris Cité. We are grateful to three anonymous reviewers for
251 constructive comments on an earlier version of this manuscript. Parts of this work were supported by IPGP
252 multidisciplinary program PARI, and by Region Île-de-France SESAME Grant no. 12015908.
253

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## FIGURE CAPTIONS

Figure 1. Sn isotopic composition versus Sn content in tektites, showing predicted isotopic fractionation (calculated using equation 1) from an initial terrestrial upper crust composition as Sn is lost from the reservoir. The different colour lines represent calculations using different hypothetical fractionation factors (i.e., α values), as indicated. The half-filled symbol indicates the Muong Nong type tektite, MN8309. Error bars reflect the internal error or the external reproducibility, whichever is larger. Where error bars are not visible, uncertainties are smaller than the data point.

Figure 2. Comparison between tektite data for Sn isotopes and a) Cu isotopes and b) Zn isotopes. Dashed lines represent linear regressions through the data, with R² values as indicated on the figure. The half-filled symbol indicates the Muong Nong type tektite, MN8309. The upper-most symbol indicates the moldavite Chlum, which was excluded from the linear regression on plot (a) as it is an outlier in both Cu and Sn isotope space. Error bars reflect the internal error or the external reproducibility, whichever is larger. Where error bars are not visible, uncertainties are smaller than the data point.

## TABLE CAPTION

Table 1. Tin, Cu, and Zn isotopic and concentration data for tektites and USGS reference materials.

Table 1 footnote. Tin isotope and concentration data for USGS reference materials are from Creech et al. (2017). Zinc isotope data are from Moynier et al. (2009), with the exception of AGV-2, which is from Moynier et al. (2010), and all Zn isotope data are relative to JMC-Lyon. Copper isotope data from Moynier et al. (2010), with the exception of BCR-2 which is from Chen et al. (2016), and all Cu isotope data are relative to NIST SRM 976. Cu and Zn concentration data for USGS reference materials are GeoReM recommended values.
<figure><img src="image_2.png" /></figure>
<figure><img src="image_3.png" /></figure>

<figure><img src="image_4.png" /></figure>
<table><thead><tr><th>Field</th><th>Type</th><th>Sample ID</th><th>δ<sup>122/118</sup>Sn<br>(‰)</th><th>±<br>(2 sd)</th><th>[Sn]<br>(µg g<sup>-1</sup>)</th><th>δ<sup>65/63</sup>Cu<br>(‰)</th><th>±<br>(2 sd)</th><th>[Cu]<br>(µg g<sup>-1</sup>)</th><th>δ<sup>66/64</sup>Zn<br>(‰)</th><th>±<br>(2 sd)</th><th>[Zn]<br>(µg g<sup>-1</sup>)</th></tr></thead><tbody><tr><td>North American</td><td>Bediasite</td><td>BED 8402</td><td>1.400</td><td>0.180</td><td>0.754</td><td>2.60</td><td>0.10</td><td>6.5</td><td>1.46</td><td>0.09</td><td>26</td></tr><tr><td>Central European</td><td>Moldavite</td><td>Jankov 1</td><td>1.352</td><td>0.028</td><td>0.853</td><td></td><td></td><td></td><td>1.92</td><td>0.09</td><td>29</td></tr><tr><td>Central European</td><td>Moldavite</td><td>Jankov 2</td><td>2.230</td><td>0.120</td><td>0.570</td><td>6.98</td><td>0.10</td><td>0.1</td><td>1.93</td><td>0.09</td><td>23</td></tr><tr><td>Central European</td><td>Moldavite</td><td>Jankov 3</td><td>1.725</td><td>0.051</td><td>0.619</td><td>4.41</td><td>0.10</td><td>0.1</td><td></td><td></td><td>24</td></tr><tr><td>Central European</td><td>Moldavite</td><td>Chlum</td><td>2.530</td><td>0.150</td><td>0.486</td><td>1.99</td><td>0.10</td><td>0.4</td><td>2.27</td><td>0.09</td><td>19</td></tr><tr><td>Australasian</td><td>Hainan</td><td>HSF1</td><td>1.600</td><td>0.100</td><td>0.379</td><td>3.11</td><td>0.10</td><td>2.2</td><td>2.16</td><td>0.09</td><td>8</td></tr><tr><td>Australasian</td><td>Muong Nong</td><td>MN8309</td><td>0.460</td><td>0.180</td><td>1.000</td><td>0.02</td><td>0.10</td><td>11.4</td><td>0.61</td><td>0.09</td><td>74</td></tr><tr><td>BHVO-2</td><td>Basalt</td><td></td><td>0.452</td><td>0.027</td><td>1.90</td><td>0.10</td><td>0.07</td><td>129.3</td><td>0.25</td><td>0.01</td><td>103.9</td></tr><tr><td>BCR-2</td><td>Basalt</td><td></td><td>0.404</td><td>0.650</td><td>2.36</td><td>0.20</td><td>0.09</td><td>19.7</td><td>0.27</td><td>0.06</td><td>129.5</td></tr><tr><td>GSP-2</td><td>Granodiorite</td><td></td><td>0.180</td><td>0.220</td><td>8.32</td><td></td><td></td><td>43.0</td><td></td><td></td><td>120.0</td></tr><tr><td>AGV-2</td><td>Andesite</td><td></td><td>0.310</td><td>0.120</td><td>2.07</td><td>0.10</td><td>0.11</td><td>51.5</td><td>0.25</td><td>0.09</td><td>86.7</td></tr></tbody></table>