<figure><img src="image_12.png" /></figure>

FIGURE 10. Triple oxygen isotope compositions (Δ¹⁷O vs. δ¹⁸O) of eight individual chips (~2 mg each) from two different fragments of Elmshorn (E03, E07) in comparison with the compositions of ordinary chondrites (H, L, LL) and other noncarbonaceous clan meteorites (Ang, angrites; Aub, aubrites; Bra, brachinites; EC, enstatite chondrites; HED, howardites, eucrites, diogenites; SNC, shergottites, nakhlites, chassignites) and the bulk silicate Earth (BSE). Meteorite reference compositions were compiled from the Meteoritical Bulletin Database and are shown with Kernel density estimation contours, with the outermost contours for a given meteorite group encompassing 70% of the corresponding data populations. The composition of the BSE was taken from Peters et al. (2021).

The MS (log χ) gives more or less the same result but is less robust considering the metal abundance.

The hysteresis properties, with very low coercivity ($B_C$=2.9 mT), low $M_{RS}/M_S$ (1.16 × 10⁻²), and high $B_{CR}/B_C$ (30.0) are typical of equilibrated H chondrites, with induced magnetic properties dominated by multidomain kamacite (Gattacceca et al., 2014). The $S_{-300}$ value of 0.51 indicates the presence of significant high-coercivity ferromagnetic minerals that can be identified as tetrataenite in the cloudy zone structure (Gattacceca et al., 2014). The coercivity spectra derived from IRM acquisition for the two samples can be fitted with two components with coercivity peaks at 4.7 and 143 mT (238 mg sample), and 65 and 353 mT (267 mg sample). Although there is some significant intersample variability, the existence of a component with very high coercivity indicates that the tetrataenite in the cloudy zone microstructure is ordered.

The two Elmshorn samples from stone E03 have magnetic properties typical of equilibrated H chondrites. This result is expected for the H6 clast and shows that the second sample of the stone representing the fine-grained clastic main lithology is also dominated by H chondrite components. The magnetic properties show a rock with metal under the form of multidomain kamacite and remanence properties dominated by the cloudy zone microstructure with high coercivity.

<figure><img src="image_13.png" /></figure>

FIGURE 11. The Ti isotope composition of Elmshorn (gray star) is consistent with both the simultaneously analyzed OC Forest Vale and literature values of individual OCs (yellow symbols). The data reveal deficits in $ε^{46}$Ti and $ε^{50}$Ti relative to Earth, indicating their formation in the inner solar system, i.e., the NC (noncarbonaceous meteorite) reservoir. Colored fields represent averages of meteorite groups (line) with 2 SD uncertainty (envelope) based on literature data (for data compilation and references, see Rüfenacht et al., 2023). Individual data points represent bulk meteorite samples, which were analyzed in the same laboratory as Elmshorn at ETH Zurich and are published in Rüfenacht et al. (2023). Aca, acapulcoites; EC, enstatite chondrites; Meso, mesosiderites; OC, ordinary chondrites. Literature data of OCs are from Trinquier et al. (2009), Zhang et al. (2011, 2012), Williams (2015), Burkhardt et al. (2017), Bischoff et al. (2017), Bischoff, Barrat, et al. (2019), Gerber et al. (2017), Williams et al. (2021), and Rüfenacht et al. (2023). Figure adapted from Rüfenacht et al. (2023).

This high coercivity indicates that the tetrataenite in the cloudy zone was not disordered by transient thermal events following its formation during parent body metamorphic cooling, indicating the absence of shock above shock level S3 (Dos Santos et al., 2015; Gattacceca et al., 2014).

The sample from stone E07 shows completely different magnetic properties. It can be characterized by significantly lower metal abundance and the values for magnetic properties are very close to those of L chondrites. However, it should be considered that on such small samples (Table 12) it is difficult to be definitive, because Ms depends on the relative abundance of kamacite, taenite, and tetrataenite (higher nickel leads to lower Ms). Thus, a large kamacite grain or a large taenite grain can affect the result significantly.
<figure><img src="image_13.png" /></figure>

FIGURE 12. The Ti and Cr isotope compositions of Elmshorn (gray star) overlap with the group average of OCs within analytical uncertainty. Therefore, Elmshorn belongs to the category of noncarbonaceous chondrites, which are assumed to have formed from inner solar system material. The averages and corresponding uncertainties are taken from the compilation of Rüfenacht et al. (2023). Aca, acapulcoites; Ang, angrites; Aub, aubrites; Bra, brachinites; CC, carbonaceous chondrites; EC, enstatite chondrites; IAB sil, IAB silicates; Meso, mesosiderites; Win, winonaites.

DISCUSSION

General Aspects and the Significance of Radionuclide
Concentrations from Gamma Spectrometry

From the recovered 21 fragments, most studies were
done on sample E03, which hit the roof of a house and
scattered into many fragments. Further studies for
comparison were performed on sample E07.
Nondestructive magnetic properties were obtained from
most of the samples (Figure 16), whereas radionuclide
concentrations were obtained from stones E01 and E02.

The short-lived radionuclides of the Elmshorn meteorite measured from May 4 until June 4, 2023, confirm the connection of the Elmshorn meteorite with the bolide event over Schleswig-Holstein (the state Elmshorn is located in) on April 25, 2023, since the presence of short-lived cosmogenic radionuclides with half-lives as short as 5.6 days proves the recent exposure to cosmic rays for both stones, the Elmshorn E02 (233.5 g) and the E01 (3731 g) stone (Table 11).

The U, Th, and K concentrations of the Elmshorn
chondrite are in the same range as those found in gamma
spectrometric studies of recent OC falls, like Stubenberg or
Renchen (Bischoff et al., 2017; Bischoff, Barrat, et al.,
2019). Compared to Flensburg, the U and Th values are
similar, but Elmshorn shows a higher potassium content.

The short-lived cosmogenic radionuclides are also in
the range of values measured for the Braunschweig,
Stubenberg, or Renchen meteorites (Bartoschewitz et al.,
2017; Bischoff et al., 2017; Bischoff, Barrat, et al., 2019).
Flensburg also showed similar activities, except of ⁶⁰Co: its
distinctly higher value in Flensburg was explained by a
larger depth of the fragment within the meteoroid
(Bischoff et al., 2021).

Classification of Elmshorn

Based on the inspection of the open surfaces (due to
fragmentation) and the polished thin sections, the
brecciated texture of Elmshorn is obvious (Figure 4).
Within a dominating grayish clastic groundmass, large
light- and dark-colored fragments can easily be
recognized (Figure 4). Thus, Elmshorn is a breccia. Based
on the randomly analyzed olivines and low-Ca
pyroxenes, Elmshorn certainly contains unequilibrated
type 3 lithologies. Strongly recrystallized and well-
equilibrated type 6 clasts exist as well. Although some
components (including glass-rich chondrules) are of low
petrologic type 3, several lithologies were found that
contain almost equilibrated (type 3.9–4.0) olivines but
still have less equilibrated pyroxene. This behavior is
often found in type 3.8–4 OCs, because the Fe–Mg
exchange and, consequently, the equilibration of olivine
is significantly faster than the Fe–Mg exchange in low-Ca
pyroxene. Many of these type 3.9–4 lithologies with
almost equilibrated olivine compositions point toward an
intermediate H/L or L chondrite heritage (Figure 8). On
the other hand, the light-colored type 6 fragment as well
as many other constituents of the meteorite are clearly of
H group origin, as shown in Figure 8, which represents
the results of randomly obtained olivine compositions.
Overall, we have an impact-produced mixture dominated
by H and H/L (or L) chondrite lithologies.

The coexistence of components with H and L (or
H/L) group characteristics is also suggested considering
the results of the density and magnetic properties. Based
on the densities obtained for the different pieces
(3.334 ± 0.003 [E01], 3.349 ± 0.010 [E02], and
3.448 ± 0.010 g cm⁻³ [E03]) the clear difference is of
diagnostic significance. Since the published values for H
chondrites and L chondrites are 3.42 ± 0.18 g cm⁻³ and
3.36 ± 0.16 g cm⁻³, respectively (Consolmagno et al.,
2008), it appears that one of the three brecciated pieces
from Elmshorn is dominated by H chondrite lithologies
(the 51.62 g piece from E03) and the two other, larger ones
by L chondritic components. The MS also confirms the
results of the density analyses. Considering samples with
mass above 3 g, the MS varies between log χ = 5.19 ± 0.04
and 4.96 ± 0.02 (Figure 16, Table S3). Comparing values
for falls of log χ = 5.32 ± 0.10 for H, and log
<figure><img src="image_14.png" /><figcaption>FIGURE 12. The Ti and Cr isotope compositions of Elmshorn (gray star) overlap with the group average of OCs within analytical uncertainty. Therefore, Elmshorn belongs to the category of noncarbonaceous chondrites, which are assumed to have formed from inner solar system material. The averages and corresponding uncertainties are taken from the compilation of Rüfenacht et al. (2023). Aca, acapulcoites; Ang, angrites; Aub, aubrites; Bra, brachinites; CC, carbonaceous chondrites; EC, enstatite chondrites; IAB sil, IAB silicates; Meso, mesosiderites; Win, winonaites.</figcaption></figure>

DISCUSSION

General Aspects and the Significance of Radionuclide
Concentrations from Gamma Spectrometry

From the recovered 21 fragments, most studies were
done on sample E03, which hit the roof of a house and
scattered into many fragments. Further studies for
comparison were performed on sample E07.
Nondestructive magnetic properties were obtained from
most of the samples (Figure 16), whereas radionuclide
concentrations were obtained from stones E01 and E02.

The short-lived radionuclides of the Elmshorn meteorite measured from May 4 until June 4, 2023, confirm the connection of the Elmshorn meteorite with the bolide event over Schleswig-Holstein (the state Elmshorn is located in) on April 25, 2023, since the presence of short-lived cosmogenic radionuclides with half-lives as short as 5.6 days proves the recent exposure to cosmic rays for both stones, the Elmshorn E02 (233.5 g) and the E01 (3731 g) stone (Table 11).

The U, Th, and K concentrations of the Elmshorn
chondrite are in the same range as those found in gamma
spectrometric studies of recent OC falls, like Stubenberg or
Renchen (Bischoff et al., 2017; Bischoff, Barrat, et al.,
2019). Compared to Flensburg, the U and Th values are
similar, but Elmshorn shows a higher potassium content.

The short-lived cosmogenic radionuclides are also in
the range of values measured for the Braunschweig,
Stubenberg, or Renchen meteorites (Bartoschewitz et al.,
2017; Bischoff et al., 2017; Bischoff, Barrat, et al., 2019).
Flensburg also showed similar activities, except of ⁶⁰Co: its
distinctly higher value in Flensburg was explained by a
larger depth of the fragment within the meteoroid
(Bischoff et al., 2021).

Classification of Elmshorn

Based on the inspection of the open surfaces (due to
fragmentation) and the polished thin sections, the
brecciated texture of Elmshorn is obvious (Figure 4).
Within a dominating grayish clastic groundmass, large
light- and dark-colored fragments can easily be
recognized (Figure 4). Thus, Elmshorn is a breccia. Based
on the randomly analyzed olivines and low-Ca
pyroxenes, Elmshorn certainly contains unequilibrated
type 3 lithologies. Strongly recrystallized and well-
equilibrated type 6 clasts exist as well. Although some
components (including glass-rich chondrules) are of low
petrologic type 3, several lithologies were found that
contain almost equilibrated (type 3.9–4.0) olivines but
still have less equilibrated pyroxene. This behavior is
often found in type 3.8–4 OCs, because the Fe–Mg
exchange and, consequently, the equilibration of olivine
is significantly faster than the Fe–Mg exchange in low-Ca
pyroxene. Many of these type 3.9–4 lithologies with
almost equilibrated olivine compositions point toward an
intermediate H/L or L chondrite heritage (Figure 8). On
the other hand, the light-colored type 6 fragment as well
as many other constituents of the meteorite are clearly of
H group origin, as shown in Figure 8, which represents
the results of randomly obtained olivine compositions.
Overall, we have an impact-produced mixture dominated
by H and H/L (or L) chondrite lithologies.

The coexistence of components with H and L (or
H/L) group characteristics is also suggested considering
the results of the density and magnetic properties. Based
on the densities obtained for the different pieces
(3.334 ± 0.003 [E01], 3.349 ± 0.010 [E02], and
3.448 ± 0.010 g cm⁻³ [E03]) the clear difference is of
diagnostic significance. Since the published values for H
chondrites and L chondrites are 3.42 ± 0.18 g cm⁻³ and
3.36 ± 0.16 g cm⁻³, respectively (Consolmagno et al.,
2008), it appears that one of the three brecciated pieces
from Elmshorn is dominated by H chondrite lithologies
(the 51.62 g piece from E03) and the two other, larger ones
by L chondritic components. The MS also confirms the
results of the density analyses. Considering samples with
mass above 3 g, the MS varies between log χ = 5.19 ± 0.04
and 4.96 ± 0.02 (Figure 16, Table S3). Comparing values
for falls of log χ = 5.32 ± 0.10 for H, and log
<figure><img src="image_14.png" /></figure>

FIGURE 13. Xe isotopic compositions of Elmshorn 1 and 2 from stone E03 normalized to Xe-Q (Busemann et al., 2000). The dashed lines represent mixing lines of varying ratios between Q and air. The Xe-HL composition is taken from Huss and Lewis (1994), and the Xe-air from Basford et al. (1973). The Xe-trapped component is dominated by Q. A slight cosmogenic contribution ($>1\sigma$) to $^{124}$Xe might be discernible, though this should typically affect $^{126}$Xe even more. Both samples show short-lived $^{129}$I-derived $^{129}$Xe excesses.

<figure><img src="image_15.png" /></figure>

FIGURE 14. Specific activity of Elmshorn (black square) calculated from IAMS data with 1-sigma uncertainties compared to radius- and depth-dependent (saturation) production rate calculations for $^{26}$Al and $^{41}$Ca for OCs (Leya & Masarik, 2009). The production rates are based on the chemical composition in Table S2.

$\chi = 4.87 \pm 0.10$ for L (from Rochette et al., 2003), most of the Elmshorn stones look like being a mixture of H and L chondrite components. A similar conclusion is reached by

measuring the saturation magnetization of ~500 mg samples. The obtained values of Ms = 36.5 Am$^2$ kg$^{-1}$ for H-dominated and Ms = 20.4 Am$^2$ kg$^{-1}$ for supposed L-
<figure><img src="image_15.png" /></figure>

FIGURE 13. Xe isotopic compositions of Elmshorn 1 and 2 from stone E03 normalized to Xe-Q (Busemann et al., 2000). The dashed lines represent mixing lines of varying ratios between Q and air. The Xe-HL composition is taken from Huss and Lewis (1994), and the Xe-air from Basford et al. (1973). The Xe-trapped component is dominated by Q. A slight cosmogenic contribution ($>1\sigma$) to $^{124}$Xe might be discernible, though this should typically affect $^{126}$Xe even more. Both samples show short-lived $^{129}$I-derived $^{129}$Xe excesses.

<figure><img src="image_16.png" /></figure>

FIGURE 14. Specific activity of Elmshorn (black square) calculated from IAMS data with 1-sigma uncertainties compared to radius- and depth-dependent (saturation) production rate calculations for $^{26}$Al and $^{41}$Ca for OCs (Leya & Masarik, 2009). The production rates are based on the chemical composition in Table S2.

$\chi = 4.87 \pm 0.10$ for L (from Rochette et al., 2003), most of the Elmshorn stones look like being a mixture of H and L chondrite components. A similar conclusion is reached by

measuring the saturation magnetization of ~500 mg samples. The obtained values of Ms = 36.5 Am$^2$ kg$^{-1}$ for H-dominated and Ms = 20.4 Am$^2$ kg$^{-1}$ for supposed L-
<figure><img src="image_16.png" /></figure>

FIGURE 15. The three macroscopically distinct areas shown in Figure 4 (light and dark lithology from E03, as well as the dominating clastic groundmass [medium-light]) were identified in the thin section Elmshorn PL23029 and investigated by obtaining specular reflectance spectra of several designated areas of interest. Black arrows denote RBs typical for olivine (spectrum a) containing additional peaks (spectrum c), and albitic feldspar, and low-Ca pyroxene (spectrum b). The red spectrum is albite (ID167) (see database details in Weber et al. (2018) and inset for comparison of the RB positions). The position of the CF, which is a material-dependent reflectance minimum and indicated by a blue bar is in agreement with dominantly silicate-comprised material. (a) 609 Elmshorn PL 23029 dark lithology bulk spectrum: (b) 609 Elmshorn PL 23029 light coarse-grained bulk spectrum: (c) 609 Elmshorn PL 23029 medium-light multiclastic bulk spectrum. Spectra are offset for clarity. Depending on the abundance of metal and sulfide phases present in the measurement spot, several spectra show a general baseline enhancement (not visible here owing to offset).

dominated lithologies are very similar to values of 40.46 ± 6.99 and 17.93 ± 6.09 Am² kg⁻¹ for H and L chondrite falls, respectively (Gattacceca et al., 2014). The weighted overall mean value of log χ = 5.07 ± 0.03 is in between the average values of 4.87 and 5.32 for falls of L and H chondrites, respectively (Rochette et al., 2003). Assuming that Elmshorn represents a mix of such typical OC materials, the estimate yields an H chondrite contribution of about 30–40 wt%.

Consequently, Elmshorn can be described based on
the chemical compositions of olivine and low-Ca
pyroxene and density and magnetic considerations as an
H-H/L (or H-L) breccia. Since we have clasts of different
petrologic types (3–6), the bulk rock of Elmshorn could
potentially be classified as an H-H/L3-6 or (H-L3-6)
chondrite breccia. However, such a classification would

be inconsistent with the results of the O isotope analyses. All eight O isotope analyses from two different stones (one dominated by H chondrite lithologies, the other dominated by L chondrite lithologies) show typical values for H chondrites. Thus, the oxygen isotope compositions are unambiguous. They clearly indicate an H chondrite heritage even for those rocks that were characterized as H/L or L chondrites based on petrologic data (e.g., olivine compositions) and considerations concerning density and MS. In summary, Elmshorn shows extremely anomalous behavior. Taking the oxygen isotope composition as an accepted tool of classification into account, consequently, Elmshorn has to be classified as an “anomalous H3-6 chondrite breccia.” Titanium and Cr isotope analyses confirm that it is an OC.

As defined earlier for the shock classification of breccias, the fragment with the lowest degree of shock defines the shock degree of a brecciated bulk rock (Bischoff, Schleiting, et al., 2019; Stöffler et al., 1991, 2018). In many fragments, undulose extinction in olivine is the typical effect of shock metamorphism and unshocked fragments do not exist. Thus, an S2 (C-S2) shock classification for the Elmshorn breccia is appropriate.

Formation of Elmshorn

As demonstrated earlier, Elmshorn contains various
types of fragments that have seen various degrees of
metamorphism and recrystallisation (Figure 5). This is
well documented by the coexistence of type 5 or 6
fragments (Figure 5) and of fragments having glass-
bearing chondrules with strongly zoned olivine (Fa₀-₂₇:
Figure 6). Thus, Elmshorn clearly contains lithic
components from the interior of the parent body(ies) as
well as material from (near) surface locations. One type of
material is of H chondrite heritage, as indicated by
equilibrated lithologies having mean olivine compositions
of Fa₁₉-₂₀ (Figure 8c). Another main component of
Elmshorn can be described as an equilibrated (type 4) or
almost equilibrated (~type 3.8–3.9) lithology with mean
olivine compositions of ~Fa₂₁-₂₃ (Figure 8d). Thus, the
latter components have olivine compositions related to
olivine in typical L chondrites (~Fa₂₂-₂₇). As such,
Elmshorn consists of main components related to two
independent precursor planetesimals. The coexistence of
these two components is confirmed by the physical
properties (density, MS) that indicate both an H and L (or
H/L) chondrite relationship.

We suggest that the two parent bodies had already
experienced shock processing, brecciation, and lithification
prior to the disruption and re-accretion events that
occurred possibly about 2.8 Gyr ago based on the gas
retention ages (Table 10). This is indicated by the
occurrence of several types of melt rocks (e.g., Figure 9a
<figure><img src="image_17.png" /></figure>

FIGURE 15. The three macroscopically distinct areas shown in Figure 4 (light and dark lithology from E03, as well as the dominating clastic groundmass [medium-light]) were identified in the thin section Elmshorn PL23029 and investigated by obtaining specular reflectance spectra of several designated areas of interest. Black arrows denote RBs typical for olivine (spectrum a) containing additional peaks (spectrum c), and albitic feldspar, and low-Ca pyroxene (spectrum b). The red spectrum is albite (ID167) (see database details in Weber et al. (2018) and inset for comparison of the RB positions). The position of the CF, which is a material-dependent reflectance minimum and indicated by a blue bar is in agreement with dominantly silicate-comprised material. (a) 609 Elmshorn PL 23029 dark lithology bulk spectrum: (b) 609 Elmshorn PL 23029 light coarse-grained bulk spectrum: (c) 609 Elmshorn PL 23029 medium-light multiclastic bulk spectrum. Spectra are offset for clarity. Depending on the abundance of metal and sulfide phases present in the measurement spot, several spectra show a general baseline enhancement (not visible here owing to offset).

dominated lithologies are very similar to values of 40.46 ± 6.99 and 17.93 ± 6.09 Am² kg⁻¹ for H and L chondrite falls, respectively (Gattacceca et al., 2014). The weighted overall mean value of log χ = 5.07 ± 0.03 is in between the average values of 4.87 and 5.32 for falls of L and H chondrites, respectively (Rochette et al., 2003). Assuming that Elmshorn represents a mix of such typical OC materials, the estimate yields an H chondrite contribution of about 30–40 wt%.

Consequently, Elmshorn can be described based on
the chemical compositions of olivine and low-Ca
pyroxene and density and magnetic considerations as an
H-H/L (or H-L) breccia. Since we have clasts of different
petrologic types (3–6), the bulk rock of Elmshorn could
potentially be classified as an H-H/L3-6 or (H-L3-6)
chondrite breccia. However, such a classification would

be inconsistent with the results of the O isotope analyses. All eight O isotope analyses from two different stones (one dominated by H chondrite lithologies, the other dominated by L chondrite lithologies) show typical values for H chondrites. Thus, the oxygen isotope compositions are unambiguous. They clearly indicate an H chondrite heritage even for those rocks that were characterized as H/L or L chondrites based on petrologic data (e.g., olivine compositions) and considerations concerning density and MS. In summary, Elmshorn shows extremely anomalous behavior. Taking the oxygen isotope composition as an accepted tool of classification into account, consequently, Elmshorn has to be classified as an “anomalous H3-6 chondrite breccia.” Titanium and Cr isotope analyses confirm that it is an OC.

As defined earlier for the shock classification of breccias, the fragment with the lowest degree of shock defines the shock degree of a brecciated bulk rock (Bischoff, Schleiting, et al., 2019; Stöffler et al., 1991, 2018). In many fragments, undulose extinction in olivine is the typical effect of shock metamorphism and unshocked fragments do not exist. Thus, an S2 (C-S2) shock classification for the Elmshorn breccia is appropriate.

Formation of Elmshorn

As demonstrated earlier, Elmshorn contains various
types of fragments that have seen various degrees of
metamorphism and recrystallisation (Figure 5). This is
well documented by the coexistence of type 5 or 6
fragments (Figure 5) and of fragments having glass-
bearing chondrules with strongly zoned olivine (Fa₀-₂₇:
Figure 6). Thus, Elmshorn clearly contains lithic
components from the interior of the parent body(ies) as
well as material from (near) surface locations. One type of
material is of H chondrite heritage, as indicated by
equilibrated lithologies having mean olivine compositions
of Fa₁₉–₂₀ (Figure 8c). Another main component of
Elmshorn can be described as an equilibrated (type 4) or
almost equilibrated (~type 3.8–3.9) lithology with mean
olivine compositions of ~Fa₂₁–₂₃ (Figure 8d). Thus, the
latter components have olivine compositions related to
olivine in typical L chondrites (~Fa₂₂–₂₇). As such,
Elmshorn consists of main components related to two
independent precursor planetesimals. The coexistence of
these two components is confirmed by the physical
properties (density, MS) that indicate both an H and L (or
H/L) chondrite relationship.

We suggest that the two parent bodies had already
experienced shock processing, brecciation, and lithification
prior to the disruption and re-accretion events that
occurred possibly about 2.8 Gyr ago based on the gas
retention ages (Table 10). This is indicated by the
occurrence of several types of melt rocks (e.g., Figure 9a
<figure><img src="image_17.png" /><figcaption>FIGURE 16. Illustration of the magnetic susceptibility (MS, in $10^{-9} \text{ m}^3 \text{ kg}^{-1}$) of samples with different masses from Elmshorn shown as black points. The 11 measured fragments of the 156 g piece (E03: Tables S1 and S3) shattered on the roof of a house on “Gärtnerstrasse” are indicated by white centers. The two pieces studied in more detail in this work are highlighted by red outer circles. All data plot close to the transition zone between H and L chondrites. The average values of L and H chondrite falls are $4.87 \pm 0.10$ and $5.32 \pm 0.10$, respectively (Rochette et al., 2003). The dashed line represents the weighted mean.</figcaption></figure>

and Figure S4), some of which are certainly of impact origin. A typical example of an impact melt rock clast is shown in Figure 9a, illustrating the formation of immiscible metal-sulfide spherules in a silicate melt matrix. Based on its shape, this fragment must have been originally part of a larger melt unit. It remains unsolved, however, whether the fragment represents a piece of a former melt pool or melt vein. The occurrence of olivine fragments (Fa$_{20}$, Fa$_{29}$) may indicate that the melt formed within an unequilibrated part of the parent body, perhaps in a near-surface type 3 layer. Another strange melt rock (fragment M) is metal poor (Figure S4) with unusual Al-rich mafic silicates (Table 2). Other impact-related clasts are shown in Figure 9, including various types of shock-darkened clasts (Figure 9b,c) and sulfide-silicate associations (Figure 9d). Elmshorn contains even more unusual clasts that had to be part of larger units on a former parent body, and their formation and brecciation requires multiple impact processing steps. Since the brecciated main lithology of Elmshorn does not contain solar wind-implanted noble gases, the different components cannot have been part of a parent body regolith. Thus, Elmshorn is a fragmental breccia. The brecciated nature without the presence of solar wind is even more difficult to understand given that Elmshorn also frequently contains type 3 clasts with glass-rich chondrules (Figures 5 and 6) that may represent lithologies close to the surface. The mixing of these different clasts in a near-surface environment without solar wind access is unusual.

The most straightforward explanation is that the breccia of Elmshorn represents a reaccreted rock after a

catastrophic collision between H and H/L chondrite parent bodies, complete disruption, and reassembly. This is the only conceivable way to prevent the implantation of solar wind gases in this kind of complex breccia, implying that the mixed components reassembled in some depth of the newly formed (at least) second generation parent body that was lithified like other breccia on planetary bodies by later impact processes, as described by Kieffer (1975) and Bischoff et al. (1983). A similar process could have resulted in the lack of solar wind in samples of Asteroid $2008TC_3$ from the Almahata Sitta strewn field, a breccia containing even more diverse materials, though here a loss of fragile matrix between the various lithologies has been suggested (Bischoff, Bannemann, et al., 2022; Goodrich et al., 2019). Considering the process of late addition of diverse components by small impacts into the surface layers of a large first-generation OC parent body, it appears unrealistic that all the described fragmental components were added to the surface materials without including at least traces of solar wind gases.

## Alternative Possibilities Concerning the Formation Process

We should at least mention and briefly discuss (and/or exclude) more exotic processes in order to understand the lack of a solar wind signature in the bulk breccia of Elmshorn: (a) It is highly unlikely that during the disruption and reassembly processes a fine-grained matrix that included all solar wind signatures on the precursor planetesimals was lost. All clasts in Elmshorn
<figure><img src="image_18.png" /><figcaption>FIGURE 16. Illustration of the magnetic susceptibility (MS, in $10^{-9} \text{ m}^3\text{kg}^{-1}$) of samples with different masses from Elmshorn shown as black points. The 11 measured fragments of the 156 g piece (E03: Tables S1 and S3) shattered on the roof of a house on “Gärtnerstrasse” are indicated by white centers. The two pieces studied in more detail in this work are highlighted by red outer circles. All data plot close to the transition zone between H and L chondrites. The average values of L and H chondrite falls are $4.87 \pm 0.10$ and $5.32 \pm 0.10$, respectively (Rochette et al., 2003). The dashed line represents the weighted mean.</figcaption></figure>

and Figure S4), some of which are certainly of impact origin. A typical example of an impact melt rock clast is shown in Figure 9a, illustrating the formation of immiscible metal-sulfide spherules in a silicate melt matrix. Based on its shape, this fragment must have been originally part of a larger melt unit. It remains unsolved, however, whether the fragment represents a piece of a former melt pool or melt vein. The occurrence of olivine fragments (Fa$_{20}$, Fa$_{29}$) may indicate that the melt formed within an unequilibrated part of the parent body, perhaps in a near-surface type 3 layer. Another strange melt rock (fragment M) is metal poor (Figure S4) with unusual Al-rich mafic silicates (Table 2). Other impact-related clasts are shown in Figure 9, including various types of shock-darkened clasts (Figure 9b,c) and sulfide-silicate associations (Figure 9d). Elmshorn contains even more unusual clasts that had to be part of larger units on a former parent body, and their formation and brecciation requires multiple impact processing steps. Since the brecciated main lithology of Elmshorn does not contain solar wind-implanted noble gases, the different components cannot have been part of a parent body regolith. Thus, Elmshorn is a fragmental breccia. The brecciated nature without the presence of solar wind is even more difficult to understand given that Elmshorn also frequently contains type 3 clasts with glass-rich chondrules (Figures 5 and 6) that may represent lithologies close to the surface. The mixing of these different clasts in a near-surface environment without solar wind access is unusual.

The most straightforward explanation is that the breccia of Elmshorn represents a reaccreted rock after a

catastrophic collision between H and H/L chondrite parent bodies, complete disruption, and reassembly. This is the only conceivable way to prevent the implantation of solar wind gases in this kind of complex breccia, implying that the mixed components reassembled in some depth of the newly formed (at least) second generation parent body that was lithified like other breccia on planetary bodies by later impact processes, as described by Kieffer (1975) and Bischoff et al. (1983). A similar process could have resulted in the lack of solar wind in samples of Asteroid $2008TC_3$ from the Almahata Sitta strewn field, a breccia containing even more diverse materials, though here a loss of fragile matrix between the various lithologies has been suggested (Bischoff, Bannemann, et al., 2022; Goodrich et al., 2019). Considering the process of late addition of diverse components by small impacts into the surface layers of a large first-generation OC parent body, it appears unrealistic that all the described fragmental components were added to the surface materials without including at least traces of solar wind gases.

## Alternative Possibilities Concerning the Formation Process

We should at least mention and briefly discuss (and/or exclude) more exotic processes in order to understand the lack of a solar wind signature in the bulk breccia of Elmshorn: (a) It is highly unlikely that during the disruption and reassembly processes a fine-grained matrix that included all solar wind signatures on the precursor planetesimals was lost. All clasts in Elmshorn
<figure><img src="image_18.png" /></figure>

FIGURE 17. A micro-FT-IR spot measurement of the dark lithology of the Chelyabinsk meteorite (spectrum b) is compared to a spot measurement of a portion (200 × 200 µm) of the dark lithology of Elmshorn (spectrum a). Arrows denote typical olivine-related RB locations common in both spectra. However, Elmshorn displays additional RBs between 947 and 917 cm⁻¹ owing to the presence of low-Ca pyroxene. The CF is shifted toward shorter wavenumbers (1140 cm⁻¹) when compared to the Chelyabinsk spectrum (1221 cm⁻¹).

seem compacted early and tightly and show no evidence for a once present additional fine-grained component. (b) Shielding from solar wind could be imaginable, but this would either require a very early process, within the first perhaps ~5 Myr of the solar system, when the nebula gas was still present, or an extremely large parent body which could have once maintained a protective atmosphere. (c) Finally, it appears also unlikely that a very fast occurring regolithic process prevented the accumulation of detectable solar wind during formation of the breccia or that the residence time in a regolith was too short.

## Significance of Spectroscopic Research

All three studied lithologies from Elmshorn show a dominantly crystalline spectrum in the investigated areas (arrows in Figure 17 point at prominent Reststrahlen bands). The dark fine-grained and the light coarse-grained lithology (Figure 4) both display olivine-dominated spectra (Hofmeister, 1987). However, the olivine-rich groundmass that constitutes the dark fine-grained portion of the clast is adorned with additional peaks that are inconsistent with olivine and might point at the presence of “albitic” feldspars (see inset spectrum in Figure 17 for comparison), whereas the presence of chromite or

phosphate minerals, which were optically identified in the clast (Figure 7c), cannot be spectrally resolved. The light multiclastic main lithology appears to be dominated by a low-Ca pyroxene and shows additional RBs that point at the presence of additional silicate minerals that cannot be unambiguously identified: however, they are likely albitic feldspars (see inset red spectrum in Figure 17 for comparison). Neither metal nor sulfides can be resolved by diagnostic RBs in this measurement setup owing to the materials' extremely low spectral contrast in this spectral range: instead, their presence is indirectly shown in an overall increased intensity (e.g., metals in Stojic et al., 2021). Prominent water bands were not detected in the spectra, indicating a continuous processing of the rock under dry conditions. A comparison with the shock-darkened lithology of the Chelyabinsk meteorite (Figure 9; Kohout et al., 2020; Morlok et al., 2017) shows that the most prominent RB of olivine is located at 885 cm⁻¹ (11.3 µm), which is common for both spectra. However, additional peaks belonging to low-Ca pyroxene in the dark portion of the Elmshorn meteorite might be indicative of a lesser shock degree than that of Chelyabinsk, which is of shock stage S4.

## Complex Breccias and the Mixing of OC Clasts

Inspecting the broken surfaces and the polished thin sections of Elmshorn (Figure 4) showed, as did the results of physical properties (density, MS) and of randomly obtained olivine compositions (Figure 8), that the rock is a complex breccia, indicating the presence of an impact-produced mixture of H and H/L (or L) chondrite lithologies and other types of clasts (e.g., Figures 5, 7, 9, and Figures S4–S6). In comparison, Kaidun and Almahata Sitta are probably the most spectacular breccias with a huge and even much wider variety of xenolithic clasts (e.g., Bischoff et al., 2010; Bischoff, Bannemann, et al., 2022; Goodrich et al., 2014; Goodrich et al., 2019; Horstmann et al., 2010; Horstmann & Bischoff, 2014; Ivanov, 1989; Zolensky & Ivanov, 2003; Zolensky et al., 1996, 2010). Also, some OC breccias have a huge variety of parent body lithologies as well as xenoliths, of which Adzhi-Bogdo (stone) and NWA 869 are excellent examples (Bischoff et al., 1993, Metzler et al., 2010, 2011; Welten et al., 2011). The Adzhi-Bogdo (LL3-6) chondrite regolith breccia contains fragmental breccia clasts, shock-darkened fragments, highly recrystallized clasts (sometimes with internal shock veins), melt rock clasts, and xenolithic L chondrite and achondritic clasts including granite-like lithologies (Bischoff et al., 1993, 1996; Terada & Bischoff, 2009). Similarly, NWA 869 contains unequilibrated and equilibrated chondrite clasts, impact melt rocks, an unequilibrated microbreccia, and several other objects (Metzler et al., 2011). Xenolithic fragments
<figure><img src="image_19.png" /><figcaption>FIGURE 17. A micro-FT-IR spot measurement of the dark lithology of the Chelyabinsk meteorite (spectrum b) is compared to a spot measurement of a portion (200 × 200 µm) of the dark lithology of Elmshorn (spectrum a). Arrows denote typical olivine-related RB locations common in both spectra. However, Elmshorn displays additional RBs between 947 and 917 cm⁻¹ owing to the presence of low-Ca pyroxene. The CF is shifted toward shorter wavenumbers (1140 cm⁻¹) when compared to the Chelyabinsk spectrum (1221 cm⁻¹).</figcaption></figure>

seem compacted early and tightly and show no evidence for a once present additional fine-grained component. (b) Shielding from solar wind could be imaginable, but this would either require a very early process, within the first perhaps ~5 Myr of the solar system, when the nebula gas was still present, or an extremely large parent body which could have once maintained a protective atmosphere. (c) Finally, it appears also unlikely that a very fast occurring regolithic process prevented the accumulation of detectable solar wind during formation of the breccia or that the residence time in a regolith was too short.

## Significance of Spectroscopic Research

All three studied lithologies from Elmshorn show a dominantly crystalline spectrum in the investigated areas (arrows in Figure 17 point at prominent Reststrahlen bands). The dark fine-grained and the light coarse-grained lithology (Figure 4) both display olivine-dominated spectra (Hofmeister, 1987). However, the olivine-rich groundmass that constitutes the dark fine-grained portion of the clast is adorned with additional peaks that are inconsistent with olivine and might point at the presence of “albitic” feldspars (see inset spectrum in Figure 17 for comparison), whereas the presence of chromite or

phosphate minerals, which were optically identified in the clast (Figure 7c), cannot be spectrally resolved. The light multiclastic main lithology appears to be dominated by a low-Ca pyroxene and shows additional RBs that point at the presence of additional silicate minerals that cannot be unambiguously identified: however, they are likely albitic feldspars (see inset red spectrum in Figure 17 for comparison). Neither metal nor sulfides can be resolved by diagnostic RBs in this measurement setup owing to the materials' extremely low spectral contrast in this spectral range: instead, their presence is indirectly shown in an overall increased intensity (e.g., metals in Stojic et al., 2021). Prominent water bands were not detected in the spectra, indicating a continuous processing of the rock under dry conditions. A comparison with the shock-darkened lithology of the Chelyabinsk meteorite (Figure 9; Kohout et al., 2020; Morlok et al., 2017) shows that the most prominent RB of olivine is located at 885 cm⁻¹ (11.3 µm), which is common for both spectra. However, additional peaks belonging to low-Ca pyroxene in the dark portion of the Elmshorn meteorite might be indicative of a lesser shock degree than that of Chelyabinsk, which is of shock stage S4.

## Complex Breccias and the Mixing of OC Clasts

Inspecting the broken surfaces and the polished thin sections of Elmshorn (Figure 4) showed, as did the results of physical properties (density, MS) and of randomly obtained olivine compositions (Figure 8), that the rock is a complex breccia, indicating the presence of an impact-produced mixture of H and H/L (or L) chondrite lithologies and other types of clasts (e.g., Figures 5, 7, 9, and Figures S4–S6). In comparison, Kaidun and Almahata Sitta are probably the most spectacular breccias with a huge and even much wider variety of xenolithic clasts (e.g., Bischoff et al., 2010; Bischoff, Bannemann, et al., 2022; Goodrich et al., 2014; Goodrich et al., 2019; Horstmann et al., 2010; Horstmann & Bischoff, 2014; Ivanov, 1989; Zolensky & Ivanov, 2003; Zolensky et al., 1996, 2010). Also, some OC breccias have a huge variety of parent body lithologies as well as xenoliths, of which Adzhi-Bogdo (stone) and NWA 869 are excellent examples (Bischoff et al., 1993, Metzler et al., 2010, 2011; Welten et al., 2011). The Adzhi-Bogdo (LL3-6) chondrite regolith breccia contains fragmental breccia clasts, shock-darkened fragments, highly recrystallized clasts (sometimes with internal shock veins), melt rock clasts, and xenolithic L chondrite and achondritic clasts including granite-like lithologies (Bischoff et al., 1993, 1996; Terada & Bischoff, 2009). Similarly, NWA 869 contains unequilibrated and equilibrated chondrite clasts, impact melt rocks, an unequilibrated microbreccia, and several other objects (Metzler et al., 2011). Xenolithic fragments
have also been encountered in some accretionary type 3 breccias and other chondrite breccias: examples are Glanerbrug (Niemeier & Bischoff, 2006; Welten et al., 1992) and Villalbeto de la Pena (Bischoff et al., 2013; Dyl et al., 2012). Villalbeto de la Pena is an L6 breccia with a winonaite-related clast, while Glanerbrug is a very complex fragmental breccia representing a mixture of L and LL chondrite components, with the host rock being of LL chondritic origin (Niemeier & Bischoff, 2006; Welten et al., 1992). Similarly, Gattacceca et al. (2017) describe the brecciated LL6 chondrite Northwest Africa (NWA) 5764 that contains a >16 cm³ L4 clast. However, in general, mixing of clasts from different OC groups is relatively rare: In the LL chondrite St. Mesmin, intensely shocked H-group chondrite fragments were found (Dodd, 1974), and Rubin et al. (1983) described an LL5 clast in the Dimmitt H chondrite regolith breccia. Some other reports of identifying foreign OC clasts in meteoritic breccias have been made by Lipschutz et al. (c) based on chemical, mineralogical, and/or oxygen isotope characteristics. The detection of H chondrite clasts in the Roosevelt Co. (L5) chondrite has been described based on chemical and mineralogical data as well as on oxygen isotope characteristics (Lipschutz et al., 1983). Thus, the discovery of a few H chondrite clasts in L chondrite hosts has rarely been observed, but the roughly 50:50 mixing of H- and H/L- (or L-) group-like components in Elmshorn as mainly indicated by the results on the MS (Figure 16) has, to our knowledge, never been observed.

## The Elmshorn Meteorite and the Fall Statistics in Central Europe

In the last 10 years, 11 meteorite falls have been recovered in an area with less than a 500-km radius. Ten falls were OCs, while Flensburg represents a small extraordinary C1 chondrite of only 24 g (Bischoff et al., 2021). Considering the other meteorite falls of Braunschweig (L6: Bartoschewitz et al., 2017), Hradec Králové (LL5: 2016: The Meteoritical Bulletin), Broek in Waterland (L6, 2017: The Meteoritical Bulletin), Žd'ár nad Sázavou (L3: Spurný, 2016; Spurný et al., 2016), Ejby (H5/6: Haack et al., 2019; Spurný et al., 2017), Stubenberg (LL6: Bischoff et al., 2017; Ebert & Bischoff, 2016b; Spurný et al., 2016), Renchen (L5-6: Bischoff, Barrat, et al., 2019), Kindberg (L6, 2020: The Meteoritical Bulletin), and Antonin (Bischoff, Patzek, et al., 2022; Shrbeny et al., 2022), Elmshorn is the 10th recovered OC fall since 2013. Thus, it is obvious that the number of meteorite falls in Central Europe is remarkable, and it is certainly (at least in part) related to the successful work of the European Fireball Network and the excellent initiatives of the American Meteor Society (AMS:

https://www.amsmeteors.org/) and the International Meteor Organization (IMO: https://fma.imo.net).

## Conclusions

Elmshorn is the 11th recovered meteorite fall in the last 10 years in Central Europe within an area having a radius less than 500 km and the 10th OC (the other fall, Flensburg, is a small extraordinary C1 chondrite).

In total, 21 stones with a mass of 4277 g were recovered within a strewn field of about 1.5 × 2.5 km² (Figure 2). The presence of short-lived cosmogenic radionuclides with half-lives as short as 5.6 days (Table 11) proves that the Elmshorn meteorite was recently exposed to cosmic rays in space.

Considering the densities of the individual stones, two samples were found to have densities of about 3.34 ± 0.01 g cm⁻³, while the third one was found to have a significantly higher density of 3.45 ± 0.01 g cm⁻³: these values are similar to those of L and H chondrites, respectively. The MS is highly variable between different stones, which suggests that the Elmshorn individuals consist of a mixture of H and L chondrite-like components.

Inspection of the broken surfaces and the polished thin sections revealed the brecciated texture of Elmshorn (Figure 4). Randomly obtained olivine compositions indicate the presence of an impact-produced mixture of H and H/L (or L) chondrite lithologies (Figure 8). Fragments include H6 chondrite clasts from the interior of a parent body as well as near-surface materials (clasts of types 3 and 4) mixed together with shock-darkened fragments and various clasts of different types of (impact) melts (e.g., Figures 5 and 9).

Because the samples, which show L chondrite characteristics based on physical properties (density, MS: Table 12 and Table S3), have O isotopic compositions of H chondrites (Figure 10), Elmshorn is classified as an anomalous H chondrite breccia. In line with this, the nucleosynthetic Ti and Cr isotope data places Elmshorn with OCs. Consequently, equilibrated, type 4 lithologies with mean olivine compositions of Fa₂₁⁻₂₃ obviously belong to the H group chondrite components.

The breccia does not contain solar wind-implanted noble gases, indicating that its different components cannot have been part of a parent body regolith. The gas retention ages of about 2.8 Gyr possibly indicate the closure time after the catastrophic collision between H and H/L (or L) chondrite parent bodies, while the CRE age for Elmshorn, which had a preatmospheric radius of 25–40 cm, is ~17–20 Myr.

In such a case of a complex polymict fragmental breccia the use of physical properties alone, like MS and
have also been encountered in some accretionary type 3 breccias and other chondrite breccias: examples are Glanerbrug (Niemeier & Bischoff, 2006; Welten et al., 1992) and Villalbeto de la Pena (Bischoff et al., 2013; Dyl et al., 2012). Villalbeto de la Pena is an L6 breccia with a winonaite-related clast, while Glanerbrug is a very complex fragmental breccia representing a mixture of L and LL chondrite components, with the host rock being of LL chondritic origin (Niemeier & Bischoff, 2006; Welten et al., 1992). Similarly, Gattacceca et al. (2017) describe the brecciated LL6 chondrite Northwest Africa (NWA) 5764 that contains a >16 cm³ L4 clast. However, in general, mixing of clasts from different OC groups is relatively rare: In the LL chondrite St. Mesmin, intensely shocked H-group chondrite fragments were found (Dodd, 1974), and Rubin et al. (1983) described an LL5 clast in the Dimmitt H chondrite regolith breccia. Some other reports of identifying foreign OC clasts in meteoritic breccias have been made by Lipschutz et al. (c) based on chemical, mineralogical, and/or oxygen isotope characteristics. The detection of H chondrite clasts in the Roosevelt Co. (L5) chondrite has been described based on chemical and mineralogical data as well as on oxygen isotope characteristics (Lipschutz et al., 1983). Thus, the discovery of a few H chondrite clasts in L chondrite hosts has rarely been observed, but the roughly 50:50 mixing of H- and H/L- (or L-) group-like components in Elmshorn as mainly indicated by the results on the MS (Figure 16) has, to our knowledge, never been observed.

## The Elmshorn Meteorite and the Fall Statistics in Central Europe

In the last 10 years, 11 meteorite falls have been recovered in an area with less than a 500-km radius. Ten falls were OCs, while Flensburg represents a small extraordinary C1 chondrite of only 24 g (Bischoff et al., 2021). Considering the other meteorite falls of Braunschweig (L6: Bartoschewitz et al., 2017), Hradec Králové (LL5: 2016: The Meteoritical Bulletin), Broek in Waterland (L6, 2017: The Meteoritical Bulletin), Žd'ár nad Sázavou (L3: Spurný, 2016; Spurný et al., 2016), Ejby (H5/6: Haack et al., 2019; Spurný et al., 2017), Stubenberg (LL6: Bischoff et al., 2017; Ebert & Bischoff, 2016b; Spurný et al., 2016), Renchen (L5-6: Bischoff, Barrat, et al., 2019), Kindberg (L6, 2020: The Meteoritical Bulletin), and Antonin (Bischoff, Patzek, et al., 2022; Shrbeny et al., 2022), Elmshorn is the 10th recovered OC fall since 2013. Thus, it is obvious that the number of meteorite falls in Central Europe is remarkable, and it is certainly (at least in part) related to the successful work of the European Fireball Network and the excellent initiatives of the American Meteor Society (AMS:

https://www.amsmeteors.org/) and the International Meteor Organization (IMO: https://fma.imo.net).

## Conclusions

Elmshorn is the 11th recovered meteorite fall in the last 10 years in Central Europe within an area having a radius less than 500 km and the 10th OC (the other fall, Flensburg, is a small extraordinary C1 chondrite).

In total, 21 stones with a mass of 4277 g were recovered within a strewn field of about 1.5 × 2.5 km² (Figure 2). The presence of short-lived cosmogenic radionuclides with half-lives as short as 5.6 days (Table 11) proves that the Elmshorn meteorite was recently exposed to cosmic rays in space.

Considering the densities of the individual stones, two samples were found to have densities of about 3.34 ± 0.01 g cm⁻³, while the third one was found to have a significantly higher density of 3.45 ± 0.01 g cm⁻³: these values are similar to those of L and H chondrites, respectively. The MS is highly variable between different stones, which suggests that the Elmshorn individuals consist of a mixture of H and L chondrite-like components.

Inspection of the broken surfaces and the polished thin sections revealed the brecciated texture of Elmshorn (Figure 4). Randomly obtained olivine compositions indicate the presence of an impact-produced mixture of H and H/L (or L) chondrite lithologies (Figure 8). Fragments include H6 chondrite clasts from the interior of a parent body as well as near-surface materials (clasts of types 3 and 4) mixed together with shock-darkened fragments and various clasts of different types of (impact) melts (e.g., Figures 5 and 9).

Because the samples, which show L chondrite characteristics based on physical properties (density, MS: Table 12 and Table S3), have O isotopic compositions of H chondrites (Figure 10), Elmshorn is classified as an anomalous H chondrite breccia. In line with this, the nucleosynthetic Ti and Cr isotope data places Elmshorn with OCs. Consequently, equilibrated, type 4 lithologies with mean olivine compositions of Fa₂₁⁻₂₃ obviously belong to the H group chondrite components.

The breccia does not contain solar wind-implanted noble gases, indicating that its different components cannot have been part of a parent body regolith. The gas retention ages of about 2.8 Gyr possibly indicate the closure time after the catastrophic collision between H and H/L (or L) chondrite parent bodies, while the CRE age for Elmshorn, which had a preatmospheric radius of 25–40 cm, is ~17–20 Myr.

In such a case of a complex polymict fragmental breccia the use of physical properties alone, like MS and
density, is not sufficient to allow an *unambiguous* assignment between H and L chondrites.

*Acknowledgments*—One of the studied samples was donated by Michael and Vanessa Pöhlmann, and we greatly acknowledge this wonderful support. We further thank Stephanie Adler, Ulla Heitmann, Maik Trogisch, Dennis Kohl, Oliver Sachs, Siegfried Haberer, Carsten Jonas, Oliver Lenzen, Lukasz Smula, Magda Skirzewska, Peter Steier, and Carlos Vivo-Vilches for technical, analytical, and photographic assistance and help as well as Celeste Brennecka for editorial support. We acknowledge the helpful reviews of Alan Rubin and Josep Trigo-Rodriguez and thank the Associate Editor Mike Zolensky. Discussion with Ingo Leya on production rates is highly appreciated. We also acknowledge the help of members of Fa. Digimold Reverse Engineering (96515 Sonneberg, Germany), who digitalized the largest sample and Emil Azar of the company 3D-MT in Augsburg (Germany). This work is partly funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Project-ID 263649064—TRR 170 and TRR 170 Publication No. 214. M.P. is funded by a Sofja Kovalevskaja Award of the Alexander von Humboldt Foundation. This work (R.M.L.A., H.B., M.E., M.R., M.S.) has partially been carried out within the framework of the NCCR PlanetS supported by the Swiss National Science Foundation under grant 51NF40_205606. Open Access funding enabled and organized by Projekt DEAL.

*Data Availability Statement*—Data available on request from the authors.

*Editorial Handling*—Dr. Michael Zolensky

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Bischoff, A., and Keil, K. 1984. Al-Rich Objects in Ordinary Chondrites: Related Origin of Carbonaceous and
density, is not sufficient to allow an *unambiguous* assignment between H and L chondrites.

*Acknowledgments*—One of the studied samples was donated by Michael and Vanessa Pöhlmann, and we greatly acknowledge this wonderful support. We further thank Stephanie Adler, Ulla Heitmann, Maik Trogisch, Dennis Kohl, Oliver Sachs, Siegfried Haberer, Carsten Jonas, Oliver Lenzen, Lukasz Smula, Magda Skirzewska, Peter Steier, and Carlos Vivo-Vilches for technical, analytical, and photographic assistance and help as well as Celeste Brennecka for editorial support. We acknowledge the helpful reviews of Alan Rubin and Josep Trigo-Rodriguez and thank the Associate Editor Mike Zolensky. Discussion with Ingo Leya on production rates is highly appreciated. We also acknowledge the help of members of Fa. Digimold Reverse Engineering (96515 Sonneberg, Germany), who digitalized the largest sample and Emil Azar of the company 3D-MT in Augsburg (Germany). This work is partly funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Project-ID 263649064—TRR 170 and TRR 170 Publication No. 214. M.P. is funded by a Sofja Kovalevskaja Award of the Alexander von Humboldt Foundation. This work (R.M.L.A., H.B., M.E., M.R., M.S.) has partially been carried out within the framework of the NCCR PlanetS supported by the Swiss National Science Foundation under grant 51NF40_205606. Open Access funding enabled and organized by Projekt DEAL.

*Data Availability Statement*—Data available on request from the authors.

*Editorial Handling*—Dr. Michael Zolensky

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Steiger, R. H., and Jäger, E. 1977. Subcommission on Geochronology: Convention on the Use of Decay Constants in Geo- and Cosmochronology. *Earth and Planetary Science Letters* 36: 359–362.

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Terada, K., and Bischoff, A. 2009. Asteroidal Granite-like Magmatism 4.53 Gyr ago. *The Astrophysical Journal* 699: L68–L71.

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Wieler, R. 2002. Cosmic-Ray-Produced Noble Gases in Meteorites. *Reviews in Mineralogy and Geochemistry* 47: 125–170.

Williams, N. H. 2015. The Origin of Titanium Isotopic Anomalies within Solar System Material PhD thesis, The University of Manchester.

Williams, N. H., Fehr, M. A., Parkinson, I. J., Mandl, M. B., and Schönbächler, M. 2021. Titanium Isotope Fractionation in Solar System Materials. *Chemical Geology* 568: 120009.

Wostbrock, J. A., Cano, E. J., and Sharp, Z. D. 2020. An Internally Consistent Triple Oxygen Isotope Calibration of Standards for Silicates, Carbonates and Air Relative to VSMOW2 and SLAP2. *Chemical Geology* 533: 119432.

Zhang, J., Dauphas, N., Davis, A. M., Leya, I., and Fedkin, A. 2012. The Proto-Earth as a Significant Source of Lunar Material. *Nature Geoscience* 5: 251–55.

Zhang, J., Dauphas, N., Davis, A. M., and Pourmand, A. 2011. A New Method for MC-ICPMS Measurement of
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## SUPPORTING INFORMATION

Additional supporting information may be found in the online version of this article.

**Table S1.** The Elmshorn finds (GPS coordinates of the locations referring to the WGS84 datum).

**Table S2.** Bulk compositional data for Elmshorn used here to determine the CRE ages and for Monte-Carlo production rate calculations for $^{22}$Na (Figure S7), $^{26}$Al and $^{41}$Ca (Figure 14); (1) Bulk chemistry measured with ICP-AES and ICP-SFMS (Table 5 in the manuscript); (2) average H chondrite composition taken from Alexander, 2019; (3) average H chondrite composition from Lodders and Fegley (1998); (4) calculated for the sum of all concentrations to reach 100 wt%.

**Table S3.** Magnetic susceptibility (in $10^{-9} \text{ m}^3 \text{ kg}^{-1}$) of the majority of Elmshorn fragments (see Figure 16).

**Figure S1.** A CT slice of the specimen E02 (Table S1) of 233.5 g showing (a) sparse chondrules (dark gray), metal (white), and sulfide grains (light gray) as well as an elongated metal-sulfide intergrowth on the left side (arrow). (b) A large (~5.5 mm) nodule (arrow) consisting of sulfide and putatively chromite in the center of the sample. (c) A fragment with an intergrowth of silicates (dark gray, left edge), and an area with a high abundance of metal and sulfide (arrow). (d) Fragment with a significantly higher abundance of metal and sulfide in the top left.

Zolensky, M. E., and Ivanov, A. 2003. The Kaidun Microbreccia Meteorite: A Harvest from the Inner and Outer Asteroid Belt. *Chemie der Erde—Geochemistry* 63: 185-246.

Zolensky, M. E., Ivanov, A. V., Yang, S. V., Mittlefehldt, D. W., and Ohsumi, K. 1996. The Kaidun Meteorite: Mineralogy of an Unusual CM1 Lithology. *Meteoritics & Planetary Science* 31: 484-493.

**Figure S2.** A CT slice of a piece from the shattered E03 specimen of 51.62 g showing (a) millimeter-sized grains of metal and sulfide. (b) An area with a higher abundance of metal and sulfide at the top is indicated by the arrow. An elongated metal-sulfide association is noticeable. (c) Zoom-in from (b) illustrating the elongated metal-sulfide intergrowth. A ~3 mm-sized porphyritic chondrule is also visible in the neighborhood (metal-free, dark area). (d) Potential shock-darkened fragment with Schlieren-like metal and sulfide.

**Figure S3.** Several CT scans of specimen E21 with a weight of 1.09 g.

**Figure S4.** (a) Fragment M from E03 is an unusual melt rock clast with skeletal (equilibrated) olivine ($Fa_{26}$) embedded in a fine-grained groundmass (plane polarized light). (b) Fragment M in BSE image. (c) The porphyritic objects in a fine-grained groundmass consist of an intergrowth of two different phases (d), from which the darker one appears to be Ca pyroxene (BSE images).

**Figure S5.** The L3.9/4 chondrite fragments from E03 are difficult to identify and are indicated by the slightly lighter olivine grains compared with those of the surroundings.

**Figure S6.** Microscopic images from components in stone E07.

**Figure S7.** Specific $^{22}$Na activity measured in Elmshorn (red line with associated 1-sigma uncertainties) compared to radius- and depth-dependent (saturation) production rate for $^{22}$Na for L chondrites (Leya et al., 2021).
Titanium Isotopic Composition: Identification of Correlated Isotope Anomalies in Meteorites. *Journal of Analytical Atomic Spectrometry* 26: 2197-2205.

Zolensky, M., Herrin, J., Mikouchi, T., Ohsumi, K., Friedrich, J., Steele, A., Rumble, D., et al. 2010. Mineralogy and Petrography of the Almahata Sitta Ureilite. *Meteoritics & Planetary Science* 45: 1618-37.

## SUPPORTING INFORMATION

Additional supporting information may be found in the online version of this article.

**Table S1.** The Elmshorn finds (GPS coordinates of the locations referring to the WGS84 datum).

**Table S2.** Bulk compositional data for Elmshorn used here to determine the CRE ages and for Monte-Carlo production rate calculations for ²²Na (Figure S7), ²⁶Al and ⁴¹Ca (Figure 14); (1) Bulk chemistry measured with ICP-AES and ICP-SFMS (Table 5 in the manuscript); (2) average H chondrite composition taken from Alexander, 2019; (3) average H chondrite composition from Lodders and Fegley (1998); (4) calculated for the sum of all concentrations to reach 100 wt%.

**Table S3.** Magnetic susceptibility (in 10⁻⁹ m³ kg⁻¹) of the majority of Elmshorn fragments (see Figure 16).

**Figure S1.** A CT slice of the specimen E02 (Table S1) of 233.5 g showing (a) sparse chondrules (dark gray), metal (white), and sulfide grains (light gray) as well as an elongated metal-sulfide intergrowth on the left side (arrow). (b) A large (~5.5 mm) nodule (arrow) consisting of sulfide and putatively chromite in the center of the sample. (c) A fragment with an intergrowth of silicates (dark gray, left edge), and an area with a high abundance of metal and sulfide (arrow). (d) Fragment with a significantly higher abundance of metal and sulfide in the top left.

Zolensky, M. E., and Ivanov, A. 2003. The Kaidun Microbreccia Meteorite: A Harvest from the Inner and Outer Asteroid Belt. *Chemie der Erde—Geochemistry* 63: 185-246.

Zolensky, M. E., Ivanov, A. V., Yang, S. V., Mittlefehldt, D. W., and Ohsumi, K. 1996. The Kaidun Meteorite: Mineralogy of an Unusual CM1 Lithology. *Meteoritics & Planetary Science* 31: 484-493.

**Figure S2.** A CT slice of a piece from the shattered E03 specimen of 51.62 g showing (a) millimeter-sized grains of metal and sulfide. (b) An area with a higher abundance of metal and sulfide at the top is indicated by the arrow. An elongated metal-sulfide association is noticeable. (c) Zoom-in from (b) illustrating the elongated metal-sulfide intergrowth. A ~3 mm-sized porphyritic chondrule is also visible in the neighborhood (metal-free, dark area). (d) Potential shock-darkened fragment with Schlieren-like metal and sulfide.

**Figure S3.** Several CT scans of specimen E21 with a weight of 1.09 g.

**Figure S4.** (a) Fragment M from E03 is an unusual melt rock clast with skeletal (equilibrated) olivine (Fa₂₆) embedded in a fine-grained groundmass (plane polarized light). (b) Fragment M in BSE image. (c) The porphyritic objects in a fine-grained groundmass consist of an intergrowth of two different phases (d), from which the darker one appears to be Ca pyroxene (BSE images).

**Figure S5.** The L3.9/4 chondrite fragments from E03 are difficult to identify and are indicated by the slightly lighter olivine grains compared with those of the surroundings.

**Figure S6.** Microscopic images from components in stone E07.

**Figure S7.** Specific ²²Na activity measured in Elmshorn (red line with associated 1-sigma uncertainties) compared to radius- and depth-dependent (saturation) production rate for ²²Na for L chondrites (Leya et al., 2021).