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ASSESSING THE HETEROGENEITY OF THE TISSINT SHERGOTTITE USING RB-SR, SM-ND AND LU-HF SYSTEMATICS

------

A Thesis Presented to the Faculty of the

Department of and Atmospheric Sciences

University of Houston

------

In Partial Fulfillment

of the Requirements for the Degree

Master of Science

------

By

Stephanie Elaine Suarez

August 2019

ASSESSING THE HETEROGENEITY OF THE TISSINT SHERGOTTITE STREWN FIELD USING RB-SR, SM-ND AND LU-HF ISOTOPE SYSTEMATICS

______Stephanie Elaine Suarez

APPROVED:

______Dr. Thomas Lapen, Advisor

______Dr. Alexander Robinson

______Dr. Brian Beard

______Dr. Dan E. Wells, Dean, College of Natural Sciences and Mathematics

ii ACKNOWLEDGEMENTS

I would first like to acknowledge my advisor Dr. Tom Lapen for the opportunity to work on this amazing project. Thank you for your patience and guidance throughout this entire process.

Next, I would like to thank my committee members Dr. Brian Beard for his assistance operating the TIMS and Dr. Alexander Robinson for his input and assistance.

Thank you to Dr. Minako Righter, for her assistance operating the MC-ICP-MS, training me in the clean lab, and instilling the importance of having work-life balance. Our collaborator Anthony ‘Tony’ Irving for his wisdom on geology. I would also like to thank our other collaborators for insightful conversations.

My mother Cecelia 'Cece' Suarez, my reason for striving for a career that will one day give us a better life. Our numerous dogs that we have rescued and cared for during the course of this thesis. Your tiny paws will always have a special place in my heart.

Thank you to the supportive faculty, staff and students I have come across at the Earth and Atmospheric Science department. I treasure the daily conversations we have had on our best and worst days. Thank you to my former undergraduate research advisor Dr.

Elizabeth Catlos for giving me the opportunity to become a researcher as well as our collaborator Dr. Michael Brookfield for his continued guidance.

And lastly, anyone who I may have overlooked that has mentored me over the years or inspired me to keep going.

iii ASSESSING THE HETEROGENEITY OF THE TISSINT SHERGOTTITE STREWN FIELD USING RB-SR, SM-ND AND LU-HF ISOTOPE SYSTEMATICS

------

An Abstract of a Thesis

Presented to the Faculty of the

Department of Earth and Atmospheric Sciences

University of Houston

------

In Partial Fulfillment

of the Requirements for the Degree

Master of Science

------

By

Stephanie Elaine Suarez

August 2019

iv Abstract

Tissint, the 5th witnessed Martian fall, occurred on July 18, 2011 east of

Tata, Morocco. While most studies of Tissint classify it as a shergottite relatively depleted in lithophile incompatible trace elements (e.g., light REE), crystallization age determinations have been variable. Currently, there is a discrepancy in crystallization age determination amongst three separate labs (UH: University of Houston; LLNL: Lawrence

Livermore National Labs; and NASA-JSC: NASA Johnson Space Center) using combinations of Lu-Hf, Sm-Nd, and Rb-Sr analyses. Each lab tested one single fragment from the entire Tissint meteorite strewn field, which included samples (UWB1),

(ASU#1744), (UNM#645). Sm-Nd analyses were performed at all three labs and produced two different dates. Analyses from two of the three labs, UH and LLNL, are in agreement and give a combined Sm-Nd age of 593±25 Ma for samples UWB1 and

ASU#1744. Analysis at NASA-JSC provided a date of 472±36 Ma (sample UNM#645).

This is approximately a 120 Ma difference in crystallization ages for separate samples analyzed from the strewn field.

To confirm whether materials of different isotopic compositions and ages were co-mingled resulting in a heterogeneous strewn field, eight separately-collected fragments from the Tissint strewn field, including the sample analyzed at JSC

(UNM#645) were examined using Rb-Sr, Sm-Nd and Lu-Hf isotopic systems. Mineral and leached bulk rocks analyzed at UH and LLNL define isochrons of 571±84 Ma,

559±39 Ma and 590±49 Ma, respectively. In all three isotopic systems, the analyses performed at UH and LLNL plot along the same isochron with slopes consistent with a

v ~590 Ma igneous crystallization age, including UNM#645 dated at 495±35 Ma by

NASA-JSC. While the Lu-Hf isotopic system indicates no evidence of contamination or element mobility, the Rb-Sr and Sm-Nd isotopic systems show evidence for element mobility and potential mixing with an isotopic component not in equilibrium with the igneous phases. Despite these issues, there is no evidence for multiple igneous sources.

Fragments identified so far are cogenetic and the Tissint strewn field appears to be homogeneous.

vi Table of Contents

Introduction ...... 1

Sample Descriptions ...... 10

Methods ...... 12

3.1 Sample Preparation ...... 12

3.2 Sample Digestion ...... 12

3.3 Ion-exchange chromatography ...... 13 3.3.1 Rb-Sr ...... 13 3.3.2 Lu-Hf and Sm-Nd ...... 14

3.4 Mass Spectrometry ...... 15 3.4.1 Multi-collector Inductively Coupled Mass Spectrometry (MC-ICPMS) ...... 15 3.4.1.1 Lu ...... 15 3.4.1.2 Hf ...... 16 3.4.1.3 Sm ...... 17 3.4.1.4 Nd ...... 17 3.4.2 Thermal Ionization Mass Spectrometry (TIMS) ...... 18

Results ...... 19

4.1 Lu-Hf ...... 19

4.2 Rb-Sr ...... 22

4.3 Sm-Nd ...... 24

Discussion ...... 26

5.1 Crystallization Age Comparison ...... 26

5.2 Isotope systematics of leachates and residues ...... 28

Conclusions ...... 32

References ...... 34

vii List of Figures, Tables and Equations

Figures 1. Mixing curves for calculated source compositions for Martian 4 2. Hand specimens of Tissint collected in Morroco in 2011 5 3. Proposed mechanism for a heterogenous strewn field 9 4. Hand specimens of Tissint used in this study 11 5. Lu-Hf isochron 21 6. Rb-Sr isochron 23 7. Sm-Nd isochron 25 8. All internal isochron ages 27 9. Rb-Sr Leachate of Tissint and other 1.1Ma ejected Martian meteorites 31

Tables 1. Compilation of Tissint ages from LLNL, JSC, and UH 7 2. Lu-Hf Data for Tissint 20 3. Rb-Sr Data for Tissint 22 4. Sm-Nd Data for Tissint 24 5. Ages determined for Tissint from previously published data and this study 27

Equations 1. Isochron Age 19

viii

Chapter 1

Introduction

Martian meteorites are rocks that were once a part of and have since landed on Earth. that impact Mars’ surface have the potential to eject materials into space; some of which crosses Earth's orbit and fall as meteorites. (Melosh, 1984; Head and Melosh, 2000). Analysis of these Martian meteorites, our only available physical material from Mars, can provide valuable information about the timing and nature of the planet’s ongoing magmatism. (Nyquist et al., 2001).

Martian meteorites are currently categorized into groups by and include Shergottites, , Chassignites, , and polymict .

Shergottites, the most abundant class of Martian meteorites, are mafic to ultramafic igneous rocks that have a wide array of crystallization ages, mineralogy, textures, trace element and radiogenic isotope compositions. Isotopic and petrologic analyses of shergottites can provide information on Martian source reservoir interactions and timing of large-scale planetary differentiation.

We have little to no spatial context of where these meteorites originated, there have been attempts to identify particular source regions by utilizing remote sensing data and the Crater Size Frequency Distribution (CSFD). We can pair chronology of meteorites with these data to hypothesize the spatial relationships between Martian meteorites of differing geochemical imprints and ultimately identify potential source craters. Partial melting in Mars’ mantle has produced large volcanic centers that characterize a large portion of Mars’ surface (Robbins et al., 2011). These major volcanic

1 plains are Elysium, Hellas Region, Syrtis Major, , and on average consist of thick

40-60 m (Mouginis-Mark and Yoshioka 1998) piles of lava flows and intrusions. There are multiple generations of craters visible on the surface of Mars, some of which are located in these vast, and relatively young volcanic fields that contain inter-fingering lava flows.

It has been speculated the Tharsis region contains potential source craters of shergottites in comparison to nahklites and chassignites that are hypothesized to be derived from the Elysium region (Cohen et al., 2017). Relative ages determined by crater counting of the calderas in some of the prominent volcanoes in the Tharsus region indicates that volcanism in the area ceased approximately 150 Ma (Robins et al., 2011).

This is complemented by absolute ages of shergottites through radiometric dating that show a range 165-2403 Ma (Jones, 1986; Nyquist et al., 2001, 2009; Borg and Drake,

2005; Bouvier 2005, 2008; Shih et al., 2009; Lapen et al., 2017).

Ejection ages can also assist Martian meteorites. For example, samples with the same ejection ages and similar trace element and isotopic compositions are likely to be ejected from the same crater. A meteorite’s crystallization age determines when a sample was formed on Mars from magma. The ejection age, the summation of a meteorite’s cosmic ray exposure age and terrestrial resident age, determines when the meteorite was ejected from Mars’ surface (Nyquist et al., 2001). By examining both the ejection and crystallization ages we can then propose potential ejection sites (Nyquist et al., 2001;

Christen et al., 2005; Herzog and Caffee, 2014; Wieler et al., 2016; Lapen et al., 2017).

Because Martian meteorites are derived from rare impact events, Martian meteorites provide a bias sampling of the . Major element analyses of

2 Shergotties plot as subalkaline while data collected by MSL ChemCam and MER APXS onboard Mars exploration rovers reveal that the surface of Mars contains alkaline-rich basaltic rocks as well as sedimentary rocks. An impact regolith NWA 7034, and its paired meteorites are comparable to Martian crust. (Edwards et al. 2017). Despite not having representative samples from the Martian crust, shergottites are still highly valuable in determining igneous processes and sources.

3 A.

B.

B.

Fig. 1. Tissint is categorized as a depleted shergottite for all three isotopic systems. Analyses of shergottites show interactions between Enriched, and two depleted reservoirs. 1a. 3 component mixing model for shergottite Lu-Hf and Sm-Nd source compositions calculated using equations of Nyquist et al. (2001) and mantle end-member compositions of Debaille et al. (2008). 1b. Inset from Fig. 1a shows a best-fit mixing hyperbola for source Rb/Sr and Sm/Nd compositions of shergottites. (Lapen et al. 2017).

4 Shergottites have been classified based on their textures into subgroups; basaltic, -phyric, gabbroic, poikilitic (Filiberto 2014, Bridges and Warren 2006).

Geochemically, shergottites are sorted into enriched, intermediate, and depleted groups based on their rare earth element (REE) compositions and initial radiogenic isotopic compositions (Borg and Draper, 2003). Shergottites are interpreted to be sourced from mixtures of three mantle end member compositions; one enriched and two depleted in incompatible trace elements (Fig.1) (Borg et al., 2003; and Draper, 2003; Debaille et al.,

2008; Lapen et al., 2010; 2017). Absolute ages of shergottites through radiometric dating show a range of 165-2403 Ma (Jones, 1986; Nyquist et al., 2001 and references therein,

2009; Borg and Drake, 2005; Shih et al., 2009; Lapen et al., 2017).

A. B.

Fig. 2. Hand and thin section specimen of Tissint. 2a.1.1kg specimen with black fusion crust and exposed interior. Melt is present in the form of glass veins. Scale is in centimeters (Chennaoui Aoudjehane et al., 2012). 2b. BSE image of a thin section of Tissint with zoned olivine macrocryst. Scale is in millimeters (Balta et al. 2013).

5 A particular olivine-phyric depleted shergottite, Tissint, was an observed fall that occurred on July 18, 2011 near Oued Drâa valley, east of Tata, Morocco. Tissint is the

5th witnessed Martian ; others include , Shergotty, Nakhla, and

Zagami (Brenecka 2014). Fig. 2a shows a hand sample of Tissint with a fusion crust that formed upon entry into Earth’s atmosphere, as well as the melt veins that formed during ejection from Mars’ surface. A backscattered electron (BSE) image of a Tissint specimen

(Fig. 2b) shows a porphyritic texture with olivine macrocrysts that display chemical zoning, and other fine-grained minerals such as olivine, and maskelynite.

Tissint is classified as an olivine-phyric shergottite composed of olivine, plagioclase

(maskelynite), (pigeonite and augite), oxides (chromite, ilmenite, magnetite, ulvöspinel), sulfide (pyrrhotite), and phosphate (merrillite) (Chennaoui Aoudjehane et al.,

2012; Irving et al. 2012). Tissint has a Mars ejection age of 1.10 ± 0.15 Ma (Nishiizumi et al., 2011; Wieler et al., 2016) and shares this ejection age with at least 11 other depleted shergottites (Lapen et al., 2017).

Previous studies that aimed to determine the igneous crystallization age of Tissint

(Brennecka et al. 2014, Grosshans et al. 2013, Shih et al. 2014) indicate conflicting results. There is a discrepancy in the crystallization age amongst three separate institutions University of Houston (UH), Lawrence Livermore National Laboratory

(LLNL) and NASA-JSC using combinations of Lu-Hf, Sm-Nd and Rb-Sr analyses (Table

1). Sm-Nd isotope analyses were performed by all three institutions and produced two different dates. Analytical results from UH (Grosshans, 2013) and LLNL (Brennecka et al., 2014) are in agreement and give a Sm-Nd date of 593 ± 25 Ma (all uncertainties are reported at the 2σ level) when all data are regressed together (Irving and Lapen 2016).

6 Sm-Nd isotopic analysis of Tissint at NASA-JSC provided a date of 472 ± 36 Ma (Shih et al. 2014). This is about a 120 Ma difference in age between three separate fragments of

Tissint from the strewn field. Each study tested one single fragment from the entire

Tissint meteorite strewn field, which included samples UWB1, ASU#1744, UNM#645.

Analyses yield initial 143Nd/144Nd ratios converted to epsilon values (ε143Nd =

([((143Nd/144Nd sample) / (143Nd/144NdCHUR)) – 1] × 10,000) relative to a chondritic uniform reservoir at the measured age of ε143Nd of +42.1 +/- 0.4 for UH and LLNL, while the value determined at NASA-JSC is ε143Nd +44.4 +/- 1.0.

UH1 LLNL2 NASA-JSC3 Sm-Nd 616 ± 67 Ma 587 ± 28 Ma 472 ± 36 Ma Rb-Sr - 560 ± 30 Ma 495 ± 35 Ma Lu-Hf 583 ± 86 Ma - - Aliquot UWB1 ASU #1744 UNM #645

Table 1. Summary of Sm-Nd, Rb-Sr and Lu-Hf ages from 1. (Grosshans et al. 2013) 2. (Brennecka et al. 2014). 3. (Shih et al. 2014)

Analyses at all three laboratories seem robust given that they have intra- laboratory concordance and the three Tissint fragments used were verified to be from the strewn field. Therefore, analytical errors and initial sampling can be ruled out as explanations of the age and geochemical distinctions between the groups of data.

The hypothesis to explain the different isotopic results is that the Tissint meteorite strewn field is heterogeneous and composed of launch-paired volcanic strata that fell to

Earth at the same time. Tissint, along with at least 11 other depleted olivine-phyric shergottites, have an ejection age of 1.1 Ma and exhibit a progression of crystallization ages from 347 Ma to 2403 Ma. These 12 depleted shergottites are believed to be from the same impact crater on Mars surface (Lapen et al. 2017). 7 This suite of meteorites was a large succession of volcanic strata from the same provenance that was ejected from Mars’ surface by a large impact. The current age discrepancy for Tissint could, in theory, represent two of these lava flows of differing ages that became comingled during the ejection. These proposed fragments of different flows or sills would have been launch-paired during the initial ejection and travel-paired as they fell during one observed fall (Fig 3.).

This hypothesis can be applied to a terrestrial analog, the Columbia River

Group (CRBG). The CRBG is composed of continental flood that range in age 6-

16 Ma. If a modern-day impact were to occur in Washington, it would create a chaotic collision and possibly mix some of the layered basalt flows. Two or more of these layers can become travel-paired. We are proposing this hypothetical situation could have occurred on Mars surface 1.1 Ma. In summary, the isotopic data suggests that the Tissint strewn field could be heterogeneous.

The focus of this project is to investigate potential heterogeneity of the Tissint strewn field. In previous studies a single fragment was analyzed for isotopic compositions. This study analyzed several fragments of Tissint to provide a more comprehensive and representative sampling of the strewn field.

8

Fig. 3. Cartoon (not to scale) of purposed launching mechanism of launch and travel paired depleted shergottites resulting in a heterogenous strewn field.

9 Chapter 2

Sample Descriptions

Tissint was recovered at its landing site near Oued Drâa valley, east of Tata,

Morocco (Chennaoui Aoudjehane et al., 2012). Over 20kg of olivine-phyric shergottite fragments, many of which are partially fusion crusted, have been recovered from the strewn field (Chennaoui Aoudjehane et al., 2012). These individual fragments are ideal for petrologic and isotopic analyses as they were quickly retrieved after landing, reducing the chances of terrestrial and other potential terrestrial contamination. Tissint is an olivine-phyric porphyritic shergottite that contains subhedral to euhedral olivine macrocrysts (up to 2.0 mm), with a fine-grained groundmass consisting of olivine, pyroxene (pigeonite and augite), maskelynite, and minor phases such as oxides (Ti- chromite, ulvöspinel, ilmenite), sulfides (pyrrhotite), and phosphate (merrillite). Both olivine and pyroxene show Mg rich cores that progress to Fe rich rims. Shock features formed upon impact ejection from the Martian surface are present in the form of amorphous phases such as maskelyinte and black-green-brown glass melt pockets and veins. Based on petrographic analysis by Balta et al. (2013), Baziotis et al. (2013), and

Chennaoui Aoudjehane et al. (2012), modal abundances in Tissint are 16-30% olivine, pyroxene 50-60%, plagioclase 14-22%, 1-5% oxides.

Eight individual specimens from the Tissint strewn field were analyzed in this study and consisted of 7 solid fragments (TS1-TS6, ET), and a fine-grained powder aliquot from another individual fragment (UNM#645) (Fig. 4).

10 a. b. Fig. 4. Hand specimen of Tissint used in analysis. a.TS1 b.TS2 c.TS3 d.TS4 e.TS5 f.TS6 g,UNM #645 h. Tissint ET .647 g 1 cm .683 g 1 cm c. d.

.853 g 1 cm .563 g 1 cm e. f.

.563 g 1 cm 2.18 g 1 cm

g.

1.00 g 1 cm h.h.

.063 g 1 cm

11 Chapter 3

Methods

3.1 Sample Preparation

In total, 8 pieces of Tissint were processed for isotopic analyses, 7 solid fragments of Tissint (TS1-TS6, Tissint ET) and a fine-grained powder (UNM#645). 180 milligrams from each of the 7 solid fragments were coarsely crushed using an agate mortar and pestle and glass and fusion crust fragments were removed using tweezers under a binocular microscope. This material was then crushed into a finer powder. The overall crushing occurred in two sessions, during the first session (session 1) 80 milligrams were crushed for Rb-Sr analyses and in the second session (session 2) 100 milligrams were crushed for Lu-Hf and Sm-Nd analyses. Samples in the first crushing session included

TS1-TS6, UNM #645 while session two included TS1-TS6, UNM#645, and Tissint ET.

The 80 mg powder was leached with 2ml of 1.0 N HCl solution at room temperature for

10 minutes. The liquid from this solution was then pipetted into a separate beaker; care was taken not to pipette any solid residue. The residues were rinsed with 1ml of ultrapure milliQ water to rinse off remnant acid and were combined with the leachate. The 100 mg samples comprising the second sample crushing session were not leached.

3.2 Sample Digestion

Residues in session 1, and whole rock aliquots in session 2 were digested using a

Milestone UltraWAVE high-pressure microwave digestion instrument at the University of Houston (UH). The digestion process converts the solid sample into a solution in preparation for column chemistry. Each sample was weighed and put in a Savillex®

12 beaker. In preparation, the samples were pre-digested in 0.5 ml twice distilled (2x) HNO3 and 2 ml 2x 29M HF for 24 hours at 100°C on a hotplate. The samples were dried on a hotplate, brought back up in 3 ml 2x ~15M HNO, then transferred to the PTFE Teflon microwave inserts. Samples were loaded along with 1 ml 2x ~29M HF, and 1ml 1x ~12M

HCl. Samples were digested for 2 hours and 30 minutes at 250 ° C. After microwave digestion, the samples were transferred back into their original Savillex® beakers and dried on a hotplate. The samples were further dissolved in 4 ml 2x ~8M HNO3 and dried followed by dissolutions and drying in 3 ml once distilled (1x) ~6M HCl until the entire solution was clear of any fluoride salts after centrifuging. One percent of the solution was analyzed for Sm, Nd, Lu, and Hf concentrations with an Agilent 8800 QQQ-ICPMS at UH in order to determine the ideal amount of 87Rb-87Sr, 149Sm-150Nd, and 176Lu-178Hf mixed spikes to add.

3.3 Ion-exchange chromatography

3.3.1 Rb-Sr

Samples analyzed for Rb-Sr underwent four sets of column chemistry to isolate Rb and Sr as outlined in Beard et al. (2013). The first set of columns uses

DOWEX 1x8-200 mesh resin and 6M HCl to remove Fe from the samples. The second set of columns uses AG 50Wx8 200-400 mesh resin and HCl to produce a Rb-rich fraction, a Sr-rich fraction, and a REE fraction. The Rb-rich and Sr-rich cuts were further purified: Rb cuts were processed using BioRad AG MP-50 resin using 2.2 HCl and the

Sr-rich cuts were purified with Eichrom Sr-spec resin with 4M and 2% HNO3. After the purified samples were dried, 3 microliters of 1M H3PO4 was added to each Sr cut and the

13 Sr was dried down in preparation for isotopic analysis by thermal ionization mass spectrometry (TIMS). Ten microliters of 0.01M H3PO4 was added to each Rb cut. The

Rb was dried down in preparation for Rb isotope analysis by (TIMS). In addition to the samples, a total procedural blank and USGS rock standard BCR-2 were prepared and processed in parallel with the samples.

3.3.2 Lu-Hf and Sm-Nd

The digested samples were run through five sets of ion-exchange columns to isolate

Lu, Hf, Sm, Nd following procedures outlined in Lapen et al. (2004; 2010). The first set of columns uses DOWEX 1x8-200 mesh resin and 6M HCl to remove Fe from the samples. The second set of columns uses cation Eichrom Ln-spec resin. REE and major elements are collected after the samples are loaded on the resin by passing 6M HCl.

Hafnium was separated from other high field strength elements (Ti, Zr, Ta, and W) using combinations of H2O2, citric acid, HCl, and dilute HF (Munker et al. 2001). The REE and major element cuts are loaded into the third set of columns. These columns use Eichrom

RE-spec resin and 4.5M HCl to separate the REEs from other cations in the solution. The third set of columns used pre filter resin to remove organics by passing 2% HNO3

+ through samples. The final set of columns use a cation resin converted to NH4 form along with α-hydroxy-isobutaic (HIBA) acid. Lu, Sm, and Nd are collected from this set of columns using 0.15M α-HIBA and 0.21M α-HIBA acid. Lu cuts underwent an additional set of pre filter resin columns after HIBA columns. After the samples are dried,

50 μl 2x 14M HNO3 is added to each sample and dried. This step prepares the sample for isotope analysis by converting the acid in the sample to HNO3.

14 3.4 Mass Spectrometry

3.4.1 Multi-collector Inductively Coupled Mass Spectrometry (MC- ICPMS)

The Nu-Plasma II multi collector inductively coupled plasma mass spectrometer

(MC-ICP-MS) at the University of Houston was used for analyzing Hf, Lu, Hf, and Sm fractions from each sample. Prior to analyses samples underwent a concentration check to determine the best method for running all samples and standards at comparable concentrations. The procedure starts by bringing Lu, Sm, and Nd samples up in 800 ml

2% HNO3 and Hf samples up in 1 ml in 2% HNO3-1% HF. Samples are visibly inspected to ensure that they were dissolved completely. 10 µL is pipetted into an auto sampler vial containing 490 µL of 2% HNO3 (or 2% HNO3-1% HF when working with Hf) and were analyzed on the MC-ICP-MS. Based on the pre-concentration test, each sample was diluted to a desired concentration.

3.4.1.1 Lu

Luetitum samples and standards were introduced into the mass spectrometer via a micro-concentric desolvating nebulizer (Cetac Aridus II) in a 2% HNO3 matrix at 5 and

10 ppb. Prior to introduction of sample, 60 seconds on-peak zero measurements were made using the same blank acid that was used during sample preparation. The masses monitored during analysis were 171, 172, 173, 174, 175, 176, and 177 (cups L5, L4, L3,

L2, L1, Ax, and H1 respectively). Isobaric interference of 176Hf on 176Lu was monitored with 177Hf and a 176Hf/177Hf ratio of 0.283. Hf isobar corrections on Lu are negligible.

Because it is difficult to separate Yb from Lu and isobaric corrections of 176Yb on 176Lu

15 are large, we employed the isobaric interference and mass bias corrections for 175Lu/176Lu ratios of Vervoort et al. (2004).

3.4.1.2 Hf

Hafnium isotope analysis is similar to the Lu analysis, except that Hf samples were brought up using a 2% HNO3-1% HF solution before being introduced into the

MC-ICPMS. The masses monitored during analysis were 173, 174, 175, 176, 177, 178,

179, 180, 181, and 182 (cups L3, L2, L1, Ax, H1, H2, H3, H4, H5, and H6 respectively.

Prior to introduction of sample, 60 seconds on-peak zero measurements were made using the same blank acid that was used during sample preparation. During analysis, the masses

173, 175, 181, and 182 were monitored to remove the 176Lu and 176Yb isobaric interferences on 176Hf, 180W + 180Ta interference on 180Hf, as well as 181Ta interference on

181Hf. The isobaric interferences were corrected using the following isotopic compositions: 176Lu/175Lu = 0.02656, 180Ta/181Ta = 0.000123, 176Yb/172Yb = 0.5845, and

180W/182W = 0.004521. The instrumental mass fractionation on the isobaric interference correcting isotope ratios were compensated for by normalizing to 179Hf/177Hf = 0.7325 using an exponential law prior to adjustment of 176Hf and 180Hf ion intensities.

Instrumental mass bias and spike subtraction methods followed those in Lapen et al.

(2004). The 176Hf/177Hf operating values for the UW JMC-475 standard used during the analyses were; 20 ppb = 0.282161 ± 0.000012 (2σ, n = 8). The 176Hf/177Hf operating values for the in-house standards used during analyses were; UH AMES 20 ppb =

0.282359 ± 0.000018 (2σ, n = 9). The 176Hf/177Hf operating values for USGS standard

BHVO-2 were 0.283085 ± 0.0041% (n = 2).

16 3.4.1.3 Sm

Samarium isotope analysis method is similar to the Lu and Nd methods. Sm samples were ran at 40 ppb. The masses monitored during analysis were 144, 145, 146,

147, 148, 149, 150, 151, 152, 153, 15 154, 155, and 156 (cups L5, L4, L3, L2, L1, Ax,

H1, H2, H3, H4, H5, H6, and H7 respectively). Masses 146 and 155 were monitored for

146Nd and 155Gd in order to calculate the isobar intensities of 144Nd, 148Nd, 150Nd, and

154Gd. These intensities were then used to remove the 144Nd isobaric interference on

144Sm, the 148Nd isobaric interference on 148Sm, the 150Nd isobaric interference on 150Sm, the 152Gd isobaric interference on 152Sm, and the 154Gd interference on 154Sm. The isobaric interferences were corrected using the following isotopic compositions;

152Gd/155Gd = 0.013686, 154Gd/155Gd = 0.147335, 144Nd/146Nd = 1.38523, 148Nd/146Nd =

0.334642, 150Nd/146Nd = 0.327534, and 147Sm/152Sm = 0.560825.

3.4.1.4 Nd

Neodymium isotope analysis method is similar to the Lu and Sm methods. The masses monitored during analysis were 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, and 150 (cups L5, L4, L3, L2, L1, Ax, H1, H2, H3, H4, and H5 respectively). The masses

140 and 147 were monitored for 140Ce and 147Sm in order to calculate the isobar intensities of 142Ce, 144Sm, 148Sm, and 150Sm. These intensities were then used to remove the 142Ce isobaric interference on 142Nd, the 144Sm isobaric interference on 144Nd, the

148Sm isobaric interference on 148Nd, and the 150Sm interference on 150Nd. The isobaric interferences were corrected using the following isotopic compositions; 142Ce/140Ce =

0.7219, 144Sm/147Sm = 0.205023, 148Sm/147Sm = 0.749697, and 150Sm/147Sm = 0.4921.

17 Instrumental mass bias and spike subtraction methods followed those in Lapen et al.

(2004). The 143Nd/144Nd operating values for the JNdi (Nu) standard used during the analyses were; 40 ppb = 0.512120 ± 0.000012 (2σ, n = 7). The 143Nd/144Nd operating values for the in-house standard, UH AMES used during the analyses were; 40 ppb =

0.511990 ± 0.000017 (2σ, n = 6). The 143Nd/144Nd operating values for USGS standard

BHVO-2 were 0.512981 ± 0.0024% (n = 4).

3.4.2 Thermal Ionization Mass Spectrometry (TIMS)

87Rb/86Sr and 87Sr/86Sr isotope ratios of the samples were measured using a

Micromass Sector 54 thermal ionization mass spectrometer at the University of

Wisconsin-Madison following methods of Beard et al. (2013). For Sr analysis of residues, outgassed Ta filaments were loaded with H3PO4 and for Sr leachates, Re filaments were loaded with a TaF activator and H3PO4. Rubidium was loaded onto Ta filaments with H3PO4.

Strontium isotope analyses were done using a multi-collector three-jump dynamic analysis with internal exponential normalization to an 86Sr/88Sr value of 0.1194. The reported uncertainties for the 86Sr/88Sr ratio are the 2-SE determined by in-run statistics.

Repeat analysis of 10ng Sr loads of NIST SRM-987 Sr isotope standard ran during the same period as the samples were analyzed yielded an average 87Sr/86Sr value of 0.710276

± 0.000012 (2 SD, n = 7). Analyses of Rb were done using a multi-Faraday collector static routine. The weighted average 87Rb/85Rb ratio of 5 analyses of 10 ng of NIST

SRM-984 was 0.38535 ± 0.00091 (2 SD; n=5).

18 Chapter 4

Results

This study’s data was compiled with data from Brennecka et al. (2014) and

Grosshans et al. (2013) to create isochrons. The crystallization ages for the sample were calculated from the internal isochron lines formed by the compositions of the mineral separates. The equation to calculate the crystallization age (T) is as follows:

(Equation 1)

( )( ) T = ln 1 + ( ) ( ) where l is the decay constant and the initial daughter ratio is the y-intercept of the isochron. The decay constants used for all calculations are 1.865 x 10-11 for 176Lu- 176Hf and 6.54 x 10-12 for 147Sm- 143Nd (Scherer et al., 2001; Faure and Mensing, 2005) and

1.393 x 10-11 for 87Rb-87Sr (Nebel et al. 2011).

4.1 Lu-Hf

The 176Lu/177Hf and 176Hf/177Hf isotope ratios of the 8 Tissint fragments (TS1,

TS2, TS3, TS5, TS6, UNM#645, Tissint ET) are summarized in Table 2. The 176Hf/177Hf ratio of all 7 residues are identical within error. The data points of 7 whole rock fractions fit perfectly on the isochron obtained using weakly-leached mineral separates in

Grosshans et al. (2013) yielding a compiled age of 571±84 Ma, an initial 176Hf/177Hf value of 0.284059±0.000046 and an MSWD = 1.5 (Fig. 5).

19 Sample TS4 did not plot on the isochron and was not used for calculations. It was excluded from this report because it suffered contamination during preparation.

Reanalysis for this sample is pending.

Table 2. Lu-Hf data for Tissint.

Sample # Name Weight (g) Lu (ppm) Hf (ppm) 176Lu/177Hf 176Hf/177Hf 2SE% 18NH119 TS1 0.09732 0.1447 0.7206 0.02335 0.284360 0.0041

18NH120 TS2 0.10633 0.1647 0.8394 0.02282 0.284368 0.0041

18NH121 TS3 0.09929 0.1535 0.7893 0.02262 0.284363 0.0041

18NH123 TS5 0.09365 0.1582 0.7873 0.02337 0.284367 0.0041

18NH124 TS6 0.11179 0.1360 0.6867 0.02302 0.284372 0.0041 UNM 18NH125 0.10356 0.1556 0.7885 0.02295 0.284362 0.0041 #645 Tissint 18NH126 0.09836 0.1593 0.7887 0.02348 0.284386 0.0041 ET

20

Fig 5. Lu-Hf isochron. Line calculated from Plagioclase, Pyroxene mineral separates and whole rock fractions from Grosshans et al. 2013 and the 7 whole rock fractions from this study. The decay constant used for 176Lu isochron is 1.865 x 10-11 (Scherer et al. 2011).

21 4.2 Rb-Sr

The 87Rb/86Sr and 87Sr/86Sr isotope ratios of the 7 Tissint fragments (TS1-TS6,

UNM#645) are summarized in Table 3. The 87Sr/ 86Sr ratio of 7 residues are identical within error (0.700955-0.700977). The data points of 7 residue fit on the isochron obtained using weakly-leached mineral separates in Brennecka et al.(2014), yielding a compiled age of 559 ± 39 Ma, an initial 87Sr/86Sr value of 0.700762 ± 000015, and MSWD=1.9 (Fig. 6).

Table 3. Rb-Sr data for Tissint.

Sample # Name Weight(g) Rb(ng) Sr(ng) 87Rb/86Sr 87Sr/86Sr 2SE

18SN52 TS1-R 0.08756 38.30 23.11 0.0244 0.700968 0.000012

18SN53 TS2-R 0.09372 57.05 24.04 0.0242 0.700958 0.000012

18SN54 TS3-R 0.08809 14.64 24.54 0.0241 0.700959 0.000012

18SN55 TS4-R 0.08481 20.59 24.20 0.0252 0.700966 0.000012

18SN56 TS5-R 0.08605 29.86 23.76 0.0257 0.700977 0.000012

18SN57 TS6-R 0.09415 28.66 22.29 0.0256 0.700955 0.000012 UNM 18SN58 0.10845 27.99 22.32 0.0274 0.700977 0.000012 #645-R 18SN61 TS1-L - 33.99 0.24 0.0331 0.702211 0.000012

18SN62 TS2-L - 57.01 0.24 0.0257 0.701830 0.000012

18SN63 TS3-L - 21.61 0.23 0.0220 0.701999 0.000012

18SN64 TS4-L - 17.02 0.24 0.0496 0.702198 0.000012

18SN65 TS5-L - 23.77 0.26 0.0349 0.701881 0.000012

18SN66 TS6-L - 20.69 0.21 0.0251 0.701222 0.000012 UNM 18SN67 - 14.54 0.38 0.0543 0.701695 0.000009 #645-L 22

Fig 6. Rb-Sr isochron. Line calculated from Olivine, Plagioclase, Pyroxene mineral separates from Brennecka et al. 2014 and the 7 whole rock residues from this study. 87 -11 87 87 The decay constant used for Rb isochron is and 1.393 x 10 for Rb- Sr (Nebel et al. 2011).

23 4.3 Sm-Nd

The 147Sm/144Nd and 143Nd/144Nd isotope ratios of the 8 Tissint fragments (TS1-

TS6, UNM#645, Tissint ET) are summarized in Table 4. The data points of 5 whole rock

fractions (TS2, TS3, TS4, Tissint ET, UNM#645) fit on the isochron obtained using

weakly-leached mineral separates in Brennecka et al. (2014), and Grosshans et al. (2013)

yielding a compiled age of 590 ± 49 Ma, an initial 143Nd/144Nd value of 0.51402±0.00012

and MSWD = 3.0 (Fig. 7).

Samples TS1 and TS6 did not plot on the isochron and were not used for

calculations. The reason for these samples not plotting on the isochron is uncertain.

However, for martian meteorites it has been observed that the Sm-Nd system can suffer

disturbance associated with Martian weathering of phosphates (Lapen et al. 2010).

Table 4. Sm-Nd data for Tissint.

Weight Sm Sample # Description (g) (ppm) Nd (ppm) 147Sm/144Nd 143Nd/144Nd 18NH119 TS1 0.09732 0.742 1.215 0.3692 0.515340 18NH120 TS2 0.10633 0.865 1.384 0.3862 0.515502 18NH121 TS3 0.09929 0.796 1.243 0.3872 0.515515 18NH122 TS4 0.12332 0.779 1.217 0.3875 0.515509 18NH123 TS5 0.09365 0.821 1.291 0.3847 0.515465 18NH124 TS6 0.11179 0.695 0.947 0.4443 0.517983 18NH125 UNM #645 0.10356 0.812 1.270 0.3868 0.515490 18NH126 Tissint ET 0.09836 0.825 1.288 0.3878 0.515524

24

Fig 7. Sm-Nd isochron. Line calculated from leached mineral separates from Brennecka et al. 2014, mineral separates from Grosshans et al. 2013 and (5) whole rock residues from this study. The decay constant used for 147Sm isochron is 6.54 x 10-12 (Faure and Mensing, 2005).

25 Chapter 5

Discussion

5.1 Crystallization Age Comparison

The whole rock residues analyzed for Lu-Hf, Rb-Sr and Sm-Nd in this study and the phases analyzed by Brennecka et al. (2014) and Grosshans et al. (2013) are isotopically indistinguishable; their isotopic systematics fall on the same isochron in all three systems (Figs. 4,5,6). These data indicate that all fragments are isotopically indistinguishable (within uncertainty), including the UNM#645 sample dated at 495 ± 35

Ma by Shih et al. (2014). We cannot explain the age discrepancy, but we can confirm that sample UNM#645 is isochronous with and isotopically indistinguishable from the other samples analyzed. The calculated dates using data compiled from Brennecka et al.

(2014), and Grosshans et al. (2013) for Lu-Hf, Rb-Sr, and Sm-Nd are 571 ± 84 Ma, 590 ±

49 ma and 559 ± 39 Ma, respectively. Implications of these data are that all fragments analyzed so far are cogenetic and that the Tissint strewn field appears to be homogeneous. Given that all samples in this study and previous data from ASU #1744 and UWB1 are in agreement, the samples appear to be from the same igneous unit.

26 Table 5. Ages determined for Tissint from previously published and reported data in this study.

# System Age Uncertainty (2σ) Source 1 147Sm-143Nd 596 23 Brennecka et al. (2012) 2 147Sm-143Nd 590 12 Brennecka et al. (2013) 3 147Sm-143Nd 616 67 Grosshans et al. (2013) 4 147Sm-143Nd 472 36 Shih et al. (2014) 5 147Sm-143Nd 593 25 Irving and Lapen (2016) 6 147Sm-143Nd 590 49 This Study 7 147Sm-143Nd 587 28 Brennecka et al. (2014) 8 87Rb-87Sr 560 30 Brennecka et al. (2013) 9 87Rb-87Sr 621 17 Park et al. (2013) 10 87Rb-87Sr 560 30 Brennecka et al. (2014) 11 87Rb-87Sr 495 35 Shih et al. (2014) 12 87Rb-87Sr 559 39 This Study 13 176Lu-176Hf 571 84 This Study 14 176Lu-176Hf 583 86 Grosshans et al. (2013) 15 40Ar/39Ar 610 33 Park et al. (2013)

27

Fig 8. Compilation of Tissint ages. Listed in table 5.

5.2 Isotope systematics of leachates and residues

The 1 N HCl leaching experiments successfully removed labile Sr-bearing materials that are not in isotopic equilibrium with the residues (Fig. 9). 87Sr/86Sr isotope ratios of the leachates are well within the range of depleted shergottites (i.e., the present- day ratios are sub-chondritic), but are slightly too radiogenic for a given Rb/Sr ratio to be related to the Sr in the residues of Tissint. The origin of this labile Sr could be terrestrial

(unlikely, given that it is a fall) or from Mars, but the more radiogenic Sr is clearly not hosted in the insoluble residues (silicates, sulfide, and oxides). If the Sr was from Mars, perhaps hosted as fracture or mineral grain coatings, the maximum 87Rb/86Sr ratio of the

Sr source, assuming it is derived from ancient reservoirs (~4.51 Ga), is ~0.045, compared to 0.28 for bulk Mars. This highly subchondritic value is well within the range of

28 87Rb/86Sr ratios of depleted shergottites (Barrat et al. 2014) and likely precludes enriched or evolved crustal material as the source of the labile Sr.

87Rb/86Sr and 87Sr/86Sr ratios for other launch-paired meteorites are variable in comparison to Tissint. Rb-Sr whole rock from NWA 1195 (Symes et al. 2008) and DaG

476 (Borg et al. 2002) likely include products of terrestrial and thus plot outside the scale of Figure 9, however, whole rock fractions of Y-98 (Shih et al. 2005) lie within the range of Tissint leachates. The leaching processes used for DaG 476 was not sufficient to remove terrestrial alteration products such as calcite and thus the whole rock residue is not representative of Martian compositions (Borg 2002). The "least disturbed" minerals of other launch-paired meteorites NWA 1195, and DaG 476 (Borg et al., 2002; Symes et al. 2008) are within the range of the leachates in this study and Brennecka et al. (2014).

(Fig 9.).

The Sr isotopic compositions of the Tissint leachates are within the range of the

Sr isotopic compositions of other depleted shergottites and well below the range of terrestrial weathering products or an enriched crustal reservoir on Mars. The 87Sr/86Sr ratio of terrestrial weathering products found in surrounding deserts are 0.709 to 0.713

(Symes et al. 2008) while the maximum for depleted shergottites, excluding contamination currently belongs to Dhofar 019 with a value of 0.702146 (Borg et al.

2001). Thus, the labile Sr need not be derived from an enriched reservoir on Mars, but instead could be from Sr derived from other units in the depleted shergottite igneous pile.

This seems to be the simplest explanation given that most depleted shergottites are related to a single ejection event, and likely a single ejection location.

29 In situ trace element and Pb isotopic analyses of impact melt glass and associated sulfide minerals (mostly pyrrhotite) of subsample TS2 indicate that exogenous materials were not incorporated into the Tissint impact melt glass (Lapen et al. 2019). Thus, the

‘radiogenic’ Sr is likely just a component of thin mineral coatings, perhaps related to the shock ejection event that launched most of the depleted shergottites at 1.1 Ma (Lapen et al. 2017).

Three bulk fragments of Tissint analyzed in this study plotted below the Sm-Nd isochron, which was potentially caused by element redistribution in altered phases. Bulk rock fragments of Tissint contain phosphate (merrilite), which is highly susceptible to alterations. In-situ trace element analysis of mineral phases in Tissint reveal that most Sm and Nd is hosted merrilitte (Balta et al. 2013; Kuchka et al. 2017). Since Tissint did not endure terrestrial weathering, it was likely altered on Mars. During any aqueous weathering and shock melting, REE hosted in phosphate, which can account for the majority of REE in the sample, could be redistributed. Therefore, analyses of samples with disturbed phosphate are not representative of the true age or source composition. In order to deal with disturbed phosphates, fragments are typically leached in 1 M HCl (e.g.,

Borg et al. 1997) prior to analyses. The analytical protocol employed here did not incorporate this leaching step because that could adversely affect the Lu-Hf isotope systematics (e.g., Lapen et al., 2003). Given that this was not a procedure in our study, it is plausible that these three samples succumbed to alteration on the Martian surface.

Further tests of samples NWA 6162, 4925, 2046, 2626, and 5789 will assess this hypothesis.

30

Fig 9. Leachates and Mineral separates of Tissint from this study and Brennecka et al. (2014). Rb-Sr whole rock from NWA 1195 (Symes et al. 2008) and DaG 476 (Borg et al. 2002) Y-98 (Shih et al. 2005)

31 Chapter 6

Conclusions

Lu-Hf, Sm-Nd, Rb-Sr isotope data from 8 whole rock fragments of Tissint, including UNM#645, indicate that they are related to a single igneous unit. Isotopic analyses of Tissint yield 176Lu-176Hf, 87Rb-87Sr and 147Sm-143Nd isochron ages of 571 ±

84 Ma, 559 ± 39 Ma and 590 ± 49 Ma, respectively. Fragments analyzed lie on the same isochron as data by Brennecka et al. (2013) and Grosshans et al. (2013). There is a 120

Ma difference between these data and those of Shih et al. (2014) however, UNM #645 was isochronous in all three isotopic systems. We cannot offer an explanation for the current discrepancy.

87Rb-87Sr analyses of leachates indicate that labile components hosting soluble Rb and Sr are not in isotopic equilibrium with the igneous assemblage. The Sr isotopic compositions of the leachate are within the range of depleted shergottites, perhaps indicating sources from the igneous pile on Mars.

Sm-Nd analyses of whole rock fragments indicate that the isotope systematics were easily disturbed and not as robust as the Lu-Hf system. Most Sm-Nd is hosted in phases that are easily altered by water along with the potential element redistribution upon impact, which signals that these fragments underwent alteration on the Martian surface.

Given the isotopic similarities between all fragments within the three isotopic systems it suggests that the Tissint strewn field is isotopically homogenous and from the same igneous unit that is a part of the larger volcanic center. These were ejected at the

32 same time 1.1 Ma years ago and labile isotopes suggest this ejection event coated minerals of Tissint. Fragments identified so far are cogenetic and the Tissint strewn field appears to be homogeneous.

33 References

Balta, J. B., Sanborn M.E., Udry A., Wadhwa M., McSween H.Y., (2015) Petrology and Trace Element Geochemistry of Tissint, the Newest Shergottite Fall. & Planetary Science 50.1 : 63-85.

Baziotis I.P., Liu Y., Decarli P.S., Melosh H.J., Mcsween H.Y., Bodnar R.J., Taylor, L.A., (2013) The Tissint as Evidence for the Largest Impact Excavation. Nature Communications 4.1: 1404.

Beard B.L., Ludois J.M., Lapen, T.J., Johnson, C.M., (2013) Pre-4.0 billion year weathering on Mars constrained by Rb-Sr geochronology on meteorite ALH84001. Earth Planet. Sci.Lett. 361:173-182.

Borg, L. E. and Draper, D. S., (2003) A petrogenetic model for the origin and compositional variation of the martian basaltic meteorites. Meteoritics & Planetary Science, v. 38, p. 1713-1731.

Borg L. E., and Drake M. J., (2005) A review of meteorite evidence for the timing of magmatism and of surface or near-surface liquid , Journal of Geophysical Research, 110, E12S03.

Borg L.E., Nyquist L.E., Taylor L.A., Wiesmann H., Shih C.Y., (1997) Constraints on Martian differentiation processes from Rb-Sr and Sm-Nd isotopic analyses of the basaltic shergottite QUE 94201 Geochim. Cosmochim. Acta, 61 (1997), pp. 4915-4931

Borg L.E., Nyquist L.E., Reese Y., Wiesmann H., Shih C.Y., Taylor L.A., Ivanova M., (2001) The age of Dhofar 019 and its relationship to the other martian meteorites, 32nd Lunar and Planetary Science Conference, #1144

Borg L. E., Nyquist L. E., Reese Y., Wiesmann H., (2002) Constraints on the petrogenesis of Martian meteorites from the partially disturbed Rb-Sr and Sm-Nd isotopic systematics of LEW88516 and ALH77005. Geochimica et Cosmochimica Acta 66:2037-2053.

Borg L. E., Nyquist L. E., Wiesmann H., Shih C.-Y., Reese Y., (2003) The age of Dar al Gani 476 and the differentiation history of the Martian meteorites inferred from their radiogenic isotopic systematics. Geochimica et Cosmochimica Acta 67:3519-3536.

Bouvier A., Blichert-Toft J., Vervoort J. D. Alberede F., (2005) The age of SNC meteorites and the antiquity of the martian surface. Earth Planet. Sci. Lett. 240, 221-233.

Bouvier A., Blichert-Toft J., Vervoort J. D., Gillet, P., Alberede F., (2008) The case for old basaltic shergotties. Earth Planet. Sci. Lett. 266, 105-124.

34

Brennecka G. A., Borg L. E., Wadhwa M., (2014) Insights into the martian mantle: The age and isotopic of the meteorite Tissint, Meteoritics and Planetary Science, 49, 412-418.

Bridges J. C. and Warren P. H., (2006) The SNC Meteorites: basaltic igneous processes on Mars. Journal of the Geological Soc., 163, 229-251.

Chennaoui Aoudjehane H., Avice G., Barrat J.-A., Boudouma O., Chen G., Duke M. J. M., Franchi I. A., Gattaceca J., Grady M. M., Greenwood R. C., Herd C. D. K., Hewins R., Jambon A., Marty B., Rochette P., Smith C. L., Sautter V., Verchovsky A., Weber P., and Zanda B., (2012) Tissint Martian meteorite: A fresh look at the interior, surface, and . Science 338:785-788.

Cohen B.E., Mark D.F., Cassata W. S., Lee M.R., Tomkinson T., Smith C. L., (2017) Taking the pulse of Mars via dating of a plume-fed volcano. Nature Communications volume 8, Article number: 640

Christen F., Eugster O., Busemann H., (2005) Mars ejection times and neutron capturer effects of the nakhlites Y000593 and Y000749, the olivine-phyric shergottite Y980459, and the lherzolitic NWA1950 Antarct. Meteorite Res., 18, pp. 117-132

Debaille V., Yin Q.-Z., Brandon A. D., Jacobsen B., (2008). Martian mantle mineralogy investigated by the 176Lu-176Hf and 147Sm-143Nd systematics of shergottites, Earth and Planetary Science Letters, 269, 186-199.

Edwards, P. H., Bridges J,C., Wiens, R., Anderson, R., Dyar, D., Fisk, M., Thompson, L., Gasda.P., Filiberto, J., Schwenzer, S.P., Blaney, D., and Hutchinson, I., (2017) Basalt– trachybasalt Samples in Gale Crater, Mars." Meteoritics & Planetary Science 52.11: 2931-410.

Faure G. and Mensing T. M. (2005) Isotopes: Principles and applications. Hoboken: John Wiley & Sons, Inc. 897 p.

Filiberto, J., Gross, J., Trela, J., Ferré E.C., (2014) Gabbroic Shergottite Northwest Africa 6963: an intrusive, crustal sample of Mars. American Mineralogist 99, 601-606.

Grosshans T. E., Lapen T. J., Andreasen R., Irving A. J., (2013) Lu-Hf and Sm-Nd ages and source compositions for depleted shergotitte Tissint, 44th Lunar and Planetary Science Conference, #2872.

J. N. Head, H. J. Melosh, (2000) Launch velocity distribution of the martian clan meteorites, 31st Lunar and Planetary Science Conference, #1937

Herzog G. F., Caffee M. W., Cosmic-ray exposure ages of meteorites, In Meteorites and Cosmochemical Processes. Volume 1 of Treatise on Cheochemistry, 419-454 (2014).

35

Irving A. J., Kuehner S. M., Tanaka R., Herd C. D. K., Chen G., Lapen T. J., (2012) The Tissint depleted permafic olvine-phyric shergottite: Petrologic, elemental and isotopic characterization of a recent Martian fall in Morocco, 43rd Lunar and Planetary Science Conference, #2510

Jones J. H., (1986) A discussion of isotopic systematics and mineral zoning in the shergottites- Evidence for a 180 m.y igneous crystallization age, Geochimica et Cosmochimica Acta, 50, 969-977.

Kuchka C.R., Herd C.D.K., Walton E.L., Guan Y., Liu Y., (2017) Martian low- temperature alteration materials in shock-melt pockets in Tissint: Constraints on their preservation in shergottite meteorites. Geochimica Et Cosmochimica Acta, 210(C), 228- 246.

Lapen T.J., Mahlen N.J., Johnson C. M., Beard B.L., (2004) High precision Lu and Hf isotope analyses of both spiked and unspiked samples: A new approach, Geochem Geophyics Geosystems, 5 Q01010, doi: 10.1029/2003GC000582

Lapen T. J., Righter M., Brandon A. D., Debaille V., Beard B. L., Shafer J. T., and Peslier A. H., (2010) A younger age for ALH 84001 and its geochemical link to shergottite sources in Mars. Science 328:347-351.

Lapen, T. J., Righter, M., Andreasen, R., Irving, A. J., Satkoski, A. M., Beard, B. L., Nishiizumi, K., Jull, A. J. T., Caffee, M. W., (2017) Two Billion Years of Magmatism Recorded from a Single Mars Meteorite Ejection Site, Science Advances, v. 3, no. 2, e1600922

Lapen T.J., Suarez S.E., Righter M., Irving A.J., Righter K., (2019) Trace Element and Pb Isotope Geochemistry of Tissint Impact Melt Glass and Sulfide Reveal No Contamination by , 50th Lunar and Planetary Science Conference, #2921

H. J. Melosh (1984) Impact ejection, spallation, and the origin of meteorites. Icarus 59, 234–260

Mouginis-Mark, P.J., and Yoshioka, M.T., (1998) The long lava flows of Elysium Planita, Mars. Journal of Geophysical Research: Planets, 103(E8), 19389-19400.

Münker, C., Weyer, S., Scherer, E., Mezger, K., (2001) Separation of high field strength elements (Nb, Ta, Zr, Hf) and Lu from rock samples for MC‐ICPMS measurements. Geochemistry Geophysics Geosystems, 2.

Nebel O., Scherer E.E., Mezger K., (2011) Evaluation of the 87Rb decay constant by age comparison against the U–Pb system Earth Planet. Sci. Lett., 301 (2011), pp. 1-8

36 Nishiizumi K., Nagao K., Caffee M. W., Jull A.J.T., Irving A.J., (2011) Cosmic-ray exposure chronologies of depleted olivine-phyric shergottites, 40th Lunar and Planetary Science Conference, #1435

Nyquist L. E., Bogard D. D., Shih C.-Y., Greshake A., Stöffler D., Eugster O., (2001) Ages and geologic histories of Martian meteorites. Chronology and Evolution of Mars 96:105-165.

Nyquist L. E., Bogard D. D., Shih C.-Y., Park J., Reese Y. D., Irving A. J., (2009), Concordant Rb-Sr, Sm-Nd, and Ar-Ar ages for Northwest Africa 1460: A 346 Ma old basaltic shergottite related to “lherzolitic” shergottites, Geochimica et Cosmochimica Acta, 73, 4288-4309.

Robbins, S. J., Di Achille, G., and Hynek, B. M., (2011) The Volcanic History of Mars: High-Resolution Crater-Based Studies of the Calderas of 20 Volcanoes, Icarus, v. 211, p. 1179-1203, doi: 10.1016/j.icarus.2010.11.012

Scherer E., Münker C., Mezger K., (2001) Calibration of the Lutetium-Hafnium clock. Science 293:683-687.

Shih C.-Y., Nyquist L. E., Wiesmann H., Reese Y., Misawa K., (2005) Rb-Sr and SmNd dating of olivine-phyric shergottite Yamato 980459: Petrogenesis of depleted shergottites. Antarctic Meteorite Research 18:46-65.

Shih C.-Y., Nyquist L. E., Reese Y., (2009) Rb-Sr and Sm-Nd studies of olivine-phyric shergottites RBT 04262 and LAR 06319: Isotopic evidence for relationship to enriched basaltic shergottites, 40th Lunar and Planetary Science Conference, #1360

Shih C.-Y., Nyquist L. E., Park J., Age C. B., (2014) Sm-Nd and Rb-Sr Isotopic systematics of a heavily shocked Martian meteorite Tissint and petrogenesis of depleted shergottites, 45th Lunar and Planetary Science Conference, #1184

Symes S. J. K., Borg L. E., Shearer C. K., Irving A. J., (2008) The age of the Martian meteorite Northwest Africa 1195 and the differentiation history of the shergottites. Geochimica et Cosmochimica Acta 72:1696-1710.

Vervoort J. D., Patchett P. J., Söderlund U., Baker M., (2004) Isotopic composition of Yb and the determination of Lu concentrations and Lu/Hf ratios by isotope dilution using MC-ICPMS. Geochemistry Geophysics Geosystems 5:Q11002, doi:10.1029/2004GC000721.

37 Wieler R., Huber L., Busemann H., Seiler S., Leya I., Maden C., Masarik J., Meier M. M. M., Nagao K., Trappitsch R., Irving A. J., (2016) Noble gases in 18 Martian meteorites and Northwest Africa 7812—Exposure ages, trapped gases, and a re-evaluation of the evidence for solar cosmic ray-produced neon in shergottites and other . Meteoritics & Planetary Science 51:407–428.

38