Insights into the Martian mantle: The age and isotopics of the meteorite fall Tissint

The recent witnessed fall of the meteorite Tissint represents the delivery of a pristine new sample from the surface of Mars. This meteorite provides an unprecedented opportunity to study a variety of aspects about the planet's evolution. Using the Rb–Sr and Sm–Nd isotopic systems, we determined that Tissint, a depleted shergottite, has a crystallization age of 574 ± 20 Ma, an initial ε¹⁴³Nd = +42.2 ± 0.5, and an initial ⁸⁷Sr/⁸⁶Sr = 0.700760 ± 11. These initial Nd and Sr isotopic compositions suggest that Tissint originated from a mantle source on Mars that is distinct from the source reservoirs of the other Martian meteorites. The known crystallization ages, geochemical characteristics, ejection ages, and ejection dynamics of Tissint and other similarly grouped Martian meteorites suggest that they are likely derived from a source crater up to approximately 90 km in diameter with an age of approximately 1 Ma that is located on terrain that is approximately 600 million years old.     

NanoSIMS analysis of organic carbon from the Tissint Martian meteorite: Evidence for the past existence of subsurface organic‐bearing fluids on Mars

Two petrographic settings of carbonaceous components, mainly filling open fractures and occasionally enclosed in shock‐melt veins, were found in the recently fallen Tissint Martian meteorite. The presence in shock‐melt veins and the deuterium enrichments (δD up to +1183‰) of these components clearly indicate a pristine Martian origin. The carbonaceous components are kerogen‐like, based on micro‐Raman spectra and multielemental ratios, and were probably deposited from fluids in shock‐induced fractures in the parent rock of Tissint. After precipitation of the organic matter, the rock experienced another severe shock event, producing the melt veins that encapsulated a part of the organic matter. The C isotopic compositions of the organic matter (δ¹³C = ?12.8 to ?33.1‰) are significantly lighter than Martian atmospheric CO₂ and carbonate, providing a tantalizing hint for a possible biotic process. Alternatively, the organic matter could be derived from carbonaceous chondrites, as insoluble organic matter from the latter has similar chemical and isotopic compositions. The presence of organic‐rich fluids that infiltrated rocks near the surface of Mars has significant implications for the study of Martian paleoenvironment and perhaps to search for possible ancient biological activities on Mars.     

Constraints on the water,chlorine, and fluorine content of the Martian mantle

Previous estimates of the volatile contents of Martian basalts, and hence their source regions, ranged from nearly volatile‐free through estimates similar to those found in terrestrial subduction zones. Here, we use the bulk chemistry of Martian meteorites, along with Martian apatite and amphibole chemistry, to constrain the volatile contents of the Martian interior. Our estimates show that the volatile content of the source region for the Martian meteorites is similar to the terrestrial Mid‐Ocean‐Ridge Mantle source. Chlorine is enriched compared with the depleted terrestrial mantle but is similar to the terrestrial enriched source region; fluorine is similar to the terrestrial primitive mantle; and water is consistent with the terrestrial mantle. Our results show that Martian magmas were not volatile saturated; had water/chlorine and water/fluorine ratios ~0.4–18; and are most similar, in terms of volatiles, to terrestrial MORBs. Presumably, there are variations in volatile content in the Martian interior as suggested by apatite compositions, but more bulk chemical data, especially for fluorine and water, are required to investigate these variations. Finally, the Noachian Martian interior, as exemplified by surface basalts and NWA 7034, may have had higher volatile contents.     

On the original igneous source of Martian fines

The composition of the silicate portion of Martian regolith fines indicates derivation of the fines from mafic to ultramafic igneous rocks, probably rich in pyroxene. Rock types similar in chemical and mineralogical composition include terrestrial Archean basalts and certain achondrite meteorites. If these igneous rocks weathered nearly isochemically, the nontronitic clays proposed earlier as an analog to Martian fines could be formed. Flood basalts of pyroxenitic lavas may be widespread and characteristic of early volcanism on Mars, analogous to maria flood basalts on the Moon and early Precambrian basaltic komatiites on Earth. Compositional differences between lunar, terrestrial, and Martian flood basalts may be related to differences in planetary sizes and mantle compositions of the respective planetary objects.     

Ejection of Martian meteorites

Abstract— We investigated the transfer of meteorites from Mars to Earth with a combined mineralogical and numerical approach. We used quantitative shock pressure barometry and thermodynamic calculations of post‐shock temperatures to constrain the pressure/temperature conditions for the ejection of Martian meteorites. The results show that shock pressures allowing the ejection of Martian meteorites range from 5 to 55 GPa, with corresponding post‐shock temperature elevations of 10 to about 1000 °C. With respect to shock pressures and post‐shock temperatures, an ejection of potentially viable organisms in Martian surface rocks seems possible. A calculation of the cooling time in space for the most highly shocked Martian meteorite Allan Hills (ALH) 77005 was performed and yielded a best‐fit for a post‐shock temperature of 1000 °C and a meteoroid size of 0.4 to 0.6 m. The final burial depths of the sub‐volcanic to volcanic Martian rocks as indicated by textures and mineral compositions of meteorites are in good agreement with the postulated size of the potential source region for Martian meteorites during the impact of a small projectile (200 m), as defined by numerical modeling (Artemieva and Ivanov 2004). A comparison of shock pressures and ejection and terrestrial ages indicates that, on average, highly shocked fragments reach Earth‐crossing orbits faster than weakly shocked fragments. If climatic changes on Mars have a significant influence on the atmospheric pressure, they could account for the increase of recorded ejection events of Martian meteorites in the last 5 Ma.     

Noble gas adsorption with and without mechanical stress: Not Martian signatures but fractionated air

Abstract– Sample preparation, involving physical and chemical methods, is an unavoidable step in geochemical analysis. From a noble gas perspective, the two important effects are loss of sample gas and/or incorporation of air, which are significant sources of analytical artifacts. This article reports on the effects of sample exposure to laboratory air without mechanical influence and during sample grinding. The experiments include pure adsorption on terrestrial analog materials (gibbsite and olivine) and grinding of Martian meteorites. A consistent observation is the presence of an elementally fractionated air component in the samples studied. This is a critical form of terrestrial contamination in meteorites as it often mimics the heavy noble gas signatures of known extra‐terrestrial end‐members that are the basis of important conclusions about the origin and evolution of a meteorite. Although the effects of such contamination can be minimized by avoiding elaborate sample preparation protocols, caution should be exercised in interpreting the elemental ratios (Ar/Xe, Kr/Xe), especially in the low‐temperature step extractions. The experiments can also be transferred to the investigation of Martian meteorites with long terrestrial residence times, and to Mars, where the Mars Science Laboratory mission will be able to measure noble gas signatures in the current atmosphere and in rocks and soils collected on the surface in Gale crater.     

Oxygen fugacity in the Martian mantle controlled by carbon: New constraints from the nakhlite MIL 03346

Abstract— Pyroxene structural data, along with analyses of titanomagnetite, fayalite and mesostasis of the new nakhlite Miller Range (MIL) 03346, define equilibration near 1 bar, 1100 °C, and oxygen fugacity near the FMQ buffer. There is a clear progression of oxygen fugacity (fO₂) in Martian meteorites from reduced Allan Hills (ALH) 84001 to intermediate shergottites to oxidized nakhlites. This trend can be explained by polybaric graphite‐CO‐CO₂ equilibria in the Martian mantle. Shergottites would have formed at pressures between 1.2 and 3.0 GPa, and nakhlite parent liquids formed at pressures >3.0 GPa, consistent with geochemical and petrologic data for the shergottites and nahklites. Carbon buffering in the Martian mantle could be responsible for variation in fO₂ in Martian meteorites (rather than assimilation or crustal interaction), as well as C‐H‐O fluids that could be the source of ˜30 ppb CH₄ detected by recent spacecraft missions. The conundrum of an oxidized current mantle and basalts, but reduced early mantle during core‐mantle equilibrium exists for both the Earth and Mars. A polybaric buffering role for graphite can explain this discrepancy for Mars, and thus it may not be necessary to have an oxidation mechanism like the dissociation of MgFe‐perovskite to account for the oxidized terrestrial mantle.     

The chlorine isotope composition of Martian meteorites 2. Implications for the early solar system and the formation of Mars

We determined the chlorine isotope composition of 16 Martian meteorites using gas source mass spectrometry on bulk samples and in situ secondary ion microprobe analysis on apatite grains. Measured δ³⁷Cl values range from ?3.8 to +8.6‰. The olivine‐phyric shergottites are the isotopically lightest samples, with δ³⁷Cl mostly ranging from ?4 to ?2‰. Samples with evidence for a crustal component have positive δ³⁷Cl values, with an extreme value of 8.6‰. Most of the basaltic shergottites have intermediate δ³⁷Cl values of ?1 to 0‰, except for Shergotty, which is similar to the olivine‐phyric shergottites. We interpret these data as due to mixing of a two‐component system. The first component is the mantle value of ?4 to ?3‰. This most likely represents the original bulk Martian Cl isotope value. The other endmember is a ³⁷Cl‐enriched crustal component. We speculate that preferential loss of ³⁵Cl to space has resulted in a high δ³⁷Cl value for the Martian surface, similar to what is seen in other volatile systems. The basaltic shergottites are a mixture of the other two endmembers. The low δ³⁷Cl value of primitive Mars is different from Earth and most chondrites, both of which are close to 0‰. We are not aware of any parent‐body process that could lower the δ³⁷Cl value of the Martian mantle to ?4 to ?3‰. Instead, we propose that this low δ³⁷Cl value represents the primordial bulk composition of Mars inherited during accretion. The higher δ³⁷Cl values seen in many chondrites are explained by later incorporation of ³⁷Cl‐enriched HCl‐hydrate.     

Ancient geologic events on Mars revealed by zircons and apatites from the Martian regolith breccia NWA 7034

Zircons and apatites in clasts and matrix from the Martian breccia NWA 7034 are well documented, timing ancient geologic events on Mars. Furthermore, in this study, zircon trace elemental content, apatite volatile content, and apatite volatile isotopic compositions measured in situ could constrain the evolution of those geologic events. The U‐Pb dates of zircons in basalt, basaltic andesite, trachyandesite igneous clasts, and the matrix are similar (4.4 Ga) suggesting intense volcanism on ancient Mars. However, two metamict zircon grains found in the matrix have an upper intercept date of ~4465 Ma in crystalline, whereas amorphous areas have a lower intercept date of 1634 ± 93 Ma. The younger date is consistent with the date of apatites (1530 ± 65 Ma), suggesting a metamorphic event that completely reset the U‐Pb system in both the amorphous areas of zircon and all apatites. δD values in all apatites negatively correlate with water content in a two‐endmember mixing trend. The D (δD up to 2459‰) and ³⁷Cl heavy core (3.8‰) of a large apatite grain suggest a D‐, ³⁷Cl‐rich fluid during the metamorphic event ~1.6 Ga ago, consistent with the trace elements Y, Hf and Ti and P in zircons. The fluid was also therefore P‐rich. The D‐, ³⁷Cl‐poor H₂O‐rich rim (<313‰) suggests the degassing of water from the Martian Cl‐poor interior at a later time. This D‐, ³⁷Cl‐poor Martian mantle reservoir could have derived from volcanic intrusions postdating the younger metamorphic event recorded in NWA 7034.     

The provenance,formation, and implications of reduced carbon phases in Martian meteorites

This review is intended to summarize the current observations of reduced carbon in Martian meteorites, differentiating between terrestrial contamination and carbon that is indigenous to Mars. Indeed, the identification of Martian organic matter is among the highest priority targets for robotic spacecraft missions in the next decade, including the Mars Science Laboratory and Mars 2020. Organic carbon compounds are essential building blocks of terrestrial life, so the occurrence and origin (biotic or abiotic) of organic compounds on Mars is of great significance; however, not all forms of reduced carbon are conducive to biological systems. This paper discusses the significance of reduced organic carbon (including methane) in Martian geological and astrobiological systems. Specifically, it summarizes current thinking on the nature, sources, and sinks of Martian organic carbon, a key component to Martian habitability. Based on this compilation, reduced organic carbon on Mars, including detections of methane in the Martian atmosphere, is best described through a combination of abiotic organic synthesis on Mars and infall of extraterrestrial carbonaceous material. Although conclusive signs of Martian life have yet to be revealed, we have developed a strategy for life detection on Mars that can be utilized in future life‐detection studies.     

Metamorphism in the Martian crust

Compositions of basaltic and ultramafic rocks analyzed by Mars rovers and occurring as Martian meteorites allow predictions of metamorphic mineral assemblages that would form under various thermophysical conditions. Key minerals identified by remote sensing roughly constrain temperatures and pressures in the Martian crust. We use a traditional metamorphic approach (phase diagrams) to assess low‐grade/hydrothermal equilibrium assemblages. Basaltic rocks should produce chlorite + actinolite + albite + silica, accompanied by laumontite, pumpellyite, prehnite, or serpentine/talc. Only prehnite‐bearing assemblages have been spectrally identified on Mars, although laumontite and pumpellyite have spectra similar to other uncharacterized zeolites and phyllosilicates. Ultramafic rocks are predicted to produce serpentine, talc, and magnesite, all of which have been detected spectrally on Mars. Mineral assemblages in both basaltic and ultramafic rocks constrain fluid compositions to be H₂O‐rich and CO₂‐poor. We confirm the hypothesis that low‐grade/hydrothermal metamorphism affected the Noachian crust on Mars, which has been excavated in large craters. We estimate the geothermal gradient (>20 °C km^?1) required to produce the observed assemblages. This gradient is higher than that estimated from radiogenic heat‐producing elements in the crust, suggesting extra heating by regional hydrothermal activity.     

A New Martian Meteorite: the Dhofar 019 Shergottite with an Exposure Age of 20 Million Years

The isotopic composition of the noble gases of the new Martian meteorite, the Dhofar 019 shergottite, found in the desert in the territory of the Sultanate of Oman on January 24, 2001, was investigated. Stepwise thermal annealing with isotopic analysis of each of the noble-gas temperature fractions was employed to determine the component composition. The concentration of the trapped noble gases in the new Martian meteorite Dhofar 019 is relatively high, although it lies within the range of concentrations in known SNC meteorites. A characteristic feature of all the trapped noble gases is the presence of two main components: a low-temperature, probably terrestrial atmospheric, component, trapped during the weathering of the meteorite on Earth, and a high-temperature trapped Martian component. Owing to the different ratios of the quantities of the two components, the trapped neon, argon, krypton, and xenon differ markedly in the kinetics of their release. The isotopic composition of the noble gases varies accordingly. The trapped xenon was found to contain two Martian components. One of them, with typical ratios of ¹²⁹Xe/¹³²Xe and ¹³²Xe/⁸⁴Kr, is representative of xenon and krypton of the Martian atmosphere; the other, of gases of the Martian mantle. Variations of the isotopic compositions of helium, neon, and argon (and also, to a lesser extent, of krypton and xenon) during the thermal annealing of the Dhofar 019 meteorite clearly point to a large proportion of cosmogenic as well as trapped components. The concentration of cosmogenic neon and argon in the meteorite is unusually high. This corresponds to a maximum exposure age among other SNC meteorites: 20 million years. Estimates of the potassium–argon age (gas-retention age) yielded the figure of 560 million years, which is within the range of values obtained for SNC meteorites by other authors, who used the rubidium–strontium and the potassium–argon technique.     

Siderophile and chalcophile element abundances in shergottites: Implications for Martian core formation

Elemental abundances for volatile siderophile and chalcophile elements for Mars inform us about processes of accretion and core formation. Such data are few for Martian meteorites, and are often lacking in the growing number of desert finds. In this study, we employed laser ablation inductively coupled plasma–mass spectrometry (LA‐ICP‐MS) to analyze polished slabs of 15 Martian meteorites for the abundances of about 70 elements. This technique has high sensitivity, excellent precision, and is generally accurate as determined by comparisons of elements for which literature abundances are known. However, in some meteorites, the analyzed surface is not representative of the bulk composition due to the over‐ or underrepresentation of a key host mineral, e.g., phosphate for rare earth elements (REE). For other meteorites, the range of variation in bulk rastered analyses of REE is within the range of variation reported among bulk REE analyses in the literature. An unexpected benefit has been the determination of the abundances of Ir and Os with a precision and accuracy comparable to the isotope dilution technique. Overall, the speed and small sample consumption afforded by this technique makes it an important tool widely applicable to small or rare meteorites for which a polished sample was prepared. The new volatile siderophile and chalcophile element abundances have been employed to determine Ge and Sb abundances, and revise Zn, As, and Bi abundances for the Martian mantle. The new estimates of Martian mantle composition support core formation at intermediate pressures (14 ± 3 GPa) in a magma ocean on Mars.     

Understanding the textures and origin of shock melt pockets in Martian meteorites from petrographic studies,comparisons with terrestrial mantle xenoliths,and experimental studies

Abstract— We present a textural comparison of localized shock melt pockets in Martian meteorites and glass pockets in terrestrial, mantle‐derived peridotites. Specific textures such as the development of sieve texture on spinel and pyroxene, and melt migration and reaction with the host rock are identical between these two apparently disparate sample sets. Based on petrographic and compositional observations it is concluded that void collapse/variable shock impedance is able to account for the occurrence of pre‐terrestrial sulfate‐bearing secondary minerals in the melts, high gas emplacement efficiencies, and S, Al, Ca, and Na enrichments and Fe and Mg depletion of shock melt compositions compared to the host rock; previously used as arguments against such a formation mechanism. Recent experimental studies of xenoliths are also reviewed to show how these data further our understanding of texture development and can be used to shed light on the petrogenesis of shock melts in Martian meteorites.     

Martian meteorite Tissint records unique petrogenesis among the depleted shergottites

Tissint, a new unaltered piece of Martian volcanic materials, is the most silica‐poor and Mg‐Fe‐rich igneous rock among the “depleted” olivine‐phyric shergottites. Fe‐Mg zoning of olivine suggests equilibrium growth (<0.1 °C h^?1) in the range of Fo_80–56 and olivine overgrowth (Fo_55–18) through a process of rapid disequilibrium (~1.0–5.0 °C h^?1). The spatially extended (up to 600 μm) flat‐top Fe‐Mg profiles of olivine indicates that the early‐stage cooling rate of Tissint was slower than the other shergottites. The chemically metastable outer rim of olivine (55) consists of oscillatory phosphorus zoning at the impact‐induced melt domains and grew rapidly compared to the early to intermediate‐stage crystallization of the Tissint bulk. High‐Ca pyroxene to low‐Ca pyroxene and high‐Ca pyroxene to plagioclase ratios of Tissint are more comparable to the enriched basaltic and enriched olivine‐phyric shergottites. Dominance of augite over plagioclase induced augite to control the Ca‐buffer in the residual melt suppressing the plagioclase crystallization, which also caused a profound effect on the Al‐content in the late‐crystallized pyroxenes. Mineral chemical stability, phase‐assemblage saturation, and pressure–temperature path of evolution indicates that the parent magma entered the solidus and left the liquidus field at a depth of 40–80 km in the upper mantle. Petrogenesis of Tissint appears to be similar to LAR 06319, an enriched olivine‐phyric shergottite, during the early to intermediate stage of crystallization. A severe shock‐induced deformation resulted in remelting (10–15 vol%), recrystallization (most Fe‐rich phases), and exhumation of Tissint in a time scale of 1–8 yr. Tissint possesses some distinct characteristics, e.g., impact‐induced melting and deformation, forming phosphorus‐rich recrystallization rims of olivine, and shock‐induced melt domains without relative enrichment of LREEs compared to the bulk; and shared characteristics, e.g., modal composition and magmatic evolution with the enriched basaltic shergottites, evidently reflecting unique mantle source in comparison to the clan of the depleted members.     

The composition and thickness of the crust of Mars estimated from rare earth elements and neodymium-isotopic compositions of Martian meteorites

Abstract— Isotopic and trace element compositions of Martian meteorites show that early differentiation of Mars produced complementary crustal and mantle reservoirs that were sampled by later magmatic events. This paper describes a mass balance model that estimates the rare earth element (REE) content and thickness of the crust of Mars from the compositions of shergottites. The diverse REE and Nd isotopic compositions of shergottites are most easily explained by variable addition of light rare earth element (LREE)–enriched crust to basaltic magmas derived from LREE-depleted mantle source regions. Antarctic shergottites EET 79001, ALH 77005, LEW 88516, and QUE 94201 all have strongly LREE-depleted patterns and positive initial ¹⁴³Nd isotopic compositions, which is consistent with the generation of these magmas from depleted mantle sources and little or no interaction with enriched crust. In contrast, Shergotty and Zagami have negative initial ¹⁴³Nd isotopic compositions and less pronounced depletions of the LREE, which have been explained by incorporation of enriched crustal components into mantle-derived magmas (Jones, 1989; Longhi, 1991; Borg et al., 1997). The mass balance model presented here derives the REE composition of the crustal component in Shergotty by assuming it represents a mixture between a mantle-derived magma similar in composition to EET 79001A and a LREE-enriched crustal component. The amount of crust in Shergotty is constrained by mixing relations based on Nd-isotopic compositions, which allows the REE pattern of the crustal component to be calculated by mass balance. The effectiveness of this model is demonstrated by the successful recovery of important characteristics of the Earth's continental crust from terrestrial Columbia River basalts. Self-consistent results for Nd-isotopic compositions and REE abundances are obtained if Shergotty contains ～10–30% of LREE-enriched crust with >10 ppm Nd. This crustal component would have moderately enriched LREE (Sm/Nd = 0.25–0.27; ¹⁴⁷Sm/¹⁴⁴Nd = 0.15–0.17; La/Yb = 2.7–3.8), relatively unfractionated heavy rare earth elements (HREE), and no Eu anomaly. Crust with these characteristics can be produced from a primitive lherzolitic Martian mantle by modest amounts (2–8%) of partial melting, and it would have a globally averaged thickness of <45 km, which is consistent with geophysical estimates. Mars may serve as a laboratory to investigate planetary differentiation by extraction of a primary basaltic crust.     

Terrestrial and Martian weathering signatures of xenon components in shergottite mineral separates

Abstract– Xenon‐isotopic ratios, step‐heating release patterns, and gas concentrations of mineral separates from Martian shergottites Roberts Massif (RBT) 04262, Dar al Gani (DaG) 489, Shergotty, and Elephant Moraine (EET) 79001 lithology B are reported. Concentrations of Martian atmospheric xenon are similar in mineral separates from all meteorites, but more weathered samples contain more terrestrial atmospheric xenon. The distributions of xenon from the Martian and terrestrial atmospheres among minerals in any one sample are similar, suggesting similarities in the processes by which they were acquired. However, in opaque and maskelynite fractions, Martian atmospheric xenon is released at higher temperatures than terrestrial atmospheric xenon. It is suggested that both Martian and terrestrial atmospheric xenon were initially introduced by weathering (low temperature alteration processes). However, the Martian component was redistributed by shock, accounting for its current residence in more retentive sites. The presence or absence of detectable ¹²⁹Xe from the Martian atmosphere in mafic minerals may correspond to the extent of crustal contamination of the rock’s parent melt. Variable contents of excess ¹²⁹Xe contrast with previously reported consistent concentrations of excess ⁴⁰Ar, suggesting distinct sources contributed these gases to the parent magma.     

Chemical layering in the upper mantle of Mars: Evidence from olivine‐hosted melt inclusions in Tissint

Melting of Martian mantle, formation, and evolution of primary magma from the depleted mantle were previously modeled from experimental petrology and geochemical studies of Martian meteorites. Based on in situ major and trace element study of a range of olivine‐hosted melt inclusions in various stages of crystallization of Tissint, a depleted olivine–phyric shergottite, we further constrain different stages of depletion and enrichment in the depleted mantle source of the shergottite suite. Two types of melt inclusions were petrographically recognized. Type I melt inclusions occur in the megacrystic olivine core (Fo_76‐70), while type II melt inclusions are hosted by the outer mantle of the olivine (Fo_66‐55). REE‐plot indicates type I melt inclusions, which are unique because they represent the most depleted trace element data from the parent magmas of all the depleted shergottites, are an order of magnitude depleted compared to the type II melt inclusions. The absolute REE content of type II displays parallel trend but somewhat lower value than the Tissint whole‐rock. Model calculations indicate two‐stage mantle melting events followed by enrichment through mixing with a hypothetical residual melt from solidifying magma ocean. This resulted in ~10 times enrichment of incompatible trace elements from parent magma stage to the remaining melt after 45% crystallization, simulating the whole‐rock of Tissint. We rule out any assimilation due to crustal recycling into the upper mantle, as proposed by a recent study. Rather, we propose the presence of Al, Ca, Na, P, and REE‐rich layer at the shallower upper mantle above the depleted mantle source region during the geologic evolution of Mars.     

Convective activity in a Martian magma chamber recorded by P‐zoning in Tissint olivine

The Tissint Martian meteorite is an unusual depleted olivine‐phyric shergottite, reportedly sourced from a mantle‐derived melt within a deep magma chamber. Here, we report major and trace element data for Tissint olivine and pyroxene, and use these data to provide new insights into the dynamics of the Tissint magma chamber. The presence of irregularly spaced oscillatory phosphorous (P)‐rich bands in olivine, along with geochemical evidence indicative of a closed magmatic system, implies that the olivine grains were subject to solute trapping caused by vigorous crystal convection within the Tissint magma chamber. Calculated equilibration temperatures for the earliest crystallizing (antecrystic) olivine cores suggest a Tissint magma source temperature of 1680 °C, and a local Martian mantle temperature of 1560 °C during the late Amazonian—the latter being consistent with the ambient mantle temperature of Archean Earth.