Yi Chen

We present a thermodynamic model for silicate melt designed to calculate partial melting relations in high-titanium (high-Ti; >6 wt % TiO2), volatile free mafic to ultramafic magmatic systems, such as those that generated lunar basalts. The melt model adopts the framework of (Tomlinson & Holland, Journal of Petrology, 62, egab012, 2021), which represents melts in typical peridotitic systems. To adapt this melt model for high-Ti systems, we first incorporate an algebraic correction and then re-calibrate the enthalpies of selected end-members. We demonstrate our melt model’s performance by comparing phase relations from four experimental datasets with calculations from our melt model, in conjunction with the models for solid phases from (Tomlinson & Holland, Journal of Petrology, 62, egab012, 2021). Calculations successfully reproduce the available experimental melt compositions, solidus, liquidus, and the progressive loss of solid phases throughout the melting interval. In particular, the model accurately delineates the position of the ilmenite melt-out curve—an essential capability for effectively modeling high-Ti magma petrogenesis. We therefore recommend this model for applications to high-Ti systems involving Ti-rich phases at the solidus. This study enables thermodynamic modeling in high-Ti magmatic systems, expanding the scope of thermodynamic modeling for future petrological research.

Ferroan anorthosites (FANs) reflect the nature of the Moon’s crust formed during the late-stage lunar magma ocean (LMO). Remote sensing suggests a hemispheric dichotomy in crustal composition, with the farside anorthositic highlands being more magnesian than the nearside. Lacking direct compositional and chronological constraints from farside anorthosites, whether this crustal dichotomy reflects asynchronous LMO solidification or post-LMO crustal reworking remains uncertain. Here we present an integrated petrological, geochemical, and geochronological study of farside anorthosite clasts returned by the Chang’e-6 mission. These clasts exhibit both mineralogical and compositional similarity with nearside Apollo FANs, supporting a comparable LMO-derived primary crust on both hemispheres. A zircon-bearing anorthosite domain contains recrystallised plagioclase enriched in rare earth elements (REE), thorium, and phosphorus, suggesting thermal reworking and metasomatism by a KREEP (potassium, REE, and phosphorus)-rich magma. High-precision lead-lead dating of zircon constrains this reworking event to 4,410 ± 8 Ma, establishing a local lower bound for farside LMO solidification. These findings establish a critical chronological benchmark for farside LMO solidification and offer direct evidence of a comparable primary crust across the Moon, constraining the origin of the crustal dichotomy to post-LMO reworking.

Asteroid impact, playing a key role in shaping the Moon, is a consequence of the orbital dynamical evolution of the Solar System. While the impact flux can be deduced from lunar craters, the impactor populations and their temporal variations remain poorly understood. We analyzed Fe‐Ni metals in 40 impact clasts from the Chang'e‐6 lunar soils and demonstrated that most of them are asteroidal remnants. The majority of these clasts (27 out of 40) originated from local basalt, where the asteroidal materials were accumulated after basaltic eruption at 2.8 billion years ago (Ga). The remaining 13 clasts are exotic feldspathic materials, delivered from the ancient lunar highlands, preserving asteroid remnants from ∼4.3 Ga to the present. By classifying the asteroid impactors based on the Ni, Co, P, Ir, and Au contents of the metals, we identified distinct impactor populations for the two clast types. All carbonaceous chondrite metals are exclusively found in seven of the basaltic impact clasts, providing robust evidence for a late‐stage bombardment by carbonaceous asteroids. The significant increase in carbonaceous impactors can be attributed to orbital dynamical events between 4.3 and 2.8 Ga, including giant planet migration, the Yarkovsky effect, or breakup of large carbonaceous asteroids. These findings, together with the exponentially declining impact flux, imply that only a small proportion of carbonaceous asteroids were delivered to the early Earth‐Moon system, and provide further constraints on the dynamical evolution of the Solar System.

The radiometric ages of the returned samples are the cornerstone of lunar cratering chronology models. However, all the previous samples were from the lunar nearside and the radiometric ages of those samples that can be associated with particular surfaces are <4.0 billion years. On 25 June 2024, Chang’e-6 successfully returned 1.935-kilogram samples from the lunar farside. The samples included local basalts with an age of 2807 ± 3 million years and the norites with an age of 4247 ± 5 million years likely corresponding to the age of the South Pole–Aitken basin. With these radiometric ages, we refined the lunar chronology function (CF) and verified that it is still consistent with a combination of an exponential decrease and a linear rate. We further derived the impacting rate and found it supports a smooth decay instead of abrupt changes of the impactor flux at early times. The refined lunar CF can be used to obtain more reliable ages for unsampled lunar areas and provide critical constraint for the lunar early impact history.

A new EPMA method for determining minor and trace elements ( e.g. , Al, P, Ti, Y, Yb, Lu, Hf, Th, and U) in zircon was developed. It features low detection limits ( e.g. , Ti, 9 μg g ⁻¹ , 3 σ ), high spatial resolution (<3 μm), and high analytical accuracy.

Lunar volcanism provides critical insights into the Moon's thermochemical evolution. We present petrological and geochemical analyses of six very‐low‐Ti (VLT) basalt fragments from Chang'e‐6 (CE6) samples. These basalts yield a Pb‐Pb age of around 2.9 Ga, representing the youngest reported VLT volcanism. They are slightly older than the low‐Ti basalts from the same soils and exhibit distinct pyroxene compositions and ²³⁸ U/ ²⁰⁴ Pb ratios, indicating derivation from distinct mantle sources. Compared to Apollo and Luna VLT basalts, these samples share similarly depleted Sr‐Pb isotopes but display elevated rare earth element concentrations and TiO ₂ contents. These basalts most likely derived from low‐degree melting of an olivine‐orthopyroxene source followed by 30%–40% fractional crystallization. Further diffusion chronometry reveals rapid magma ascent from magma chamber to surface, likely facilitated by the thin lunar crust resulting from the South Pole‐Aitken basin‐forming impact. Our results provide new insights into the petrogenesis of volcanic activity on the lunar farside.

Crustal recycling, a fundamental process promoting planetary differentiation, is conventionally attributed to plate tectonics on Earth. However, the mechanisms driving this process in tectonically stagnant regimes remain ambiguous. The heavy sulfur isotope (δ ³⁴ S = 2.0–2.4‰) composition of troilites in the newly-discovered 4.2 Ga high-Al basalt from the South Pole–Aitken (SPA) basin indicates the incorporation of surficial degassed ³⁴ S-enriched crustal materials into the mantle. Numerical simulations of the SPA-forming impact and the induced mantle convection show that uplifted molten crustal materials are exposed to vacuum for about one hour, leading to degassing and enrichment of ³⁴ S, then transported to depths greater than 200 km to provide a hybrid mantle source for high-Al basaltic magmatism. Our integrated petrological geochemical numerical study provides the mechanistic validation of impact-driven crustal recycling on the Moon, fundamentally advancing our capacity to decode early crust–mantle evolution in terrestrial bodies within the inner Solar System.

Magnetite is a principal paleomagnetic recorder on Earth, but lunar magnetism is thought to be dominated by metallic iron and Fe-Ni alloys, with magnetite rare and typically sub-micrometer within troilite. We identify nanometer- to micrometer-scale magnetite in pentlandite-troilite assemblages from a Chang’e-5 regolith breccia. Magnetite occurs at and within pentlandite, locally enclosing pentlandite nanoinclusions, implying a formation pathway distinct from troilite-hosted occurrences. Textures and compositions indicate sequential crystallization from an impact-generated Fe-Ni-S-O melt: rapid pentlandite growth along troilite margins followed by magnetite nucleation at sulfide-silicate interfaces. The lunar low oxygen fugacity stabilizes Fe ²⁺ -enriched magnetite, unlike terrestrial analogues. High crystallinity and single-domain to single-vortex states indicate strong remanence stability, making these grains reliable recorders of the contemporaneous lunar magnetic fields. These results broaden the inventory of lunar magnetic carriers, demonstrate impact-driven magnetite formation under lunar redox conditions, and motivate use of magnetite to refine the Moon’s magnetic history.