FeO Abundances Research Articles

Surface Ages in the Vicinity of the Chang’e-6 Landing Site

The samples from lunar farside have great significance for the study of the Moon, and even the solar system. Chang’e-6 landed successfully on the southern mare of the Apollo basin and returned ~2 kg of samples from lunar farside. To provide a better understanding for the background of the returned samples, we conducted detailed crater size-frequency distribution (CSFD) measurements in the Chang’e-6 landing region, the southern mare of the Apollo basin. The southern mare is divided into the western mare (W region) and the eastern mare (E region), and then subdivided into five subunits (W1, W2, W3, W4, W5) and three units (E1, E2, E3), respectively, according to the elevation, TiO2, and FeO abundances. Within the W2 and W5 region, more detailed subunits were separated out. The results show that the southern mare surface was active during two epochs, the Imbrian period and the Eratosthenian period. The basalt eruption lasted for ~1.7 Ga, from 3.28 Ga of the eastern mare to 1.54 Ga of the western mare. The W region is younger than the E region, while the three units of the E region have an age of ~3.2 Ga. The ages of the western mare basalts range from 2.98 Ga to 1.54 Ga, lasting for 1.4 Ga. It is worth noting that the age of the basalt at the Chang’e-6 sampling site is ~1.68 Ga, indicating the samples returned may include components with this very young age.

Mineralogical Characterization of the Lunar South Polar Region: 1. The Artemis Exploration Zone

AbstractThe lunar south pole is a region of focused scientific and exploration interest, with several crewed and robotic missions to this region planned within the next decade. Understanding the mineralogy of the region is essential to inform landing site characterization and selection and provides the key context for interpreting samples and in situ observations. At high latitudes, extreme illumination conditions (high phase angles) can negatively impact the data quality of orbital instruments. This is especially true for passive near‐infrared spectrometers such as the Moon Mineralogy Mapper (M3) and the Kaguya Spectral Profiler, which measure the spectral properties of the surface using reflected sunlight. Using Moon Mineralogy Mapper data, we observed that the south polar region is associated with a detectable mafic signature consistent with the presence of pyroxenes. The strongest mafic signatures are associated with the South Pole—Aitken Basin, suggesting that impact melt and basin ejecta from the lower crust and upper mantle are present within this region. This observation is validated in several ways: (a) comparisons between M3 data acquired during different mission phases, (b) comparisons between multiple spectral parameters sensitive to the presence of mafic minerals, (c) comparisons between the north and south lunar polar regions, and (d) comparisons with publicly available Kaguya polar mineralogy maps and Lunar Prospector elemental abundances. We also investigate the nature of an anomalous high‐albedo region within 2–3° of the south pole observed in Lunar Orbiter Laser Altimeter reflectance data exhibiting a spatially conflicting apparent FeO abundance pattern between several data sets.

In-situ mapping of iron and titanium with the visible and near-infrared image spectrometer (VNIS) along the Yutu-2 rover traverse on the farside of the moon

In January 2019, China's Chang'E-4 probe successfully landed in the Von Kármán crater of the Moon's farside's South Pole-Aitken basin. Till August 2021, the Yutu-2 rover had worked for >32 lunar days. The Visible and Near-infrared Image Spectrometer (VNIS) is one of scientific payloads on board the rover that can collect in-situ spectral data. This provides a unique perspective for investigating the composition of the lunar surface materials. In this work, a local-scale FeO and TiO2 abundance mapping approach based on the in-situ VNIS data was proposed to utilize the fine spectral-spatial hyperspectral information. Improved FeO and TiO2 abundance inversion models were performed on each unshaded pixel to generate abundance maps. Experimental results obtained on 115 VNIS observation data along the Yutu-2's routing path confirm the effectiveness of the proposed approach, especially in the complex observation scenarios. Comparing with the in-orbit data products and the in-situ abundance results obtained by the reference methods, the effectiveness of the proposed in-situ FeO and TiO2 abundance mapping approach is validated. Furthermore, the proposed approach allows a detailed analysis of chemical properties and spatial distribution of lunar surface materials, and helps to discover abnormal targets according to the serial spectral observations along the rover's routing path, which reveals the great potential in more precise lunar surface material identification and analysis applications.

Dark mantles over domes and rilles on the Moon: Evidence for pyroclastic materials

A collection of dark mantles covering volcanic domes and surrounding rilles were examined. Remotely sensed information on FeO and TiO2 content, clinopyroxene (CPX) and olivine (where olivine is an assumed proxy for glass) abundance, band center positions near 1 and 2 μm, and a parameter related to OH and/or H2O content were assessed for these mantling deposits. Based on our examination of these dark mantles associated with domes and rilles we found that all of the examined dark mantles had higher FeO abundances than the surroundings. The Birt E pit of Rima Birt and the mantle over the Manilius-1 dome are higher in glass and lower in CPX than their surroundings and with deeper band depth near 3 μm: all these indicators suggest higher pyroclastic glass abundance. The mantle at Rima Calippus is also nominally glass-rich although its band depth near 3 μm is comparable to nearby mare basalts and thus is not taken to be unusually hydrated. The dark mantles associated with the Yangel-1 and Cauchy-5 domes are higher in CPX, lower in glass, and higher in TiO2 content with low band depth near 3 μm indicating they are glass-poor and nominally rich in ilmenite. The Hyginus crater of Rima Hyginus is distinct from the other studied mantles in that it has higher TiO2 content, lower CPX abundance, higher glass or olivine, and weak 3 μm band depth. Also, the band minimum near 1 μm deos not occur at a longer wavelength than surrounding mare suggesting that in this instance the higher olivine (as a proxy for glass) might actually be due to olivine rather than glass. Thus, in the study of dark mantles associated with domes and rilles each represents deposits and eruptions that need to be characterized on a case-by-case basis rather than as a collective group.

A neural network topographic correction method for the Lunar Reconnaissance Orbiter Diviner Christiansen feature map

Topographic correction for lunar optical and thermal infrared remote sensing images is a challenging task. Although geometrical, photometrical or albedo-dependent correction methods have been used in an attempt to eliminate topographic effects in the initial lunar reflectance and emissivity images, these methods did not perform well on lunar steep slopes, large crater interiors or walls. In this paper, a novel neural network topographic correction (NNTC) model that was trained based on the relationships between flat (< 0.1° slope angle) and rugged pixels with similar Kaguya FeO abundance and optical maturity parameters (OMATs) (relative ratio < 0.1%) was applied to the Lunar Reconnaissance Orbiter (LRO) Diviner standard Christiansen feature (CF) image. The topographic correction accuracy is 0.03 μm, and no outliers are produced. Visual comparisons with the previous topographic corrected reflectance and emissivity images indicate that the topographic effects on various slope and aspect pixels were effectively corrected. The excavated anorthosite materials in the highland crater (such as the Jackson, Giordano Bruno and Tycho) interiors, surroundings, ejecta, and ray deposits have very similar NNTC CF values. The crater structures in maria or cryptomaria are identified more clearly. In addition, the NNTC method has the potential to be a universal topographic correction method for lunar optical and thermal infrared images, and it provides reliable data sources and a new method for space weathering correction.

Extracting Mare-like Cryptomare Deposits in Cryptomare Regions Based on CE-2 MRM Data Using SVM Method

A new kind of surface material is found and defined in the Balmer–Kapteyn (B-K) cryptomare region, Mare-like cryptomare deposits (MCD), representing highland debris mixed by mare deposits with a certain fraction. This postulates the presence of surface materials in the cryptomare regions. In this study, to objectively verify the existence of the MCD in the cryptomare regions, based on the Chang’E-2 microwave radiometer (MRM) data, the support vector machine (SVM) method was adopted, where the K-means algorithm was used to optimize the training samples and the random forest algorithm was used to select the proper band features. Finally, the extracted MCD is identified with the datasets including Lunar Reconnaissance Orbiter Wide Angle Camera, Diviner, and Clementine UV–VIS. The main findings are as follows: (1) Compared to the range outlined via the TB counter, the range of the MCD is objectively extracted using the SVM method in the B-K cryptomare region, which is reasonably indicated by the FeO abundance, TiO2 abundance, and rock abundance distributions. (2) The MCDs were extracted in the Dewar, Lomonosov–Fleming (L-F), and Schiller–Schickard (S-S) regions, indicating that the MCDs are widely distributed in the cryptomaria. (3) The presence of MCDs is concentrated in a limited region, accounting for 64.9%, 52.3%, 76.4%, and 64%, respectively, in the range of Dewar, L-F, S-S, and B-K regions identified using the optical data. The occurrence of the MCD gives a new understanding of the surface evolution in the cryptomare regions.

The effect of variations in cooling rates on mineral compositions in mid-ocean ridge basalts

We present textural and chemical analyses of minerals from a 150 m thick sequence of submarine mid-ocean ridge basalts from the South China Sea in order to showcase the effect of variations in magma cooling rates on mineral texture and mineral composition. Groundmass plagioclase and clinopyroxene show gradual changes in texture and composition as flows grade from slowly cooled, meter-thick massive flows to more rapidly cooled dm-thick pillow lobes with quenched glassy margins. The corresponding change in cooling-rate is estimated to vary from <1 to ≥100 °C/h. With increasing cooling rate, plagioclase forms elongated, sector-zoned swallow-tail crystals. Sector zoning is associated with increasing FeO (up to 1.5 wt%) and MgO (up to 0.6 wt%) abundances at near-constant anorthite (An), related to a two orders of magnitude increase in growth rate. Sr, Ba, Li and Ti abundances remain constant and appear unaffected by kinetic factors at such growth rates. With increasing cooling rate clinopyroxene becomes dendritic, and its composition is sensitive to changes in crystallization conditions. Increasing cooling rate (<1 to ≥100 °C/h) leads to increasing Al2O3 (average of 3.2 to 4.3 wt%), TiO2 (1.3 to 2.8 wt%) and Na2O (0.37 to 0.44 wt%) and a decrease in SiO2 (50.1 to 46.4 wt%) and Mg#Fetot, i.e., molar MgO/(MgO + FeOtot), from 71.3 to 53.1. Trace element abundances (Y, Zr, Ce, V, Sr) in clinopyroxene increase by up to an order of magnitude at cooling rates ≥100 °C/h and become more heterogeneous spatially. These results support experimental evidence that rapid crystal growth leads to significant departure of mineral compositions from equilibrium, in particular for clinopyroxene. Although plagioclase composition remains relatively insensitive to changes in growth conditions at the studied cooling rates, the sensitivity of clinopyroxene composition to growth rates imply that it should be used with caution as a tool to infer magmatic crystallization conditions.

Precise mapping of the Moon with the Clementine Ultraviolet/Visible Camera

The Ultraviolet/Visible (UVVIS) camera on the Clementine spacecraft provided a global, multispectral view of the Moon. Scientists commonly use individual observations and derived products (optical maturity, mineral abundance, etc.) over 25 years later, addressing questions concerning the composition and relative age of surface features. However, since the mission concluded, our knowledge of lunar topography and the locations of features on the surface have improved with results from the Lunar Reconnaissance Orbiter (LRO) and Gravity Recovery and Interior Laboratory (GRAIL) missions. Before this work, cross-mission comparisons were impaired by spatial offsets between the derived products, which are as large as 2.5 km in some regions. Lunar Reconnaissance Orbiter Camera (LROC) Wide Angle Camera (WAC) images, acquired under similar lighting conditions, were used as a cartographic reference. We used image-based feature-matching algorithms to automatically derive control points to improve the positional accuracy of each UVVIS observation with the LROC WAC basemap. From ground control points, we calculate a precise camera model (focal length, optical distortion, etc.) for the UVVIS camera and update the pointing for each UVVIS image. Using the updated geometric information and projecting the UVVIS image to the LOLA global shape model, we map the five-band multispectral UVVIS mosaic, the optical maturity map, and FeO and TiO2 abundance maps. We also analyze pitch observations of the polar regions to investigate the influence phase angle has on the derived optical maturity. The new images are registered to the GRAIL-based LRO geodetic framework within a WAC pixel (Ground Sampling Distance ∼75 m; average UVVIS sigma0 = 0.084), creating a foundational geospatial data product that does not require any manual interpretation or nonlinear warping of map products to align with the current lunar reference frame.

The EUV Reflectance of Mercury's Surface Measured by BepiColombo/PHEBUS

AbstractOn 9 and 10 October 2021, Probing the Hermean Exosphere by Ultraviolet Spectroscopy aboard BepiColombo observed the disk‐integrated reflected light from the Sun by Mercury in the spectral range 90–160 nm at a phase angle of 70°. These observations are used to derive the EUV reflectance of the surface of Mercury in this wavelength range for the first time since the Mariner 10 observations in 1974–1975. Our observations are in agreement with a surface of Mercury darker by a factor ∼0.5–0.6 compared to the Moon in this wavelength range, with an average reflectance of 0.3% at a phase angle of 70°. This lower reflectance of Mercury could be due to the lower abundance of FeO. The derived reflectance near 160 nm is close to the derived reflectance at 220 nm by MESSENGER/MASCS at a similar phase angle. Possible spectral variations measured between 110 and 140 nm could be attributed to SiO2 glass, but the signal to noise ratio is low and other observations, possible at several periods during the rest of the cruise, are needed to confirm this last result.

Possible Chemical Composition And Interior Structure Models Of Venus Inferred From Numerical Modelling

Abstract Venus’ mass and radius are similar to those of Earth. However, dissimilarities in atmospheric properties, geophysical activity, and magnetic field generation could hint toward significant differences in the chemical composition and interior evolution of the two planets. Although various explanations for the differences between Venus and Earth have been proposed, the currently available data are insufficient to discriminate among the different solutions. Here we investigate the possible range of models for Venus’ structure. We assume that core segregation happened as a single-stage event. The mantle composition is inferred from the core composition using a prescription for metal-silicate partitioning. We consider three different cases for the composition of Venus defined via the bulk Si and Mg content, and the core’s S content. Permissible ranges for the core size, mantle, and core composition as well as the normalized moment of inertia (MoI) are presented for these compositions. A solid inner core could exist for all compositions. We estimate that Venus’ MoI is 0.317–0.351 and its core size 2930–4350 km for all assumed compositions. Higher MoI values correspond to more oxidizing conditions during core segregation. A determination of the abundance of FeO in Venus’ mantle by future missions could further constrain its composition and internal structure. This can reveal important information on Venus’ formation and evolution, and, possibly, the reasons for the differences between Venus and our home planet.

The Geological History of the Chang’e-5 Sample Return Region

Chang’e-5 (CE-5), China’s first sample-return mission, has successfully landed in Oceanus Procellarum near Mons Rümker. It is important to have a detailed study of the geological evolution of the CE-5 sample return region. This work aims to study the geological background, topography, geomorphology, major chemical composition, mineralogy, and chronology of the landing site region. First, we used the map of topography obtained by the Kaguya TC merged Digital Terrain Model (DTM) to analyze the topographic characteristics. Then, we used the Kaguya Multiband Imager (MI) reflectance data to derive FeO and TiO2 abundance and the hyperspectral data of the Moon Mineralogy Mapper (M3) onboard the Chandrayaan-1 spacecraft to study the mineralogy of the landing site region. Later, we defined and dated the geological units of the landing area using the crater size–frequency distribution (CSFD) method. Finally, we conducted a detailed analysis of the volcanism and tectonism that occurred in the CE-5 landing area. The study region has experienced multi-stage magmatic activities (~3.36 Ga to ~1.22 Ga) and formed multiple mare units with different chemical and mineral compositions. The relationship between the wrinkle ridges cut by small impact craters suggests that the U7/Em5 has experienced Copernican aged tectonism recently ~320 Ma. The U7/Em5 unit where the Chang’e-5 sample return mission landed is dominantly composed of mature pyroxene and the basalts are mainly high-iron and mid-titanium basalts. Additionally, the analysis of pure basalt in the U7/Em5 suggests that the samples returned by the CE-5 mission may contain the ejecta and ray materials of young craters, including sharp B, Harding, Copernicus, and Aristarchus.

Lunar Surface Composition Constraints from Maturity-corrected Far-ultraviolet Reflectance Maps

Abstract Far-ultraviolet (FUV) observations by the Lunar Reconnaissance Orbiter Lyman Alpha Mapping Project (LAMP) have shown that the lunar surface reflectance in the ultraviolet is sensitive to changes in both composition and maturity at wavelengths &gt;170 nm. This can lead to uncertainties in the interpretation of features that appear in maps created using LAMP data from this wavelength range. Here we utilize a correction based on the optical maturity parameter to remove large-scale immaturity features from LAMP spectral slope and band ratio maps. After performing the correction, the LAMP maps more accurately represent the FUV lunar surface in the context of composition. Corrected LAMP maps show good correlation with lunar FeO, plagioclase, and bulk silicate abundance maps for moderate- to high-iron regions, indicating a sensitivity in the LAMP data to differences in mineral composition in those regions. These maps represent a unique view into a relatively unexplored region of the spectrum and showcase the ability to perform compositional mapping and mineral identification using FUV remote-sensing measurements.

Multispectral imaging and hyperspectral scanning of the first dissection of core 73002: Preliminary results

AbstractWe measured the multispectral images and a hyperspectral profile during the first dissection pass of core 73002, and here, we present preliminary results. Both multispectral images and hyperspectral data show systematic darkening and reddening from bottom to top of the core, indicating an increasing maturity from the subsurface to surface soils. Our estimated FeO and TiO2 abundances are 9 (±1) wt% and 1.8 (±0.5) wt%, and their homogeneous distributions imply no compositional stratigraphy was sampled by core 73002. The in situ regolith reworking depth is about 14 cm as inferred from the optical maturity (OMAT) profile, corresponding to a time range of about 61 million years. Mineralogy and Mg# (molar Mg/[Mg+Fe]) calculated using hyperspectral data and radiative transfer modeling show as expected the core is dominated by plagioclase and low‐Ca pyroxene, and the average Mg# is 61 (±10). Our work shows that spectroscopy has a great potential to be applied in the preliminary examination of future extraterrestrial samples from outside of the glovebox.

Lunar Subsurface Mineralogy and Density Profile Modelling based on Moon Mineralogy Mapper Observation

AbstractThe methods of deriving FeO and TiO2 contents from the Clementine spacecraft data were discussed, and an approach was developed to derive the content from the measurements using the Moon Mineralogy Mapper (M3) instrument on Chandrayaan‐1. The density of lunar bedrock was then modeled on the basis of the derived FeO and TiO2 abundances. The FeO and TiO2 abundances derived from the M3 data were compared with the previous results of the Clementine data and were in good agreement. The FeO abundance data also agreed well with the Lunar Prospector data, which were used as an independent source. The previous Clementine and newly M3 derived abundances were compared with the laboratory measured FeO and TiO2 contents in the Apollo and Luna returned samples. The Clementine derived FeO content was systematically 1%–2% lower than the laboratory measurements in all the returned samples. The M3 derived content agreed well with the returned Apollo samples and was within ±2.8% of the laboratory measurements. The Clementine derived TiO2 abundance was systematically 0.1%–4% higher than the laboratory measurements of the returned samples. The M3 derived TiO2 agreed well (±0.6%) with the laboratory measurements of the returned samples, except for samples with high TiO2 content. However, these results should be carefully interpreted because the error range requires verification. No error analysis was provided with the previous Clementine derived contents.

Possible Non‐Mare Lithologies in the Regolith at the Chang’E‐5 Landing Site: Evidence From Remote Sensing Data

AbstractThe Chang’E‐5 (CE‐5) mission returned a total of 1,731 g of lunar regolith from the northern Oceanus Procellarum (NOP). Despite that the CE‐5 landing site is covered by Eratosthenian‐aged mare basalts, non‐mare lithologies might also have been collected owing to the lateral mixing introduced by nearby craters. Here we employed FeO and thorium abundance data obtained by the Lunar Prospector Gamma Ray Spectrometer to investigate the chemical composition of the NOP region. Four major compositional groups (feldspathic highland materials, Imbrium basin ejecta, Aristarchus ejecta, and mare basalts) and several subgroups have been identified. Their corresponding geographical locations were constrained using an interactive scatter‐plot tool in ENVI® software. We also determined the first‐order mixing trends occurring within the NOP region as well as the CE‐5 landing site. Aristarchus crater may have contributed highly evolved materials to the CE‐5 site. Rock fragments derived from Aristarchus ejecta are important for the interpretation of magmatic differentiation and non‐mare volcanism on the Moon. We proposed that thorium enrichments of CE‐5 landing site are due to the geochemical nature of local mare basalts rather than impact mixing. Highland ejecta, along with mare basalts, would expand Apollo and Luna sample collection diversity.

Deriving iron contents from past and future Venus surface spectra with new high-temperature laboratory emissivity data.

In situ information on the surface composition of Venus is based on measurements of a small number of landing sites. In the laboratory, we measured the emissivity of a range of igneous rocks at temperatures up to 480°C. We show that high-temperature laboratory spectra of basalts are consistent with the only existing multispectral data from the surface of Venus obtained by the photometers on the Venera 9 and 10 landers. We derive the FeO abundances for these landing sites of 12.2 and 9.5 weight %, respectively. From orbit, Venus' surface is only observable on the nightside through small spectral windows near 1 μm where the CO2 atmosphere is largely transparent. The new laboratory data show that different rock types can be distinguished using only a small set of spectral bands. Therefore, future orbital spectral observations can provide a much-needed global composition map.

Young lunar mare basalts in the Chang'e-5 sample return region, northern Oceanus Procellarum

Chang'e-5, China's first lunar sample return mission, is targeted to land in northern Oceanus Procellarum, within a region selected on the basis of 1) its location away from the Apollo-Luna sampling region, 2) the presence of the Procellarum KREEP Terrane (PKT), 3) the occurrence of one of the youngest lunar mare basalts (Em4), and 4) its association with Rima Sharp. In order to provide context for returned sample analyses, we conducted a comprehensive study of the regional and global settings, geomorphology, composition, mineralogy, and chronology of the Em4 mare basalts. Superposed on Imbrian-aged low-Ti basalts, Em4 covers 37,000 km2 and is composed of Eratosthenian-aged (∼1.53 Ga), high-Ti basalts with a mean thickness of ∼51 m and a volume between ∼1450 and 2350 km3. Minor variations in TiO2 and FeO abundance occur within the unit and the thorium content averages ∼6.7 ppm, typical of PKT mare basaltic regolith. No specific source vents (e.g., fissures, cones, domes) were found within the unit. We show that Rima Sharp is actually composed of three major rilles, whose source vents are located outside of, and which flow into, and merge in Em4, suggesting that they may be among the sources for Em4. Regolith thickness averages ∼7 m and there is abundant evidence for vertical and lateral mixing; the most likely sources of distal ejecta are Aristarchus, Harpalus, and Sharp B craters. Returned samples from local and distant materials delivered by impact will thus provide significant new insights into lunar geochronology, inner Solar System impact fluxes, the age of very young mare basalts, the role of the PKT in the generation of mare basalts, the role of sinuous rilles in lava flow emplacement, and the thermal evolution of the Moon.

Constraints on the Abundances of Carbon and Silicon in Mercury's Core From Experiments in the Fe‐Si‐C System

AbstractThe composition of a planet's core has important implications for the thermal and magmatic evolution of that planet. Here, we conducted carbon (C) solubility experiments on iron‐silicon (Fe‐Si) metal mixtures (up to 35 wt% [~52 atom%] Si) at 1 GPa and 800–1800°C to determine the carbon concentration at graphite saturation (CCGS) in metallic melt and crystalline metal with varying proportions of Fe and Si to constrain the C content of Mercury's core. Our results, combined with those in the literature, show that composition is the major controlling factor for carbon solubility in Fe‐rich metal with minimal effects from temperature and pressure. Moreover, there is a strong anticorrelation between the abundances of carbon and silicon in iron‐rich metallic systems. Based on the previous estimates of &lt;1–25 wt% Si in Mercury's core, our results indicate that a carbon‐saturated Mercurian core has 0.5–6.4 wt% C, with 6.4 wt% C corresponding to an Si‐free, Fe core and 0.5 wt% C corresponding to an Fe‐rich core with 25 wt% Si. The upper end of estimated FeO abundances in the mantle (up to 2.2 wt%) are consistent with a core that has &lt;1 wt% Si and up to 6.4 wt% C, which would imply that bulk Mercury has a superchondritic Fe/Si ratio. However, the lower end of estimated FeO (≤0.05 wt%) supports CB chondrite‐like bulk compositions of Mercury with core Si abundances in the range of 5–18.5 wt% and C abundances in the range of 0.8–4.0 wt%.

Geochronology, Oxidization State and Source of the Daocheng Batholith, Yidun Arc: Implications for Regional Metallogenesis

The Daocheng batholith consists of granite, granodiorite and K-feldspar megacrystic granite, which is located in the north Yidun Arc. It is a barren batholith in contrast to plutons of the same age that contain major copper deposits, such as Pulang to the south. In the Daocheng, abundant mafic microgranular enclaves (MMEs) mainly developed within granodiorite and K-feldspar megacrystic granite, which are characterized by quenched apatite, quartz eyes and plagioclase phenocrysts. LA-ICP-MS zircon U–Pb dating of host granodiorite yielded ages ranging from 223 Ma to 210 Ma, with a weighted mean of 215.3 ± 1.8 Ma. Zircons from MMEs yielded ages ranging from 218 Ma to 209 Ma, with a weighted mean of 214.2 ± 1.4 Ma. Geochemical analyses show that granodiorite is high-K, calc-alkaline and I-type, with SiO2 contents ranging from 67.90% to 70.54%. These rocks are metaluminous to marginally peraluminous (A/CNK = 0.98–1.00) and moderately rich in alkalis with K2O ranging from 3.28% to 4.59% and Na2O ranging from 3.18% to 3.20%, with low MgO (1.08%–1.29%), Cr (12.7 ppm–16.8 ppm), Ni (5.19 ppm–6.16 ppm) and Mg# (35–49). The MMEs have relatively low SiO2 contents (56.34%–60.91%), higher Al2O3 contents (16.06%–17.98%), higher MgO and FeO abundances and are metaluminous (A/CNK = 0.82–0.83). The MMEs and host granodiorite are enriched in light rare-earth elements (LREEs) relative to heavy rare-earth elements (HREEs), with slightly negative Eu anomalies, and enriched in Th, U and large ion lithophile elements (LILEs; e.g., K, Rb and Pb), and depleted in high field strength elements (HFSEs; e.g., Nb, Ta, P and Ti), showing affinities typical of arc magmas. The zircon εHf(t) values (−6.28 to −2.33) and ancient two-stage Hf model ages of 1.92 to 1.25 Ga, indicating that the magmas are generally melts that incorporated significant portions of Precambrian crust. The relatively low silica contents and high Mg# values of the MMEs, and the linear patterns of MgO, Al2O3 and Fe2O3 with SiO2 between the MMEs and host granodiorite, showing the formation of MMEs are genetically related to magma mixing. The Daocheng granodiorite is characterized by much lower zircon Ce4+/Ce3+ (average of 3.53) and low fO2 value (average of ∆FMQ = –10.84), whereas the ore-bearing quartz monzonite porphyries in the Pulang copper deposit are characterized by much higher zircon Ce4+/Ce3+ (average of 52.10) and high fO2 value (average of ∆FMQ = 2.8), indicating the ore-bearing porphyry intrusions had much higher fO2 of magma than the ore-barren intrusions considering that the high oxygen fugacity of the magma is conducive to mineralization.

Retrieving volume FeO and TiO2 abundances of lunar regolith with CE-2 CELMS data using BPNN method**A contributed paper of the International Symposium on Lunar and Planetary Science (ISLPS) on 2018 June 12–15 at Macau University of Science and Technology.

The volume FeO and TiO2 abundances (FTAs) of lunar regolith can be more important for understanding the geological evolution of the Moon compared to the optical and gamma-ray results. In this paper, the volume FTAs are retrieved with microwave sounder (CELMS) data from the Chang’E-2 satellite using the back propagation neural network (BPNN) method. Firstly, a three-layered BPNN network with five-dimensional input is constructed by taking nonlinearity into account. Then, the brightness temperature (TB) and surface slope are set as the inputs and the volume FTAs are set as the outputs of the BPNN network. Thereafter, the BPNN network is trained with the corresponding parameters collected from Apollo, Luna, and Surveyor missions. Finally, the volume FTAs are retrieved with the trained BPNN network using the four-channel TB derived from the CELMS data and the surface slope estimated from Lunar Orbiter Laser Altimeter (LOLA) data. The rationality of the retrieved FTAs is verified by comparing with the Clementine UV-VIS results and Lunar Prospector (LP) GRS results. The retrieved volume FTAs enable us to re-evaluate the geological features of the lunar surface. Several important results are as follows. Firstly, very-low-Ti (<1.5 wt.%) basalts are the most spatially abundant, and the surfaces with TiO2 > 5 wt.% constitute less than 10% of the maria. Also, two linear relationships occur between the FeO abundance (FA) and the TiO2 abundance before and after the threshold, 16 wt.% for FA. Secondly, a new perspective on mare volcanism is derived with the volume FTAs in several important mare basins, although this conclusion should be verified with more sources of data. Thirdly, FTAs in the lunar regolith change with depth to the uppermost surface, and the change is complex over the lunar surface. Finally, the distribution of volume FTAs hints that the highlands crust is probably homogeneous, at least in terms of the microwave thermophysical parameters.