Evidence for explosive silicic volcanism on the Moon from the extended distribution of thorium near the Compton-Belkovich Volcanic Complex

IntroductionThe Chang&#8217;e-5 (CE-5) mission is China&#8217;s first lunar sample return mission. CE-5 landed at Northern Oceanus Procellarum (43.1&#176;N, 51.8&#176;W) on December 1, 2020, collected 1731 g of lunar samples, and returned to the Earth on December 17, 2020. The CE-5 landing site is ~170 km ENE of Mons R&#252;mker [1], characterized by some of the youngest mare basalts (Em4/P58) on the Moon [2,3], which are never sampled by the Apollo or Luna missions [4]. This study describes the geologic background of the CE-5 landing site in order to provide context for the ongoing sample analysis.Northern Oceanus ProcellarumNorthern Oceanus Procellarum is in the northwest lunar nearside, and the center of the Procellarum-KREEP-Terrane [5], characterized by elevated heat-producing elements and prolonged volcanism. This region exhibits a huge volcanic complex, i.e., Mons R&#252;mker [1], and two episodes of mare eruptions, i.e., Imbrian-aged low-Ti mare basalts in the west and Eratosthenian-aged high-Ti mare basalts (Em3 and Em4/P58) in the east [2]. The longest sinuous rille on the Moon [6], Rima Sharp, extends across Em4/P58. Both the Imbrian-aged (NW-SE) and Eratosthenian-aged (NE-SW) basalts display wrinkle ridges, indicating underlying structures, with different dominant orientations [2].Young Mare BasaltsThe Em4/P58 mare basaltic unit, on which CE-5 landed, is one of the youngest mare basalts on the Moon. Various researchers found different CSFD results; however, all of them point to an Eratosthenian age for Em4/P85 (1.21 Ga [2], 1.33 Ga [7,8], 1.53 Ga [3], 1.91 Ga [9]), and there are minor age variations across Em4/P58 [3]. Em4/P58 mare basalts have high-Ti, relatively high-olivine and high-Th abundances, while clinopyroxene is the most abundant mineral type [2,3]. Em4/P58 mare basalts cover an area of ~37,000 km2, with a mean thickness of ~51 m and volume of ~1450-2350 km3 [3]. No specific source vents were found within the unit, and Rima Sharp is the most likely source region for the Em4/P58 mare basalts [3].Scientific Significance of the Returned SamplesThe scientific significance of the young mare basalts is summarized in our previous studies [2,3]. In [3], we first summarized the 27 fundamental questions that may be answered by the returned CE-5 samples, including questions about chronology, petrogenesis, regional setting, geodynamic & thermal evolution, and regolith formation (Tab. 1 in [3]), especially calibrating the lunar chronology function, constraining the lunar dynamo status, unraveling the deep mantle properties, and assessing the Procellarum-KREEP-Terrain structures.References[1] Zhao J. et al. (2017) JGR, 122, 1419&#8211;1442. [2] Qian Y. et al (2018) JGR, 123, 1407&#8211;1430. [3] Qian Y. et al. (2021) EPSL, 555, 116702. [4] Tart&#232;se R. et al. (2019) Space Sci. Rev., 215, 54. [5] Jolliff B. L. et al. (2000) JGR, 105, 4197&#8211;4216. [6] Hurwitz D. M. et al. (2013) Planet. Space Sci., 79&#8211;80, 1&#8211;38. [7] Hiesinger H. et al. (2003) JGR, 108, 1&#8211;1 (2003). [8] Hiesinger H. et al. (2011) Geol. Soc. Am., 477, 1&#8211;51. [9] Morota T. et al. (2011) EPSL, 302, 255&#8211;266.

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Geologic Interpretation of the Study of Lunar Rocks

Symposium - International Astronomical Union ◽

10.1017/s0074180900097576 ◽

1972 ◽

Vol 47 ◽

pp. 231-245

Author(s):

Lubomír Kopecký

Keyword(s):

Temperature Interval ◽

Central Peak ◽

Volcanic Complex ◽

The Moon ◽

Tectonic Structure ◽

Central Type ◽

North Eastern ◽

Lunar Rocks ◽

Geologic Interpretation ◽

Basic Rocks

The hypothesis on an internal origin of lunar rocks of gabbroic type is supported by experimental petrologic data obtained by the author. The temperature interval of their crystallization from a dry silicate melt is given.Lunar gabbroic rocks of the Tranquillity Base are compared with paleobasalts of north-eastern Bohemia, eucrites and associated rocks of the British Isles and meteoritic eucrites of poikilophitic texture.The metasomatic origin of lunar anorthosites displaying a mosaic texture in deeper parts of the volcanic apparatus is postulated.An analogy is thought to exist between the Tertiary volcanic areas of Mull, Ardnamurchan and Rum in Scotland and the Ptolemaeus, Alphonsus and Arzachel regions of the Moon in the overall tectonic structure and the development of tectono-volcanic cirques. By analogy the possibility of the presence of more basic rocks in the rim and on the floor of the Moon subsidence calderas and of more acidic rocks of anorthositic to trachyandesitic chemistry in the central peak is presumed.The mode of origin of double-craters of Cyrillus-Theophilus type is suggested to be similar to the origin of two consecutive volcanic rings of Mull.The ring- and radial complexes of wrinkle ridges of Lamont type are compared with cone sheets and radial dykes of the central type tectono-volcanic complex of Mull.

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Compton–Belkovich Volcanic Complex (CBVC): An ash flow caldera on the Moon

Icarus ◽

10.1016/j.icarus.2015.02.024 ◽

2015 ◽

Vol 253 ◽

pp. 115-129 ◽

Cited By ~ 9

Author(s):

M. Chauhan ◽

S. Bhattacharya ◽

S. Saran ◽

P. Chauhan ◽

A. Dagar

Keyword(s):

Volcanic Complex ◽

The Moon

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Evidences for Bimodal volcanism on 4-Vesta Asteroid from impact-melt clast

10.5194/epsc2020-548 ◽

2020 ◽

Author(s):

Dwijesh Ray ◽

Sambhunath Ghosh

Keyword(s):

Melt Inclusions ◽

Bulk Composition ◽

Parent Body ◽

Total Iron ◽

Volcanic Complex ◽

Element Geochemistry ◽

Silicic Volcanism ◽

Impact Melt ◽

Acid Volcanism ◽

The Impact

Silicic / acid volcanism has not been widely described either on Moon, Mars or in Asteroid 4 Vesta. The occurrence of sialic crustal rocks on the lunar surface is extremely limited. Reports on silicic (non-mare) volcanic rocks on Moon is found to be associated in Compton-Belkovich volcanic complex, Hansteen Alpha volcanic crater, Lassell massif, Gruithuisen domes and ejecta of Aristarchus crater (Clegg-Watkins et al., 2017). The occurrence of several volcanic constructs (e.g. collapse features, domes) and volatile-rich pyroclastics in association with silicic rocks further emphasize existence of viscous magmas on Moon. A localized occurrence of silicic volcanism on Mars is also envisaged by the presence of tridymite in mudstone of Gale crater (Morris et al., 2016). However, the exact formation mechanism of silicic volcanism on Moon, Mars or even in 4-Vesta has been largely hindered due to lack of silicic meteorite samples or mission-returned samples. The HED (Howardite, Eucrite, Diogenite) meteorites is considered to have originated from a common parent body Asteroid 4-Vesta. Recent Dawn mission also attempts to validate its geologic context and formulate a possible HED-Vesta connection (McSween et al., 2013). Based on Dawn findings, Vesta&#8217;s surface appears to be similar to a mixture of basaltic eucrite and diogenite resembling a more complex breccia howardite (De Sanctis et al., 2012; Prettyman et al., 2012). A variety of clasts are apparently common in howardite. Here, we report the petrography and major element geochemistry of a new impact-melt clast from Lohawat howardite. Our results show that the clast composition is unique and unlikely to be explained by typical impact melting of HED mafic lithologies. One of the impact melts (~20&#181; across) hosted in ferroaugite (Wo42En2.7Fs55.3) clast substantially differ in composition from the other impact-melt (~50&#181; across) hosted in ilmenite clast, specially in terms of SiO2 wt%, CaO wt%, K2O wt% and K2O / (K2O + Na2O) ratio. Moreover, one appears nearly homogeneous in contrast to evolved nature with limited heterogeneity as compared to other. Both the melts are oblong-shaped, smooth textured with sharp outline and embedded in the host monomict mineral clast of different composition belonging to possible parent of cumulate eucrite. The average bulk composition of Lohawat is consistent with basaltic crusts (SiO2 ~50.3-51.8 wt%, Al2O3 ~3.5-8.2 wt%, total iron-magnesia ~31.2-38.0 wt%, CaO ~2.2-7.6 wt%) (Chattopadhyay et al. 1998; Sisodia et al. 2001; Ghosh, 2011). Supplement to basaltic volcanism, we report for the first time the incipient acid volcanism in a HED meteorite based on two impact melt inclusions of nearly rhyolitic composition (SiO2 ~76-79.5 wt%, Al2O3 ~11.4 - 12.8 wt%, total alkali ~3 - 8 wt% with K2O/ (Na2O + K2O) ~0.21-0.95, CaO ~ 0.8 - 4.67wt% and low total iron-magnesia ~1-2 wt%). Our study thus reinforces to conceive the idea that some rhyolitic crusts formed due to differentiation of mafic magma were exposed on Vesta and heterogeneity of Vestan surface is definitely different from one as previously thought. References: Clegg-Watkins, R.N. et al. 2016, Icarus 285:169-184. Morris, R.V. et al. 2016, 113:7071-7076. McSween, H.Y. et al. 2013, MAPS 48:2090-2104. De Sanctis, M.C. et al. 2012, Science 336:697-700. Prettyman, T.H. et al. 2012, Science 338:242-246. Chattopadhyay, B. et al. 1998. JGSI 51:171-174. Sisodia, M.S. et al. 2001 MAPS 36:1457-1466. Ghosh, S. IJG 65:251-264.

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