Compton–Belkovich Volcanic Complex (CBVC): An ash flow caldera on the Moon
Introduction
Volcanoes are manifestation of a planet’s internal dynamics and are/were operational on several planetary bodies and their satellites such as Mars, Venus, Mercury, Moon and Io (Wilson, 2009, Prockter et al., 2010). The complex interactions between the rising magma and surrounding host rocks in the crust of a terrestrial planetary body is directly manifested by these volcanoes and their characteristic distribution and morphology provide a significant insight into their relationship with tectonism, style of eruption, chemistry and volatile content of the eruption products (Head and Wilson, 1986).
In the Moon’s geological history, after impact cratering, volcanism is the most dominant process which has modified its crust, and comprises primarily of basalts, occurring preferentially on its nearside (Head, 1975, Head and Wilson, 1992). Nearly all the lunar basalts are represented by vast lava flows that make up flat mare plains, with only a small fraction of the mare regions covered by positive topographic surface features, such as domes, cones, and shields of basaltic composition (Head and Gifford, 1980). Rock samples belonging to highly evolved composition could not be considered lacking on the Moon as clasts of granite, monzonite, felsites have been recorded during the returned Apollo missions (Rutherford and Hess, 1975, Rutherford and Hess, 1978, Rutherford et al., 1976, Ryerson and Hess, 1978, Ryder, 1976, Ryder and Martinez, 1991, Taylor et al., 1980, Warren et al., 1983, Warren et al., 1987, Jolliff, 1991, Jolliff et al., 1999, Seddio et al., 2013). This evolved silicic volcanism which is an SiO2-rich portion of the continuum extending from basaltic volcanism and characterized by its high viscosity and low mass diffusivity, forms thick, slow moving flows, domes and explosive eruptions (Eichelberger, 1995). Until early eighties no observations were made of silicic lavas on the Moon. Advances in remote sensing have provided evidence for the existence of silicic volcanic constructs on the Moon mostly in the form of a few non-mare domal features like Gruithuisen domes, Hansteen Alpha, Mairan T, Lassell Massif. They are termed as red spots and characterized by steep slopes, high-albedo and strong absorption in the ultraviolet relative to visible region (e.g. Malin, 1974, Wood and Head, 1975, Head and McCord, 1978, Chevrel et al., 1999, Hawke et al., 2003). Morphologically, these red spots show a much wider range and are surface manifestations of more viscous and highly evolved rocks such as terrestrial rhyolites and dacites (Bruno et al., 1991, Wilson and Head, 2003, Hawke et al., 2003, Glotch et al., 2011).
Compton–Belkovich Volcanic Complex (CBVC), comprising varied morphological features like domes, collapsed features, pyroclasts (Jolliff et al., 2011a, Jolliff et al., 2011b) is one such rare manifestation of evolved silicic magmatism (Jolliff et al., 2012) on the far side of the Moon. Its uniqueness lies in its being located in the highland or non-mare region of the Moon on the lunar far side, isolated from the Procellarum KREEP Terrane (PKT) where the other red spots are located. Recent reports of endogenic water at the CBVC (Bhattacharya et al., 2013a, Bhattacharya et al., 2013b, Petro et al., 2013) have further added to its uniqueness as well as curiosity to understand its geology.
The lack of plate tectonics on the Moon has facilitated the preservation of evidence of its early volcanic history, and the lack of an atmosphere, hydrosphere, and biosphere has precluded the effects of the main agents that alter the Earth’s surface. It, thus, provides an opportunity to better understand the morphological features on the Moon. Present study is a morphological and structural investigation of various volcanic features of the CBVC region, using high-resolution remote sensing data and their petrological implications to better understand silicic magmatism on the Moon.
Section snippets
Data used
For detailed morphological analysis, high-resolution Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) (Robinson et al., 2010) mosaic of the CBVC region having a spatial resolution of ∼2 m/pixel and LROC Wide Angle Camera (WAC) images from Lunar Reconnaissance Orbiter (LRO) (Robinson et al., 2010) mission have been used. The LROC-NAC provides up to 0.5 m/pixel panchromatic images over a 5 km swath and Wide Angle Camera (WAC) offers 100-m scale images in seven color bands over a
Observations from LROC data
Previous studies on morphological features of CBVC (Jolliff et al., 2011a, Jolliff et al., 2011b) provide an opportunity to examine in more detail the various volcanic landforms that originated and evolved over time at the studied site. CBVC lies ∼900 km from the North Pole on the lunar far side between 98.5 and 101.0°E longitude and 60.7 to 61.6°N latitude, situated between Belkovich and Compton craters to its northwest and southeast, respectively. Fig. 1 shows the location map of CBVC on the
Radar observations
Earth-based radar observations of the near side of the Moon at different wavelengths have revealed the distribution, depth, and embedded rock abundance at several pyroclastic deposits (e.g., Thompson et al., 1973, Zisk et al., 1974, Carter et al., 2009). Recent studies have reported low values of radar backscatter and Circular Polarization Ratio (CPR, average S-band CPR values in the range of 0.38 ± 0.23) within the CBVC region, presumably caused by fine-grained pyroclastic deposits mantling
Discussions
The lithology of Compton–Belkovich Volcanic Complex is compositionally evolved, having highly silicic nature of rhyolitic affinity (Greenhagen et al., 2010, Glotch et al., 2010, Gillis et al., 2002, Jolliff et al., 2011a, Jolliff et al., 2011b, Jolliff et al., 2012). Earlier morphological observations by Jolliff et al., 2011a, Jolliff et al., 2011b describes the area to be a volcanic complex with elevated topography, central caldera and mantled by a thick layer of fine-grained late-stage
Regional geology and shape of the caldera at the CBVC
The overall morphology of a volcanic area and location of its dome is affected by the regional tectonics of that area, which controls the geometry of the feeder dikes (Acocella and Mulugeta, 2002, Komuro, 1987, Ferguson et al., 1994). At CBVC, the whole unit of the West dome appears to be a compound structure formed from fissured lava flows. The trend of the ridges in the north and towards its eastern margin is mainly NW–SE and NNW–SSE. The two linear structural features parallel to the dome
Evolutionary model of CBVC
The magnitude and the style of volcanic eruptions on the Moon may not be the same as that on the Earth, but the basic principles remain same and the caldera formation process is more or less similar throughout the Solar System (Sanchez and Shcherbakov, 2012). The evolution of Compton–Belkovich volcanic complex can be understood by considering the morphological observations and its regional geology. Based on the silicic caldera formation stages described by various researchers (e.g. Scandone and
Area of silicic magmatic activity
The varied morphological features as observed at Compton–Belkovich volcanic complex are the manifestations of an evolved silicic magmatism (Jolliff et al., 2012) and its presence on the Moon implies that such features, though rare, are not completely absent on the Moon. Formation of such features may be related with the generation of heat source, development of a magma chamber, its differentiation, eruptions and collapse. CBVC, therefore, could be compared to a terrestrial volcanic hotspot or
Conclusions
The Compton–Belkovich volcanic complex being a localized extrusive silicic volcanic area on the Moon, expresses complex episodes of volcanism through time. The study of its various morphological and structural features suggests that the area is manifestation of silicic magmatism that has differentiated and evolved through time in episode of events to give rise to the present morphology. The elongations of domes indicate that the regional tectonic stresses related to earlier basin formation and
Acknowledgments
We express our sincere thanks to Shri. A.S. Kiran Kumar, Director, Space Applications Centre (SAC), Indian Space Research Organisation (ISRO), Ahmedabad for his constant support and encouragement. We are also thankful to Dr. P.K. Pal, Deputy Director, EPSA, SAC, ISRO for his guidance and support. Thanks are due to Prof. Brad Jolliff and an anonymous reviewer for their constructive comments and suggestions on the original manuscript.
References (109)
- et al.
Experiments on surface deformation induced by pluton emplacement
Tectonophysics
(2002) - et al.
The control of overburden thickness on resurgent domes: Insights from analogue models
J. Volcanol. Geotherm. Res.
(2001) - et al.
Chondrites as samples of differentiated planetesimals
Earth Planet. Sci. Lett.
(2011) - et al.
Geometrical and mechanical constraints on the formation of ring-fault calderas
Earth Planet. Sci. Lett.
(2004) - et al.
Remote sensing of lunar pyroclastic mantling deposits
Icarus
(1985) Compositional analyses of lunar pyroclastic deposits
Icarus
(2003)- et al.
Lunar mare volcanism: Stratigraphy, eruption conditions, and the evolution of secondary crusts
Geochim. Cosmochim. Acta
(1992) - et al.
Lunar graben formation due to near-surface deformation accompanying dike emplacement
Planet. Space Sci.
(1993) - et al.
Hotspots and melting anomalies
- et al.
Gas content, eruption rate and instabilities of eruption regime in silicic volcanoes
Earth Planet. Sci. Lett.
(1991)
Experiments on cauldron formation: A polygonal cauldron and ring fractures
J. Volcanol. Geotherm. Res.
Caldera subsidence in areas of variable topographic relief: Results from analogue modeling
J. Volcanol. Geotherm. Res.
Lunar red spots: Possible pre-mare materials
Earth Planet. Sci. Lett.
Caldera morphology in the western Galapagos and implications for volcano eruptive behaviour and mechanisms of caldera formation
J. Volcanol. Geotherm. Res.
The restless resurgent CampiFlegrei nested caldera (Italy): Constraints on its evolution and configuration
J. Volcanol. Geotherm. Res.
Caldera formation by magma withdrawal from a reservoir beneath a volcanic edifice
Earth Planet. Sci. Lett.
Lunar sample 15405: Remnant of a KREEP basalt-granite differentiated pluton
Earth Planet. Sci. Lett.
Implications of liquid–liquid distribution coefficients to mineral–liquid partitioning
Geochim. Cosmochim. Acta
Magma supply, magma discharge and readjustment of the feeding system of Mount St. Helens during 1980
J. Volcanol. Geotherm. Res.
The speciation of water in silicate melts
Geochim. Cosmochim. Acta
The Taupopumice: Product of the most powerful known (ultraplinian) eruption?
J. Volcanol. Geotherm. Res.
Petrology and chemistry of two ‘‘large’’ granite clasts from the Moon
Earth Planet. Sci. Lett.
Evaluating fracture patterns within a resurgent caldera: CampiFlegrei, Italy
Bull. Volcanol.
Elliptic calderas in the Ethiopian Rift: The control of pre-existing structures
J. Volcanol. Geotherm. Res.
Magma fragmentation by rapid decompression
Nature
Endogenic water on the Moon associated with the non-mare silicic volcanism: Implications for hydrated lunar interior
Curr. Sci.
Downsag and extension at calderas: New perspectives on collapse geometries from ice-melt, mining, and volcanic subsidence
Bull. Volcanol.
Radar Remote Sensing of Planetary Surfaces
Impact crater related surficial deposits on Venus: Multipolarization radar observations with Arecibo
J. Geophys. Res.
Radar remote sensing of pyroclastic deposits in the southern Mare Serenitatis and Mare Vaporum regions of the Moon
J. Geophys. Res.
Geologic studies of planetary surfaces using radar polarimetric imaging
Proc. IEEE
Gruithuisen domes region: A candidate for an extended nonmare volcanism unit on the Moon
J. Geophys. Res.
Silicic volcanism: Ascent of viscous magmas from crustal reservoirs
Annu. Rev. Earth Planet. Sci.
Magmatic volatiles in explosive rhyolitic eruptions
Geophys. Res. Lett.
A geophysical–geological transect of the Silent Canyon caldera complex, Pahute Mesa, Nevada
J. Geophys. Res.
Structure and emplacement of a rhyolitic obsidian flow: Little Glass Mountain, Medicine Lake Highland, northern California
Geol. Soc. Am. Bull.
Textural constraints on effusive silicic volcanism: Beyond the permeable foam model
J. Geophys. Res.
Mechanism of deposition from pyroclastic flows
Am. J. Sci.
Base-surge bed forms in maar volcanoes
Am. J. Sci.
Fragmentation of magma during plinian volcanic eruptions
Bull. Volcanol.
Highly silicic compositions on the Moon
Science
The Mairan domes: Silicic volcanic constructs on the Moon
Geophys. Res. Lett.
Global silicate mineralogy of the Moon from the diviner lunar radiometer
Science
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2017, IcarusCitation Excerpt :Radar is sensitive to the roughness of a surface, and pyroclastic deposits could show up as radar dark because they are both smooth and easily penetrated by radar waves (Chauhan et al., 2015). Chauhan et al. (2015) suggested that the pyroclastics formed during or after the collapse of the caldera and now mantle the floor of the CBVC. Some of the domes within the complex appear as radar-bright, providing further evidence that any pyroclastic deposits that may have been present on the top of these features have eroded away by mass wasting.
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2017, IcarusCitation Excerpt :Further research needs to be undertaken to establish whether the Procellarum Volcanic Complexes owe their origin to: a) very discrete and fertile mantle source regions, perhaps linked to the PKT, b) preservation by preferentially erupting onto pre-existing highland topography, c) the presence of shallow sills, or d) their occurrence in a shallow mare basin in contrast to the thicker mare fill in many other impact basins that would have buried such complexes. The very rare occurrence on the Moon of the morphologically and spectroscopically distinctive Gruithuisen (Fig. 32a) and Mairan domes in northeast Oceanus Procellarum (Head and McCord, 1978; Glotch et al., 2011; Kusuma et al., 2012; Ivanov et al., 2015) and the farside domes between the craters Belkovich and Compton (Jolliff et al., 2011; Chauhan et al., 2015) (Fig. 32b) implies the localized eruption of unusually viscous, probably rhyolitic (Wilson and Head, 2003b), magma. Wilson and Head (2016a), using the improved crustal density and thickness estimates from GRAIL, and the morphologies of the Gruithuisen and Mairan domes to infer the rheological properties, eruption rates and eruption durations, concluded that, in all cases, eruptions from reservoirs trapped at the base of the crust were thermally viable.
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2016, IcarusCitation Excerpt :This region is located within the lunar highlands, which are heavily cratered, and generally anorthositic in composition. The CBVC is characterized by high surface reflectance (Clegg et al., 2014, 2015), isolated high thorium and silica contents (Jolliff et al., 2011), and volcanic morphologies, such as cones, domes, and irregular depressions (Jolliff et al., 2011; Chauhan et al., 2015). The volcanism is of particular interest because it is not basaltic, but instead represents an evolved composition with high silica content (Glotch et al., 2010; Jolliff et al., 2011).