![: Location of rift segments along NW end of Parga chasmata from [6]. Mb = Mbokomu Mons. Stars located corona, and for comparison with Figure 1, three are labelled: T = Tadaka, M = Maram and O = Onenhste coronae.](https://www.researchgate.net/profile/Naima-Hannour-2/publication/384633487/figure/fig2/AS:11431281281936889@1728063189180/Location-of-rift-segments-along-NW-end-of-Parga-chasmata-from-6-Mb-Mbokomu-Mons_Q320.jpg)
![A) Magellan SAR left look image of Cycle 1. B) Extensional lineaments; 6,650 mapped so far at 1:500,000 scale. Grouped into graben sets based on trend and geometry. C) Generalized mapping of grabens in the vicinity of Mbokomu Mons superimposed on SAR image. Stars locate multiple centres of radiating graben systems associated Mbokomu Mons. Note presence of circumferential set associated (purple) indicating a corona-like character associated with this Mons [9]. Number of additional linear and circumferential sets are present (see discussion in text). D) Lava flows and shield volcanoes.](https://www.researchgate.net/profile/Naima-Hannour-2/publication/384633487/figure/fig3/AS:11431281281936890@1728063189339/A-Magellan-SAR-left-look-image-of-Cycle-1-B-Extensional-lineaments-6-650-mapped-so_Q320.jpg)
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LAVA FLOWS AND GRABEN SYSTEMS (DYKE SWARMS) OF THE MBOKOMU MONS REGION
ALONG PARGA CHASMATA, SE FROM ATLA REGIO, VENUS. N. Hannour1, H. El Bilali2, R.E. Ernst2,
J.W. Head4, N. Youbi11Department of Geology, Faculty of Sciences-Semlalia, Cadi Ayyad University, Marrakesh,
Morocco; hannournaima83@gmail.com, youbi@uca.ac.ma, 2Department of Earth Sciences, Carleton University,
Ottawa, Ontario, Canada; hafidaelbilali@cunet.carleton.ca ; richard.ernst@ernstgeosciences.com, 4Department of
Earth, Environmental and Planetary Sciences, Brown Univerty, Providence, RI, USA.
Introduction: The relationship between chasmata
(rifts) and spatially associated volcanism (mons and
coronae) on Venus has been extensively discussed but
remains enigmatic (e.g. [1-6]). One such relevant re-
gion is along the 10,000 km long Parga Chasmata
which connects Atla Regio with Themis Regio, and we
have selected Mbokomu Mons area (located 2400 km
SE of Atla Regio) for detailed study We have complet-
ed detailed mapping (1:500,000 scale) of the graben
fissure systems, lava flows associated with Mbokomu
Mons and additional geological features such as wrin-
kle ridges and small shield volcanoes in the surround-
ing area. Our mapping builds on the previous recon-
naissance mapping (1:5,000,000 scale) of Taussig
Quadrangle (V–39) [7].
Methods : Geological mapping was carried out
using full-resolution (75m/pixel) Magellan SAR imag-
es and its altimetry data in ArcGIS v 10.6. In order to
enable more accurate and detailed interpretations, Java
Mission-Planning and Analysis for Remote Sensing
(JMARS) [8] and ArcScene (ArcMap v. 10.6) were
used to create topographic profiles and digital eleva-
tion models (DEMS), respectively. Geological units
are distinguished based on changes in radar brightness,
topography, morphology and stratigraphic relation-
ships.
Results : Detailed mapping of 11574 graben-
fissure systems associated with Mbokomu Mons and
the surrounding area reveals radiating, circumferential
and linear patterns. Graben-fissures are grouped into
separate systems with specific geometric patterns radi-
al, linear, or circumferential that reflect the propaga-
tion of underlying dyke swarms, and are often found in
spatial association with magmatic centres [9]. Mapping
of these allow us to identify four magmatic aligned
centers within Mbokomu Mons as potential sources for
these swarms. From our mapping in the summit region
the area has a rather overall high radar brightness due
to intensive emplacement of grabens. Normal faults
associated are locating rift zone segment.
Voluminous volcanism is also associated with
Mbokomu Mons, and is mapped in detail (4974 poly-
gons were mapped), and where possible their sources
were identified. Most of the lavas flow radially
downslope away from the summit, and appear to ema-
nate from the specific multiple centers (identified by
the radiating dykes) on the summit, but some flows
may be linked to specific large grabens (dykes) located
on the flanks of the main edifice. The set of flows that
are fed from multiple centers and large grabens are cut
by a system of arcuate grabens in the western sector
which postdate the Mons evolution. Efforts continue
to distinguish and assess the relationships between
dyke-induced graben, and those fractures and graben
of tectonic origin (e.g. rift faults).
Acknowledgments: Magellan SAR images obtained
from https://astrogeology.usgs.gov/search/?pmi-
target=venus based on the data from
https://pdsimaging.jpl.nasa.gov/volumes/magellan.htm
l#mgnFMAP
References: [1] Hamilton, V.E., Stofan, E.R.
(1996) Icarus, 121, 171–194. [2] Martin, P., Stofan,
E.R. (2004).35th LPSC, Abstract 1576. [3] Martin, P.,
et al. (2007) JGR, 112, E04S03. [4] Smrekar, S.E., et
al. (2010). JGR,115 No. E07010. [5] Ivanov, M.A.,
Head, J.W. (2015). Planet Space Sci., 113-114, 10-32.
[6] Graff J.R., et al.(2018). Icarus, 306, 122-138. [7]
Brian, A.W., et al. (2005). USGS SIM 2813. [8] Chris-
tensen, P.R et al. (2009). [9] Buchan, K.B and Ernst,
R.E. 2021 Gond. Res.,100, 25–43.
8045.pdfVenus Surface and Atmosphere 2023 (LPI Contrib. No. 2807)