Rift and plume: a discussion on active and passive rifting mechanisms in the Afro-Arabian rift based on synthesis of geophysical data

Issachar, Ran; Haas, Peter; Augustin, Nico; Ebbing, Jörg

doi:https://doi.org/10.5194/egusphere-2023-2467

Preprints

https://doi.org/10.5194/egusphere-2023-2467

Preprints

06 Nov 2023

| 06 Nov 2023

Status: this preprint is open for discussion.

Rift and plume: a discussion on active and passive rifting mechanisms in the Afro-Arabian rift based on synthesis of geophysical data

Ran Issachar, Peter Haas, Nico Augustin, and Jörg Ebbing

Abstract. The causal relationship between the activity of mantle plumes and continental break-up is still elusive. The Afro-Arabian rift system offers an opportunity to examine these relationship, in which an ongoing continental break-up intersects a large Cenozoic plume related flood basalt series. In the Afar region, the Gulf of Aden, the Red-Sea and the Main Ethiopian Rift form an R-R-R triple junction and separate the Ethiopian and Yemen Traps by ~600 km. We provide an up-to-date synthesis of the available geophysical and geological data from this region. We map the rift architecture in the intersection region of the rifts and review the spatio-temporal constraints in the development of the different features of the plume‐rift system.

We infer two spatial constraints in the development of the rifts: (1) the connection of the Main Ethiopian Rift to the Gulf of Aden and to the Red Sea by its northeastward propagation; (2) the abandonment of an early tectonic connection between the Red Sea and the Gulf of Aden. Additionally, chronological evidence suggests that regional uplift and flood basalt eruptions sufficiently preceded rifting. By this, we infer a progressive development in which the onset of the triple junction marks a tectonic reorganization and was the last feature to develop, after all rift arms were thoroughly developed. We argue that the classical active and passive rifting mechanisms cannot simply explain the progressive development of the Afro-Arabian rift and propose a scenario of plume-induced plate rotation that includes an interaction between active and passive mechanisms. In this scenario, the arrival of the Afar plume provided a push-force that promoted the rotation of Arabia around a nearby pole, enabling rifting and ultimately the break-up of Arabia from Africa.

Received: 24 Oct 2023 – Discussion started: 06 Nov 2023

Download & links

Ran Issachar et al.

Status: open (until 20 Dec 2023)

Post a comment Subscribe to comment alert

CC1:
'Comment on egusphere-2023-2467', Valentin Rime, 29 Nov 2023 reply
Dear authors, reviewers and editors,
As I recently worked on exactly the same topic as some parts of the present paper, namely the rift architecture and synthesis of geological history of the Afar Region (Rime et al., 2023), I hope I can bring some useful comment on this manuscript.
One important focus of the present paper is the discussion of the influence of plume on rifting (in particular triple junctions) and vice and versa (active vs. passive rifting). I think that the scenario of plume-induced rotation is interesting and plausible, but I will focus my comments on the structure and history of the Afar Region as my expertise rather lies in this part.
One of the pitfalls of this manuscript is the lack of consideration of geological data and overreliance and overinterpretation of geophysical data. For the onshore part of the Region, many geological data are available (see reference list in Rime et al., 2023) but have been overlooked in this manuscript.
This is mainly seen in fig. 11 which maps “axial segments” with black lines. As the term “axial segments” has not been defined, I’m not 100% sure what was meant, but I assume it is roughly similar to what we name “rift segment” in our paper, i.e. continuous strain accommodating areas testified by faulting and, in some cases, magmatic activity and/or formation of sedimentary basin. In our paper, we have studied the structure of the Afar Region with the same methods as this manuscript (topography, seismicity, BGA and VGG), but we have combined them with lots of surface geological data from several hundreds of references, and we came out with quite different results.
The lines represented on fig. 11 in fact represent geophysical lineations that do not necessarily represent an axial segment. Geophysical lineaments are good tools in the absence of access to the geology (e.g. Augustin et al., 2021) but in this complex area, the surface or near-surface geology, as well as other geological data need to be taken into account.
I attached a version of this figure with colours and number to be able to discuss individual mapped axial segments:
This axial segment is cross-cutting magnetic anomalies (Fournier et al., 2010) and it is barely plausible to have an axial segment cross-cutting oceanic crust there. It was apparently traced based on BGA data (fig. 8) but on the same figure (taking into account the obliquity of extension), you see an almost perfect symmetry between both side of the MOR on all dataset (topography, VGG and BGA), I thus don’t see why it is interpreted as an axial segment.

This axial segment was mapped based on VGG (fig. 10) but only represent a limit between the sediment-filled Western Guban Basin and the Ali Sabieh Block, with occurrence of shallow basement and volcanic cover (Le Gall et al., 2015; Ali, 2015; Rime et al., 2022b, 2022a, 2023). It therefore does not represent an axial segment but a boundary between two geological regions with different characteristics.

Idem but for the western margin of the Ali Sabieh Block. It just represents the limit between shallow basement with relatively thin volcanic cover on the Ali Sabieh Block and deep, massively intruded basement and thick volcanic cover in the Depression sensu stricto.

This line (we don’t know from which data it is interpreted) is incompatible with surface data. It cross-cut all structures visible on the surface that are active since the Pliocene (look at fault pattern on our map (Rime et al., 2022a) or any other map of the Depression or just Google Earth).

This line was mapped based on VGG data (fig. 10) but this lineament just represents the combination of a topographic low and the presence of a low-density sedimentary basin. The axial segments in the southern Danakil Depression are marked by the volcanic ranges and not by the sedimentary basins (Barberi et al., 1970, 1972; Barberi and Varet, 1970; Tazieff et al., 1972; Le Gall et al., 2018; Watts et al., 2020; Schaegis et al., 2021; Rime et al., 2023).

This axial segment is not curved. It represents two different overlapping segments (the Erta Ale and the Tat’Ali segments in our publication) but both are straights. In the north, the rift axis continues straight into the salt plain (Bastow et al., 2018; Schaegis et al., 2021; Hurman et al., 2023; Rime et al., 2023). Further north, there is indeed a puzzling link between the Danakil Depression and the Howlakil Bay visible on BGA data but surface geology and other geophysical data strongly suggests that the axial segment continues towards the Gulf of Zula until jumping west of the Mt. Ghedem (Viltres et al., 2020; Ruch et al., 2021; Rime et al., 2023).

This line connects several different geological features but does not represent a continuous axial segment. The southernmost part of the line represents Teru Graben (which we classify as a rift segment) but then it jumps to the western sedimentary basin of the Erta Ale (like for comment on line 5, this is not an axial segment) before finally jumping to the sedimentary basin forming the rift axis in the northern part of the Danakil Depression.

These are the main problems I see on this figure, but other lines are also questionable, and some axial segments presented in the literature could be added (Hammond et al., 2011; Rime et al., 2023).

Comments on Section 7.2: Spatial constraints in the development of the plume-rift system:
While initially presented as spatial constraints, the two tectonic events described (MER connection with the Gulf of Aden / Red Sea system and the abandonment of the Bab-el-Mandeb segment) are then suddenly considered in line 424 (and lines 402-404 indirectly) as a temporal constrain where the former happens after the latter. There is no argumentation in the text for this change between two spatially separated tectonic events and two temporally separated events. We have discussed these events in our paper (section 6) and, based on numerous geological constrains, we show that they happen roughly at the same time. If your interpretation is different, it should be explained.
I also see confusion regarding margin curvature. For a margin to be curved clockwise or counterclockwise, you have to define a direction in which you observe it. E.g., the somalian margin is curved clockwise if considered from E to W but counterclockwise if considered from W to E. As such, the comparison between margin curvature and block rotation is sketchy. I don’t believe that the curvature of the Ethiopian margin (if you mean the curvature between approx. 9°N and 14°N) is linked with the rotation of the Danakil Block but rather with the linkage between the MER and the Gulf of Aden / Red Sea / Afar Rift System.

Other comments:
Line 251-254: Not completely true. You find pre-rift trap basalts in the Depression and Late Miocene and younger (so syn-rift) lavas on the plateaus (e.g. Rime et al., 2022).

Lines 340-341: Keep also in mind that there is a microcontinent in between: the Arrata or Danakil Microplate and that the rotation of this microplate is the reason why the structure are not all aligned (Zwaan et al., 2020).

Lines 341-352: This is why we propose that the Red Sea Rift and Afar Rift are distinct. See discussion on the topic with references to the literature in section 5 of our paper.

Line 363-365: They are many papers discussing this, and it’s probably not bad to cite a few more (Tazieff et al., 1972; Barberi and Varet, 1977; Acton et al., 1991; Manighetti et al., 2001; Eagles et al., 2002; Audin et al., 2004; Kogan et al., 2012; Pagli et al., 2014; Doubre et al., 2017; Moore et al., 2021; Rime et al., 2023).

On northward propagation of the MER: this a controversial issue and the literature is not conclusive. See section 5.2.1 of our paper for reference list on the topic.

The conclusion that the Afar does not conform to a typical R-R-R triple junction with rift propagating away from the triple junction was already discussed in several papers (Mohr, 1970, 1972; Girdler, 1991; Manighetti et al., 1997; Hébert et al., 2001; Wolfenden et al., 2004; Purcell, 2018; Khalil et al., 2020; Maestrelli et al., 2022; Rime et al., 2023). It’s probably not bad to mention it.

It is mentioned several times in the manuscript that the margins of the MER are smooth, continuous and the axial ranges are parallel to the margins (e.g. line 330-331). This is only partly true. The volcanic segments of the MER are en-échellon compared to the margins and thus not completely continuous and parallel (see Corti, 2009 and numerous publications by this author).

Line 396: Numerous evidence suggest that this rotation started around 10 Ma ago (Eagles et al., 2002; McClusky et al., 2010; Reilinger and McClusky, 2011; Rime et al., 2023).

Line 393: The authors of the mentioned paper say that “the channel most likely does not have a tectonic origin”. The most likely explanation is a massive inflow event. If a hypothetical graben would be active now, it would contradict your idea that this connection is inactive. If it was inactive since the Late Miocene, there was plenty of time (and sediments) to fill it. However, I don’t discuss the fact that the Mab-el-Mandeb is an abandoned rift segment. See also the geological evidence from other references cited in our paper (sections 4.3.1 and 4.6).

Figure 1: It’s strange to have a lot of emerged land coloured in blue.

Figure 3: The Shurka el Sheik Discontinuity is not indicated in the correct place. It should be further W (like on fig. 6).

Overall, I think that the manuscript should be at least corrected regarding the position of the axial segments and some interpretation toned down, removed or better justified, in particular for the temporal relationship between the two events described in section 7.2. Finally, a more thorough literature review would have been useful. Several points raised and discussed in this manuscript were already discussed in the literature since decades and these studies should be mentioned.

Best regards,

Valentin Rime

References
Acton, G.D., Stein, S., and Engeln, J.F., 1991, Block rotation and continental extension in Afar: A comparison to oceanic microplate systems: Tectonics, v. 10, p. 501–526, doi:10.1029/90TC01792.
Ali, M.Y., 2015, Petroleum geology and hydrocarbon potential of the Guban Basin, Northern Somaliland: Journal of Petroleum Geology, v. 38, p. 433–457, doi:10.1111/jpg.12620.
Audin, L., Quidelleur, X., Coulié, E., Courtillot, V., Gilder, S., Manighetti, I., Gillot, P.-Y., Tapponnier, P., and Kidane, T., 2004, Palaeomagnetism and K-Ar and ⁴⁰ Ar/ ³⁹ Ar ages in the Ali Sabieh area (Republic of Djibouti and Ethiopia): constraints on the mechanism of Aden ridge propagation into southeastern Afar during the last 10 Myr: Geophysical Journal International, v. 158, p. 327–345, doi:10.1111/j.1365-246X.2004.02286.x.
Augustin, N., van der Zwan, F.M., Devey, C.W., and Brandsdóttir, B., 2021, 13 million years of seafloor spreading throughout the Red Sea Basin: Nature Communications, v. 12, p. 2427, doi:10.1038/s41467-021-22586-2.
Barberi, F., Borsi, S., Ferrara, G., Marinelli, G., and Varet, J., 1970, Relations between tectonics and magmatology in the northern Danakil Depression (Ethiopia): Philosophical Transactions of the Royal Society of London, v. 267, p. 293–311, doi:10.1098/rsta.1970.0037.
Barberi, F., Tazieff, H., and Varet, J., 1972, Volcanism in the Afar Depression: its tectonic and magmatic significance: Tectonophysics, v. 15, p. 19–29, doi:10.1016/B978-0-444-41087-0.50007-5.
Barberi, F., and Varet, J., 1970, The Erta Ale volcanic range (Danakil depression, northern afar, ethiopia): Bulletin Volcanologique, v. 34, p. 848–917, doi:10.1007/BF02596805.
Barberi, F., and Varet, J., 1977, Volcanism of Afar: Small-scale plate tectonics implications: Geological Society of America Bulletin, v. 88, p. 1251–1266, doi:https://doi.org/10.1130/0016-7606(1977)88<1251:VOASPT>2.0.CO;2.
Bastow, I.D., Booth, A.D., Corti, G., Keir, D., Magee, C., Jackson, C.A.-L., Warren, J., Wilkinson, J., and Lascialfari, M., 2018, The Development of Late-Stage Continental Breakup: Seismic Reflection and Borehole Evidence from the Danakil Depression, Ethiopia: Tectonics, v. 37, p. 2848–2862, doi:10.1029/2017TC004798.
Corti, G., 2009, Continental rift evolution: From rift initiation to incipient break-up in the Main Ethiopian Rift, East Africa: Earth-Science Reviews, v. 96, p. 1–53, doi:10.1016/J.EARSCIREV.2009.06.005.
Doubre, C. et al., 2017, Current deformation in Central Afar and triple junction kinematics deduced from GPS and InSAR measurements: Geophysical Journal International, v. 208, p. 936–953, doi:10.1093/gji/ggw434.
Eagles, G., Gloaguen, R., and Ebinger, C., 2002, Kinematics of the Danakil microplate: Earth and Planetary Science Letters, v. 203, p. 607–620, doi:10.1016/S0012-821X(02)00916-0.
Fournier, M. et al., 2010, Arabia-Somalia plate kinematics, evolution of the Aden-Owen-Carlsberg triple junction, and opening of the Gulf of Aden: Journal of Geophysical Research, v. 115, p. B04102, doi:10.1029/2008JB006257.
Le Gall, B., Daoud, M.A., Maury, R., Gasse, F., Rolet, J., Jalludin, M., Caminiti, A.-M., and Moussa, N., 2015, Carte géologique de la République de Djibouti: Centre d’Etude et de Recherche de Djibouti (CERD) and CCGM,.
Le Gall, B., Leleu, S., Pik, R., Jourdan, F., Chazot, G., Ayalew, D., Yirgu, G., Cloquet, C., and Chauvet, F., 2018, The Red Beds series in the Erta Ale segment, North Afar. Evidence for a 6 Ma-old post-rift basin prior to continental rupturing: Tectonophysics, v. 747–748, p. 373–389, doi:10.1016/j.tecto.2018.10.002.
Girdler, R.W., 1991, The Afro-Arabian rift system—an overview: Tectonophysics, v. 197, p. 139–153, doi:10.1016/0040-1951(91)90038-T.
Hammond, J.O.S., Kendall, J.-M., Stuart, G.W., Keir, D., Ebinger, C., Ayele, A., and Belachew, M., 2011, The nature of the crust beneath the Afar triple junction: Evidence from receiver functions: Geochemistry, Geophysics, Geosystems, v. 12, p. Q12004, doi:10.1029/2011GC003738.
Hébert, H., Deplus, C., Huchon, P., Khanbari, K., and Audin, L., 2001, Lithospheric structure of a nascent spreading ridge inferred from gravity data: The western Gulf of Aden: Journal of Geophysical Research: Solid Earth, v. 106, p. 26345–26363, doi:10.1029/2000JB900391.
Hurman, G.L., Keir, D., Bull, J.M., McNeill, L.C., Booth, A.D., and Bastow, I.D., 2023, Quantitative Analysis of Faulting in the Danakil Depression Rift of Afar: The Importance of Faulting in the Final Stages of Magma‐Rich Rifting: Tectonics, v. 42, doi:10.1029/2022TC007607.
Khalil, H.M., Capitanio, F.A., Betts, P.G., and Cruden, A.R., 2020, 3‐D Analog Modeling Constraints on Rifting in the Afar Region: Tectonics, v. 39, p. e2020TC006339, doi:10.1029/2020TC006339.
Kogan, L., Fisseha, S., Bendick, R., Reilinger, R., McClusky, S., King, R., and Solomon, T., 2012, Lithospheric strength and strain localization in continental extension from observations of the East African Rift: Journal of Geophysical Research: Solid Earth, v. 117, p. B03402, doi:10.1029/2011JB008516.
Maestrelli, D., Brune, S., Corti, G., Keir, D., Muluneh, A.A., and Sani, F., 2022, Analog and Numerical Modeling of Rift‐Rift‐Rift Triple Junctions: Tectonics, v. 41, p. e2022TC007491, doi:10.1029/2022TC007491.
Manighetti, I., King, G.C.P., Gaudemer, Y., Scholz, C.H., and Doubre, C., 2001, Slip accumulation and lateral propagation of active normal faults in Afar: Journal of Geophysical Research: Solid Earth, v. 106, p. 13667–13696, doi:10.1029/2000JB900471.
Manighetti, I., Tapponnier, P., and Gillot, P.-Y., 1997, Propagation of rifling along the Arabia-Somalia plate boundary: The Gulfs of Aden and Tadjoura: Journal of Geophysical Research: Solid Earth, v. 102, p. 2681–2710, doi:10.1029/96JB01185.
McClusky, S. et al., 2010, Kinematics of the southern Red Sea-Afar Triple Junction and implications for plate dynamics: Geophysical Research Letters, v. 37, p. 1–5, doi:10.1029/2009GL041127.
Mohr, P.A., 1972, Surface structure and plate tectonics of Afar: Tectonophysics, v. 15, p. 3–18, doi:10.1016/0040-1951(72)90045-5.
Mohr, P.A., 1970, The Afar Triple Junction and sea-floor spreading: Journal of Geophysical Research, v. 75, p. 7340–7352, doi:10.1029/JB075i035p07340.
Moore, C., Wright, T.J., and Hooper, A., 2021, Rift Focusing and Magmatism During Late-Stage Rifting in Afar: Journal of Geophysical Research: Solid Earth, v. 126, p. e2020JB021542, doi:10.1029/2020JB021542.
Pagli, C., Wang, H., Wright, T.J., Calais, E., and Lewi, E., 2014, Current plate boundary deformation of the Afar rift from a 3-D velocity field inversion of InSAR and GPS: Journal of Geophysical Research: Solid Earth, v. 119, p. 8562–8575, doi:10.1002/2014JB011391.
Purcell, P.G., 2018, Re-imagining and re-imaging the development of the East African Rift: Petroleum Geoscience, v. 24, p. 21–40, doi:10.1144/petgeo2017-036.
Reilinger, R., and McClusky, S., 2011, Nubia-Arabia-Eurasia plate motions and the dynamics of Mediterranean and Middle East tectonics: Geophysical Journal International, v. 186, p. 971–979, doi:10.1111/j.1365-246X.2011.05133.x.
Rime, V., Foubert, A., Atnafu, B., and Kidane, T., 2022a, Geological map of the Afar Depression: Zenodo, doi:10.5281/zenodo.7351643.
Rime, V., Foubert, A., Atnafu, B., and Kidane, T., 2022b, Geological map of the southern Red Sea & western Gulf of Aden region: Zenodo, doi:10.5281/zenodo.7351765.
Rime, V., Foubert, A., Ruch, J., and Kidane, T., 2023, Tectonostratigraphic evolution and significance of the Afar Depression: Earth-Science Reviews, v. 244, p. 104519, doi:10.1016/j.earscirev.2023.104519.
Ruch, J., Keir, D., Passarelli, L., Di Giacomo, D., Ogubazghi, G., and Jónsson, S., 2021, Revealing 60 years of Earthquake Swarms in the Southern Red Sea, Afar and the Gulf of Aden: Frontiers in Earth Science, v. 9, p. 690, doi:10.3389/feart.2021.664673.
Schaegis, J.-C., Rime, V., Kidane, T., Mosar, J., Filfilu Gebru, E., Atnafu, B., and Foubert, A., 2021, Novel Bathymetry of Lake Afdera Reveals Fault Structures and Volcano-Tectonic Features of an Incipient Transform Zone (Afar, Ethiopia): Frontiers in Earth Science, v. 9, p. 1, doi:10.3389/feart.2021.706643.
Tazieff, H., Varet, J., Barberi, F., and Giglia, G., 1972, Tectonic significance of the Afar (or Danakil) depression: Nature, v. 235, p. 144–147, doi:10.1038/235144a0.
Viltres, R., Jónsson, S., Ruch, J., Doubre, C., Reilinger, R., Floyd, M., and Ogubazghi, G., 2020, Kinematics and deformation of the southern Red Sea region from GPS observations: Geophysical Journal International, v. 221, p. 2143–2154, doi:https://doi.org/10.1093/gji/ggaa109.
Watts, E.J., Gernon, T.M., Taylor, R.N., Keir, D., Siegburg, M., Jarman, J., Pagli, C., and Gioncada, A., 2020, Evolution of the Alu-Dalafilla and Borale volcanoes, Afar, Ethiopia: Journal of Volcanology and Geothermal Research, v. 408, p. 107094, doi:10.1016/j.jvolgeores.2020.107094.
Wolfenden, E., Ebinger, C., Yirgu, G., Deino, A., and Ayalew, D., 2004, Evolution of the northern Main Ethiopian rift: Birth of a triple junction: Earth and Planetary Science Letters, v. 224, p. 213–228, doi:10.1016/j.epsl.2004.04.022.
Zwaan, F., Corti, G., Sani, F., Keir, D., Muluneh, A.A., Illsley‐Kemp, F., and Papini, M., 2020, Structural Analysis of the Western Afar Margin, East Africa: Evidence for Multiphase Rotational Rifting: Tectonics, v. 39, p. e2019TC006043, doi:10.1029/2019TC006043.

Reply
Citation: https://doi.org/10.5194/egusphere-2023-2467-CC1

Ran Issachar et al.

Viewed

Total article views: 84 (including HTML, PDF, and XML)

HTML	PDF	XML	Total	BibTeX	EndNote
61	20	3	84	2	2

HTML: 61
PDF: 20
XML: 3
Total: 84
BibTeX: 2
EndNote: 2

Views and downloads (calculated since 06 Nov 2023)

Month	HTML	PDF	XML	Total
Nov 2023	61	20	3	84

Cumulative views and downloads (calculated since 06 Nov 2023)

Month	HTML	PDF	XML	Total
Nov 2023	61	20	3	84

Viewed (geographical distribution)

Total article views: 82 (including HTML, PDF, and XML) Thereof 82 with geography defined and 0 with unknown origin.

Country	#	Views	%

Latest update: 29 Nov 2023

Short summary

We explore the causal relationship between the arrival of the Afar plume and the initiation of the Afro-Arabian rift. We mapped the rift architecture in the triple junction region from geophysical data and reviewed the available geological temporal evidence. We infer a progressive development of the plume-rift system and suggest an interaction between active and passive mechanisms in which the plume provided a push-force that changed the kinematics of the associated plates.


Total:	0
HTML:	0
PDF:	0
XML:	0