On alternative models for the origin of time-progressive volcanic chains

V. Puchkov, Institute of Geology, Ufimian Scientific Centre, Russia, puchkv@anrb.ru

The time-progressive character of some volcanic chains is well The time-progressive character of some volcanic chains is well known for decades and is proven with a different degree of known for decades and is proven with a different degree of reliability for many of them. The recent overviews of the primary reliability for many of them. The recent overviews of the primary data can be found in the papers of O'Neil et al. 2005, Clouard & data can be found in the papers of O'Neil et al. 2005, Clouard & Bonneville 2005, enhanced by additional information from Bonneville 2005, enhanced by additional information from many papers and booksmany papers and books ( (all references are in the poster). all references are in the poster).

The existence of such chains is a real challenge for anyone who works The existence of such chains is a real challenge for anyone who works at the problem of origin of melting anomalies.at the problem of origin of melting anomalies.

The above data were used by the author to compile a world scheme The above data were used by the author to compile a world scheme

of time-progressive chains.of time-progressive chains.

Alternative modelsAlternative modelsfor TPVC (time-progressive for TPVC (time-progressive volcanic chains)volcanic chains)

1. Plume model.1. Plume model. A standard plume and A standard plume and

plate concept of origin of plate concept of origin of TPVC at the example of TPVC at the example of the Emperor-Hawaii the Emperor-Hawaii ridge (Norton,2000)ridge (Norton,2000)

The model was first suggested by T.Wilson (1963) The model was first suggested by T.Wilson (1963) as a hypothesis of “hot spots”- surficial as a hypothesis of “hot spots”- surficial manifestations of immovable deep mantle manifestations of immovable deep mantle melting anomalies, the idea eveloped later by W. melting anomalies, the idea eveloped later by W. Morgan (1971)as a theory of plumes:convective Morgan (1971)as a theory of plumes:convective upwellings of a light hot mantle substance coming upwellings of a light hot mantle substance coming from the core-mantle boundary. It was a smart from the core-mantle boundary. It was a smart explanation, and still is, though the idea of an explanation, and still is, though the idea of an absolute horizontal immobility of plumes is absolute horizontal immobility of plumes is disproved now by paleomagnetic and geodetic disproved now by paleomagnetic and geodetic data (Antretter et al., 2002; Norton, 2000; O’Neill data (Antretter et al., 2002; Norton, 2000; O’Neill et al., 2005 & oth. ). The above-presented map is et al., 2005 & oth. ). The above-presented map is in a good accordance with this concept.in a good accordance with this concept.

Some TPVCs demonstrate more complicated progression of ages Some TPVCs demonstrate more complicated progression of ages compared to Hawaii (e.g. Galapagos, Canaries), where volcanoes, once compared to Hawaii (e.g. Galapagos, Canaries), where volcanoes, once lit, are slow to be extinct. But the model can be the same with an lit, are slow to be extinct. But the model can be the same with an admission that a plume is not necessarily head-and-tail or pillar-like.admission that a plume is not necessarily head-and-tail or pillar-like.

Galapagos (O’Connor et al.)

(Mazarovich, 2000)

The ITRF (International Terrestrial Reference The ITRF (International Terrestrial Reference Frame), 2005, Frame), 2005, http://http://itrf.ensg.ign.fritrf.ensg.ign.fr//, showing , showing vectors of the modern plate movements, is vectors of the modern plate movements, is also in a good conformity with the above also in a good conformity with the above model, though the direction of plate model, though the direction of plate movements changed in time, as it is movements changed in time, as it is demonstrated in the left cutoff.demonstrated in the left cutoff.

Note specially:Note specially: i. the normal character of TPVCs at the East i. the normal character of TPVCs at the East

Pacific;Pacific; ii. the oblique character of the chains relatively ii. the oblique character of the chains relatively

to the MOR in the Southern Atlantic, while they to the MOR in the Southern Atlantic, while they are subparallel to the vectors; are subparallel to the vectors;

iii. Cobb, Bowie and Yellostone chains are iii. Cobb, Bowie and Yellostone chains are oriented the same way as the vectors, oriented the same way as the vectors, notwithstanding the fact that they are situated notwithstanding the fact that they are situated at the different sides of the plate boundary; at the different sides of the plate boundary;

iv. Reunion and Kerguelen chains cross the MOR, iv. Reunion and Kerguelen chains cross the MOR, because the plates at both sides of the MOR because the plates at both sides of the MOR drift in the same direction.drift in the same direction.

It also cannot be a It also cannot be a coincidence that coincidence that the young (active the young (active or recently extinct or recently extinct volcanoes at the volcanoes at the ends of the chains ends of the chains sit over sit over superswellssuperswells..

Time-progressive volcanic chains of the world Сompiled by V.Puchkov, 2008

Time-progressive volcanic chain,the arrow indicates the age growth.Numbers - ages in Ma.Letters and bracketed numbers in italics - names and references.

The same,with the active or young (less that 1 Ma) volcanoat the end

A line connecting a single volcanic trail over an active plate margin

Currently or recently ridge-centered melting anomaly

Time-progressive volcanic pre-drift cracks

Contours of Pacific (I) and African-North Atlantic (II) superswells (LLVSPs) at CMB

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Superswells and LIPS [Burke,Torsvik, 2004]Superswells and LIPS [Burke,Torsvik, 2004]

Based on paleomag data, Based on paleomag data, these authors have these authors have shown that positions of shown that positions of LIPs (Large Igneous LIPs (Large Igneous Provinces) reconstructed Provinces) reconstructed to the time of their to the time of their eruptions are situated eruptions are situated within or at the edges of within or at the edges of two superswells at CMB, two superswells at CMB, with minor exceptions.with minor exceptions.

The background map shows the SMEAN shear-wave tomography model [Becker,Boschi 2002], which is based on an average of three global intermediate wavelength shear-wave tomography models. Note that δVs color contours are highlighting the red (slower speed) and blue (higher speed) regions.

We have shown in the We have shown in the previous slide, based on a previous slide, based on a different approach, that different approach, that active or shortly extinct active or shortly extinct volcanoes at the ends of volcanoes at the ends of time-progressive chains time-progressive chains follow the same patternfollow the same pattern

The later scheme of Burke et al (2008) shows also some hot spots (pink crosses). It manages better with the “exceptions”, connected with Columbia River anomaly, but still has difficulties with Afar hotspot. I shall try to explain it later.

2. Model of a Propagating crack of 2. Model of a Propagating crack of

lithosphere connected with cooling stresslithosphere connected with cooling stress

These forces, presumably These forces, presumably connected with cooling connected with cooling stress,stress, do not exist do not exist virtually (by themselves). virtually (by themselves). They are added They are added vectorially to much vectorially to much greater forces driving greater forces driving lithospheric plates (slab lithospheric plates (slab pull, mantle drag and pull, mantle drag and ridge push). The resulting ridge push). The resulting forces cannot produce forces cannot produce such effect.such effect.

Therefore the model Therefore the model contradicts the plate contradicts the plate tectonicstectonics

(Stuart, Foulger, Barall, 2007)

A generalized world stress mapA generalized world stress map based on the research in the frame of based on the research in the frame of LITHOSPHERE Program (Zoback et al., 1992)LITHOSPHERE Program (Zoback et al., 1992)

1- tension, 2 – compression with thrusting, 3 – compression with formation of 1- tension, 2 – compression with thrusting, 3 – compression with formation of diagonal wrench faults, 4 – plate boundaries, 5- trajectories of plate movementsdiagonal wrench faults, 4 – plate boundaries, 5- trajectories of plate movements

Lithgow-Bertelloni and Guynn,2004Lithgow-Bertelloni and Guynn,2004 Note a scale (greater by an order) Note a scale (greater by an order)

and stresses parallel to Hawaian and stresses parallel to Hawaian TPVCTPVC

Another objections.Another objections. 1. The propagation of time-progressive chains in all oceans 1. The propagation of time-progressive chains in all oceans

is organized as predicted by plume-and-plate tectonics. If is organized as predicted by plume-and-plate tectonics. If so, why do we need more explanations? so, why do we need more explanations? Occam's razor: Occam's razor: “entia non sunt multiplicanda praeter necessitatem", “entia non sunt multiplicanda praeter necessitatem", (”one should not increase, beyond what is necessary, the (”one should not increase, beyond what is necessary, the number of entities required to explain anything”). number of entities required to explain anything”).

2. Why the crack propagation is not affected by the 2. Why the crack propagation is not affected by the strongeststrongest anisotropy of oceanic, transitional and continental anisotropy of oceanic, transitional and continental lithosphere, lithosphere, crossed by many chains; crossed by many chains; 3. Why the Reunion, Kerguelen and New England-Great 3. Why the Reunion, Kerguelen and New England-Great Meteor Meteor TPVCs overrode the active MORs and after that co-TPVCs overrode the active MORs and after that co-existed with existed with them for some time;them for some time; 4. Why LIPs and TPVCs are correlated with 4. Why LIPs and TPVCs are correlated with superswells, superswells, as might be predicted by the plume theory;as might be predicted by the plume theory; 5. Why the “cracks” tapped fertile sources, producing 5. Why the “cracks” tapped fertile sources, producing OIBs, OIBs, while the MORs - depleted ones?while the MORs - depleted ones?

However However there are TPVCsthere are TPVCs called forth by plate called forth by plate tectonicstectonics

The propagating crack The propagating crack idea by itself is useful in idea by itself is useful in explanation of TPVCs explanation of TPVCs connected with time-connected with time-progressive graben progressive graben formation. In some cases formation. In some cases they preceded splitting they preceded splitting apart of the apart of the supercontiment and supercontiment and ocean floor spreading, in ocean floor spreading, in some they seem to some they seem to precede the future split-precede the future split-up of a lesser continent.up of a lesser continent.

In the TPVC world map In the TPVC world map presented in the next presented in the next slide such lineaments are slide such lineaments are shown tentatively in blue shown tentatively in blue colourcolour

To the left: a successionof a spreading onset in the Atlantic (Khain,2003)

To the right: stages To the right: stages of development of development of a prograding rift of a prograding rift (Martin, 1983)(Martin, 1983)

Filho et al.

3.The model of a drifting fertile “blob”3.The model of a drifting fertile “blob”Another alternative model is that of easily melting magma sources (pyroxenite “blobs”), drifting in an asthenosphere in the same direction as the overlying lithosphere, but quicker (Anderson, 2007).

The model, worked out in detail (Cuffaro, Doglioni, 2007 ), suits ad hoc the Pacific chains (except Easter and Galapagos where the orientation is opposite to predicted), but at a global scale it fails because it contradicts also to the behavior of time-progressive chains in the Eastern Atlantic and Indian oceans.

A comparison of the map of time-progressive volcanic chains,presented A comparison of the map of time-progressive volcanic chains,presented here , with the schemes explaining the model of Cuffaro and Doglioni here , with the schemes explaining the model of Cuffaro and Doglioni (2007) shows contradictions (the next slide). The idea of a uniformly (2007) shows contradictions (the next slide). The idea of a uniformly eastward-flowing mantle, with asthenosphere and lithosphere uniformly eastward-flowing mantle, with asthenosphere and lithosphere uniformly lagging behind, predicts the time succession directions for the chains of lagging behind, predicts the time succession directions for the chains of the SE Pacific, Indian and East Atlantic oceans as the SE Pacific, Indian and East Atlantic oceans as contrary to what is contrary to what is observedobserved. .

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Suggested vectors of plate movements Suggested mantle flow

The very idea of a pyroxenite “blob” (basic in The very idea of a pyroxenite “blob” (basic in composition) hanging in asthenosphere for many composition) hanging in asthenosphere for many tens of Ma, conflicts with the nature of tens of Ma, conflicts with the nature of asthenosphere, the latter demonstrating readily asthenosphere, the latter demonstrating readily the effects of Archimedes law. When situated the effects of Archimedes law. When situated deeper than 50 km, the “blob” exists as an deeper than 50 km, the “blob” exists as an eclogite which is much denser that the ambient eclogite which is much denser that the ambient peridotite and must sink, if not supported by a peridotite and must sink, if not supported by a plume upwelling or heated by it. When situated plume upwelling or heated by it. When situated higher than the phase transition zone, it turns higher than the phase transition zone, it turns into gabbro which is much lighter than the into gabbro which is much lighter than the peridotite and therefore must finally strike the peridotite and therefore must finally strike the bottom of lithosphere.bottom of lithosphere.

Nevertheless, the idea of pyroxenite as an easily melting Nevertheless, the idea of pyroxenite as an easily melting part of the Earth's mantle seems, by itself, part of the Earth's mantle seems, by itself, to be very promising. It really can be of a great benefit to be very promising. It really can be of a great benefit for the plate tectonic approach in explanation of shallow, for the plate tectonic approach in explanation of shallow, top-asthenospheric decompression-induced top-asthenospheric decompression-induced melting anomalies (Anderson, 2007, Foulger, 2007). melting anomalies (Anderson, 2007, Foulger, 2007). But it can be also extremely useful for the real plume But it can be also extremely useful for the real plume model as it became evident recently from an example model as it became evident recently from an example of the deep-sourced Hawaiian magmas of the deep-sourced Hawaiian magmas

(Sobolev et al., 2005; Yaxley, Sobolev 2007).(Sobolev et al., 2005; Yaxley, Sobolev 2007).

Conclusions.Conclusions. The plume model fits in the best way the The plume model fits in the best way the

features of the chosen time-progressive features of the chosen time-progressive volcanic chains: coincidence of their volcanic chains: coincidence of their orientation and time successions with orientation and time successions with directions of plate movements, directions of plate movements, independence of the chains on “shallow” independence of the chains on “shallow” structures and processes in lithosphere and structures and processes in lithosphere and asthenosphere, connection of the young ends asthenosphere, connection of the young ends of chains with superswells at CMB. of chains with superswells at CMB. On the other hand, the alternative hypotheses lead On the other hand, the alternative hypotheses lead

to useful ideas of a real role of crack propagation to useful ideas of a real role of crack propagation in time-progressive volcanism, importance in time-progressive volcanism, importance of mantle-hosted eclogite-pyroxenite melting anomalies,of mantle-hosted eclogite-pyroxenite melting anomalies, and possibility of passive, purely plate tectonic rifting and possibility of passive, purely plate tectonic rifting mechanism leading to a shallow decompressional mechanism leading to a shallow decompressional hotspot melting. hotspot melting.

Probably it is a way to a conciliation of competing Probably it is a way to a conciliation of competing theories.theories.