A record of plume-induced plate rotation triggering seafloor spreading and subduction initiation

Abstract

The formation of a global network of plate boundaries surrounding a mosaic of lithospheric fragments was a key step in the emergence of Earth’s plate tectonics. So far, propositions for plate boundary formation are regional in nature but how plate boundaries are being created over 1000s of km in short periods of geological time remains elusive. Here, we show from geological observations that a >12,000 km long plate boundary formed between the Indian and African plates around 105 Ma with subduction segments from the eastern Mediterranean region to a newly established India-Africa rotation pole in the west-Indian ocean where it transitioned into a ridge between India and Madagascar. We find no plate tectonics-related potential triggers of this plate rotation and identify coeval mantle plume rise below Madagascar-India as the only viable driver. For this, we provide a proof of concept by torque balance modeling revealing that the Indian and African cratonic keels were important in determining plate rotation and subduction initiation in response to the spreading plume head. Our results show that plumes may provide a non-plate-tectonic mechanism for large plate rotation initiating divergent and convergent plate boundaries far away from the plume head that may even be an underlying cause of the emergence of modern plate tectonics.

Noise in the Cretaceous Quiet Zone uncovers plate tectonic chain reaction

“…We test our concept of a plate tectonic chain reaction through a case study of the initiation of a major intra-oceanic subduction zone in the Neotethys Ocean. During the mid-Cretaceous, an intra-oceanic subduction zone formed from a trench-trench-trench triple junction with a subduction zone that had already existed since Jurassic time along the southern Eurasian margin 19,22 to the west Indian Ocean, where the plate boundary transitioned into a rift (and later ridge) that ended in a ridge-ridge-ridge triple junction in the Southern Ocean 11 . This initiation of the intra-Neotethyan subduction zone generated a socalled double, in-line subduction zone configuration between Africa and Eurasia and formed a new plate consisting predominantly of Neotethyan oceanic lithosphere 23 (Fig.…”

“…But to set off a global plate reorganization, plate motion changes induced by such isolated dynamic triggers must be able to cascade to neighbouring plates, for which a mechanism has so far not been identified.We hypothesize that when a trigger causes a plate motion change, this change may in turn trigger subsequent plate motion changes, in what we conceptualize as a 'plate tectonic chain reaction'.Geodynamic analysis has long identified that the main drivers of plate motion are the negative buoyancy of subducted lithosphere (slab pull), and occasional short-lived and subtle effects of spreading mantle plume heads below the lithosphere (plume push [9][10][11] ). Formation of new, or the abandonment of preexisting plate boundaries (mid-oceanic ridges or subduction zones), at times combined with the arrival of mantle plumes, are thus widely regarded to form the dynamic underpinning of observed plate motion changes 7,[9][10][11][12][13][14][15] . Initiation of subduction of a plate, either spontaneously 16 or forced (for instance by ridge subduction 7,17 , or by arrest, relocation, or reversal of subduction) will change where and on which plates slab pull is exerted 14 .…”

“…Geodynamic analysis has long identified that the main drivers of plate motion are the negative buoyancy of subducted lithosphere (slab pull), and occasional short-lived and subtle effects of spreading mantle plume heads below the lithosphere (plume push [9][10][11] ). Formation of new, or the abandonment of preexisting plate boundaries (mid-oceanic ridges or subduction zones), at times combined with the arrival of mantle plumes, are thus widely regarded to form the dynamic underpinning of observed plate motion changes 7,[9][10][11][12][13][14][15] . Initiation of subduction of a plate, either spontaneously 16 or forced (for instance by ridge subduction 7,17 , or by arrest, relocation, or reversal of subduction) will change where and on which plates slab pull is exerted 14 .…”

“…Recently, the study of ophiolites in Oman and Anatolia revealed that the formation of an intra-oceanic subduction zone around 105 Ma was forced by far-field stress changes 18 . This subduction zone formed in the Neotethys Ocean in the modern eastern Mediterranean region and continued to the western Indian Ocean, where it transitioned into a spreading ridge between India and Madagascar 11 . Its formation is proposed to result from the push of the Morondava plume head (Fig.…”

“…Its formation is proposed to result from the push of the Morondava plume head (Fig. 1b) causing a India-Africa plate motion change at ~105 Ma 11 . By 96-92 Ma, this subduction zone developed sufficient slab pull to drive upper plate extension widely recorded in the age of the crust of supra-subduction zone ophiolites from the Manuscript submitted to Nature Geoscience…”