Supercontinent Cyclicity: Relevant Data, Constraints, Limitations and Aspects Requiring Particular Attention

Abstract:

Much data and information have been collected in recent years which have contributed to ideas on the apparently cyclical development of supercontinents since at least the late Archaean. Unfortunately, many of the datasets do not permit direct comparison or are limited in either spatial or temporal extent. Concerted efforts have been made in several IGCP project (440, 509 and now 648) to address some of these issues and to facilitate more consistent data compilation and availability, especially for geochronology, regional geology, large igneous provinces and ore deposits. Existing and new compilations for palaeomagnetics and geochemistry are being added to these existing systems so as to facilitate interoperability and querying.

Geochronology for igneous and metamorphic material provides clear evidence for cyclical events and permits distinctions not evident in detrital zircon spectra. Alternative ways to process data permit more robust interpretations so as to partly overcome sample bias related to preservation. The growing dataset also permits direct quantitative identification of potential provenance sources for detrital studies, drawing on information from multiple continents where necessary. When overlayed on a developing plate reconstruction model back to the early Proterozoic, these and other data provide important constraints on model validity. Spatial patterns for igneous and metamorphic activity, geochemical signature of igneous intrusions and of ore deposit type provide important additional constraints. 

Plate reconstruction models which require the presence of all known crustal blocks and continual integrity across multiple age steps both better constrain feasible models and identify critical blocks for which additional information are essential. They also demonstrate the importance of linear arcs when cosntraining permissible plate motions.

Modern reconstruction software such as Paleogis and GPlates allow one to effectively visualise an evolving earth, its geodyamic settings and associated ore deposits. Integration of additional information from the deeper earth, such as seismic tomography and the location of past subduction zones and slab graveyards should complete the cycle of information and further constrain viable plate models.