Drilling the solid earth: global geodynamic cycles and earth evolution

John W Shervais,Nicholas Arndt,Kathryn M Goodenough

doi:10.1007/s00531-014-1073-y

Abstract

The physical and chemical evolution of the Earth is driven by geodynamic cycles that are global in scale, operating over 4.57 Ga of Earth’s history. Some processes are truly cyclic, e.g., the Wilson Cycle, while others are irreversible (e.g., core formation). Heat and mass transfer between the lowermost mantle (e.g., core-mantle boundary) and the surface drives these global geodynamic processes. Subduction of lithospheric plates transfers cool fractionated material into the lower mantle and leads indirectly to the formation of new oceanic lithosphere, while the rise of thermochemical plumes recycles the remnants of these plates back to the surface, driven by heat transfer across the core–mantle boundary. These global geodynamic cycles are responsible for hotspot volcanism, the formation of continental crust, collisional orogenies, continental rifting, subduction zone processes (arcs, accretionary prisms), and ore deposits. Each of these presents opportunities for investigation by continental scientific drilling. In addition, these cycles affect other processes that are targets of continental scientific drilling: the origin and evolution of life and an oxygenated atmosphere, the impact of large volcanic eruptions on climate, and geological hazards such as earthquakes and volcanic eruptions. In this paper, we present the scientific rationale for continental scientific drilling to study global geodynamic processes, review past successes in this realm that were sponsored in part by ICDP, and suggest potential new targets for drilling campaigns that focus on solid earth evolution. This paper builds on discussions at the 2013 ICDP Science Meeting on the future of continental scientific drilling, held in Potsdam in November 2013.

Highlights

The geodynamic evolution of Earth began shortly after accretion at 4.57 Ga and continues today
This paper summarizes discussions of key questions to be addressed in global geodynamics by participants at the International Continental Drilling Program (ICDP) Science Meeting in Potsdam, November 2013, We focus on fundamental research driven by the need to understand how the Earth operates, both at present and throughout geological history
These may be grouped into three broad groups: (1) the geodynamic effects of thermochemical plumes; (2) plate margins; and (3) geodynamic processes in deep time

Summary

Introduction

The geodynamic evolution of Earth began shortly after accretion at 4.57 Ga and continues today. The changes in continental accretion processes through time, and the effects that the supercontinent cycle had on global climate and the evolution of life, are targets ripe for investigation by well-targeted continental scientific drilling projects (Behrman and Yang 2007; Nance and Murphy 2013) These tectonic cycles link to cycles of fluid flow and element transport within the crust, and to cycling between the atmosphere and hydrosphere and the solid earth. In addition to the fundamental questions listed above, global geodynamic cycles and heat and mass transfer link to other themes identified by ICDP as significant areas for future research (e.g., climate and ecosystem evolution, energy and mineral resources, natural hazards, and hidden biosphere).

Summary of ICDP successes

Findings

Summary