ANIMATION OF PLATE MOTIONS AND OPHIOLITE GENESIS THROUGH TIME

A computer animation is presented that illustrates past plate motions, the evolution of major plate boundaries, and the origin and emplacement of over 200 ophiolite complexes. Plate motions during the last 150 million years are based on linear magnetic anomalies and the tectonic fabric of the ocean floor revealed by satellite altimetry, in combination with 'absolute' motion trajectories determined by the Indian and Atlantic hotspot tracks and paleomagnetism. Pre-Mesozoic plate motions, however, are less well constrained and are based on less precise paleomagnetic data, lithologic indicators of climate, biogeographic inferences, and the timing of continental rifts and collisions. In addition to the motion of the plates, the animation shows the continuous evolution of global plate boundaries, the locations of ophiolite formation, and the locations of ophiolite emplacement during times of continent-continent, and continent-arc collision. The computer animation is based on the PALEOMAP finite rotation model that describes the movement of over 500 plates and terranes since the Late Precambrian. The ophiolite database compiled by the authors records the present-day latitude/ longitude of each ophiolite locality as well as the igneous and tectonic environment of origin, age and mode of tectonic emplacement, the source of the information, reliability codes for the age of origin and emplacement, as well as relevant petrologic characteristics. The purpose of the animation was to both show the history of ophiolites in a plate tectonic framework, as well as answer fundamental questions concerning the tempo and mode of ophiolite formation and emplacement. Are most ophiolites formed at mid-ocean ridges or in suprasubduction zone environments? How long after formation at spreading centers are ophiolites emplaced? Is there any spatial or temporal pattern to ophiolite formation and emplacement? These are fundamental questions that have led to different controversies in the evolution of the ophiolite concept through time. Preliminary analysis of the animation suggests that both the age of origin and the age of emplacement of ophiolites are not random, but clustered, episodically. The timing of "ophiolite events" appears to be closely related to times of global plate reorganization.